# slib

## Table of Contents

- SLIB
- 1 The Library System
  - 1.1 Feature
  - 1.2 Require
  - 1.3 Library Catalogs
  - 1.4 Catalog Creation
  - 1.5 Catalog Vicinities
  - 1.6 Compiling Scheme
    - 1.6.1 Module Conventions
    - 1.6.2 Module Manifests
    - 1.6.3 Module Semantics
    - 1.6.4 Top-level Variable References
    - 1.6.5 Module Analysis
- 2 Universal SLIB Procedures
  - 2.1 Vicinity
  - 2.2 Configuration
  - 2.3 Input/Output
  - 2.4 System
  - 2.5 Miscellany
    - 2.5.1 Mutual Exclusion
    - 2.5.2 Legacy
- 3 Scheme Syntax Extension Packages
  - 3.1 Defmacro
    - 3.1.1 Defmacroexpand
  - 3.2 R4RS Macros
  - 3.3 Macro by Example
    - 3.3.1 Caveat
  - 3.4 Macros That Work
    - 3.4.1 Definitions
    - 3.4.2 Restrictions
  - 3.5 Syntactic Closures
    - 3.5.1 Syntactic Closure Macro Facility
      - 3.5.1.1 Terminology
      - 3.5.1.2 Transformer Definition
      - 3.5.1.3 Identifiers
      - 3.5.1.4 Acknowledgements
  - 3.6 Syntax-Case Macros
    - 3.6.1 Notes
  - 3.7 Define-Structure
  - 3.8 Define-Record-Type
  - 3.9 Fluid-Let
  - 3.10 Binding to multiple values
  - 3.11 Guarded LET* special form
  - 3.12 Guarded COND Clause
  - 3.13 Yasos
    - 3.13.1 Terms
    - 3.13.2 Interface
    - 3.13.3 Setters
    - 3.13.4 Examples
- 4 Textual Conversion Packages
  - 4.1 Precedence Parsing
    - 4.1.1 Precedence Parsing Overview
    - 4.1.2 Rule Types
    - 4.1.3 Ruleset Definition and Use
    - 4.1.4 Token definition
    - 4.1.5 Nud and Led Definition
    - 4.1.6 Grammar Rule Definition
  - 4.2 Format (version 3.1)
    - 4.2.1 Format Interface
    - 4.2.2 Format Specification (Format version 3.1)
      - 4.2.2.1 Implemented CL Format Control Directives
      - 4.2.2.2 Not Implemented CL Format Control Directives
      - 4.2.2.3 Extended, Replaced and Additional Control Directives
      - 4.2.2.4 Configuration Variables
      - 4.2.2.5 Compatibility With Other Format Implementations
  - 4.3 Standard Formatted I/O
    - 4.3.1 stdio
    - 4.3.2 Standard Formatted Output
      - 4.3.2.1 Exact Conversions
      - 4.3.2.2 Inexact Conversions
      - 4.3.2.3 Other Conversions
    - 4.3.3 Standard Formatted Input
  - 4.4 Program and Arguments
    - 4.4.1 Getopt
    - 4.4.2 Getopt—
    - 4.4.3 Command Line
    - 4.4.4 Parameter lists
    - 4.4.5 Getopt Parameter lists
    - 4.4.6 Filenames
    - 4.4.7 Batch
  - 4.5 HTML
  - 4.6 HTML Forms
  - 4.7 HTML Tables
    - 4.7.1 HTML editing tables
    - 4.7.2 HTML databases
  - 4.8 HTTP and CGI
  - 4.9 Parsing HTML
  - 4.10 URI
  - 4.11 Parsing XML
    - 4.11.1 String Glue
    - 4.11.2 Character and Token Functions
    - 4.11.3 Data Types
    - 4.11.4 Low-Level Parsers and Scanners
    - 4.11.5 Mid-Level Parsers and Scanners
    - 4.11.6 High-level Parsers
    - 4.11.7 Parsing XML to SXML
  - 4.12 Printing Scheme
    - 4.12.1 Generic-Write
    - 4.12.2 Object-To-String
    - 4.12.3 Pretty-Print
  - 4.13 Time and Date
    - 4.13.1 Time Zone
    - 4.13.2 Posix Time
    - 4.13.3 Common-Lisp Time
    - 4.13.4 Time Infrastructure
  - 4.14 NCBI-DNA
  - 4.15 Schmooz
- 5 Mathematical Packages
  - 5.1 Bit-Twiddling
    - 5.1.1 Bitwise Operations
    - 5.1.2 Integer Properties
    - 5.1.3 Bit Within Word
    - 5.1.4 Field of Bits
    - 5.1.5 Bits as Booleans
  - 5.2 Modular Arithmetic
  - 5.3 Irrational Integer Functions
  - 5.4 Irrational Real Functions
  - 5.5 Prime Numbers
  - 5.6 Random Numbers
    - 5.6.1 Exact Random Numbers
    - 5.6.2 Inexact Random Numbers
  - 5.7 Discrete Fourier Transform
  - 5.8 Cyclic Checksum
  - 5.9 Graphing
    - 5.9.1 Character Plotting
    - 5.9.2 PostScript Graphing
      - 5.9.2.1 Column Ranges
      - 5.9.2.2 Drawing the Graph
      - 5.9.2.3 Graphics Context
      - 5.9.2.4 Rectangles
      - 5.9.2.5 Legending
      - 5.9.2.6 Legacy Plotting
      - 5.9.2.7 Example Graph
  - 5.10 Solid Modeling
  - 5.11 Color
    - 5.11.1 Color Data-Type
      - 5.11.1.1 External Representation
      - 5.11.1.2 White
    - 5.11.2 Color Spaces
    - 5.11.3 Spectra
    - 5.11.4 Color Difference Metrics
    - 5.11.5 Color Conversions
    - 5.11.6 Color Names
    - 5.11.7 Daylight
  - 5.12 Root Finding
  - 5.13 Minimizing
  - 5.14 The Limit
  - 5.15 Commutative Rings
  - 5.16 Rules and Rulesets
  - 5.17 How to Create a Commutative Ring
  - 5.18 Matrix Algebra
- 6 Database Packages
  - 6.1 Relational Database
    - 6.1.1 Using Databases
    - 6.1.2 Table Operations
      - 6.1.2.1 Single Row Operations
      - 6.1.2.2 Match-Keys
      - 6.1.2.3 Multi-Row Operations
      - 6.1.2.4 Indexed Sequential Access Methods
      - 6.1.2.5 Sequential Index Operations
      - 6.1.2.6 Table Administration
    - 6.1.3 Database Interpolation
    - 6.1.4 Embedded Commands
      - 6.1.4.1 Database Extension
      - 6.1.4.2 Command Intrinsics
      - 6.1.4.3 Define-tables Example
      - 6.1.4.4 The *commands* Table
      - 6.1.4.5 Command Service
      - 6.1.4.6 Command Example
    - 6.1.5 Database Macros
      - 6.1.5.1 Within-database
      - 6.1.5.2 Within-database Example
    - 6.1.6 Database Browser
  - 6.2 Relational Infrastructure
    - 6.2.1 Base Table
      - 6.2.1.1 The Base
      - 6.2.1.2 Base Tables
      - 6.2.1.3 Base Field Types
      - 6.2.1.4 Composite Keys
      - 6.2.1.5 Base Record Operations
      - 6.2.1.6 Match Keys
      - 6.2.1.7 Aggregate Base Operations
      - 6.2.1.8 Base ISAM Operations
    - 6.2.2 Catalog Representation
    - 6.2.3 Relational Database Objects
    - 6.2.4 Database Operations
  - 6.3 Weight-Balanced Trees
    - 6.3.1 Construction of Weight-Balanced Trees
    - 6.3.2 Basic Operations on Weight-Balanced Trees
    - 6.3.3 Advanced Operations on Weight-Balanced Trees
    - 6.3.4 Indexing Operations on Weight-Balanced Trees
- 7 Other Packages
  - 7.1 Data Structures
    - 7.1.1 Arrays
    - 7.1.2 Subarrays
    - 7.1.3 Array Mapping
    - 7.1.4 Array Interpolation
    - 7.1.5 Association Lists
    - 7.1.6 Byte
    - 7.1.7 Byte/Number Conversions
    - 7.1.8 MAT-File Format
    - 7.1.9 Portable Image Files
    - 7.1.10 Collections
    - 7.1.11 Dynamic Data Type
    - 7.1.12 Hash Tables
    - 7.1.13 Macroless Object System
    - 7.1.14 Concepts
    - 7.1.15 Procedures
    - 7.1.16 Examples
      - 7.1.16.1 Inverter Documentation
      - 7.1.16.2 Number Documention
      - 7.1.16.3 Inverter code
    - 7.1.17 Priority Queues
    - 7.1.18 Queues
    - 7.1.19 Records
  - 7.2 Sorting and Searching
    - 7.2.1 Common List Functions
      - 7.2.1.1 List construction
      - 7.2.1.2 Lists as sets
      - 7.2.1.3 Lists as sequences
      - 7.2.1.4 Destructive list operations
      - 7.2.1.5 Non-List functions
    - 7.2.2 Tree operations
    - 7.2.3 Chapter Ordering
    - 7.2.4 Sorting
    - 7.2.5 Topological Sort
    - 7.2.6 Hashing
    - 7.2.7 Space-Filling Curves
      - 7.2.7.1 Hilbert Space-Filling Curve
      - 7.2.7.2 Gray code
      - 7.2.7.3 Bitwise Lamination
      - 7.2.7.4 Peano Space-Filling Curve
      - 7.2.7.5 Sierpinski Curve
    - 7.2.8 Soundex
    - 7.2.9 String Search
    - 7.2.10 Sequence Comparison
  - 7.3 Procedures
    - 7.3.1 Type Coercion
    - 7.3.2 String-Case
    - 7.3.3 String Ports
    - 7.3.4 Line I/O
    - 7.3.5 Multi-Processing
    - 7.3.6 Metric Units
      - 7.3.6.1 SI Prefixes
      - 7.3.6.2 Binary Prefixes
      - 7.3.6.3 Unit Symbols
  - 7.4 Standards Support
    - 7.4.1 RnRS
    - 7.4.2 With-File
    - 7.4.3 Transcripts
    - 7.4.4 Rev2 Procedures
    - 7.4.5 Rev4 Optional Procedures
    - 7.4.6 Multi-argument / and -
    - 7.4.7 Multi-argument Apply
    - 7.4.8 Rationalize
    - 7.4.9 Promises
    - 7.4.10 Dynamic-Wind
    - 7.4.11 Eval
    - 7.4.12 Values
    - 7.4.13 SRFI
      - 7.4.13.1 SRFI-1
  - 7.5 Session Support
    - 7.5.1 Repl
    - 7.5.2 Quick Print
    - 7.5.3 Debug
    - 7.5.4 Breakpoints
    - 7.5.5 Tracing
  - 7.6 System Interface
    - 7.6.1 Directories
    - 7.6.2 Transactions
    - 7.6.3 CVS
  - 7.7 Extra-SLIB Packages
- 8 About SLIB
  - 8.1 Installation
    - 8.1.1 Unpacking the SLIB Distribution
    - 8.1.2 Install documentation and slib script
    - 8.1.3 Configure Scheme Implementation to Locate SLIB
    - 8.1.4 Loading SLIB Initialization File
    - 8.1.5 Build New SLIB Catalog for Implementation
    - 8.1.6 Implementation-specific Instructions
  - 8.2 The SLIB script
  - 8.3 Porting
  - 8.4 Coding Guidelines
    - 8.4.1 Modifications
  - 8.5 Copyrights
    - 8.5.1 Putting code into the Public Domain
    - 8.5.2 Explicit copying terms
    - 8.5.3 Example: Company Copyright Disclaimer
  - 8.6 About this manual
    - 8.6.1 GNU Free Documentation License
- Index
- Procedure and Macro Index
- Variable Index
- Concept and Feature Index

Next: The Library System, Previous: (dir), Up: (dir)

## SLIB

This manual is for SLIB (version 3b1, July 2008), the portable Scheme library.

Copyright © 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.

> Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License.”

Next: Universal SLIB Procedures, Previous: Top, Up: Top

## 1 The Library System

SLIB is a portable library for the programming language Scheme. It provides a platform independent framework for using packages of Scheme procedures and syntax. As distributed, SLIB contains useful packages for all Scheme implementations. Its catalog can be transparently extended to accomodate packages specific to a site, implementation, user, or directory.

Next: Require, Previous: The Library System, Up: The Library System

### 1.1 Feature

SLIB denotes features by symbols. SLIB maintains a list of features supported by a Scheme session. The set of features provided by a session may change during that session. Some features are properties of the Scheme implementation being used. The following intrinsic features detail what sort of numbers are available from an implementation:

- 'inexact
- 'rational
- 'real
- 'complex
- 'bignum

SLIB initialization (in `require.scm`) tests and provides any of these numeric features which are appropriate.

Other features correspond to the presence of packages of Scheme procedures or syntax (macros).

— Function: provided? feature

> Returns `#t` if feature is present in the current Scheme session; otherwise `#f`. More specifically, `provided?` returns `#t` if the symbol feature is the `software-type`, the `scheme-implementation-type` 1, or if feature has been provided by a module already loaded; and `#f` otherwise.

> In some implementations `provided?` tests whether a module has been `require`d by any module or in any thread; other implementations will have `provided?` reflect only the modules `require`d by that particular session or thread.

> To work portably in both scenarios, use `provided?` only to test whether intrinsic properties (like those above) are present.

> The feature argument can also be an expression calling `and`, `or`, and `not` of features. The boolean result of the logical question asked by feature is returned.

The generalization of `provided?` for arbitrary features and catalog is `feature-eval`:

— Function: feature-eval expression provided?

> Evaluates `and`, `or`, and `not` forms in expression, using the values returned by calling provided? on the leaf symbols. `feature-eval` returns the boolean result of the logical combinations.

— Procedure: provide feature

> Informs SLIB that feature is supported in this session.

         (provided? 'foo)    => #f
         (provide 'foo)
         (provided? 'foo)    => #t

Next: Library Catalogs, Previous: Feature, Up: The Library System

### 1.2 Require

SLIB creates and maintains a catalog mapping features to locations of files introducing procedures and syntax denoted by those features.

— Variable: *catalog*

> Is an association list of features (symbols) and pathnames which will supply those features. The pathname can be either a string or a pair. If pathname is a pair then the first element should be a macro feature symbol, `source`, `compiled`, or one of the other cases described in Library Catalogs. The cdr of the pathname should be either a string or a list.

At the beginning of each section of this manual, there is a line like `(require '`feature`)`. The Scheme files comprising SLIB are cataloged so that these feature names map to the corresponding files.

SLIB provides a form, `require`, which loads the files providing the requested feature.

— Procedure: require feature

> - If `(provided?` feature`)` is true, then `require` just returns.
> - Otherwise, if feature is found in the catalog, then the corresponding files will be loaded and `(provided?` feature`)` will henceforth return `#t`. That feature is thereafter `provided`.
> - Otherwise (feature not found in the catalog), an error is signaled.

There is a related form `require-if`, used primarily for enabling compilers to statically include modules which would be dynamically loaded by interpreters.

— Procedure: require-if condition feature

> Requires feature if condition is true.

The `random` module uses `require-if` to flag `object->string` as a (dynamic) required module.

         (require 'byte)
         (require 'logical)
         (require-if 'compiling 'object->string)

The `batch` module uses `require-if` to flag `posix-time` as a module to load if the implementation supports large precision exact integers.

         (require-if '(and bignum compiling) 'posix-time)

The catalog can also be queried using `slib:in-catalog?`.

— Function: slib:in-catalog? feature

> Returns a `CDR` of the catalog entry if one was found for the symbol feature in the alist `*catalog*` (and transitively through any symbol aliases encountered). Otherwise, returns `#f`. The format of catalog entries is explained in Library Catalogs.

Next: Catalog Creation, Previous: Require, Up: The Library System

### 1.3 Library Catalogs

Catalog files consist of one or more association lists. In the circumstance where a feature symbol appears in more than one list, the latter list's association is retrieved. Here are the supported formats for elements of catalog lists:

`(`feature`.` <symbol>`)`
  Redirects to the feature named <symbol>.
`(`feature`. "`<path>`")`
  Loads file <path>.
`(`feature`source "`<path>"`)`
  `slib:load`s the Scheme source file <path>.
`(`feature`compiled "`<path>"`...)`
  `slib:load-compiled`s the files <path> ....
`(`feature`aggregate` <symbol>`...)`
  `require`s the features <symbol> ....

The various macro styles first `require` the named macro package, then just load <path> or load-and-macro-expand <path> as appropriate for the implementation.

`(`feature`defmacro "`<path>"`)`
  `defmacro:load`s the Scheme source file <path>.
`(`feature`macro-by-example "`<path>"`)`
  `defmacro:load`s the Scheme source file <path>.

`(`feature`macro "`<path>"`)`
  `macro:load`s the Scheme source file <path>.
`(`feature`macros-that-work "`<path>"`)`
  `macro:load`s the Scheme source file <path>.
`(`feature`syntax-case "`<path>"`)`
  `macro:load`s the Scheme source file <path>.
`(`feature`syntactic-closures "`<path>"`)`
  `macro:load`s the Scheme source file <path>.

Next: Catalog Vicinities, Previous: Library Catalogs, Up: The Library System

### 1.4 Catalog Creation

At the start of an interactive session no catalog is present, but is created with the first catalog inquiry (such as `(require 'random)`). Several sources of catalog information are combined to produce the catalog:

- standard SLIB packages.
- additional packages of interest to this site.
- packages specifically for the variety of Scheme which this session is running.
- packages this user wants to always have available. This catalog is the file `homecat` in the user's HOME directory.
- packages germane to working in this (current working) directory. This catalog is the file `usercat` in the directory to which it applies. One would typically `cd` to this directory before starting the Scheme session.
- packages which are part of an application program.

SLIB combines the catalog information which doesn't vary per user into the file `slibcat` in the implementation-vicinity. Therefore `slibcat` needs change only when new software is installed or compiled. Because the actual pathnames of files can differ from installation to installation, SLIB builds a separate catalog for each implementation it is used with.

The definition of `*slib-version*` in SLIB file `require.scm` is checked against the catalog association of `*slib-version*` to ascertain when versions have changed. It is a reasonable practice to change the definition of `*slib-version*` whenever the library is changed. If multiple implementations of Scheme use SLIB, remember that recompiling one `slibcat` will update only that implementation's catalog.

The compilation scripts of Scheme implementations which work with SLIB can automatically trigger catalog compilation by deleting `slibcat` or by invoking `require` of a special feature:

— Procedure: require 'new-catalog

> This will load `mklibcat`, which compiles and writes a new `slibcat`.

Another special feature of `require` erases SLIB's catalog, forcing it to be reloaded the next time the catalog is queried.

— Procedure: require #f

> Removes SLIB's catalog information. This should be done before saving an executable image so that, when restored, its catalog will be loaded afresh.

Next: Compiling Scheme, Previous: Catalog Creation, Up: The Library System

### 1.5 Catalog Vicinities

Each file in the table below is descibed in terms of its file-system independent vicinity (see Vicinity). The entries of a catalog in the table override those of catalogs above it in the table.

`implementation-vicinity` `slibcat`
  This file contains the associations for the packages comprising SLIB, the `implcat` and the `sitecat`s. The associations in the other catalogs override those of the standard catalog.
`library-vicinity` `mklibcat.scm`
  creates `slibcat`.
`library-vicinity` `sitecat`
  This file contains the associations specific to an SLIB installation.
`implementation-vicinity` `implcat`
  This file contains the associations specific to an implementation of Scheme. Different implementations of Scheme should have different `implementation-vicinity`.
`implementation-vicinity` `mkimpcat.scm`
  if present, creates `implcat`.
`implementation-vicinity` `sitecat`
  This file contains the associations specific to a Scheme implementation installation.
`home-vicinity` `homecat`
  This file contains the associations specific to an SLIB user.
`user-vicinity` `usercat`
  This file contains associations affecting only those sessions whose working directory is `user-vicinity`.

Here is an example of a `usercat` catalog. A program in this directory can invoke the ``run`' feature with `(require 'run)`.

         ;;; "usercat": SLIB catalog additions for SIMSYNCH.     -*-scheme-*-
         (
          (simsynch      . "../synch/simsynch.scm")
          (run           . "../synch/run.scm")
          (schlep        . "schlep.scm")
         )

Copying `usercat` to many directories is inconvenient. Application programs which aren't always run in specially prepared directories can nonetheless register their features during initialization.

— Procedure: catalog:read vicinity catalog

> Reads file named by string catalog in vicinity, resolving all paths relative to vicinity, and adds those feature associations to *catalog*.

> `catalog:read` would typically be used by an application program having dynamically loadable modules. For instance, to register factoring and other modules in *catalog*, JACAL does:

>               (catalog:read (program-vicinity) "jacalcat")

For an application program there are three appropriate venues for registering its catalog associations:

- in a `usercat` file in the directory where the program runs; or
- in an `implcat` file in the `implementation-vicinity`; or
- in an application program directory; loaded by calling `catalog:read`.

Previous: Catalog Vicinities, Up: The Library System

### 1.6 Compiling Scheme

To use Scheme compilers effectively with SLIB the compiler needs to know which SLIB modules are to be compiled and which symbols are exported from those modules.

The procedures in this section automate the extraction of this information from SLIB modules. They are guaranteed to work on SLIB modules; to use them on other sources, those sources should follow SLIB conventions.

Next: Module Manifests, Previous: Compiling Scheme, Up: Compiling Scheme

#### 1.6.1 Module Conventions

- All the top-level `require` commands have one quoted argument and are positioned before other Scheme definitions and expressions in the file.
- Any conditionally `require`d SLIB modules 2 also appear at the beginning of their files conditioned on the feature `compiling` using `require-if` (see require-if).

                (require 'logical)
                (require 'multiarg/and-)
                (require-if 'compiling 'sort)
                (require-if 'compiling 'ciexyz)

- Schmooz-style comments preceding a definition, identify that definition as an exported identifier (see Schmooz). For non-schmooz files, putting ``;@`' at the beginning of the line immediately preceding the definition (`define`, `define-syntax`, or `defmacro`) suffices.

                ;@
                (define (identity <obj>) <obj>)

- Syntax (macro) definitions are grouped at the end of a module file.
- Modules defining macros do not invoke those macros. SLIB macro implementations are exempt from this rule.

  An example of how to expand macro invocations is:

                (require 'macros-that-work)
                (require 'yasos)
                (require 'pprint-file)
                (pprint-filter-file "collect.scm" macwork:expand)

Next: Module Semantics, Previous: Module Conventions, Up: Compiling Scheme

#### 1.6.2 Module Manifests

`(require 'manifest)` In some of these examples, slib:catalog is the SLIB part of the catalog; it is free of compiled and implementation-specific entries. It would be defined by:

         (define slib:catalog (cdr (member (assq 'null *catalog*) *catalog*)))

— Function: file->requires file provided? catalog

> Returns a list of the features `require`d by file assuming the predicate provided? and association-list catalog.

         (define (provided+? . features)
           (lambda (feature)
             (or (memq feature features) (provided? feature))))

         (file->requires "obj2str.scm" (provided+? 'compiling) '())
                 => (string-port generic-write)

         (file->requires "obj2str.scm" provided? '())
                 => (string-port)

— Function: feature->requires feature provided? catalog

> Returns a list of the features `require`d by feature assuming the predicate provided? and association-list catalog.

         (feature->requires 'batch (provided+? 'compiling) *catalog*)
                 => (tree line-i/o databases parameters string-port
                            pretty-print common-list-functions posix-time)

         (feature->requires 'batch provided? *catalog*)
                 => (tree line-i/o databases parameters string-port
                            pretty-print common-list-functions)

         (feature->requires 'batch provided? '((batch . "batch")))
                 => (tree line-i/o databases parameters string-port
                            pretty-print common-list-functions)

— Function: feature->requires* feature provided? catalog

> Returns a list of the features transitively `require`d by feature assuming the predicate provided? and association-list catalog.

— Function: file->requires* file provided? catalog

> Returns a list of the features transitively `require`d by file assuming the predicate provided? and association-list catalog.

— Function: file->loads file

> Returns a list of strings naming existing files loaded (load slib:load slib:load-source macro:load defmacro:load syncase:load synclo:load macwork:load) by file or any of the files it loads.

         (file->loads (in-vicinity (library-vicinity) "scainit.scm"))
                 => ("/usr/local/lib/slib/scaexpp.scm"
                     "/usr/local/lib/slib/scaglob.scm"
                     "/usr/local/lib/slib/scaoutp.scm")

— Function: load->path exp

> Given a `(load '<expr>)`, where <expr> is a string or vicinity stuff), `(load->path <expr>)` figures a path to the file. `load->path` returns that path if it names an existing file; otherwise #f.

         (load->path '(in-vicinity (library-vicinity) "mklibcat"))
                 => "/usr/local/lib/slib/mklibcat.scm"

— Function: file->definitions file definer ...

> Returns a list of the identifier symbols defined by SLIB (or SLIB-style) file file. The optional arguments definers should be symbols signifying a defining form. If none are supplied, then the symbols `define-operation`, `define`, `define-syntax`, and `defmacro` are captured.

         (file->definitions "random.scm")
                 => (*random-state* make-random-state
                    seed->random-state copy-random-state random
                    random:chunk)

— Function: file->exports file definer ...

> Returns a list of the identifier symbols exported (advertised) by SLIB (or SLIB-style) file file. The optional arguments definers should be symbols signifying a defining form. If none are supplied, then the symbols `define-operation`, `define`, `define-syntax`, and `defmacro` are captured.

         (file->exports "random.scm")
                 => (make-random-state seed->random-state
                     copy-random-state random)

         (file->exports "randinex.scm")
                 => (random:solid-sphere! random:hollow-sphere!
                     random:normal-vector! random:normal
                     random:exp random:uniform)

— Function: feature->export-alist feature catalog

> Returns a list of lists; each sublist holding the name of the file implementing feature, and the identifier symbols exported (advertised) by SLIB (or SLIB-style) feature feature, in catalog.

— Function: feature->exports feature catalog

> Returns a list of all exports of feature.

In the case of `aggregate` features, more than one file may have export lists to report:

         (feature->export-alist 'r5rs slib:catalog))
                 => (("/usr/local/lib/slib/values.scm"
                      call-with-values values)
                     ("/usr/local/lib/slib/mbe.scm"
                      define-syntax macro:expand
                      macro:load macro:eval)
                     ("/usr/local/lib/slib/eval.scm"
                      eval scheme-report-environment
                      null-environment interaction-environment))

         (feature->export-alist 'stdio *catalog*)
                 => (("/usr/local/lib/slib/scanf.scm"
                      fscanf sscanf scanf scanf-read-list)
                     ("/usr/local/lib/slib/printf.scm"
                      sprintf printf fprintf)
                     ("/usr/local/lib/slib/stdio.scm"
                      stderr stdout stdin))

         (feature->exports 'stdio slib:catalog)
                 => (fscanf sscanf scanf scanf-read-list
                      sprintf printf fprintf stderr stdout stdin)

Next: Top-level Variable References, Previous: Module Manifests, Up: Compiling Scheme

#### 1.6.3 Module Semantics

For the purpose of compiling Scheme code, each top-level `require` makes the identifiers exported by its feature's module `defined` (or defmacroed or defined-syntaxed) within the file (being compiled) headed with those requires.

Top-level occurrences of `require-if` make defined the exports from the module named by the second argument if the feature-expression first argument is true in the target environment. The target feature `compiling` should be provided during this phase of compilation.

Non-top-level SLIB occurences of `require` and `require-if` of quoted features can be ignored by compilers. The SLIB modules will all have top-level constructs for those features.

Note that aggregate catalog entries import more than one module. Implementations of `require` may or may not be transitive; code which uses module exports without requiring the providing module is in error.

In the SLIB modules `modular`, `batch`, `hash`, `common-lisp-time`, `commutative-ring`, `charplot`, `logical`, `common-list-functions`, `coerce` and `break` there is code conditional on features being `provided?`. Most are testing for the presence of features which are intrinsic to implementations (inexacts, bignums, ...).

In all cases these `provided?` tests can be evaluated at compile-time using `feature-eval` (see feature-eval). The simplest way to compile these constructs may be to treat `provided?` as a macro.

Next: Module Analysis, Previous: Module Semantics, Up: Compiling Scheme

#### 1.6.4 Top-level Variable References

`(require 'top-refs)` These procedures complement those in Module Manifests by finding the top-level variable references in Scheme source code. They work by traversing expressions and definitions, keeping track of bindings encountered. It is certainly possible to foil these functions, but they return useful information about SLIB source code.

— Function: top-refs obj

> Returns a list of the top-level variables referenced by the Scheme expression obj.

— Function: top-refs<-file filename

> filename should be a string naming an existing file containing Scheme source code. `top-refs<-file` returns a list of the top-level variable references made by expressions in the file named by filename.

> Code in modules which filename `require`s is not traversed. Code in files loaded from top-level is traversed if the expression argument to `load`, `slib:load`, `slib:load-source`, `macro:load`, `defmacro:load`, `synclo:load`, `syncase:load`, or `macwork:load` is a literal string constant or composed of combinations of vicinity functions and string literal constants; and the resulting file exists (possibly with ".scm" appended).

The following function parses an Info Index. 3

— Function: exports<-info-index file n ...

> n ... must be an increasing series of positive integers. `exports<-info-index` returns a list of all the identifiers appearing in the nth ... (info) indexes of file. The identifiers have the case that the implementation's `read` uses for symbols. Identifiers containing spaces (eg. `close-base on base-table`) are not included. #f is returned if the index is not found.

> Each info index is headed by a ``* Menu:`' line. To list the symbols in the first and third info indexes do:

>               (exports<-info-index "slib.info" 1 3)

Previous: Top-level Variable References, Up: Compiling Scheme

#### 1.6.5 Module Analysis

`(require 'vet)`

— Function: vet-slib file1 ...

> Using the procedures in the `top-refs` and `manifest` modules, `vet-slib` analyzes each SLIB module and file1, ..., reporting about any procedure or macro defined whether it is:

> orphaned
>   defined, not called, not exported;
> missing
>   called, not defined, and not exported by its `require`d modules;
> undocumented-export
>   Exported by module, but no index entry in `slib.info`;

> And for the library as a whole:

> documented-unexport
>   Index entry in `slib.info`, but no module exports it.

> This straightforward analysis caught three full days worth of never-executed branches, transitive require assumptions, spelling errors, undocumented procedures, missing procedures, and cyclic dependencies in SLIB.

> The optional arguments file1, ... provide a simple way to vet prospective SLIB modules.

Next: Scheme Syntax Extension Packages, Previous: The Library System, Up: Top

## 2 Universal SLIB Procedures

The procedures described in these sections are supported by all implementations as part of the ``*.init`' files or by `require.scm`.

Next: Configuration, Previous: Universal SLIB Procedures, Up: Universal SLIB Procedures

### 2.1 Vicinity

A vicinity is a descriptor for a place in the file system. Vicinities hide from the programmer the concepts of host, volume, directory, and version. Vicinities express only the concept of a file environment where a file name can be resolved to a file in a system independent manner. Vicinities can even be used on flat file systems (which have no directory structure) by having the vicinity express constraints on the file name.

All of these procedures are file-system dependent. Use of these vicinity procedures can make programs file-system independent.

These procedures are provided by all implementations. On most systems a vicinity is a string.

— Function: make-vicinity dirpath

> Returns dirpath as a vicinity for use as first argument to `in-vicinity`.

— Function: pathname->vicinity path

> Returns the vicinity containing path.

>               (pathname->vicinity "/usr/local/lib/scm/Link.scm")
>                                   => "/usr/local/lib/scm/"

— Function: program-vicinity

> Returns the vicinity of the currently loading Scheme code. For an interpreter this would be the directory containing source code. For a compiled system (with multiple files) this would be the directory where the object or executable files are. If no file is currently loading, then the result is undefined. Warning: `program-vicinity` can return incorrect values if your program escapes back into a `load` continuation.

— Function: library-vicinity

> Returns the vicinity of the shared Scheme library.

— Function: implementation-vicinity

> Returns the vicinity of the underlying Scheme implementation. This vicinity will likely contain startup code and messages and a compiler.

— Function: user-vicinity

> Returns the vicinity of the current directory of the user. On most systems this is `""` (the empty string).

— Function: home-vicinity

> Returns the vicinity of the user's HOME directory, the directory which typically contains files which customize a computer environment for a user. If scheme is running without a user (eg. a daemon) or if this concept is meaningless for the platform, then `home-vicinity` returns `#f`.

— Function: vicinity:suffix? chr

> Returns the ``#t`' if chr is a vicinity suffix character; and `#f` otherwise. Typical vicinity suffixes are ``/`', ``:`', and ``\`',

— Function: in-vicinity vicinity filename

> Returns a filename suitable for use by `slib:load`, `slib:load-source`, `slib:load-compiled`, `open-input-file`, `open-output-file`, etc. The returned filename is filename in vicinity. `in-vicinity` should allow filename to override vicinity when filename is an absolute pathname and vicinity is equal to the value of `(user-vicinity)`. The behavior of `in-vicinity` when filename is absolute and vicinity is not equal to the value of `(user-vicinity)` is unspecified. For most systems `in-vicinity` can be `string-append`.

— Function: sub-vicinity vicinity name

> Returns the vicinity of vicinity restricted to name. This is used for large systems where names of files in subsystems could conflict. On systems with directory structure `sub-vicinity` will return a pathname of the subdirectory name of vicinity.

— Function: with-load-pathname path thunk

> path should be a string naming a file being read or loaded. `with-load-pathname` evaluates thunk in a dynamic scope where an internal variable is bound to path; the internal variable is used for messages and `program-vicinity`. `with-load-pathname` returns the value returned by thunk.

Next: Input/Output, Previous: Vicinity, Up: Universal SLIB Procedures

### 2.2 Configuration

These constants and procedures describe characteristics of the Scheme and underlying operating system. They are provided by all implementations.

— Constant: char-code-limit

> An integer 1 larger that the largest value which can be returned by `char->integer`.

— Constant: most-positive-fixnum

> In implementations which support integers of practically unlimited size, most-positive-fixnum is a large exact integer within the range of exact integers that may result from computing the length of a list, vector, or string.

> In implementations which do not support integers of practically unlimited size, most-positive-fixnum is the largest exact integer that may result from computing the length of a list, vector, or string.

— Constant: slib:tab

> The tab character.

— Constant: slib:form-feed

> The form-feed character.

— Function: software-type

> Returns a symbol denoting the generic operating system type. For instance, `unix`, `vms`, `macos`, `amiga`, or `ms-dos`.

— Function: slib:report-version

> Displays the versions of SLIB and the underlying Scheme implementation and the name of the operating system. An unspecified value is returned.

>               (slib:report-version) => slib "3b1" on scm "5b1" on unix

— Function: slib:report

> Displays the information of `(slib:report-version)` followed by almost all the information neccessary for submitting a problem report. An unspecified value is returned. — Function: slib:report #t

> > provides a more verbose listing. — Function: slib:report filename

> > > Writes the report to file `filename`.

> > >               (slib:report)
> > >               =>
> > >               slib "3b1" on scm "5b1" on unix
> > >               (implementation-vicinity) is "/usr/local/lib/scm/"
> > >               (library-vicinity) is "/usr/local/lib/slib/"
> > >               (scheme-file-suffix) is ".scm"
> > >               loaded slib:features :
> > >                       trace alist qp sort
> > >                       common-list-functions macro values getopt
> > >                       compiled
> > >               implementation slib:features :
> > >                       bignum complex real rational
> > >                       inexact vicinity ed getenv
> > >                       tmpnam abort transcript with-file
> > >                       ieee-p1178 r4rs rev4-optional-procedures hash
> > >                       object-hash delay eval dynamic-wind
> > >                       multiarg-apply multiarg/and- logical defmacro
> > >                       string-port source current-time record
> > >                       rev3-procedures rev2-procedures sun-dl string-case
> > >                       array dump char-ready? full-continuation
> > >                       system
> > >               implementation *catalog* :
> > >                       (i/o-extensions compiled "/usr/local/lib/scm/ioext.so")
> > >                       ...

Next: System, Previous: Configuration, Up: Universal SLIB Procedures

### 2.3 Input/Output

These procedures are provided by all implementations.

— Function: file-exists? filename

> Returns `#t` if the specified file exists. Otherwise, returns `#f`. If the underlying implementation does not support this feature then `#f` is always returned.

— Function: delete-file filename

> Deletes the file specified by filename. If filename can not be deleted, `#f` is returned. Otherwise, `#t` is returned.

— Function: open-file filename modes

> filename should be a string naming a file. `open-file` returns a port depending on the symbol modes:

> r
>   an input port capable of delivering characters from the file.
> rb
>   a binary input port capable of delivering characters from the file.
> w
>   an output port capable of writing characters to a new file by that name.
> wb
>   a binary output port capable of writing characters to a new file by that name.

> If an implementation does not distinguish between binary and non-binary files, then it must treat rb as r and wb as w.

> If the file cannot be opened, either #f is returned or an error is signalled. For output, if a file with the given name already exists, the effect is unspecified.

— Function: port? obj

> Returns `#t` if obj is an input or output port, otherwise returns `#f`.

— Procedure: close-port port

> Closes the file associated with port, rendering the port incapable of delivering or accepting characters.

> `close-file` has no effect if the file has already been closed. The value returned is unspecified.

— Function: call-with-open-ports proc ports ...
— Function: call-with-open-ports ports ... proc

> Proc should be a procedure that accepts as many arguments as there are ports passed to `call-with-open-ports`. `call-with-open-ports` calls proc with ports .... If proc returns, then the ports are closed automatically and the value yielded by the proc is returned. If proc does not return, then the ports will not be closed automatically unless it is possible to prove that the ports will never again be used for a read or write operation.

— Function: tmpnam

> Returns a pathname for a file which will likely not be used by any other process. Successive calls to `(tmpnam)` will return different pathnames.

— Function: current-error-port

> Returns the current port to which diagnostic and error output is directed.

— Procedure: force-output
— Procedure: force-output port

> Forces any pending output on port to be delivered to the output device and returns an unspecified value. The port argument may be omitted, in which case it defaults to the value returned by `(current-output-port)`.

— Function: file-position port
— Function: file-position port #f

> port must be open to a file. `file-position` returns the current position of the character in port which will next be read or written. If the implementation does not support file-position, then `#f` is returned. — Function: file-position port k

> > port must be open to a file. `file-position` sets the current position in port which will next be read or written. If successful, `#f` is returned; otherwise `file-position` returns `#f`.

— Function: output-port-width
— Function: output-port-width port

> Returns the width of port, which defaults to `(current-output-port)` if absent. If the width cannot be determined 79 is returned.

— Function: output-port-height
— Function: output-port-height port

> Returns the height of port, which defaults to `(current-output-port)` if absent. If the height cannot be determined 24 is returned.

Next: Miscellany, Previous: Input/Output, Up: Universal SLIB Procedures

### 2.4 System

These procedures are provided by all implementations.

— Procedure: slib:load-source name

> Loads a file of Scheme source code from name with the default filename extension used in SLIB. For instance if the filename extension used in SLIB is `.scm` then `(slib:load-source "foo")` will load from file `foo.scm`.

— Procedure: slib:load-compiled name

> On implementations which support separtely loadable compiled modules, loads a file of compiled code from name with the implementation's filename extension for compiled code appended.

— Procedure: slib:load name

> Loads a file of Scheme source or compiled code from name with the appropriate suffixes appended. If both source and compiled code are present with the appropriate names then the implementation will load just one. It is up to the implementation to choose which one will be loaded.

> If an implementation does not support compiled code then `slib:load` will be identical to `slib:load-source`.

— Procedure: slib:eval obj

> `eval` returns the value of obj evaluated in the current top level environment. Eval provides a more general evaluation facility.

— Procedure: slib:eval-load filename eval

> filename should be a string. If filename names an existing file, the Scheme source code expressions and definitions are read from the file and eval called with them sequentially. The `slib:eval-load` procedure does not affect the values returned by `current-input-port` and `current-output-port`.

— Procedure: slib:warn arg1 arg2 ...

> Outputs a warning message containing the arguments.

— Procedure: slib:error arg1 arg2 ...

> Outputs an error message containing the arguments, aborts evaluation of the current form and responds in a system dependent way to the error. Typical responses are to abort the program or to enter a read-eval-print loop.

— Procedure: slib:exit n
— Procedure: slib:exit

> Exits from the Scheme session returning status n to the system. If n is omitted or `#t`, a success status is returned to the system (if possible). If n is `#f` a failure is returned to the system (if possible). If n is an integer, then n is returned to the system (if possible). If the Scheme session cannot exit, then an unspecified value is returned from `slib:exit`.

— Function: browse-url url

> Web browsers have become so ubiquitous that programming languagues should support a uniform interface to them.

> If a browser is running, `browse-url` causes the browser to display the page specified by string url and returns `#t`.

> If the browser is not running, `browse-url` starts a browser displaying the argument url. If the browser starts as a background job, `browse-url` returns `#t` immediately; if the browser starts as a foreground job, then `browse-url` returns `#t` when the browser exits; otherwise (if no browser) it returns `#f`.

Previous: System, Up: Universal SLIB Procedures

### 2.5 Miscellany

These procedures are provided by all implementations.

— Function: identity x

> identity returns its argument.

> Example:

>               (identity 3)
>                  => 3
>               (identity '(foo bar))
>                  => (foo bar)
>               (map identity lst)
>                  == (copy-list lst)

#### 2.5.1 Mutual Exclusion

An exchanger is a procedure of one argument regulating mutually exclusive access to a resource. When a exchanger is called, its current content is returned, while being replaced by its argument in an atomic operation.

— Function: make-exchanger obj

> Returns a new exchanger with the argument obj as its initial content.

>               (define queue (make-exchanger (list a)))

> A queue implemented as an exchanger holding a list can be protected from reentrant execution thus:

>               (define (pop queue)
>                 (let ((lst #f))
>                   (dynamic-wind
>                       (lambda () (set! lst (queue #f)))
>                       (lambda () (and lst (not (null? lst))
>                                       (let ((ret (car lst)))
>                                         (set! lst (cdr lst))
>                                         ret)))
>                       (lambda () (and lst (queue lst))))))

>               (pop queue)         => a

>               (pop queue)         => #f

#### 2.5.2 Legacy

The following procedures were present in Scheme until R4RS (see Language changes). They are provided by all SLIB implementations.

— Constant: t

> Defined as `#t`.

— Constant: nil

> Defined as `#f`.

— Function: last-pair l

> Returns the last pair in the list l. Example:

>               (last-pair (cons 1 2))
>                  => (1 . 2)
>               (last-pair '(1 2))
>                  => (2)
>                   == (cons 2 '())

Next: Textual Conversion Packages, Previous: Universal SLIB Procedures, Up: Top

## 3 Scheme Syntax Extension Packages

Syntax extensions (macros) included with SLIB.

Next: R4RS Macros, Previous: Scheme Syntax Extension Packages, Up: Scheme Syntax Extension Packages

### 3.1 Defmacro

Defmacros are supported by all implementations.

— Function: gentemp

> Returns a new (interned) symbol each time it is called. The symbol names are implementation-dependent

>               (gentemp) => scm:G0
>               (gentemp) => scm:G1

— Function: defmacro:eval e

> Returns the `slib:eval` of expanding all defmacros in scheme expression e.

— Function: defmacro:load filename

> filename should be a string. If filename names an existing file, the `defmacro:load` procedure reads Scheme source code expressions and definitions from the file and evaluates them sequentially. These source code expressions and definitions may contain defmacro definitions. The `macro:load` procedure does not affect the values returned by `current-input-port` and `current-output-port`.

— Function: defmacro? sym

> Returns `#t` if sym has been defined by `defmacro`, `#f` otherwise.

— Function: macroexpand-1 form
— Function: macroexpand form

> If form is a macro call, `macroexpand-1` will expand the macro call once and return it. A form is considered to be a macro call only if it is a cons whose `car` is a symbol for which a `defmacro` has been defined.

> `macroexpand` is similar to `macroexpand-1`, but repeatedly expands form until it is no longer a macro call.

— Macro: defmacro name lambda-list form ...

> When encountered by `defmacro:eval`, `defmacro:macroexpand*`, or `defmacro:load` defines a new macro which will henceforth be expanded when encountered by `defmacro:eval`, `defmacro:macroexpand*`, or `defmacro:load`.

#### 3.1.1 Defmacroexpand

`(require 'defmacroexpand)`

— Function: defmacro:expand* e

> Returns the result of expanding all defmacros in scheme expression e.

Next: Macro by Example, Previous: Defmacro, Up: Scheme Syntax Extension Packages

### 3.2 R4RS Macros

`(require 'macro)` is the appropriate call if you want R4RS high-level macros but don't care about the low level implementation. If an SLIB R4RS macro implementation is already loaded it will be used. Otherwise, one of the R4RS macros implemetations is loaded.

The SLIB R4RS macro implementations support the following uniform interface:

— Function: macro:expand sexpression

> Takes an R4RS expression, macro-expands it, and returns the result of the macro expansion.

— Function: macro:eval sexpression

> Takes an R4RS expression, macro-expands it, evals the result of the macro expansion, and returns the result of the evaluation.

— Procedure: macro:load filename

> filename should be a string. If filename names an existing file, the `macro:load` procedure reads Scheme source code expressions and definitions from the file and evaluates them sequentially. These source code expressions and definitions may contain macro definitions. The `macro:load` procedure does not affect the values returned by `current-input-port` and `current-output-port`.

Next: Macros That Work, Previous: R4RS Macros, Up: Scheme Syntax Extension Packages

### 3.3 Macro by Example

`(require 'macro-by-example)` A vanilla implementation of Macro by Example (Eugene Kohlbecker, R4RS) by Dorai Sitaram, (dorai @ cs.rice.edu) using `defmacro`.

- generating hygienic global `define-syntax` Macro-by-Example macros cheaply.
- can define macros which use `...`.
- needn't worry about a lexical variable in a macro definition clashing with a variable from the macro use context
- don't suffer the overhead of redefining the repl if `defmacro` natively supported (most implementations)

#### 3.3.1 Caveat

These macros are not referentially transparent (see Macros). Lexically scoped macros (i.e., `let-syntax` and `letrec-syntax`) are not supported. In any case, the problem of referential transparency gains poignancy only when `let-syntax` and `letrec-syntax` are used. So you will not be courting large-scale disaster unless you're using system-function names as local variables with unintuitive bindings that the macro can't use. However, if you must have the full r4rs macro functionality, look to the more featureful (but also more expensive) versions of syntax-rules available in slib Macros That Work, Syntactic Closures, and Syntax-Case Macros.

— Macro: define-syntax keyword transformer-spec

> The keyword is an identifier, and the transformer-spec should be an instance of `syntax-rules`.

> The top-level syntactic environment is extended by binding the keyword to the specified transformer.

>               (define-syntax let*
>                 (syntax-rules ()
>                   ((let* () body1 body2 ...)
>                    (let () body1 body2 ...))
>                   ((let* ((name1 val1) (name2 val2) ...)
>                      body1 body2 ...)
>                    (let ((name1 val1))
>                      (let* (( name2 val2) ...)
>                        body1 body2 ...)))))

— Macro: syntax-rules literals syntax-rule ...

> literals is a list of identifiers, and each syntax-rule should be of the form

> `(`pattern template`)`

> where the pattern and template are as in the grammar above.

> An instance of `syntax-rules` produces a new macro transformer by specifying a sequence of hygienic rewrite rules. A use of a macro whose keyword is associated with a transformer specified by `syntax-rules` is matched against the patterns contained in the syntax-rules, beginning with the leftmost syntax-rule. When a match is found, the macro use is trancribed hygienically according to the template.

> Each pattern begins with the keyword for the macro. This keyword is not involved in the matching and is not considered a pattern variable or literal identifier.

Next: Syntactic Closures, Previous: Macro by Example, Up: Scheme Syntax Extension Packages

### 3.4 Macros That Work

`(require 'macros-that-work)` Macros That Work differs from the other R4RS macro implementations in that it does not expand derived expression types to primitive expression types.

— Function: macro:expand expression
— Function: macwork:expand expression

> Takes an R4RS expression, macro-expands it, and returns the result of the macro expansion.

— Function: macro:eval expression
— Function: macwork:eval expression

> `macro:eval` returns the value of expression in the current top level environment. expression can contain macro definitions. Side effects of expression will affect the top level environment.

— Procedure: macro:load filename
— Procedure: macwork:load filename

> filename should be a string. If filename names an existing file, the `macro:load` procedure reads Scheme source code expressions and definitions from the file and evaluates them sequentially. These source code expressions and definitions may contain macro definitions. The `macro:load` procedure does not affect the values returned by `current-input-port` and `current-output-port`.

References:

The Revised^4 Report on the Algorithmic Language Scheme Clinger and Rees [editors]. To appear in LISP Pointers. Also available as a technical report from the University of Oregon, MIT AI Lab, and Cornell.

Macros That Work. Clinger and Rees. POPL '91.

The supported syntax differs from the R4RS in that vectors are allowed as patterns and as templates and are not allowed as pattern or template data.

         transformer spec  ==>  (syntax-rules literals rules)

         rules  ==>  ()
                  |  (rule . rules)

         rule  ==>  (pattern template)

         pattern  ==>  pattern_var      ; a symbol not in literals
                    |  symbol           ; a symbol in literals
                    |  ()
                    |  (pattern . pattern)
                    |  (ellipsis_pattern)
                    |  #(pattern*)                     ; extends R4RS
                    |  #(pattern* ellipsis_pattern)    ; extends R4RS
                    |  pattern_datum

         template  ==>  pattern_var
                     |  symbol
                     |  ()
                     |  (template2 . template2)
                     |  #(template*)                   ; extends R4RS
                     |  pattern_datum

         template2  ==>  template
                      |  ellipsis_template

         pattern_datum  ==>  string                    ; no vector
                          |  character
                          |  boolean
                          |  number

         ellipsis_pattern  ==> pattern ...

         ellipsis_template  ==>  template ...

         pattern_var  ==>  symbol   ; not in literals

         literals  ==>  ()
                     |  (symbol . literals)

#### 3.4.1 Definitions

Scope of an ellipsis
  Within a pattern or template, the scope of an ellipsis (`...`) is the pattern or template that appears to its left.
Rank of a pattern variable
  The rank of a pattern variable is the number of ellipses within whose scope it appears in the pattern.
Rank of a subtemplate
  The rank of a subtemplate is the number of ellipses within whose scope it appears in the template.
Template rank of an occurrence of a pattern variable
  The template rank of an occurrence of a pattern variable within a template is the rank of that occurrence, viewed as a subtemplate.
Variables bound by a pattern
  The variables bound by a pattern are the pattern variables that appear within it.
Referenced variables of a subtemplate
  The referenced variables of a subtemplate are the pattern variables that appear within it.
Variables opened by an ellipsis template
  The variables opened by an ellipsis template are the referenced pattern variables whose rank is greater than the rank of the ellipsis template.

#### 3.4.2 Restrictions

No pattern variable appears more than once within a pattern.

For every occurrence of a pattern variable within a template, the template rank of the occurrence must be greater than or equal to the pattern variable's rank.

Every ellipsis template must open at least one variable.

For every ellipsis template, the variables opened by an ellipsis template must all be bound to sequences of the same length.

The compiled form of a rule is

         rule  ==>  (pattern template inserted)

         pattern  ==>  pattern_var
                    |  symbol
                    |  ()
                    |  (pattern . pattern)
                    |  ellipsis_pattern
                    |  #(pattern)
                    |  pattern_datum

         template  ==>  pattern_var
                     |  symbol
                     |  ()
                     |  (template2 . template2)
                     |  #(pattern)
                     |  pattern_datum

         template2  ==>  template
                      |  ellipsis_template

         pattern_datum  ==>  string
                          |  character
                          |  boolean
                          |  number

         pattern_var  ==>  #(V symbol rank)

         ellipsis_pattern  ==>  #(E pattern pattern_vars)

         ellipsis_template  ==>  #(E template pattern_vars)

         inserted  ==>  ()
                     |  (symbol . inserted)

         pattern_vars  ==>  ()
                         |  (pattern_var . pattern_vars)

         rank  ==>  exact non-negative integer

where V and E are unforgeable values.

The pattern variables associated with an ellipsis pattern are the variables bound by the pattern, and the pattern variables associated with an ellipsis template are the variables opened by the ellipsis template.

If the template contains a big chunk that contains no pattern variables or inserted identifiers, then the big chunk will be copied unnecessarily. That shouldn't matter very often.

Next: Syntax-Case Macros, Previous: Macros That Work, Up: Scheme Syntax Extension Packages

### 3.5 Syntactic Closures

`(require 'syntactic-closures)`

— Function: macro:expand expression
— Function: synclo:expand expression

> Returns scheme code with the macros and derived expression types of expression expanded to primitive expression types.

— Function: macro:eval expression
— Function: synclo:eval expression

> `macro:eval` returns the value of expression in the current top level environment. expression can contain macro definitions. Side effects of expression will affect the top level environment.

— Procedure: macro:load filename
— Procedure: synclo:load filename

> filename should be a string. If filename names an existing file, the `macro:load` procedure reads Scheme source code expressions and definitions from the file and evaluates them sequentially. These source code expressions and definitions may contain macro definitions. The `macro:load` procedure does not affect the values returned by `current-input-port` and `current-output-port`.

#### 3.5.1 Syntactic Closure Macro Facility

A Syntactic Closures Macro Facility
by Chris Hanson
9 November 1991

This document describes syntactic closures, a low-level macro facility for the Scheme programming language. The facility is an alternative to the low-level macro facility described in the Revised^4 Report on Scheme. This document is an addendum to that report.

The syntactic closures facility extends the BNF rule for transformer spec to allow a new keyword that introduces a low-level macro transformer:

         transformer spec := (transformer expression)

Additionally, the following procedures are added:

         make-syntactic-closure
         capture-syntactic-environment
         identifier?
         identifier=?

The description of the facility is divided into three parts. The first part defines basic terminology. The second part describes how macro transformers are defined. The third part describes the use of identifiers, which extend the syntactic closure mechanism to be compatible with `syntax-rules`.

##### 3.5.1.1 Terminology

This section defines the concepts and data types used by the syntactic closures facility.

- Forms are the syntactic entities out of which programs are recursively constructed. A form is any expression, any definition, any syntactic keyword, or any syntactic closure. The variable name that appears in a `set!` special form is also a form. Examples of forms:

                17
                #t
                car
                (+ x 4)
                (lambda (x) x)
                (define pi 3.14159)
                if
                define

- An alias is an alternate name for a given symbol. It can appear anywhere in a form that the symbol could be used, and when quoted it is replaced by the symbol; however, it does not satisfy the predicate `symbol?`. Macro transformers rarely distinguish symbols from aliases, referring to both as identifiers.
- A syntactic environment maps identifiers to their meanings. More precisely, it determines whether an identifier is a syntactic keyword or a variable. If it is a keyword, the meaning is an interpretation for the form in which that keyword appears. If it is a variable, the meaning identifies which binding of that variable is referenced. In short, syntactic environments contain all of the contextual information necessary for interpreting the meaning of a particular form.
- A syntactic closure consists of a form, a syntactic environment, and a list of identifiers. All identifiers in the form take their meaning from the syntactic environment, except those in the given list. The identifiers in the list are to have their meanings determined later. A syntactic closure may be used in any context in which its form could have been used. Since a syntactic closure is also a form, it may not be used in contexts where a form would be illegal. For example, a form may not appear as a clause in the cond special form. A syntactic closure appearing in a quoted structure is replaced by its form.

##### 3.5.1.2 Transformer Definition

This section describes the `transformer` special form and the procedures `make-syntactic-closure` and `capture-syntactic-environment`.

— Syntax: transformer expression

> Syntax: It is an error if this syntax occurs except as a transformer spec.

> Semantics: The expression is evaluated in the standard transformer environment to yield a macro transformer as described below. This macro transformer is bound to a macro keyword by the special form in which the `transformer` expression appears (for example, `let-syntax`).

> A macro transformer is a procedure that takes two arguments, a form and a syntactic environment, and returns a new form. The first argument, the input form, is the form in which the macro keyword occurred. The second argument, the usage environment, is the syntactic environment in which the input form occurred. The result of the transformer, the output form, is automatically closed in the transformer environment, which is the syntactic environment in which the `transformer` expression occurred.

> For example, here is a definition of a push macro using `syntax-rules`:

>               (define-syntax  push
>                 (syntax-rules ()
>                   ((push item list)
>                    (set! list (cons item list)))))

> Here is an equivalent definition using `transformer`:

>               (define-syntax push
>                 (transformer
>                  (lambda (exp env)
>                    (let ((item
>                           (make-syntactic-closure env '() (cadr exp)))
>                          (list
>                           (make-syntactic-closure env '() (caddr exp))))
>                      `(set! ,list (cons ,item ,list))))))

> In this example, the identifiers `set!` and `cons` are closed in the transformer environment, and thus will not be affected by the meanings of those identifiers in the usage environment `env`.

> Some macros may be non-hygienic by design. For example, the following defines a loop macro that implicitly binds `exit` to an escape procedure. The binding of `exit` is intended to capture free references to `exit` in the body of the loop, so `exit` must be left free when the body is closed:

>               (define-syntax loop
>                 (transformer
>                  (lambda (exp env)
>                    (let ((body (cdr exp)))
>                      `(call-with-current-continuation
>                        (lambda (exit)
>                          (let f ()
>                            ,@(map (lambda  (exp)
>                                      (make-syntactic-closure env '(exit)
>                                                              exp))
>                                    body)
>                            (f))))))))

> To assign meanings to the identifiers in a form, use `make-syntactic-closure` to close the form in a syntactic environment.

— Function: make-syntactic-closure environment free-names form

> environment must be a syntactic environment, free-names must be a list of identifiers, and form must be a form. `make-syntactic-closure` constructs and returns a syntactic closure of form in environment, which can be used anywhere that form could have been used. All the identifiers used in form, except those explicitly excepted by free-names, obtain their meanings from environment.

> Here is an example where free-names is something other than the empty list. It is instructive to compare the use of free-names in this example with its use in the `loop` example above: the examples are similar except for the source of the identifier being left free.

>               (define-syntax let1
>                 (transformer
>                  (lambda (exp env)
>                    (let ((id (cadr exp))
>                          (init (caddr exp))
>                          (exp (cadddr exp)))
>                      `((lambda (,id)
>                          ,(make-syntactic-closure env (list id) exp))
>                        ,(make-syntactic-closure env '() init))))))

> `let1` is a simplified version of `let` that only binds a single identifier, and whose body consists of a single expression. When the body expression is syntactically closed in its original syntactic environment, the identifier that is to be bound by `let1` must be left free, so that it can be properly captured by the `lambda` in the output form.

> To obtain a syntactic environment other than the usage environment, use `capture-syntactic-environment`.

— Function: capture-syntactic-environment procedure

> `capture-syntactic-environment` returns a form that will, when transformed, call procedure on the current syntactic environment. procedure should compute and return a new form to be transformed, in that same syntactic environment, in place of the form.

> An example will make this clear. Suppose we wanted to define a simple `loop-until` keyword equivalent to

>               (define-syntax loop-until
>                 (syntax-rules ()
>                   ((loop-until id init test return step)
>                    (letrec ((loop
>                              (lambda (id)
>                                (if test return (loop step)))))
>                      (loop init)))))

> The following attempt at defining `loop-until` has a subtle bug:

>               (define-syntax loop-until
>                 (transformer
>                  (lambda (exp env)
>                    (let ((id (cadr exp))
>                          (init (caddr exp))
>                          (test (cadddr exp))
>                          (return (cadddr (cdr exp)))
>                          (step (cadddr (cddr exp)))
>                          (close
>                           (lambda (exp free)
>                             (make-syntactic-closure env free exp))))
>                      `(letrec ((loop
>                                 (lambda (,id)
>                                   (if ,(close test (list id))
>                                       ,(close return (list id))
>                                       (loop ,(close step (list id)))))))
>                         (loop ,(close init '())))))))

> This definition appears to take all of the proper precautions to prevent unintended captures. It carefully closes the subexpressions in their original syntactic environment and it leaves the `id` identifier free in the `test`, `return`, and `step` expressions, so that it will be captured by the binding introduced by the `lambda` expression. Unfortunately it uses the identifiers `if` and `loop` within that `lambda` expression, so if the user of `loop-until` just happens to use, say, `if` for the identifier, it will be inadvertently captured.

> The syntactic environment that `if` and `loop` want to be exposed to is the one just outside the `lambda` expression: before the user's identifier is added to the syntactic environment, but after the identifier loop has been added. `capture-syntactic-environment` captures exactly that environment as follows:

>               (define-syntax loop-until
>                 (transformer
>                  (lambda (exp env)
>                    (let ((id (cadr exp))
>                          (init (caddr exp))
>                          (test (cadddr exp))
>                          (return (cadddr (cdr exp)))
>                          (step (cadddr (cddr exp)))
>                          (close
>                           (lambda (exp free)
>                             (make-syntactic-closure env free exp))))
>                      `(letrec ((loop
>                                 ,(capture-syntactic-environment
>                                   (lambda (env)
>                                     `(lambda (,id)
>                                        (,(make-syntactic-closure env '() `if)
>                                         ,(close test (list id))
>                                         ,(close return (list id))
>                                         (,(make-syntactic-closure env '()
>                                                                   `loop)
>                                          ,(close step (list id)))))))))
>                         (loop ,(close init '())))))))

> In this case, having captured the desired syntactic environment, it is convenient to construct syntactic closures of the identifiers `if` and the `loop` and use them in the body of the `lambda`.

> A common use of `capture-syntactic-environment` is to get the transformer environment of a macro transformer:

>               (transformer
>                (lambda (exp env)
>                  (capture-syntactic-environment
>                   (lambda (transformer-env)
>                     ...))))

##### 3.5.1.3 Identifiers

This section describes the procedures that create and manipulate identifiers. Previous syntactic closure proposals did not have an identifier data type – they just used symbols. The identifier data type extends the syntactic closures facility to be compatible with the high-level `syntax-rules` facility.

As discussed earlier, an identifier is either a symbol or an alias. An alias is implemented as a syntactic closure whose form is an identifier:

         (make-syntactic-closure env '() 'a)
            => an alias

Aliases are implemented as syntactic closures because they behave just like syntactic closures most of the time. The difference is that an alias may be bound to a new value (for example by `lambda` or `let-syntax`); other syntactic closures may not be used this way. If an alias is bound, then within the scope of that binding it is looked up in the syntactic environment just like any other identifier.

Aliases are used in the implementation of the high-level facility `syntax-rules`. A macro transformer created by `syntax-rules` uses a template to generate its output form, substituting subforms of the input form into the template. In a syntactic closures implementation, all of the symbols in the template are replaced by aliases closed in the transformer environment, while the output form itself is closed in the usage environment. This guarantees that the macro transformation is hygienic, without requiring the transformer to know the syntactic roles of the substituted input subforms.

— Function: identifier? object

> Returns `#t` if object is an identifier, otherwise returns `#f`. Examples:

>               (identifier? 'a)
>                  => #t
>               (identifier? (make-syntactic-closure env '() 'a))
>                  => #t
>               (identifier? "a")
>                  => #f
>               (identifier? #\a)
>                  => #f
>               (identifier? 97)
>                  => #f
>               (identifier? #f)
>                  => #f
>               (identifier? '(a))
>                  => #f
>               (identifier? '#(a))
>                  => #f

> The predicate `eq?` is used to determine if two identifers are “the same”. Thus `eq?` can be used to compare identifiers exactly as it would be used to compare symbols. Often, though, it is useful to know whether two identifiers “mean the same thing”. For example, the `cond` macro uses the symbol `else` to identify the final clause in the conditional. A macro transformer for `cond` cannot just look for the symbol `else`, because the `cond` form might be the output of another macro transformer that replaced the symbol `else` with an alias. Instead the transformer must look for an identifier that “means the same thing” in the usage environment as the symbol `else` means in the transformer environment.

— Function: identifier=? environment1 identifier1 environment2 identifier2

> environment1 and environment2 must be syntactic environments, and identifier1 and identifier2 must be identifiers. `identifier=?` returns `#t` if the meaning of identifier1 in environment1 is the same as that of identifier2 in environment2, otherwise it returns `#f`. Examples:

>               (let-syntax
>                   ((foo
>                     (transformer
>                      (lambda (form env)
>                        (capture-syntactic-environment
>                         (lambda (transformer-env)
>                           (identifier=? transformer-env 'x env 'x)))))))
>                 (list (foo)
>                       (let ((x 3))
>                         (foo))))
>                  => (#t #f)

>               (let-syntax ((bar foo))
>                 (let-syntax
>                     ((foo
>                       (transformer
>                        (lambda (form env)
>                          (capture-syntactic-environment
>                           (lambda (transformer-env)
>                             (identifier=? transformer-env 'foo
>                                           env (cadr form))))))))
>                   (list (foo foo)
>                         (foobar))))
>                  => (#f #t)

##### 3.5.1.4 Acknowledgements

The syntactic closures facility was invented by Alan Bawden and Jonathan Rees. The use of aliases to implement `syntax-rules` was invented by Alan Bawden (who prefers to call them synthetic names). Much of this proposal is derived from an earlier proposal by Alan Bawden.

Next: Define-Structure, Previous: Syntactic Closures, Up: Scheme Syntax Extension Packages

### 3.6 Syntax-Case Macros

`(require 'syntax-case)`

— Function: macro:expand expression
— Function: syncase:expand expression

> Returns scheme code with the macros and derived expression types of expression expanded to primitive expression types.

— Function: macro:eval expression
— Function: syncase:eval expression

> `macro:eval` returns the value of expression in the current top level environment. expression can contain macro definitions. Side effects of expression will affect the top level environment.

— Procedure: macro:load filename
— Procedure: syncase:load filename

> filename should be a string. If filename names an existing file, the `macro:load` procedure reads Scheme source code expressions and definitions from the file and evaluates them sequentially. These source code expressions and definitions may contain macro definitions. The `macro:load` procedure does not affect the values returned by `current-input-port` and `current-output-port`.

This is version 2.1 of `syntax-case`, the low-level macro facility proposed and implemented by Robert Hieb and R. Kent Dybvig.

This version is further adapted by Harald Hanche-Olsen <hanche @ imf.unit.no> to make it compatible with, and easily usable with, SLIB. Mainly, these adaptations consisted of:

- Removing white space from `expand.pp` to save space in the distribution. This file is not meant for human readers anyway...
- Removed a couple of Chez scheme dependencies.
- Renamed global variables used to minimize the possibility of name conflicts.
- Adding an SLIB-specific initialization file.
- Removing a couple extra files, most notably the documentation (but see below).

If you wish, you can see exactly what changes were done by reading the shell script in the file `syncase.sh`.

The two PostScript files were omitted in order to not burden the SLIB distribution with them. If you do intend to use `syntax-case`, however, you should get these files and print them out on a PostScript printer. They are available with the original `syntax-case` distribution by anonymous FTP in `cs.indiana.edu:/pub/scheme/syntax-case`.

In order to use syntax-case from an interactive top level, execute:

         (require 'syntax-case)
         (require 'repl)
         (repl:top-level macro:eval)

See the section Repl (see Repl) for more information.

To check operation of syntax-case get `cs.indiana.edu:/pub/scheme/syntax-case`, and type

         (require 'syntax-case)
         (syncase:sanity-check)

Beware that `syntax-case` takes a long time to load – about 20s on a SPARCstation SLC (with SCM) and about 90s on a Macintosh SE/30 (with Gambit).

#### 3.6.1 Notes

All R4RS syntactic forms are defined, including `delay`. Along with `delay` are simple definitions for `make-promise` (into which `delay` expressions expand) and `force`.

`syntax-rules` and `with-syntax` (described in TR356) are defined.

`syntax-case` is actually defined as a macro that expands into calls to the procedure `syntax-dispatch` and the core form `syntax-lambda`; do not redefine these names.

Several other top-level bindings not documented in TR356 are created:

- the “hooks” in `hooks.ss`
- the `build-` procedures in `output.ss`
- `expand-syntax` (the expander)

The syntax of define has been extended to allow `(define` id`)`, which assigns id to some unspecified value.

We have attempted to maintain R4RS compatibility where possible. The incompatibilities should be confined to `hooks.ss`. Please let us know if there is some incompatibility that is not flagged as such.

Send bug reports, comments, suggestions, and questions to Kent Dybvig (dyb @ iuvax.cs.indiana.edu).

Next: Define-Record-Type, Previous: Syntax-Case Macros, Up: Scheme Syntax Extension Packages

### 3.7 Define-Structure

`(require 'structure)`

Included with the `syntax-case` files was `structure.scm` which defines a macro `define-structure`. Here is its documentation from Gambit 4.0:

— special form: define-structure name field...

> Record data types similar to Pascal records and C `struct` types can be defined using the `define-structure` special form. The identifier name specifies the name of the new data type. The structure name is followed by k identifiers naming each field of the record. The `define-structure` expands into a set of definitions of the following procedures:

> - ``make-`name' – A k argument procedure which constructs a new record from the value of its k fields.
> - `name`?`' – A procedure which tests if its single argument is of the given record type.
> - `name`-`field' – For each field, a procedure taking as its single argument a value of the given record type and returning the content of the corresponding field of the record.
> - `name`-`field`-set!`' – For each field, a two argument procedure taking as its first argument a value of the given record type. The second argument gets assigned to the corresponding field of the record and the void object is returned.

> Gambit record data types have a printed representation that includes the name of the type and the name and value of each field.

> For example:

>               > (define-structure point x y color)
>               > (define p (make-point 3 5 'red))
>               > p
>               #<point #3 x: 3 y: 5 color: red>
>               > (point-x p)
>               3
>               > (point-color p)
>               red
>               > (point-color-set! p 'black)
>               > p
>               #<point #3 x: 3 y: 5 color: black>

Next: Fluid-Let, Previous: Define-Structure, Up: Scheme Syntax Extension Packages

### 3.8 Define-Record-Type

`(require 'define-record-type)` or `(require 'srfi-9)` http://srfi.schemers.org/srfi-9/srfi-9.html

— Special Form: define-record-type <type-name> (<constructor-name> <field-tag> ...) <predicate-name> <field-spec> ...

> Where

>               <field-spec> == (<field-tag> <accessor-name>)
>                            == (<field-tag> <accessor-name> <modifier-name>)

> `define-record-type` is a syntax wrapper for the SLIB `record` module.

Next: Binding to multiple values, Previous: Define-Record-Type, Up: Scheme Syntax Extension Packages

### 3.9 Fluid-Let

`(require 'fluid-let)`

— Syntax: fluid-let `(`bindings`...)` forms...

         (fluid-let ((variable init) ...)
            expression expression ...)

The inits are evaluated in the current environment (in some unspecified order), the current values of the variables are saved, the results are assigned to the variables, the expressions are evaluated sequentially in the current environment, the variables are restored to their original values, and the value of the last expression is returned.

The syntax of this special form is similar to that of `let`, but `fluid-let` temporarily rebinds existing variables. Unlike `let`, `fluid-let` creates no new bindings; instead it assigns the values of each init to the binding (determined by the rules of lexical scoping) of its corresponding variable.

Next: Guarded LET* special form, Previous: Fluid-Let, Up: Scheme Syntax Extension Packages

### 3.10 Binding to multiple values

`(require 'receive)` or `(require 'srfi-8)`

— Special Form: receive formals expression body ...

> http://srfi.schemers.org/srfi-8/srfi-8.html

`(require 'let-values)` or `(require 'srfi-11)`

— Special Form: let-values ((formals expression) ...) body ...
— Special Form: let-values* ((formals expression) ...) body ...

> http://srfi.schemers.org/srfi-11/srfi-11.html

Next: Guarded COND Clause, Previous: Binding to multiple values, Up: Scheme Syntax Extension Packages

### 3.11 Guarded LET* special form

`(require 'and-let*)` or `(require 'srfi-2)`

— Macro: and-let* claws body ...

> http://srfi.schemers.org/srfi-2/srfi-2.html

Next: Yasos, Previous: Guarded LET* special form, Up: Scheme Syntax Extension Packages

### 3.12 Guarded COND Clause

`(require 'guarded-cond-clause)` or `(require 'srfi-61)` http://srfi.schemers.org/srfi-61/srfi-61.html

— library syntax: cond <clause1> <clause2> ...

> Syntax: Each <clause> should be of the form

>     (<test> <expression1> ...)

> where <test> is any expression. Alternatively, a <clause> may be of the form

>     (<test> => <expression>)

> The <clause> production in the formal syntax of Scheme as written by R5RS in section 7.1.3 is extended with a new option:

>     <clause> => (<generator> <guard> => <receiver>)

> where <generator>, <guard>, & <receiver> are all <expression>s.

> > Clauses of this form have the following semantics: <generator> is evaluated. It may return arbitrarily many values. <Guard> is applied to an argument list containing the values in order that <generator> returned. If <guard> returns a true value for that argument list, <receiver> is applied with an equivalent argument list. If <guard> returns a false value, however, the clause is abandoned and the next one is tried.

> The last <clause> may be an “else clause,” which has the form

>     (else <expression1> <expression2> ...).

This `port->char-list` procedure accepts an input port and returns a list of all the characters it produces until the end.

         (define (port->char-list port)
           (cond ((read-char port) char?
                  => (lambda (c) (cons c (port->char-list port))))
                 (else '())))

         (call-with-input-string "foo" port->char-list)  ==>  (#\f #\o #\o)

Previous: Guarded COND Clause, Up: Scheme Syntax Extension Packages

### 3.13 Yasos

`(require 'oop)` or `(require 'yasos)` `Yet Another Scheme Object System' is a simple object system for Scheme based on the paper by Norman Adams and Jonathan Rees: Object Oriented Programming in Scheme, Proceedings of the 1988 ACM Conference on LISP and Functional Programming, July 1988 [ACM #552880].

Another reference is:

Ken Dickey. Scheming with Objects AI Expert Volume 7, Number 10 (October 1992), pp. 24-33.

Next: Yasos interface, Previous: Yasos, Up: Yasos

#### 3.13.1 Terms

Object
  Any Scheme data object.
Instance
  An instance of the OO system; an object.
Operation
  A method.

Notes:
  The object system supports multiple inheritance. An instance can inherit from 0 or more ancestors. In the case of multiple inherited operations with the same identity, the operation used is that from the first ancestor which contains it (in the ancestor `let`). An operation may be applied to any Scheme data object—not just instances. As code which creates instances is just code, there are no classes and no meta-anything. Method dispatch is by a procedure call a la CLOS rather than by `send` syntax a la Smalltalk.
Disclaimer:
  There are a number of optimizations which can be made. This implementation is expository (although performance should be quite reasonable). See the L&FP paper for some suggestions.

Next: Setters, Previous: Yasos terms, Up: Yasos

#### 3.13.2 Interface

— Syntax: define-operation `(`opname self arg ...`)` default-body

> Defines a default behavior for data objects which don't handle the operation opname. The default behavior (for an empty default-body) is to generate an error.

— Syntax: define-predicate opname?

> Defines a predicate opname?, usually used for determining the type of an object, such that `(`opname? object`)` returns `#t` if object has an operation opname? and `#f` otherwise.

— Syntax: object `((`name self arg`...)` body`)` ...

> Returns an object (an instance of the object system) with operations. Invoking `(`name object arg`...` executes the body of the object with self bound to object and with argument(s) arg....

— Syntax: object-with-ancestors `((`ancestor1 init1`)` ...`)` operation ...

> A `let`-like form of `object` for multiple inheritance. It returns an object inheriting the behaviour of ancestor1 etc. An operation will be invoked in an ancestor if the object itself does not provide such a method. In the case of multiple inherited operations with the same identity, the operation used is the one found in the first ancestor in the ancestor list.

— Syntax: operate-as component operation self arg ...

> Used in an operation definition (of self) to invoke the operation in an ancestor component but maintain the object's identity. Also known as “send-to-super”.

— Procedure: print obj port

> A default `print` operation is provided which is just `(format` port obj`)` (see Format) for non-instances and prints obj preceded by ``#<INSTANCE>`' for instances.

— Function: size obj

> The default method returns the number of elements in obj if it is a vector, string or list, `2` for a pair, `1` for a character and by default id an error otherwise. Objects such as collections (see Collections) may override the default in an obvious way.

Next: Yasos examples, Previous: Yasos interface, Up: Yasos

#### 3.13.3 Setters

Setters implement generalized locations for objects associated with some sort of mutable state. A getter operation retrieves a value from a generalized location and the corresponding setter operation stores a value into the location. Only the getter is named – the setter is specified by a procedure call as below. (Dylan uses special syntax.) Typically, but not necessarily, getters are access operations to extract values from Yasos objects (see Yasos). Several setters are predefined, corresponding to getters `car`, `cdr`, `string-ref` and `vector-ref` e.g., `(setter car)` is equivalent to `set-car!`.

This implementation of setters is similar to that in Dylan(TM) (Dylan: An object-oriented dynamic language, Apple Computer Eastern Research and Technology). Common LISP provides similar facilities through `setf`.

— Function: setter getter

> Returns the setter for the procedure getter. E.g., since `string-ref` is the getter corresponding to a setter which is actually `string-set!`:

>               (define foo "foo")
>               ((setter string-ref) foo 0 #\F) ; set element 0 of foo
>               foo => "Foo"

— Syntax: set place new-value

> If place is a variable name, `set` is equivalent to `set!`. Otherwise, place must have the form of a procedure call, where the procedure name refers to a getter and the call indicates an accessible generalized location, i.e., the call would return a value. The return value of `set` is usually unspecified unless used with a setter whose definition guarantees to return a useful value.

>               (set (string-ref foo 2) #\O)  ; generalized location with getter
>               foo => "FoO"
>               (set foo "foo")               ; like set!
>               foo => "foo"

— Procedure: add-setter getter setter

> Add procedures getter and setter to the (inaccessible) list of valid setter/getter pairs. setter implements the store operation corresponding to the getter access operation for the relevant state. The return value is unspecified.

— Procedure: remove-setter-for getter

> Removes the setter corresponding to the specified getter from the list of valid setters. The return value is unspecified.

— Syntax: define-access-operation getter-name

> Shorthand for a Yasos `define-operation` defining an operation getter-name that objects may support to return the value of some mutable state. The default operation is to signal an error. The return value is unspecified.

Previous: Setters, Up: Yasos

#### 3.13.4 Examples

         ;;; These definitions for PRINT and SIZE are
         ;;; already supplied by
         (require 'yasos)

         (define-operation (print obj port)
           (format port
                   (if (instance? obj) "#<instance>" "~s")
                   obj))

         (define-operation (size obj)
           (cond
            ((vector? obj) (vector-length obj))
            ((list?   obj) (length obj))
            ((pair?   obj) 2)
            ((string? obj) (string-length obj))
            ((char?   obj) 1)
            (else
             (slib:error "Operation not supported: size" obj))))

         (define-predicate cell?)
         (define-operation (fetch obj))
         (define-operation (store! obj newValue))

         (define (make-cell value)
           (object
            ((cell? self) #t)
            ((fetch self) value)
            ((store! self newValue)
             (set! value newValue)
             newValue)
            ((size self) 1)
            ((print self port)
             (format port "#<Cell: ~s>" (fetch self)))))

         (define-operation (discard obj value)
           (format #t "Discarding ~s~%" value))

         (define (make-filtered-cell value filter)
           (object-with-ancestors
            ((cell (make-cell value)))
            ((store! self newValue)
            (if (filter newValue)
                (store! cell newValue)
                (discard self newValue)))))

         (define-predicate array?)
         (define-operation (array-ref array index))
         (define-operation (array-set! array index value))

         (define (make-array num-slots)
           (let ((anArray (make-vector num-slots)))
             (object
              ((array? self) #t)
              ((size self) num-slots)
              ((array-ref self index)
               (vector-ref  anArray index))
              ((array-set! self index newValue)
               (vector-set! anArray index newValue))
              ((print self port)
               (format port "#<Array ~s>" (size self))))))

         (define-operation (position obj))
         (define-operation (discarded-value obj))

         (define (make-cell-with-history value filter size)
           (let ((pos 0) (most-recent-discard #f))
             (object-with-ancestors
              ((cell (make-filtered-call value filter))
               (sequence (make-array size)))
              ((array? self) #f)
              ((position self) pos)
              ((store! self newValue)
               (operate-as cell store! self newValue)
               (array-set! self pos newValue)
               (set! pos (+ pos 1)))
              ((discard self value)
               (set! most-recent-discard value))
              ((discarded-value self) most-recent-discard)
              ((print self port)
               (format port "#<Cell-with-history ~s>"
                       (fetch self))))))

         (define-access-operation fetch)
         (add-setter fetch store!)
         (define foo (make-cell 1))
         (print foo #f)
         => "#<Cell: 1>"
         (set (fetch foo) 2)
         =>
         (print foo #f)
         => "#<Cell: 2>"
         (fetch foo)
         => 2

Next: Mathematical Packages, Previous: Scheme Syntax Extension Packages, Up: Top

## 4 Textual Conversion Packages

Next: Format, Previous: Textual Conversion Packages, Up: Textual Conversion Packages

### 4.1 Precedence Parsing

`(require 'precedence-parse)` or `(require 'parse)` This package implements:

- a Pratt style precedence parser;
- a tokenizer which congeals tokens according to assigned classes of constituent characters;
- procedures giving direct control of parser rulesets;
- procedures for higher level specification of rulesets.

Next: Rule Types, Previous: Precedence Parsing, Up: Precedence Parsing

#### 4.1.1 Precedence Parsing Overview

This package offers improvements over previous parsers.

- Common computer language constructs are concisely specified.
- Grammars can be changed dynamically. Operators can be assigned different meanings within a lexical context.
- Rulesets don't need compilation. Grammars can be changed incrementally.
- Operator precedence is specified by integers.
- All possibilities of bad input are handled 4 and return as much structure as was parsed when the error occured; The symbol `?` is substituted for missing input.

The notion of binding power may be unfamiliar to those accustomed to BNF grammars.

When two consecutive objects are parsed, the first might be the prefix to the second, or the second might be a suffix of the first. Comparing the left and right binding powers of the two objects decides which way to interpret them.

Objects at each level of syntactic grouping have binding powers.

A syntax tree is not built unless the rules explicitly do so. The call graph of grammar rules effectively instantiate the sytnax tree.

The JACAL symbolic math system (http://swiss.csail.mit.edu/~jaffer/JACAL) uses `precedence-parse`. Its grammar definitions in the file `jacal/English.scm` can serve as examples of use.

Next: Ruleset Definition and Use, Previous: Precedence Parsing Overview, Up: Precedence Parsing

#### 4.1.2 Rule Types

Here are the higher-level syntax types and an example of each. Precedence considerations are omitted for clarity. See Grammar Rule Definition for full details.

— Grammar: nofix bye exit

>               bye

> calls the function `exit` with no arguments.

— Grammar: prefix - negate

>               - 42

> Calls the function `negate` with the argument `42`.

— Grammar: infix - difference

>               x - y

> Calls the function `difference` with arguments `x` and `y`.

— Grammar: nary + sum

>               x + y + z

> Calls the function `sum` with arguments `x`, `y`, and `y`.

— Grammar: postfix ! factorial

>               5 !

> Calls the function `factorial` with the argument `5`.

— Grammar: prestfix set set!

>               set foo bar

> Calls the function `set!` with the arguments `foo` and `bar`.

— Grammar: commentfix /* */

>               /* almost any text here */

> Ignores the comment delimited by `/*` and `*/`.

— Grammar: matchfix { list }

>               {0, 1, 2}

> Calls the function `list` with the arguments `0`, `1`, and `2`.

— Grammar: inmatchfix ( funcall )

>               f(x, y)

> Calls the function `funcall` with the arguments `f`, `x`, and `y`.

— Grammar: delim ;

>               set foo bar;

> delimits the extent of the restfix operator `set`.

Next: Token definition, Previous: Rule Types, Up: Precedence Parsing

#### 4.1.3 Ruleset Definition and Use

— Variable: *syn-defs*

> A grammar is built by one or more calls to `prec:define-grammar`. The rules are appended to *syn-defs*. The value of *syn-defs* is the grammar suitable for passing as an argument to `prec:parse`.

— Constant: *syn-ignore-whitespace*

> Is a nearly empty grammar with whitespace characters set to group 0, which means they will not be made into tokens. Most rulesets will want to start with `*syn-ignore-whitespace*`

In order to start defining a grammar, either

         (set! *syn-defs* '())

or

         (set! *syn-defs* *syn-ignore-whitespace*)

— Function: prec:define-grammar rule1 ...

> Appends rule1 ... to *syn-defs*. `prec:define-grammar` is used to define both the character classes and rules for tokens.

Once your grammar is defined, save the value of `*syn-defs*` in a variable (for use when calling `prec:parse`).

         (define my-ruleset *syn-defs*)

— Function: prec:parse ruleset delim
— Function: prec:parse ruleset delim port

> The ruleset argument must be a list of rules as constructed by `prec:define-grammar` and extracted from *syn-defs*.

> The token delim may be a character, symbol, or string. A character delim argument will match only a character token; i.e. a character for which no token-group is assigned. A symbol or string will match only a token string; i.e. a token resulting from a token group.

> `prec:parse` reads a ruleset grammar expression delimited by delim from the given input port. `prec:parse` returns the next object parsable from the given input port, updating port to point to the first character past the end of the external representation of the object.

> If an end of file is encountered in the input before any characters are found that can begin an object, then an end of file object is returned. If a delimiter (such as delim) is found before any characters are found that can begin an object, then `#f` is returned.

> The port argument may be omitted, in which case it defaults to the value returned by `current-input-port`. It is an error to parse from a closed port.

Next: Nud and Led Definition, Previous: Ruleset Definition and Use, Up: Precedence Parsing

#### 4.1.4 Token definition

— Function: tok:char-group group chars chars-proc

> The argument chars may be a single character, a list of characters, or a string. Each character in chars is treated as though `tok:char-group` was called with that character alone.

> The argument chars-proc must be a procedure of one argument, a list of characters. After `tokenize` has finished accumulating the characters for a token, it calls chars-proc with the list of characters. The value returned is the token which `tokenize` returns.

> The argument group may be an exact integer or a procedure of one character argument. The following discussion concerns the treatment which the tokenizing routine, `tokenize`, will accord to characters on the basis of their groups.

> When group is a non-zero integer, characters whose group number is equal to or exactly one less than group will continue to accumulate. Any other character causes the accumulation to stop (until a new token is to be read).

> The group of zero is special. These characters are ignored when parsed pending a token, and stop the accumulation of token characters when the accumulation has already begun. Whitespace characters are usually put in group 0.

> If group is a procedure, then, when triggerd by the occurence of an initial (no accumulation) chars character, this procedure will be repeatedly called with each successive character from the input stream until the group procedure returns a non-false value.

The following convenient constants are provided for use with `tok:char-group`.

— Constant: tok:decimal-digits

> Is the string `"0123456789"`.

— Constant: tok:upper-case

> Is the string consisting of all upper-case letters ("ABCDEFGHIJKLMNOPQRSTUVWXYZ").

— Constant: tok:lower-case

> Is the string consisting of all lower-case letters ("abcdefghijklmnopqrstuvwxyz").

— Constant: tok:whitespaces

> Is the string consisting of all characters between 0 and 255 for which `char-whitespace?` returns true.

For the purpose of reporting problems in error messages, this package keeps track of the current column. When the column does not simply track input characters, `tok:bump-column` can be used to adjust the current-column.

— Function: tok:bump-column pos port

> Adds pos to the current-column for input-port port.

Next: Grammar Rule Definition, Previous: Token definition, Up: Precedence Parsing

#### 4.1.5 Nud and Led Definition

This section describes advanced features. You can skip this section on first reading.

The Null Denotation (or nud) of a token is the procedure and arguments applying for that token when Left, an unclaimed parsed expression is not extant.

The Left Denotation (or led) of a token is the procedure, arguments, and lbp applying for that token when there is a Left, an unclaimed parsed expression.

In his paper,

> Pratt, V. R. Top Down Operator Precendence. SIGACT/SIGPLAN Symposium on Principles of Programming Languages, Boston, 1973, pages 41-51

the left binding power (or lbp) was an independent property of tokens. I think this was done in order to allow tokens with NUDs but not LEDs to also be used as delimiters, which was a problem for statically defined syntaxes. It turns out that dynamically binding NUDs and LEDs allows them independence.

For the rule-defining procedures that follow, the variable tk may be a character, string, or symbol, or a list composed of characters, strings, and symbols. Each element of tk is treated as though the procedure were called for each element.

Character tk arguments will match only character tokens; i.e. characters for which no token-group is assigned. Symbols and strings will both match token strings; i.e. tokens resulting from token groups.

— Function: prec:make-nud tk sop arg1 ...

> Returns a rule specifying that sop be called when tk is parsed. If sop is a procedure, it is called with tk and arg1 ... as its arguments; the resulting value is incorporated into the expression being built. Otherwise, `(list` sop arg1`...)` is incorporated.

If no NUD has been defined for a token; then if that token is a string, it is converted to a symbol and returned; if not a string, the token is returned.

— Function: prec:make-led tk sop arg1 ...

> Returns a rule specifying that sop be called when tk is parsed and left has an unclaimed parsed expression. If sop is a procedure, it is called with left, tk, and arg1 ... as its arguments; the resulting value is incorporated into the expression being built. Otherwise, left is incorporated.

If no LED has been defined for a token, and left is set, the parser issues a warning.

Previous: Nud and Led Definition, Up: Precedence Parsing

#### 4.1.6 Grammar Rule Definition

Here are procedures for defining rules for the syntax types introduced in Precedence Parsing Overview.

For the rule-defining procedures that follow, the variable tk may be a character, string, or symbol, or a list composed of characters, strings, and symbols. Each element of tk is treated as though the procedure were called for each element.

For procedures prec:delim, ..., prec:prestfix, if the sop argument is `#f`, then the token which triggered this rule is converted to a symbol and returned. A false sop argument to the procedures prec:commentfix, prec:matchfix, or prec:inmatchfix has a different meaning.

Character tk arguments will match only character tokens; i.e. characters for which no token-group is assigned. Symbols and strings will both match token strings; i.e. tokens resulting from token groups.

— Function: prec:delim tk

> Returns a rule specifying that tk should not be returned from parsing; i.e. tk's function is purely syntactic. The end-of-file is always treated as a delimiter.

— Function: prec:nofix tk sop

> Returns a rule specifying the following actions take place when tk is parsed:

> - If sop is a procedure, it is called with no arguments; the resulting value is incorporated into the expression being built. Otherwise, the list of sop is incorporated.

— Function: prec:prefix tk sop bp rule1 ...

> Returns a rule specifying the following actions take place when tk is parsed:

> - The rules rule1 ... augment and, in case of conflict, override rules currently in effect.
> - `prec:parse1` is called with binding-power bp.
> - If sop is a procedure, it is called with the expression returned from `prec:parse1`; the resulting value is incorporated into the expression being built. Otherwise, the list of sop and the expression returned from `prec:parse1` is incorporated.
> - The ruleset in effect before tk was parsed is restored; rule1 ... are forgotten.

— Function: prec:infix tk sop lbp bp rule1 ...

> Returns a rule declaring the left-binding-precedence of the token tk is lbp and specifying the following actions take place when tk is parsed:

> - The rules rule1 ... augment and, in case of conflict, override rules currently in effect.
> - One expression is parsed with binding-power lbp. If instead a delimiter is encountered, a warning is issued.
> - If sop is a procedure, it is applied to the list of left and the parsed expression; the resulting value is incorporated into the expression being built. Otherwise, the list of sop, the left expression, and the parsed expression is incorporated.
> - The ruleset in effect before tk was parsed is restored; rule1 ... are forgotten.

— Function: prec:nary tk sop bp

> Returns a rule declaring the left-binding-precedence of the token tk is bp and specifying the following actions take place when tk is parsed:

> - Expressions are parsed with binding-power bp as far as they are interleaved with the token tk.
> - If sop is a procedure, it is applied to the list of left and the parsed expressions; the resulting value is incorporated into the expression being built. Otherwise, the list of sop, the left expression, and the parsed expressions is incorporated.

— Function: prec:postfix tk sop lbp

> Returns a rule declaring the left-binding-precedence of the token tk is lbp and specifying the following actions take place when tk is parsed:

> - If sop is a procedure, it is called with the left expression; the resulting value is incorporated into the expression being built. Otherwise, the list of sop and the left expression is incorporated.

— Function: prec:prestfix tk sop bp rule1 ...

> Returns a rule specifying the following actions take place when tk is parsed:

> - The rules rule1 ... augment and, in case of conflict, override rules currently in effect.
> - Expressions are parsed with binding-power bp until a delimiter is reached.
> - If sop is a procedure, it is applied to the list of parsed expressions; the resulting value is incorporated into the expression being built. Otherwise, the list of sop and the parsed expressions is incorporated.
> - The ruleset in effect before tk was parsed is restored; rule1 ... are forgotten.

— Function: prec:commentfix tk stp match rule1 ...

> Returns rules specifying the following actions take place when tk is parsed:

> - The rules rule1 ... augment and, in case of conflict, override rules currently in effect.
> - Characters are read until and end-of-file or a sequence of characters is read which matches the string match.
> - If stp is a procedure, it is called with the string of all that was read between the tk and match (exclusive).
> - The ruleset in effect before tk was parsed is restored; rule1 ... are forgotten.

> Parsing of commentfix syntax differs from the others in several ways. It reads directly from input without tokenizing; It calls stp but does not return its value; nay any value. I added the stp argument so that comment text could be echoed.

— Function: prec:matchfix tk sop sep match rule1 ...

> Returns a rule specifying the following actions take place when tk is parsed:

> - The rules rule1 ... augment and, in case of conflict, override rules currently in effect.
> - A rule declaring the token match a delimiter takes effect.
> - Expressions are parsed with binding-power `0` until the token match is reached. If the token sep does not appear between each pair of expressions parsed, a warning is issued.
> - If sop is a procedure, it is applied to the list of parsed expressions; the resulting value is incorporated into the expression being built. Otherwise, the list of sop and the parsed expressions is incorporated.
> - The ruleset in effect before tk was parsed is restored; rule1 ... are forgotten.

— Function: prec:inmatchfix tk sop sep match lbp rule1 ...

> Returns a rule declaring the left-binding-precedence of the token tk is lbp and specifying the following actions take place when tk is parsed:

> - The rules rule1 ... augment and, in case of conflict, override rules currently in effect.
> - A rule declaring the token match a delimiter takes effect.
> - Expressions are parsed with binding-power `0` until the token match is reached. If the token sep does not appear between each pair of expressions parsed, a warning is issued.
> - If sop is a procedure, it is applied to the list of left and the parsed expressions; the resulting value is incorporated into the expression being built. Otherwise, the list of sop, the left expression, and the parsed expressions is incorporated.
> - The ruleset in effect before tk was parsed is restored; rule1 ... are forgotten.

Next: Standard Formatted I/O, Previous: Precedence Parsing, Up: Textual Conversion Packages

### 4.2 Format (version 3.1)

`(require 'format)` or `(require 'srfi-28)`

Next: Format Specification, Previous: Format, Up: Format

#### 4.2.1 Format Interface

— Function: format destination format-string . arguments

> An almost complete implementation of Common LISP format description according to the CL reference book Common LISP from Guy L. Steele, Digital Press. Backward compatible to most of the available Scheme format implementations.

> Returns `#t`, `#f` or a string; has side effect of printing according to format-string. If destination is `#t`, the output is to the current output port and `#t` is returned. If destination is `#f`, a formatted string is returned as the result of the call. NEW: If destination is a string, destination is regarded as the format string; format-string is then the first argument and the output is returned as a string. If destination is a number, the output is to the current error port if available by the implementation. Otherwise destination must be an output port and `#t` is returned.

> format-string must be a string. In case of a formatting error format returns `#f` and prints a message on the current output or error port. Characters are output as if the string were output by the `display` function with the exception of those prefixed by a tilde (~). For a detailed description of the format-string syntax please consult a Common LISP format reference manual. For a test suite to verify this format implementation load `formatst.scm`. Please send bug reports to `lutzeb@cs.tu-berlin.de`.

> Note: `format` is not reentrant, i.e. only one `format`-call may be executed at a time.

Previous: Format Interface, Up: Format

#### 4.2.2 Format Specification (Format version 3.1)

Please consult a Common LISP format reference manual for a detailed description of the format string syntax. For a demonstration of the implemented directives see `formatst.scm`.

This implementation supports directive parameters and modifiers (`:` and `@` characters). Multiple parameters must be separated by a comma (`,`). Parameters can be numerical parameters (positive or negative), character parameters (prefixed by a quote character (`'`), variable parameters (`v`), number of rest arguments parameter (`#`), empty and default parameters. Directive characters are case independent. The general form of a directive is:

directive ::= ~{directive-parameter,}[:][@]directive-character

directive-parameter ::= [ [-|+]{0-9}+ | 'character | v | # ]

##### 4.2.2.1 Implemented CL Format Control Directives

Documentation syntax: Uppercase characters represent the corresponding control directive characters. Lowercase characters represent control directive parameter descriptions.

`~A`
  Any (print as `display` does).
  `~@A`
    left pad.
  `~`mincol`,`colinc`,`minpad`,`padchar`A`
    full padding.
`~S`
  S-expression (print as `write` does).
  `~@S`
    left pad.
  `~`mincol`,`colinc`,`minpad`,`padchar`S`
    full padding.
`~D`
  Decimal.
  `~@D`
    print number sign always.
  `~:D`
    print comma separated.
  `~`mincol`,`padchar`,`commachar`D`
    padding.
`~X`
  Hexadecimal.
  `~@X`
    print number sign always.
  `~:X`
    print comma separated.
  `~`mincol`,`padchar`,`commachar`X`
    padding.
`~O`
  Octal.
  `~@O`
    print number sign always.
  `~:O`
    print comma separated.
  `~`mincol`,`padchar`,`commachar`O`
    padding.
`~B`
  Binary.
  `~@B`
    print number sign always.
  `~:B`
    print comma separated.
  `~`mincol`,`padchar`,`commachar`B`
    padding.
`~`n`R`
  Radix n.
  `~`n`,`mincol`,`padchar`,`commachar`R`
    padding.
`~@R`
  print a number as a Roman numeral.
`~:@R`
  print a number as an “old fashioned” Roman numeral.
`~:R`
  print a number as an ordinal English number.
`~R`
  print a number as a cardinal English number.
`~P`
  Plural.
  `~@P`
    prints `y` and `ies`.
  `~:P`
    as `~P but jumps 1 argument backward.`
  `~:@P`
    as `~@P but jumps 1 argument backward.`
`~C`
  Character.
  `~@C`
    prints a character as the reader can understand it (i.e. `#\` prefixing).
  `~:C`
    prints a character as emacs does (eg. `^C` for ASCII 03).
`~F`
  Fixed-format floating-point (prints a flonum like mmm.nnn).
  `~`width`,`digits`,`scale`,`overflowchar`,`padchar`F`
  `~@F`
    If the number is positive a plus sign is printed.
`~E`
  Exponential floating-point (prints a flonum like mmm.nnn`E`ee).
  `~`width`,`digits`,`exponentdigits`,`scale`,`overflowchar`,`padchar`,`exponentchar`E`
  `~@E`
    If the number is positive a plus sign is printed.
`~G`
  General floating-point (prints a flonum either fixed or exponential).
  `~`width`,`digits`,`exponentdigits`,`scale`,`overflowchar`,`padchar`,`exponentchar`G`
  `~@G`
    If the number is positive a plus sign is printed.
`~$`
  Dollars floating-point (prints a flonum in fixed with signs separated).
  `~`digits`,`scale`,`width`,`padchar`$`
  `~@$`
    If the number is positive a plus sign is printed.
  `~:@$`
    A sign is always printed and appears before the padding.
  `~:$`
    The sign appears before the padding.
`~%`
  Newline.
  `~`n`%`
    print n newlines.
`~&`
  print newline if not at the beginning of the output line.
  `~`n`&`
    prints `~&` and then n-1 newlines.
`~|`
  Page Separator.
  `~`n`|`
    print n page separators.
`~~`
  Tilde.
  `~`n`~`
    print n tildes.
`~`<newline>
  Continuation Line.
  `~:`<newline>
    newline is ignored, white space left.
  `~@`<newline>
    newline is left, white space ignored.
`~T`
  Tabulation.
  `~@T`
    relative tabulation.
  `~`colnum,colinc`T`
    full tabulation.
`~?`
  Indirection (expects indirect arguments as a list).
  `~@?`
    extracts indirect arguments from format arguments.
`~(`str`~)`
  Case conversion (converts by `string-downcase`).
  `~:(`str`~)`
    converts by `string-capitalize`.
  `~@(`str`~)`
    converts by `string-capitalize-first`.
  `~:@(`str`~)`
    converts by `string-upcase`.
`~*`
  Argument Jumping (jumps 1 argument forward).
  `~`n`*`
    jumps n arguments forward.
  `~:*`
    jumps 1 argument backward.
  `~`n`:*`
    jumps n arguments backward.
  `~@*`
    jumps to the 0th argument.
  `~`n`@*`
    jumps to the nth argument (beginning from 0)
`~[`str0`~;`str1`~;...~;`strn`~]`
  Conditional Expression (numerical clause conditional).
  `~`n`[`
    take argument from n.
  `~@[`
    true test conditional.
  `~:[`
    if-else-then conditional.
  `~;`
    clause separator.
  `~:;`
    default clause follows.
`~{`str`~}`
  Iteration (args come from the next argument (a list)). Iteration bounding is controlled by configuration variables format:iteration-bounded and format:max-iterations. With both variables default, a maximum of 100 iterations will be performed.
  `~`n`{`
    at most n iterations.
  `~:{`
    args from next arg (a list of lists).
  `~@{`
    args from the rest of arguments.
  `~:@{`
    args from the rest args (lists).
`~^`
  Up and out.
  `~`n`^`
    aborts if n = 0
  `~`n`,`m`^`
    aborts if n = m
  `~`n`,`m`,`k`^`
    aborts if n <= m <= k

##### 4.2.2.2 Not Implemented CL Format Control Directives

`~:A`
  print `#f` as an empty list (see below).
`~:S`
  print `#f` as an empty list (see below).
`~<~>`
  Justification.
`~:^`
  (sorry I don't understand its semantics completely)

##### 4.2.2.3 Extended, Replaced and Additional Control Directives

`~`mincol`,`padchar`,`commachar`,`commawidth`D`
`~`mincol`,`padchar`,`commachar`,`commawidth`X`
`~`mincol`,`padchar`,`commachar`,`commawidth`O`
`~`mincol`,`padchar`,`commachar`,`commawidth`B`
`~`n`,`mincol`,`padchar`,`commachar`,`commawidth`R`
  commawidth is the number of characters between two comma characters.

`~I`
  print a R4RS complex number as `~F~@Fi` with passed parameters for `~F`.
`~Y`
  Pretty print formatting of an argument for scheme code lists.
`~K`
  Same as `~?.`
`~!`
  Flushes the output if format destination is a port.
`~_`
  Print a `#\space` character
  `~`n`_`
    print n `#\space` characters.
`~/`
  Print a `#\tab` character
  `~`n`/`
    print n `#\tab` characters.
`~`n`C`
  Takes n as an integer representation for a character. No arguments are consumed. n is converted to a character by `integer->char`. n must be a positive decimal number.
`~:S`
  Print out readproof. Prints out internal objects represented as `#<...>` as strings `"#<...>"` so that the format output can always be processed by `read`.
`~:A`
  Print out readproof. Prints out internal objects represented as `#<...>` as strings `"#<...>"` so that the format output can always be processed by `read`.
`~Q`
  Prints information and a copyright notice on the format implementation.
  `~:Q`
    prints format version.
`~F, ~E, ~G, ~$`
  may also print number strings, i.e. passing a number as a string and format it accordingly.

##### 4.2.2.4 Configuration Variables

Format has some configuration variables at the beginning of `format.scm` to suit the systems and users needs. There should be no modification necessary for the configuration that comes with SLIB. If modification is desired the variable should be set after the format code is loaded. Format detects automatically if the running scheme system implements floating point numbers and complex numbers.

format:symbol-case-conv
  Symbols are converted by `symbol->string` so the case type of the printed symbols is implementation dependent. `format:symbol-case-conv` is a one arg closure which is either `#f` (no conversion), `string-upcase`, `string-downcase` or `string-capitalize`. (default `#f`)
format:iobj-case-conv
  As format:symbol-case-conv but applies for the representation of implementation internal objects. (default `#f`)
format:expch
  The character prefixing the exponent value in `~E` printing. (default `#\E`)
format:iteration-bounded
  When `#t`, a `~{...~}` control will iterate no more than the number of times specified by format:max-iterations regardless of the number of iterations implied by modifiers and arguments. When `#f`, a `~{...~}` control will iterate the number of times implied by modifiers and arguments, unless termination is forced by language or system limitations. (default `#t`)
format:max-iterations
  The maximum number of iterations performed by a `~{...~}` control. Has effect only when format:iteration-bounded is `#t`. (default 100)

##### 4.2.2.5 Compatibility With Other Format Implementations

SLIB format 2.x:
  See `format.doc`.
SLIB format 1.4:
  Downward compatible except for padding support and `~A`, `~S`, `~P`, `~X` uppercase printing. SLIB format 1.4 uses C-style `printf` padding support which is completely replaced by the CL `format` padding style.
MIT C-Scheme 7.1:
  Downward compatible except for `~`, which is not documented (ignores all characters inside the format string up to a newline character). (7.1 implements `~a`, `~s`, ~newline, `~~`, `~%`, numerical and variable parameters and `:/@` modifiers in the CL sense).
Elk 1.5/2.0:
  Downward compatible except for `~A` and `~S` which print in uppercase. (Elk implements `~a`, `~s`, `~~`, and `~%` (no directive parameters or modifiers)).
Scheme->C 01nov91:
  Downward compatible except for an optional destination parameter: S2C accepts a format call without a destination which returns a formatted string. This is equivalent to a #f destination in S2C. (S2C implements `~a`, `~s`, `~c`, `~%`, and `~~` (no directive parameters or modifiers)).

This implementation of format is solely useful in the SLIB context because it requires other components provided by SLIB.

Next: Programs and Arguments, Previous: Format, Up: Textual Conversion Packages

### 4.3 Standard Formatted I/O

#### 4.3.1 stdio

`(require 'stdio)` `require`s `printf` and `scanf` and additionally defines the symbols:

— Variable: stdin

> Defined to be `(current-input-port)`.

— Variable: stdout

> Defined to be `(current-output-port)`.

— Variable: stderr

> Defined to be `(current-error-port)`.

Next: Standard Formatted Input, Previous: Standard Formatted I/O, Up: Standard Formatted I/O

#### 4.3.2 Standard Formatted Output

`(require 'printf)`

— Procedure: printf format arg1 ...
— Procedure: fprintf port format arg1 ...
— Procedure: sprintf str format arg1 ...
— Procedure: sprintf #f format arg1 ...
— Procedure: sprintf k format arg1 ...

> Each function converts, formats, and outputs its arg1 ... arguments according to the control string format argument and returns the number of characters output.

> `printf` sends its output to the port `(current-output-port)`. `fprintf` sends its output to the port port. `sprintf` `string-set!`s locations of the non-constant string argument str to the output characters.

> Two extensions of `sprintf` return new strings. If the first argument is `#f`, then the returned string's length is as many characters as specified by the format and data; if the first argument is a non-negative integer k, then the length of the returned string is also bounded by k.

> The string format contains plain characters which are copied to the output stream, and conversion specifications, each of which results in fetching zero or more of the arguments arg1 .... The results are undefined if there are an insufficient number of arguments for the format. If format is exhausted while some of the arg1 ... arguments remain unused, the excess arg1 ... arguments are ignored.

> The conversion specifications in a format string have the form:

>               % [ flags ] [ width ] [ . precision ] [ type ] conversion

> An output conversion specifications consist of an initial ``%`' character followed in sequence by:

> - Zero or more flag characters that modify the normal behavior of the conversion specification.
>   ``-`'
>     Left-justify the result in the field. Normally the result is right-justified.
>   ``+`'
>     For the signed ``%d`' and ``%i`' conversions and all inexact conversions, prefix a plus sign if the value is positive.
>   ``` '
>     For the signed ``%d`' and ``%i`' conversions, if the result doesn't start with a plus or minus sign, prefix it with a space character instead. Since the ``+`' flag ensures that the result includes a sign, this flag is ignored if both are specified.
>   ``#`'
>     For inexact conversions, ``#`' specifies that the result should always include a decimal point, even if no digits follow it. For the ``%g`' and ``%G`' conversions, this also forces trailing zeros after the decimal point to be printed where they would otherwise be elided.

>     For the ``%o`' conversion, force the leading digit to be ``0`', as if by increasing the precision. For ``%x`' or ``%X`', prefix a leading ``0x`' or ``0X`' (respectively) to the result. This doesn't do anything useful for the ``%d`', ``%i`', or ``%u`' conversions. Using this flag produces output which can be parsed by the `scanf` functions with the ``%i`' conversion (see Standard Formatted Input).

>   ``0`'
>     Pad the field with zeros instead of spaces. The zeros are placed after any indication of sign or base. This flag is ignored if the ``-`' flag is also specified, or if a precision is specified for an exact converson.
> - An optional decimal integer specifying the minimum field width. If the normal conversion produces fewer characters than this, the field is padded (with spaces or zeros per the ``0`' flag) to the specified width. This is a minimum width; if the normal conversion produces more characters than this, the field is not truncated. Alternatively, if the field width is ``*`', the next argument in the argument list (before the actual value to be printed) is used as the field width. The width value must be an integer. If the value is negative it is as though the ``-`' flag is set (see above) and the absolute value is used as the field width.
> - An optional precision to specify the number of digits to be written for numeric conversions and the maximum field width for string conversions. The precision is specified by a period (``.`') followed optionally by a decimal integer (which defaults to zero if omitted). Alternatively, if the precision is ``.*`', the next argument in the argument list (before the actual value to be printed) is used as the precision. The value must be an integer, and is ignored if negative. If you specify ``*`' for both the field width and precision, the field width argument precedes the precision argument. The ``.*`' precision is an enhancement. C library versions may not accept this syntax.

>   For the ``%f`', ``%e`', and ``%E`' conversions, the precision specifies how many digits follow the decimal-point character. The default precision is `6`. If the precision is explicitly `0`, the decimal point character is suppressed.

>   For the ``%g`' and ``%G`' conversions, the precision specifies how many significant digits to print. Significant digits are the first digit before the decimal point, and all the digits after it. If the precision is `0` or not specified for ``%g`' or ``%G`', it is treated like a value of `1`. If the value being printed cannot be expressed accurately in the specified number of digits, the value is rounded to the nearest number that fits.

>   For exact conversions, if a precision is supplied it specifies the minimum number of digits to appear; leading zeros are produced if necessary. If a precision is not supplied, the number is printed with as many digits as necessary. Converting an exact ``0`' with an explicit precision of zero produces no characters.

> - An optional one of ``l`', ``h`' or ``L`', which is ignored for numeric conversions. It is an error to specify these modifiers for non-numeric conversions.
> - A character that specifies the conversion to be applied.

> ##### 4.3.2.1 Exact Conversions

> ``b`', ``B`'
>   Print an integer as an unsigned binary number.

>   Note: ``%b`' and ``%B`' are SLIB extensions.

> ``d`', ``i`'
>   Print an integer as a signed decimal number. ``%d`' and ``%i`' are synonymous for output, but are different when used with `scanf` for input (see Standard Formatted Input).
> ``o`'
>   Print an integer as an unsigned octal number.
> ``u`'
>   Print an integer as an unsigned decimal number.
> ``x`', ``X`'
>   Print an integer as an unsigned hexadecimal number. ``%x`' prints using the digits ``0123456789abcdef`'. ``%X`' prints using the digits ``0123456789ABCDEF`'.

> ##### 4.3.2.2 Inexact Conversions

> ``f`'
>   Print a floating-point number in fixed-point notation.
> ``e`', ``E`'
>   Print a floating-point number in exponential notation. ``%e`' prints ``e`' between mantissa and exponont. ``%E`' prints ``E`' between mantissa and exponont.
> ``g`', ``G`'
>   Print a floating-point number in either fixed or exponential notation, whichever is more appropriate for its magnitude. Unless an ``#`' flag has been supplied, trailing zeros after a decimal point will be stripped off. ``%g`' prints ``e`' between mantissa and exponont. ``%G`' prints ``E`' between mantissa and exponent.
> ``k`', ``K`'
>   Print a number like ``%g`', except that an SI prefix is output after the number, which is scaled accordingly. ``%K`' outputs a dot between number and prefix, ``%k`' does not.

> ##### 4.3.2.3 Other Conversions

> ``c`'
>   Print a single character. The ``-`' flag is the only one which can be specified. It is an error to specify a precision.
> ``s`'
>   Print a string. The ``-`' flag is the only one which can be specified. A precision specifies the maximum number of characters to output; otherwise all characters in the string are output.
> ``a`', ``A`'
>   Print a scheme expression. The ``-`' flag left-justifies the output. The ``#`' flag specifies that strings and characters should be quoted as by `write` (which can be read using `read`); otherwise, output is as `display` prints. A precision specifies the maximum number of characters to output; otherwise as many characters as needed are output.

>   Note: ``%a`' and ``%A`' are SLIB extensions.

> ``%`'
>   Print a literal ``%`' character. No argument is consumed. It is an error to specify flags, field width, precision, or type modifiers with ``%%`'.

Previous: Standard Formatted Output, Up: Standard Formatted I/O

#### 4.3.3 Standard Formatted Input

`(require 'scanf)`

— Function: scanf-read-list format
— Function: scanf-read-list format port
— Function: scanf-read-list format string
— Macro: scanf format arg1 ...
— Macro: fscanf port format arg1 ...
— Macro: sscanf str format arg1 ...

> Each function reads characters, interpreting them according to the control string format argument.

> `scanf-read-list` returns a list of the items specified as far as the input matches format. `scanf`, `fscanf`, and `sscanf` return the number of items successfully matched and stored. `scanf`, `fscanf`, and `sscanf` also set the location corresponding to arg1 ... using the methods:

> symbol
>   `set!`
> car expression
>   `set-car!`
> cdr expression
>   `set-cdr!`
> vector-ref expression
>   `vector-set!`
> substring expression
>   `substring-move-left!`

> The argument to a `substring` expression in arg1 ... must be a non-constant string. Characters will be stored starting at the position specified by the second argument to `substring`. The number of characters stored will be limited by either the position specified by the third argument to `substring` or the length of the matched string, whichever is less.

> The control string, format, contains conversion specifications and other characters used to direct interpretation of input sequences. The control string contains:

> - White-space characters (blanks, tabs, newlines, or formfeeds) that cause input to be read (and discarded) up to the next non-white-space character.
> - An ordinary character (not ``%`') that must match the next character of the input stream.
> - Conversion specifications, consisting of the character ``%`', an optional assignment suppressing character ``*`', an optional numerical maximum-field width, an optional ``l`', ``h`' or ``L`' which is ignored, and a conversion code.

> Unless the specification contains the ``n`' conversion character (described below), a conversion specification directs the conversion of the next input field. The result of a conversion specification is returned in the position of the corresponding argument points, unless ``*`' indicates assignment suppression. Assignment suppression provides a way to describe an input field to be skipped. An input field is defined as a string of characters; it extends to the next inappropriate character or until the field width, if specified, is exhausted.

> > Note: This specification of format strings differs from the ANSI C and POSIX specifications. In SLIB, white space before an input field is not skipped unless white space appears before the conversion specification in the format string. In order to write format strings which work identically with ANSI C and SLIB, prepend whitespace to all conversion specifications except ``[`' and ``c`'.

> The conversion code indicates the interpretation of the input field; For a suppressed field, no value is returned. The following conversion codes are legal:

> ``%`'
>   A single % is expected in the input at this point; no value is returned.
> ``d`', ``D`'
>   A decimal integer is expected.
> ``u`', ``U`'
>   An unsigned decimal integer is expected.
> ``o`', ``O`'
>   An octal integer is expected.
> ``x`', ``X`'
>   A hexadecimal integer is expected.
> ``i`'
>   An integer is expected. Returns the value of the next input item, interpreted according to C conventions; a leading ``0`' implies octal, a leading ``0x`' implies hexadecimal; otherwise, decimal is assumed.
> ``n`'
>   Returns the total number of bytes (including white space) read by `scanf`. No input is consumed by `%n`.
> ``f`', ``F`', ``e`', ``E`', ``g`', ``G`'
>   A floating-point number is expected. The input format for floating-point numbers is an optionally signed string of digits, possibly containing a radix character ``.`', followed by an optional exponent field consisting of an ``E`' or an ``e`', followed by an optional ``+`', ``-`', or space, followed by an integer.
> ``c`', ``C`'
>   Width characters are expected. The normal skip-over-white-space is suppressed in this case; to read the next non-space character, use ``%1s`'. If a field width is given, a string is returned; up to the indicated number of characters is read.
> ``s`', ``S`'
>   A character string is expected The input field is terminated by a white-space character. `scanf` cannot read a null string.
> ``[`'
>   Indicates string data and the normal skip-over-leading-white-space is suppressed. The left bracket is followed by a set of characters, called the scanset, and a right bracket; the input field is the maximal sequence of input characters consisting entirely of characters in the scanset. ``^`', when it appears as the first character in the scanset, serves as a complement operator and redefines the scanset as the set of all characters not contained in the remainder of the scanset string. Construction of the scanset follows certain conventions. A range of characters may be represented by the construct first-last, enabling ``[0123456789]`' to be expressed ``[0-9]`'. Using this convention, first must be lexically less than or equal to last; otherwise, the dash stands for itself. The dash also stands for itself when it is the first or the last character in the scanset. To include the right square bracket as an element of the scanset, it must appear as the first character (possibly preceded by a ``^`') of the scanset, in which case it will not be interpreted syntactically as the closing bracket. At least one character must match for this conversion to succeed.

> The `scanf` functions terminate their conversions at end-of-file, at the end of the control string, or when an input character conflicts with the control string. In the latter case, the offending character is left unread in the input stream.

Next: HTML, Previous: Standard Formatted I/O, Up: Textual Conversion Packages

### 4.4 Program and Arguments

Next: Command Line, Previous: Programs and Arguments, Up: Programs and Arguments

#### 4.4.1 Getopt

`(require 'getopt)` This routine implements Posix command line argument parsing. Notice that returning values through global variables means that `getopt` is not reentrant.

Obedience to Posix format for the `getopt` calls sows confusion. Passing argc and argv as arguments while referencing optind as a global variable leads to strange behavior, especially when the calls to `getopt` are buried in other procedures.

Even in C, argc can be derived from argv; what purpose does it serve beyond providing an opportunity for argv/argc mismatch? Just such a mismatch existed for years in a SLIB `getopt--` example.

I have removed the argc and argv arguments to getopt procedures; and replaced them with a global variable:

— Variable: *argv*

> Define *argv* with a list of arguments before calling getopt procedures. If you don't want the first (0th) element to be ignored, set *optind* to 0 (after requiring getopt).

— Variable: *optind*

> Is the index of the current element of the command line. It is initially one. In order to parse a new command line or reparse an old one, *optind* must be reset.

— Variable: *optarg*

> Is set by getopt to the (string) option-argument of the current option.

— Function: getopt optstring

> Returns the next option letter in *argv* (starting from `(vector-ref argv *optind*)`) that matches a letter in optstring. *argv* is a vector or list of strings, the 0th of which getopt usually ignores. optstring is a string of recognized option characters; if a character is followed by a colon, the option takes an argument which may be immediately following it in the string or in the next element of *argv*.

> *optind* is the index of the next element of the *argv* vector to be processed. It is initialized to 1 by `getopt.scm`, and `getopt` updates it when it finishes with each element of *argv*.

> `getopt` returns the next option character from *argv* that matches a character in optstring, if there is one that matches. If the option takes an argument, `getopt` sets the variable *optarg* to the option-argument as follows:

> - If the option was the last character in the string pointed to by an element of *argv*, then *optarg* contains the next element of *argv*, and *optind* is incremented by 2. If the resulting value of *optind* is greater than or equal to `(length` *argv*`)`, this indicates a missing option argument, and `getopt` returns an error indication.
> - Otherwise, *optarg* is set to the string following the option character in that element of *argv*, and *optind* is incremented by 1.

> If, when `getopt` is called, the string `(vector-ref argv *optind*)` either does not begin with the character `#\-` or is just `"-"`, `getopt` returns `#f` without changing *optind*. If `(vector-ref argv *optind*)` is the string `"--"`, `getopt` returns `#f` after incrementing *optind*.

> If `getopt` encounters an option character that is not contained in optstring, it returns the question-mark `#\?` character. If it detects a missing option argument, it returns the colon character `#\:` if the first character of optstring was a colon, or a question-mark character otherwise. In either case, `getopt` sets the variable getopt:opt to the option character that caused the error.

> The special option `"--"` can be used to delimit the end of the options; `#f` is returned, and `"--"` is skipped.

> RETURN VALUE

> `getopt` returns the next option character specified on the command line. A colon `#\:` is returned if `getopt` detects a missing argument and the first character of optstring was a colon `#\:`.

> A question-mark `#\?` is returned if `getopt` encounters an option character not in optstring or detects a missing argument and the first character of optstring was not a colon `#\:`.

> Otherwise, `getopt` returns `#f` when all command line options have been parsed.

> Example:

>               #! /usr/local/bin/scm
>               (require 'program-arguments)
>               (require 'getopt)
>               (define argv (program-arguments))

>               (define opts ":a:b:cd")
>               (let loop ((opt (getopt (length argv) argv opts)))
>                 (case opt
>                   ((#\a) (print "option a: " *optarg*))
>                   ((#\b) (print "option b: " *optarg*))
>                   ((#\c) (print "option c"))
>                   ((#\d) (print "option d"))
>                   ((#\?) (print "error" getopt:opt))
>                   ((#\:) (print "missing arg" getopt:opt))
>                   ((#f) (if (< *optind* (length argv))
>                             (print "argv[" *optind* "]="
>                                    (list-ref argv *optind*)))
>                         (set! *optind* (+ *optind* 1))))
>                 (if (< *optind* (length argv))
>                     (loop (getopt (length argv) argv opts))))

>               (slib:exit)

#### 4.4.2 Getopt—

— Function: `getopt--` optstring

> The procedure `getopt--` is an extended version of `getopt` which parses long option names of the form ``--hold-the-onions`' and ``--verbosity-level=extreme`'. `Getopt--` behaves as `getopt` except for non-empty options beginning with ``--`'.

> Options beginning with ``--`' are returned as strings rather than characters. If a value is assigned (using ``=`') to a long option, `*optarg*` is set to the value. The ``=`' and value are not returned as part of the option string.

> No information is passed to `getopt--` concerning which long options should be accepted or whether such options can take arguments. If a long option did not have an argument, `*optarg*` will be set to `#f`. The caller is responsible for detecting and reporting errors.

>               (define opts ":-:b:")
>               (define *argv* '("foo" "-b9" "--f1" "--2=" "--g3=35234.342" "--"))
>               (define *optind* 1)
>               (define *optarg* #f)
>               (require 'qp)
>               (do ((i 5 (+ -1 i)))
>                   ((zero? i))
>                 (let ((opt (getopt-- opts)))
>                   (print *optind* opt *optarg*)))
>               -|
>               2 #\b "9"
>               3 "f1" #f
>               4 "2" ""
>               5 "g3" "35234.342"
>               5 #f "35234.342"

Next: Parameter lists, Previous: Getopt, Up: Programs and Arguments

#### 4.4.3 Command Line

`(require 'read-command)`

— Function: read-command port
— Function: read-command

> `read-command` converts a command line into a list of strings suitable for parsing by `getopt`. The syntax of command lines supported resembles that of popular shells. `read-command` updates port to point to the first character past the command delimiter.

> If an end of file is encountered in the input before any characters are found that can begin an object or comment, then an end of file object is returned.

> The port argument may be omitted, in which case it defaults to the value returned by `current-input-port`.

> The fields into which the command line is split are delimited by whitespace as defined by `char-whitespace?`. The end of a command is delimited by end-of-file or unescaped semicolon (<;>) or <newline>. Any character can be literally included in a field by escaping it with a backslach (<\>).

> The initial character and types of fields recognized are:

> ``\`'
>   The next character has is taken literally and not interpreted as a field delimiter. If <\> is the last character before a <newline>, that <newline> is just ignored. Processing continues from the characters after the <newline> as though the backslash and <newline> were not there.
> ``"`'
>   The characters up to the next unescaped <"> are taken literally, according to [R4RS] rules for literal strings (see Strings).
> ``(`', ``%'`'
>   One scheme expression is `read` starting with this character. The `read` expression is evaluated, converted to a string (using `display`), and replaces the expression in the returned field.
> ``;`'
>   Semicolon delimits a command. Using semicolons more than one command can appear on a line. Escaped semicolons and semicolons inside strings do not delimit commands.

> The comment field differs from the previous fields in that it must be the first character of a command or appear after whitespace in order to be recognized. <#> can be part of fields if these conditions are not met. For instance, `ab#c` is just the field ab#c.

> ``#`'
>   Introduces a comment. The comment continues to the end of the line on which the semicolon appears. Comments are treated as whitespace by `read-dommand-line` and backslashes before <newline>s in comments are also ignored.

— Function: read-options-file filename

> `read-options-file` converts an options file into a list of strings suitable for parsing by `getopt`. The syntax of options files is the same as the syntax for command lines, except that <newline>s do not terminate reading (only <;> or end of file).

> If an end of file is encountered before any characters are found that can begin an object or comment, then an end of file object is returned.

Next: Getopt Parameter lists, Previous: Command Line, Up: Programs and Arguments

#### 4.4.4 Parameter lists

`(require 'parameters)` Arguments to procedures in scheme are distinguished from each other by their position in the procedure call. This can be confusing when a procedure takes many arguments, many of which are not often used.

A parameter-list is a way of passing named information to a procedure. Procedures are also defined to set unused parameters to default values, check parameters, and combine parameter lists.

A parameter has the form `(`parameter-name value1`...)`. This format allows for more than one value per parameter-name.

A parameter-list is a list of parameters, each with a different parameter-name.

— Function: make-parameter-list parameter-names

> Returns an empty parameter-list with slots for parameter-names.

— Function: parameter-list-ref parameter-list parameter-name

> parameter-name must name a valid slot of parameter-list. `parameter-list-ref` returns the value of parameter parameter-name of parameter-list.

— Function: remove-parameter parameter-name parameter-list

> Removes the parameter parameter-name from parameter-list. `remove-parameter` does not alter the argument parameter-list.

> If there are more than one parameter-name parameters, an error is signaled.

— Procedure: adjoin-parameters! parameter-list parameter1 ...

> Returns parameter-list with parameter1 ... merged in.

— Procedure: parameter-list-expand expanders parameter-list

> expanders is a list of procedures whose order matches the order of the parameter-names in the call to `make-parameter-list` which created parameter-list. For each non-false element of expanders that procedure is mapped over the corresponding parameter value and the returned parameter lists are merged into parameter-list.

> This process is repeated until parameter-list stops growing. The value returned from `parameter-list-expand` is unspecified.

— Function: fill-empty-parameters defaulters parameter-list

> defaulters is a list of procedures whose order matches the order of the parameter-names in the call to `make-parameter-list` which created parameter-list. `fill-empty-parameters` returns a new parameter-list with each empty parameter replaced with the list returned by calling the corresponding defaulter with parameter-list as its argument.

— Function: check-parameters checks parameter-list

> checks is a list of procedures whose order matches the order of the parameter-names in the call to `make-parameter-list` which created parameter-list.

> `check-parameters` returns parameter-list if each check of the corresponding parameter-list returns non-false. If some check returns `#f` a warning is signaled.

In the following procedures arities is a list of symbols. The elements of `arities` can be:

`single`
  Requires a single parameter.
`optional`
  A single parameter or no parameter is acceptable.
`boolean`
  A single boolean parameter or zero parameters is acceptable.
`nary`
  Any number of parameters are acceptable.
`nary1`
  One or more of parameters are acceptable.

— Function: parameter-list->arglist positions arities parameter-list

> Returns parameter-list converted to an argument list. Parameters of arity type `single` and `boolean` are converted to the single value associated with them. The other arity types are converted to lists of the value(s).

> positions is a list of positive integers whose order matches the order of the parameter-names in the call to `make-parameter-list` which created parameter-list. The integers specify in which argument position the corresponding parameter should appear.

Next: Filenames, Previous: Parameter lists, Up: Programs and Arguments

#### 4.4.5 Getopt Parameter lists

`(require 'getopt-parameters)`

— Function: getopt->parameter-list optnames arities types aliases desc ...

> Returns *argv* converted to a parameter-list. optnames are the parameter-names. arities and types are lists of symbols corresponding to optnames.

> aliases is a list of lists of strings or integers paired with elements of optnames. Each one-character string will be treated as a single ``-`' option by `getopt`. Longer strings will be treated as long-named options (see getopt–).

> If the aliases association list has only strings as its `car`s, then all the option-arguments after an option (and before the next option) are adjoined to that option.

> If the aliases association list has integers, then each (string) option will take at most one option-argument. Unoptioned arguments are collected in a list. A ``-1`' alias will take the last argument in this list; ``+1`' will take the first argument in the list. The aliases -2 then +2; -3 then +3; ... are tried so long as a positive or negative consecutive alias is found and arguments remain in the list. Finally a ``0`' alias, if found, absorbs any remaining arguments.

> In all cases, if unclaimed arguments remain after processing, a warning is signaled and #f is returned.

— Function: getopt->arglist optnames positions arities types defaulters checks aliases desc ...

> Like `getopt->parameter-list`, but converts *argv* to an argument-list as specified by optnames, positions, arities, types, defaulters, checks, and aliases. If the options supplied violate the arities or checks constraints, then a warning is signaled and #f is returned.

These `getopt` functions can be used with SLIB relational databases. For an example, See make-command-server.

If errors are encountered while processing options, directions for using the options (and argument strings desc ...) are printed to `current-error-port`.

         (begin
           (set! *optind* 1)
           (set! *argv* '("cmd" "-?")
           (getopt->parameter-list
            '(flag number symbols symbols string flag2 flag3 num2 num3)
            '(boolean optional nary1 nary single boolean boolean nary nary)
            '(boolean integer symbol symbol string boolean boolean integer integer)
            '(("flag" flag)
              ("f" flag)
              ("Flag" flag2)
              ("B" flag3)
              ("optional" number)
              ("o" number)
              ("nary1" symbols)
              ("N" symbols)
              ("nary" symbols)
              ("n" symbols)
              ("single" string)
              ("s" string)
              ("a" num2)
              ("Abs" num3))))
         -|
         Usage: cmd [OPTION ARGUMENT ...] ...

           -f, --flag
           -o, --optional=<number>
           -n, --nary=<symbols> ...
           -N, --nary1=<symbols> ...
           -s, --single=<string>
               --Flag
           -B
           -a        <num2> ...
               --Abs=<num3> ...

         ERROR: getopt->parameter-list "unrecognized option" "-?"

Next: Batch, Previous: Getopt Parameter lists, Up: Programs and Arguments

#### 4.4.6 Filenames

`(require 'filename)`

— Function: filename:match?? pattern
— Function: filename:match-ci?? pattern

> Returns a predicate which returns a non-false value if its string argument matches (the string) pattern, false otherwise. Filename matching is like glob expansion described the bash manpage, except that names beginning with ``.`' are matched and ``/`' characters are not treated specially.

> These functions interpret the following characters specially in pattern strings:

> ``*`'
>   Matches any string, including the null string.
> ``?`'
>   Matches any single character.
> ``[...]`'
>   Matches any one of the enclosed characters. A pair of characters separated by a minus sign (-) denotes a range; any character lexically between those two characters, inclusive, is matched. If the first character following the ``[`' is a ``!`' or a ``^`' then any character not enclosed is matched. A ``-`' or ``]`' may be matched by including it as the first or last character in the set.

— Function: filename:substitute?? pattern template
— Function: filename:substitute-ci?? pattern template

> Returns a function transforming a single string argument according to glob patterns pattern and template. pattern and template must have the same number of wildcard specifications, which need not be identical. pattern and template may have a different number of literal sections. If an argument to the function matches pattern in the sense of `filename:match??` then it returns a copy of template in which each wildcard specification is replaced by the part of the argument matched by the corresponding wildcard specification in pattern. A `*` wildcard matches the longest leftmost string possible. If the argument does not match pattern then false is returned.

> template may be a function accepting the same number of string arguments as there are wildcard specifications in pattern. In the case of a match the result of applying template to a list of the substrings matched by wildcard specifications will be returned, otherwise template will not be called and `#f` will be returned.

         ((filename:substitute?? "scm_[0-9]*.html" "scm5c4_??.htm")
          "scm_10.html")
         => "scm5c4_10.htm"
         ((filename:substitute?? "??" "beg?mid?end") "AZ")
         => "begAmidZend"
         ((filename:substitute?? "*na*" "?NA?") "banana")
         => "banaNA"
         ((filename:substitute?? "?*?" (lambda (s1 s2 s3) (string-append s3 s1)))
          "ABZ")
         => "ZA"

— Function: replace-suffix str old new

> str can be a string or a list of strings. Returns a new string (or strings) similar to `str` but with the suffix string old removed and the suffix string new appended. If the end of str does not match old, an error is signaled.

         (replace-suffix "/usr/local/lib/slib/batch.scm" ".scm" ".c")
         => "/usr/local/lib/slib/batch.c"

— Function: call-with-tmpnam proc k
— Function: call-with-tmpnam proc

> Calls proc with k arguments, strings returned by successive calls to `tmpnam`. If proc returns, then any files named by the arguments to proc are deleted automatically and the value(s) yielded by the proc is(are) returned. k may be ommited, in which case it defaults to `1`. — Function: call-with-tmpnam proc suffix1 ...

> > Calls proc with strings returned by successive calls to `tmpnam`, each with the corresponding suffix string appended. If proc returns, then any files named by the arguments to proc are deleted automatically and the value(s) yielded by the proc is(are) returned.

Previous: Filenames, Up: Programs and Arguments

#### 4.4.7 Batch

`(require 'batch)` The batch procedures provide a way to write and execute portable scripts for a variety of operating systems. Each `batch:` procedure takes as its first argument a parameter-list (see Parameter lists). This parameter-list argument parms contains named associations. Batch currently uses 2 of these:

`batch-port`
  The port on which to write lines of the batch file.
`batch-dialect`
  The syntax of batch file to generate. Currently supported are:
  - unix
  - dos
  - vms
  - amigaos
  - system
  - *unknown*

The ``batch`' module uses 2 enhanced relational tables (see Using Databases) to store information linking the names of `operating-system`s to `batch-dialect`es.

— Function: batch:initialize! database

> Defines `operating-system` and `batch-dialect` tables and adds the domain `operating-system` to the enhanced relational database database.

— Variable: *operating-system*

> Is batch's best guess as to which operating-system it is running under. `*operating-system*` is set to `(software-type)` (see Configuration) unless `(software-type)` is `unix`, in which case finer distinctions are made.

— Function: batch:call-with-output-script parms file proc

> proc should be a procedure of one argument. If file is an output-port, `batch:call-with-output-script` writes an appropriate header to file and then calls proc with file as the only argument. If file is a string, `batch:call-with-output-script` opens a output-file of name file, writes an appropriate header to file, and then calls proc with the newly opened port as the only argument. Otherwise, `batch:call-with-output-script` acts as if it was called with the result of `(current-output-port)` as its third argument.

The rest of the `batch:` procedures write (or execute if `batch-dialect` is `system`) commands to the batch port which has been added to parms or `(copy-tree` parms`)` by the code:

         (adjoin-parameters! parms (list 'batch-port port))

— Function: batch:command parms string1 string2 ...

> Calls `batch:try-command` (below) with arguments, but signals an error if `batch:try-command` returns `#f`.

These functions return a non-false value if the command was successfully translated into the batch dialect and `#f` if not. In the case of the `system` dialect, the value is non-false if the operation suceeded.

— Function: batch:try-command parms string1 string2 ...

> Writes a command to the `batch-port` in parms which executes the program named string1 with arguments string2 ....

— Function: batch:try-chopped-command parms arg1 arg2 ... list

> breaks the last argument list into chunks small enough so that the command:

>               arg1 arg2 ... chunk

> fits withing the platform's maximum command-line length.

> `batch:try-chopped-command` calls `batch:try-command` with the command and returns non-false only if the commands all fit and `batch:try-command` of each command line returned non-false.

— Function: batch:run-script parms string1 string2 ...

> Writes a command to the `batch-port` in parms which executes the batch script named string1 with arguments string2 ....

> Note: `batch:run-script` and `batch:try-command` are not the same for some operating systems (VMS).

— Function: batch:comment parms line1 ...

> Writes comment lines line1 ... to the `batch-port` in parms.

— Function: batch:lines->file parms file line1 ...

> Writes commands to the `batch-port` in parms which create a file named file with contents line1 ....

— Function: batch:delete-file parms file

> Writes a command to the `batch-port` in parms which deletes the file named file.

— Function: batch:rename-file parms old-name new-name

> Writes a command to the `batch-port` in parms which renames the file old-name to new-name.

In addition, batch provides some small utilities very useful for writing scripts:

— Function: truncate-up-to path char
— Function: truncate-up-to path string
— Function: truncate-up-to path charlist

> path can be a string or a list of strings. Returns path sans any prefixes ending with a character of the second argument. This can be used to derive a filename moved locally from elsewhere.

>               (truncate-up-to "/usr/local/lib/slib/batch.scm" "/")
>               => "batch.scm"

— Function: string-join joiner string1 ...

> Returns a new string consisting of all the strings string1 ... in order appended together with the string joiner between each adjacent pair.

— Function: must-be-first list1 list2

> Returns a new list consisting of the elements of list2 ordered so that if some elements of list1 are `equal?` to elements of list2, then those elements will appear first and in the order of list1.

— Function: must-be-last list1 list2

> Returns a new list consisting of the elements of list1 ordered so that if some elements of list2 are `equal?` to elements of list1, then those elements will appear last and in the order of list2.

— Function: os->batch-dialect osname

> Returns its best guess for the `batch-dialect` to be used for the operating-system named osname. `os->batch-dialect` uses the tables added to database by `batch:initialize!`.

Here is an example of the use of most of batch's procedures:

         (require 'databases)
         (require 'parameters)
         (require 'batch)
         (require 'filename)

         (define batch (create-database #f 'alist-table))
         (batch:initialize! batch)

         (define my-parameters
           (list (list 'batch-dialect (os->batch-dialect *operating-system*))
                 (list 'operating-system *operating-system*)
                 (list 'batch-port (current-output-port)))) ;gets filled in later

         (batch:call-with-output-script
          my-parameters
          "my-batch"
          (lambda (batch-port)
            (adjoin-parameters! my-parameters (list 'batch-port batch-port))
            (and
             (batch:comment my-parameters
                            "================ Write file with C program.")
             (batch:rename-file my-parameters "hello.c" "hello.c~")
             (batch:lines->file my-parameters "hello.c"
                                "#include <stdio.h>"
                                "int main(int argc, char **argv)"
                                "{"
                                "  printf(\"hello world\\n\");"
                                "  return 0;"
                                "}" )
             (batch:command my-parameters "cc" "-c" "hello.c")
             (batch:command my-parameters "cc" "-o" "hello"
                           (replace-suffix "hello.c" ".c" ".o"))
             (batch:command my-parameters "hello")
             (batch:delete-file my-parameters "hello")
             (batch:delete-file my-parameters "hello.c")
             (batch:delete-file my-parameters "hello.o")
             (batch:delete-file my-parameters "my-batch")
             )))

Produces the file `my-batch`:

         #! /bin/sh
         # "my-batch" script created by SLIB/batch Sun Oct 31 18:24:10 1999
         # ================ Write file with C program.
         mv -f hello.c hello.c~
         rm -f hello.c
         echo '#include <stdio.h>'>>hello.c
         echo 'int main(int argc, char **argv)'>>hello.c
         echo '{'>>hello.c
         echo '  printf("hello world\n");'>>hello.c
         echo '  return 0;'>>hello.c
         echo '}'>>hello.c
         cc -c hello.c
         cc -o hello hello.o
         hello
         rm -f hello
         rm -f hello.c
         rm -f hello.o
         rm -f my-batch

When run, `my-batch` prints:

         bash$ my-batch
         mv: hello.c: No such file or directory
         hello world

Next: HTML Tables, Previous: Programs and Arguments, Up: Textual Conversion Packages

### 4.5 HTML

`(require 'html-form)`

— Function: html:atval txt

> Returns a string with character substitutions appropriate to send txt as an attribute-value.

— Function: html:plain txt

> Returns a string with character substitutions appropriate to send txt as an plain-text.

— Function: html:meta name content

> Returns a tag of meta-information suitable for passing as the third argument to `html:head`. The tag produced is ``<META NAME="name" CONTENT="content">`'. The string or symbol name can be ``author`', ``copyright`', ``keywords`', ``description`', ``date`', ``robots`', ....

— Function: html:http-equiv name content

> Returns a tag of HTTP information suitable for passing as the third argument to `html:head`. The tag produced is ``<META HTTP-EQUIV="name" CONTENT="content">`'. The string or symbol name can be ``Expires`', ``PICS-Label`', ``Content-Type`', ``Refresh`', ....

— Function: html:meta-refresh delay uri
— Function: html:meta-refresh delay

> Returns a tag suitable for passing as the third argument to `html:head`. If uri argument is supplied, then delay seconds after displaying the page with this tag, Netscape or IE browsers will fetch and display uri. Otherwise, delay seconds after displaying the page with this tag, Netscape or IE browsers will fetch and redisplay this page.

— Function: html:head title backlink tags ...
— Function: html:head title backlink
— Function: html:head title

> Returns header string for an HTML page named title. If backlink is a string, it is used verbatim between the ``H1`' tags; otherwise title is used. If string arguments tags ... are supplied, then they are included verbatim within the `<HEAD>` section.

— Function: html:body body ...

> Returns HTML string to end a page.

— Function: html:pre line1 line ...

> Returns the strings line1, lines as PREformmated plain text (rendered in fixed-width font). Newlines are inserted between line1, lines. HTML tags (``<tag>`') within lines will be visible verbatim.

— Function: html:comment line1 line ...

> Returns the strings line1 as HTML comments.

### 4.6 HTML Forms

— Function: html:form method action body ...

> The symbol method is either `get`, `head`, `post`, `put`, or `delete`. The strings body form the body of the form. `html:form` returns the HTML form.

— Function: html:hidden name value

> Returns HTML string which will cause name=value in form.

— Function: html:checkbox pname default

> Returns HTML string for check box.

— Function: html:text pname default size ...

> Returns HTML string for one-line text box.

— Function: html:text-area pname default-list

> Returns HTML string for multi-line text box.

— Function: html:select pname arity default-list foreign-values

> Returns HTML string for pull-down menu selector.

— Function: html:buttons pname arity default-list foreign-values

> Returns HTML string for any-of selector.

— Function: form:submit submit-label command
— Function: form:submit submit-label

> The string or symbol submit-label appears on the button which submits the form. If the optional second argument command is given, then `*command*=`command and `*button*=`submit-label are set in the query. Otherwise, `*command*=`submit-label is set in the query.

— Function: form:image submit-label image-src

> The image-src appears on the button which submits the form.

— Function: form:reset

> Returns a string which generates a reset button.

— Function: form:element pname arity default-list foreign-values

> Returns a string which generates an INPUT element for the field named pname. The element appears in the created form with its representation determined by its arity and domain. For domains which are foreign-keys:

> `single`
>   select menu
> `optional`
>   select menu
> `nary`
>   check boxes
> `nary1`
>   check boxes

> If the foreign-key table has a field named ``visible-name`', then the contents of that field are the names visible to the user for those choices. Otherwise, the foreign-key itself is visible.

> For other types of domains:

> `single`
>   text area
> `optional`
>   text area
> `boolean`
>   check box
> `nary`
>   text area
> `nary1`
>   text area

— Function: form:delimited pname doc aliat arity default-list foreign-values

> Returns a HTML string for a form element embedded in a line of a delimited list. Apply map `form:delimited` to the list returned by `command->p-specs`.

— Function: html:delimited-list row ...

> Wraps its arguments with delimited-list (``DL`' command.

— Function: get-foreign-choices tab

> Returns a list of the ``visible-name`' or first fields of table tab.

— Function: command->p-specs rdb command-table command

> The symbol command-table names a command table in the rdb relational database. The symbol command names a key in command-table.

> `command->p-specs` returns a list of lists of pname, doc, aliat, arity, default-list, and foreign-values. The returned list has one element for each parameter of command command.

> This example demonstrates how to create a HTML-form for the ``build`' command.

>               (require (in-vicinity (implementation-vicinity) "build.scm"))
>               (call-with-output-file "buildscm.html"
>                 (lambda (port)
>                   (display
>                    (string-append
>                     (html:head 'commands)
>                     (html:body
>                      (sprintf #f "<H2>%s:</H2><BLOCKQUOTE>%s</BLOCKQUOTE>\\n"
>                               (html:plain 'build)
>                               (html:plain ((comtab 'get 'documentation) 'build)))
>                      (html:form
>                       'post
>                       (or "http://localhost:8081/buildscm" "/cgi-bin/build.cgi")
>                       (apply html:delimited-list
>                              (apply map form:delimited
>                                     (command->p-specs build '*commands* 'build)))
>                       (form:submit 'build)
>                       (form:reset))))
>                    port)))

Next: HTTP and CGI, Previous: HTML, Up: Textual Conversion Packages

### 4.7 HTML Tables

`(require 'db->html)`

— Function: html:table options row ...
— Function: html:caption caption align
— Function: html:caption caption

> align can be ``top`' or ``bottom`'.

— Function: html:heading columns

> Outputs a heading row for the currently-started table.

— Function: html:href-heading columns uris

> Outputs a heading row with column-names columns linked to URIs uris.

— Function: html:linked-row-converter k foreigns

> The positive integer k is the primary-key-limit (number of primary-keys) of the table. foreigns is a list of the filenames of foreign-key field pages and #f for non foreign-key fields.

> `html:linked-row-converter` returns a procedure taking a row for its single argument. This returned procedure returns the html string for that table row.

— Function: table-name->filename table-name

> Returns the symbol table-name converted to a filename.

— Function: table->linked-html caption db table-name match-key1 ...

> Returns HTML string for db table table-name chopped into 50-row HTML tables. Every foreign-key value is linked to the page (of the table) defining that key.

> The optional match-key1 ... arguments restrict actions to a subset of the table. See match-key.

— Function: table->linked-page db table-name index-filename arg ...

> Returns a complete HTML page. The string index-filename names the page which refers to this one.

> The optional args ... arguments restrict actions to a subset of the table. See match-key.

— Function: catalog->html db caption arg ...

> Returns HTML string for the catalog table of db.

#### 4.7.1 HTML editing tables

A client can modify one row of an editable table at a time. For any change submitted, these routines check if that row has been modified during the time the user has been editing the form. If so, an error page results.

The behavior of edited rows is:

- If no fields are changed, then no change is made to the table.
- If the primary keys equal null-keys (parameter defaults), and no other user has modified that row, then that row is deleted.
- If only primary keys are changed, there are non-key fields, and no row with the new keys is in the table, then the old row is deleted and one with the new keys is inserted.
- If only non-key fields are changed, and that row has not been modified by another user, then the row is changed to reflect the fields.
- If both keys and non-key fields are changed, and no row with the new keys is in the table, then a row is created with the new keys and fields.
- If fields are changed, all fields are primary keys, and no row with the new keys is in the table, then a row is created with the new keys.

After any change to the table, a `sync-database` of the database is performed.

— Function: command:modify-table table-name null-keys update delete retrieve
— Function: command:modify-table table-name null-keys update delete
— Function: command:modify-table table-name null-keys update
— Function: command:modify-table table-name null-keys

> Returns procedure (of db) which returns procedure to modify row of table-name. null-keys is the list of null keys indicating the row is to be deleted when any matches its corresponding primary key. Optional arguments update, delete, and retrieve default to the `row:update`, `row:delete`, and `row:retrieve` of table-name in db.

— Function: command:make-editable-table rdb table-name arg ...

> Given table-name in rdb, creates parameter and `*command*` tables for editing one row of table-name at a time. `command:make-editable-table` returns a procedure taking a row argument which returns the HTML string for editing that row.

> Optional args are expressions (lists) added to the call to `command:modify-table`.

> The domain name of a column determines the expected arity of the data stored in that column. Domain names ending in:

> ``*`'
>   have arity ``nary`';
> ``+`'
>   have arity ``nary1`'.

— Function: html:editable-row-converter k names edit-point edit-converter

> The positive integer k is the primary-key-limit (number of primary-keys) of the table. names is a list of the field-names. edit-point is the list of primary-keys denoting the row to edit (or #f). edit-converter is the procedure called with k, names, and the row to edit.

> `html:editable-row-converter` returns a procedure taking a row for its single argument. This returned procedure returns the html string for that table row.

> Each HTML table constructed using `html:editable-row-converter` has first k fields (typically the primary key fields) of each row linked to a text encoding of these fields (the result of calling `row->anchor`). The page so referenced typically allows the user to edit fields of that row.

#### 4.7.2 HTML databases

— Function: db->html-files db dir index-filename caption

> db must be a relational database. dir must be #f or a non-empty string naming an existing sub-directory of the current directory.

> `db->html-files` creates an html page for each table in the database db in the sub-directory named dir, or the current directory if dir is #f. The top level page with the catalog of tables (captioned caption) is written to a file named index-filename.

— Function: db->html-directory db dir index-filename
— Function: db->html-directory db dir

> db must be a relational database. dir must be a non-empty string naming an existing sub-directory of the current directory or one to be created. The optional string index-filename names the filename of the top page, which defaults to `index.html`.

> `db->html-directory` creates sub-directory dir if neccessary, and calls `(db->html-files` db dir index-filename dir`)`. The ``file:`' URI of index-filename is returned.

— Function: db->netscape db dir index-filename
— Function: db->netscape db dir

> `db->netscape` is just like `db->html-directory`, but calls `browse-url` with the uri for the top page after the pages are created.

Next: Parsing HTML, Previous: HTML Tables, Up: Textual Conversion Packages

### 4.8 HTTP and CGI

`(require 'http)` or `(require 'cgi)`

— Function: http:header alist

> Returns a string containing lines for each element of alist; the `car` of which is followed by ``:` ', then the `cdr`.

— Function: http:content alist body ...

> Returns the concatenation of strings body with the `(http:header` alist`)` and the ``Content-Length`' prepended.

— Variable: *http:byline*

> String appearing at the bottom of error pages.

— Function: http:error-page status-code reason-phrase html-string ...

> status-code and reason-phrase should be an integer and string as specified in RFC 2068. The returned page (string) will show the status-code and reason-phrase and any additional html-strings ...; with *http:byline* or SLIB's default at the bottom.

— Function: http:forwarding-page title dly uri html-string ...

> The string or symbol title is the page title. dly is a non-negative integer. The html-strings ... are typically used to explain to the user why this page is being forwarded.

> `http:forwarding-page` returns an HTML string for a page which automatically forwards to uri after dly seconds. The returned page (string) contains any html-strings ... followed by a manual link to uri, in case the browser does not forward automatically.

— Function: http:serve-query serve-proc input-port output-port

> reads the URI and query-string from input-port. If the query is a valid ``"POST"`' or ``"GET"`' query, then `http:serve-query` calls serve-proc with three arguments, the request-line, query-string, and header-alist. Otherwise, `http:serve-query` calls serve-proc with the request-line, #f, and header-alist.

> If serve-proc returns a string, it is sent to output-port. If serve-proc returns a list, then an error page with number 525 and strings from the list. If serve-proc returns #f, then a ``Bad Request`' (400) page is sent to output-port.

> Otherwise, `http:serve-query` replies (to output-port) with appropriate HTML describing the problem.

This example services HTTP queries from port-number:

         (define socket (make-stream-socket AF_INET 0))
         (and (socket:bind socket port-number) ; AF_INET INADDR_ANY
              (socket:listen socket 10)        ; Queue up to 10 requests.
              (dynamic-wind
                  (lambda () #f)
                  (lambda ()
                    (do ((port (socket:accept socket) (socket:accept socket)))
                        (#f)
                      (let ((iport (duplicate-port port "r"))
                            (oport (duplicate-port port "w")))
                        (http:serve-query build:serve iport oport)
                        (close-port iport)
                        (close-port oport))
                      (close-port port)))
                  (lambda () (close-port socket))))

— Function: cgi:serve-query serve-proc

> reads the URI and query-string from `(current-input-port)`. If the query is a valid ``"POST"`' or ``"GET"`' query, then `cgi:serve-query` calls serve-proc with three arguments, the request-line, query-string, and header-alist. Otherwise, `cgi:serve-query` calls serve-proc with the request-line, #f, and header-alist.

> If serve-proc returns a string, it is sent to `(current-input-port)`. If serve-proc returns a list, then an error page with number 525 and strings from the list. If serve-proc returns #f, then a ``Bad Request`' (400) page is sent to `(current-input-port)`.

> Otherwise, `cgi:serve-query` replies (to `(current-input-port)`) with appropriate HTML describing the problem.

— Function: make-query-alist-command-server rdb command-table
— Function: make-query-alist-command-server rdb command-table #t

> Returns a procedure of one argument. When that procedure is called with a query-alist (as returned by `uri:decode-query`, the value of the ``*command*`' association will be the command invoked in command-table. If ``*command*`' is not in the query-alist then the value of ``*suggest*`' is tried. If neither name is in the query-alist, then the literal value ``*default*`' is tried in command-table.

> If optional third argument is non-false, then the command is called with just the parameter-list; otherwise, command is called with the arguments described in its table.

Next: URI, Previous: HTTP and CGI, Up: Textual Conversion Packages

### 4.9 Parsing HTML

`(require 'html-for-each)`

— Function: html-for-each file word-proc markup-proc white-proc newline-proc

> file is an input port or a string naming an existing file containing HTML text. word-proc is a procedure of one argument or #f. markup-proc is a procedure of one argument or #f. white-proc is a procedure of one argument or #f. newline-proc is a procedure of no arguments or #f.

> `html-for-each` opens and reads characters from port file or the file named by string file. Sequential groups of characters are assembled into strings which are either

> - enclosed by ``<`' and ``>`' (hypertext markups or comments);
> - end-of-line;
> - whitespace; or
> - none of the above (words).

> Procedures are called according to these distinctions in order of the string's occurrence in file.

> newline-proc is called with no arguments for end-of-line not within a markup or comment.

> white-proc is called with strings of non-newline whitespace.

> markup-proc is called with hypertext markup strings (including ``<`' and ``>`').

> word-proc is called with the remaining strings.

> `html-for-each` returns an unspecified value.

— Function: html:read-title file limit
— Function: html:read-title file

> file is an input port or a string naming an existing file containing HTML text. If supplied, limit must be an integer. limit defaults to 1000.

> `html:read-title` opens and reads HTML from port file or the file named by string file, until reaching the (mandatory) ``TITLE`' field. `html:read-title` returns the title string with adjacent whitespaces collapsed to one space. `html:read-title` returns #f if the title field is empty, absent, if the first character read from file is not ``#\<`', or if the end of title is not found within the first (approximately) limit words.

— Function: htm-fields htm

> htm is a hypertext markup string.

> If htm is a (hypertext) comment, then `htm-fields` returns #f. Otherwise `htm-fields` returns the hypertext element symbol (created by `string-ci->symbol`) consed onto an association list of the attribute name-symbols and values. Each value is a number or string; or #t if the name had no value assigned within the markup.

Next: Parsing XML, Previous: Parsing HTML, Up: Textual Conversion Packages

### 4.10 URI

`(require 'uri)` Implements Uniform Resource Identifiers (URI) as described in RFC 2396.

— Function: make-uri
— Function: make-uri fragment
— Function: make-uri query fragment
— Function: make-uri path query fragment
— Function: make-uri authority path query fragment
— Function: make-uri scheme authority path query fragment

> Returns a Uniform Resource Identifier string from component arguments.

— Function: uri:make-path path

> Returns a URI string combining the components of list path.

— Function: html:anchor name

> Returns a string which defines this location in the (HTML) file as name. The hypertext ``<A HREF="#name">`' will link to this point.

>               (html:anchor "(section 7)")
>               =>
>               "<A NAME=\"(section%207)\"></A>"

— Function: html:link uri highlighted

> Returns a string which links the highlighted text to uri.

>               (html:link (make-uri "(section 7)") "section 7")
>               =>
>               "<A HREF=\"#(section%207)\">section 7</A>"

— Function: html:base uri

> Returns a string specifying the base uri of a document, for inclusion in the HEAD of the document (see head).

— Function: html:isindex prompt

> Returns a string specifying the search prompt of a document, for inclusion in the HEAD of the document (see head).

— Function: uri->tree uri-reference base-tree
— Function: uri->tree uri-reference

> Returns a list of 5 elements corresponding to the parts (scheme authority path query fragment) of string uri-reference. Elements corresponding to absent parts are #f.

> The path is a list of strings. If the first string is empty, then the path is absolute; otherwise relative. The optional base-tree is a tree as returned by `uri->tree`; and is used as the base address for relative URIs.

> If the authority component is a Server-based Naming Authority, then it is a list of the userinfo, host, and port strings (or #f). For other types of authority components the authority will be a string.

>               (uri->tree "http://www.ics.uci.edu/pub/ietf/uri/#Related")
>               =>
>               (http "www.ics.uci.edu" ("" "pub" "ietf" "uri" "") #f "Related")

— Function: uri:split-fields txt chr

> Returns a list of txt split at each occurrence of chr. chr does not appear in the returned list of strings.

— Function: uri:decode-query query-string

> Converts a URI encoded query-string to a query-alist.

`uric:` prefixes indicate procedures dealing with URI-components.

— Function: uric:encode uri-component allows

> Returns a copy of the string uri-component in which all unsafe octets (as defined in RFC 2396) have been ``%`' escaped. `uric:decode` decodes strings encoded by `uric:encode`.

— Function: uric:decode uri-component

> Returns a copy of the string uri-component in which each ``%`' escaped characters in uri-component is replaced with the character it encodes. This routine is useful for showing URI contents on error pages.

— Function: uri:path->keys path-list ptypes

> path-list is a path-list as returned by `uri:split-fields`. `uri:path->keys` returns a list of items returned by `uri:decode-path`, coerced to types ptypes.

#### File-system Locators and Predicates

— Function: path->uri path

> Returns a URI-string for path on the local host.

— Function: absolute-uri? str

> Returns #t if str is an absolute-URI as indicated by a syntactically valid (per RFC 2396) scheme; otherwise returns #f.

— Function: absolute-path? file-name

> Returns #t if file-name is a fully specified pathname (does not depend on the current working directory); otherwise returns #f.

— Function: null-directory? str

> Returns #t if changing directory to str would leave the current directory unchanged; otherwise returns #f.

— Function: glob-pattern? str

> Returns #t if the string str contains characters used for specifying glob patterns, namely ``*`', ``?`', or ``[`'.

Before RFC 2396, the File Transfer Protocol (FTP) served a similar purpose.

— Function: parse-ftp-address uri

> Returns a list of the decoded FTP uri; or #f if indecipherable. FTP Uniform Resource Locator, ange-ftp, and getit formats are handled. The returned list has four elements which are strings or #f:

> 0. username
> 1. password
> 2. remote-site
> 3. remote-directory

Next: Printing Scheme, Previous: URI, Up: Textual Conversion Packages

### 4.11 Parsing XML

`(require 'xml-parse)` or `(require 'ssax)`

The XML standard document referred to in this module is
http://www.w3.org/TR/1998/REC-xml-19980210.html.

The present frameworks fully supports the XML Namespaces Recommendation
http://www.w3.org/TR/REC-xml-names.

#### 4.11.1 String Glue

— Function: ssax:reverse-collect-str list-of-frags

> Given the list of fragments (some of which are text strings), reverse the list and concatenate adjacent text strings. If LIST-OF-FRAGS has zero or one element, the result of the procedure is `equal?` to its argument.

— Function: ssax:reverse-collect-str-drop-ws list-of-frags

> Given the list of fragments (some of which are text strings), reverse the list and concatenate adjacent text strings while dropping "unsignificant" whitespace, that is, whitespace in front, behind and between elements. The whitespace that is included in character data is not affected.

> Use this procedure to "intelligently" drop "insignificant" whitespace in the parsed SXML. If the strict compliance with the XML Recommendation regarding the whitespace is desired, use the `ssax:reverse-collect-str` procedure instead.

#### 4.11.2 Character and Token Functions

The following functions either skip, or build and return tokens, according to inclusion or delimiting semantics. The list of characters to expect, include, or to break at may vary from one invocation of a function to another. This allows the functions to easily parse even context-sensitive languages.

Exceptions are mentioned specifically. The list of expected characters (characters to skip until, or break-characters) may include an EOF "character", which is coded as symbol *eof*

The input stream to parse is specified as a PORT, which is the last argument.

— Function: ssax:assert-current-char char-list string port

> Reads a character from the port and looks it up in the char-list of expected characters. If the read character was found among expected, it is returned. Otherwise, the procedure writes a message using string as a comment and quits.

— Function: ssax:skip-while char-list port

> Reads characters from the port and disregards them, as long as they are mentioned in the char-list. The first character (which may be EOF) peeked from the stream that is not a member of the char-list is returned.

— Function: ssax:init-buffer

> Returns an initial buffer for `ssax:next-token*` procedures. `ssax:init-buffer` may allocate a new buffer at each invocation.

— Function: ssax:next-token prefix-char-list break-char-list comment-string port

> Skips any number of the prefix characters (members of the prefix-char-list), if any, and reads the sequence of characters up to (but not including) a break character, one of the break-char-list.

> The string of characters thus read is returned. The break character is left on the input stream. break-char-list may include the symbol `*eof*`; otherwise, EOF is fatal, generating an error message including a specified comment-string.

`ssax:next-token-of` is similar to `ssax:next-token` except that it implements an inclusion rather than delimiting semantics.

— Function: ssax:next-token-of inc-charset port

> Reads characters from the port that belong to the list of characters inc-charset. The reading stops at the first character which is not a member of the set. This character is left on the stream. All the read characters are returned in a string. — Function: ssax:next-token-of pred port

> > Reads characters from the port for which pred (a procedure of one argument) returns non-#f. The reading stops at the first character for which pred returns #f. That character is left on the stream. All the results of evaluating of pred up to #f are returned in a string.

> > pred is a procedure that takes one argument (a character or the EOF object) and returns a character or #f. The returned character does not have to be the same as the input argument to the pred. For example,

> >               (ssax:next-token-of (lambda (c)
> >                                     (cond ((eof-object? c) #f)
> >                                           ((char-alphabetic? c) (char-downcase c))
> >                                           (else #f)))
> >                                   (current-input-port))

> > will try to read an alphabetic token from the current input port, and return it in lower case.

— Function: ssax:read-string len port

> Reads len characters from the port, and returns them in a string. If EOF is encountered before len characters are read, a shorter string will be returned.

#### 4.11.3 Data Types

`TAG-KIND`
  A symbol ``START`', ``END`', ``PI`', ``DECL`', ``COMMENT`', ``CDSECT`', or ``ENTITY-REF`' that identifies a markup token
`UNRES-NAME`
  a name (called GI in the XML Recommendation) as given in an XML document for a markup token: start-tag, PI target, attribute name. If a GI is an NCName, UNRES-NAME is this NCName converted into a Scheme symbol. If a GI is a QName, ``UNRES-NAME`' is a pair of symbols: `(`PREFIX`.` LOCALPART`)`.
`RES-NAME`
  An expanded name, a resolved version of an ``UNRES-NAME`'. For an element or an attribute name with a non-empty namespace URI, ``RES-NAME`' is a pair of symbols, `(`URI-SYMB`.` LOCALPART`)`. Otherwise, it's a single symbol.
`ELEM-CONTENT-MODEL`
  A symbol:
  ``ANY`'
    anything goes, expect an END tag.
  ``EMPTY-TAG`'
    no content, and no END-tag is coming
  ``EMPTY`'
    no content, expect the END-tag as the next token
  ``PCDATA`'
    expect character data only, and no children elements
  ``MIXED`'
  ``ELEM-CONTENT`'
`URI-SYMB`
  A symbol representing a namespace URI – or other symbol chosen by the user to represent URI. In the former case, `URI-SYMB` is created by %-quoting of bad URI characters and converting the resulting string into a symbol.
`NAMESPACES`
  A list representing namespaces in effect. An element of the list has one of the following forms:
  `(`prefix uri-symb`.` uri-symb`) or`
  `(`prefix user-prefix`.` uri-symb`)`
    user-prefix is a symbol chosen by the user to represent the URI.
  `(#f` user-prefix`.` uri-symb`)`
    Specification of the user-chosen prefix and a URI-SYMBOL.
  `(*DEFAULT*` user-prefix`.` uri-symb`)`
    Declaration of the default namespace
  `(*DEFAULT* #f . #f)`
    Un-declaration of the default namespace. This notation represents overriding of the previous declaration

  A NAMESPACES list may contain several elements for the same prefix. The one closest to the beginning of the list takes effect.

`ATTLIST`
  An ordered collection of (NAME . VALUE) pairs, where NAME is a RES-NAME or an UNRES-NAME. The collection is an ADT.
`STR-HANDLER`
  A procedure of three arguments: string1 string2 seed returning a new seed. The procedure is supposed to handle a chunk of character data string1 followed by a chunk of character data string2. string2 is a short string, often ``"\n"`' and even ``""`'.
`ENTITIES`
  An assoc list of pairs:

                   (named-entity-name . named-entity-body)

  where named-entity-name is a symbol under which the entity was declared, named-entity-body is either a string, or (for an external entity) a thunk that will return an input port (from which the entity can be read). named-entity-body may also be #f. This is an indication that a named-entity-name is currently being expanded. A reference to this named-entity-name will be an error: violation of the WFC nonrecursion.

`XML-TOKEN`
  This record represents a markup, which is, according to the XML Recommendation, "takes the form of start-tags, end-tags, empty-element tags, entity references, character references, comments, CDATA section delimiters, document type declarations, and processing instructions."
  kind
    a TAG-KIND
  head
    an UNRES-NAME. For XML-TOKENs of kinds 'COMMENT and 'CDSECT, the head is #f.

  For example,

                <P>                   => kind=START,      head=P
                </P>                  => kind=END,        head=P
                <BR/>                 => kind=EMPTY-EL,   head=BR
                <!DOCTYPE OMF ...>    => kind=DECL,       head=DOCTYPE
                <?xml version="1.0"?> => kind=PI,         head=xml
                &my-ent;              => kind=ENTITY-REF, head=my-ent

  Character references are not represented by xml-tokens as these references are transparently resolved into the corresponding characters.

`XML-DECL`
  The record represents a datatype of an XML document: the list of declared elements and their attributes, declared notations, list of replacement strings or loading procedures for parsed general entities, etc. Normally an XML-DECL record is created from a DTD or an XML Schema, although it can be created and filled in in many other ways (e.g., loaded from a file).
  elems
    an (assoc) list of decl-elem or #f. The latter instructs the parser to do no validation of elements and attributes.
  decl-elem
    declaration of one element:

    `(`elem-name elem-content decl-attrs`)`

    elem-name is an UNRES-NAME for the element.

    elem-content is an ELEM-CONTENT-MODEL.

    decl-attrs is an `ATTLIST`, of `(`attr-name`.` value`)` associations.

    This element can declare a user procedure to handle parsing of an element (e.g., to do a custom validation, or to build a hash of IDs as they're encountered).

  decl-attr
    an element of an `ATTLIST`, declaration of one attribute:

    `(`attr-name content-type use-type default-value`)`

    attr-name is an UNRES-NAME for the declared attribute.

    content-type is a symbol: `CDATA`, `NMTOKEN`, `NMTOKENS`, ... or a list of strings for the enumerated type.

    use-type is a symbol: `REQUIRED`, `IMPLIED`, or `FIXED`.

    default-value is a string for the default value, or #f if not given.

#### 4.11.4 Low-Level Parsers and Scanners

These procedures deal with primitive lexical units (Names, whitespaces, tags) and with pieces of more generic productions. Most of these parsers must be called in appropriate context. For example, `ssax:complete-start-tag` must be called only when the start-tag has been detected and its GI has been read.

— Function: ssax:skip-s port

> Skip the S (whitespace) production as defined by

>               [3] S ::= (#x20 | #x09 | #x0D | #x0A)

> `ssax:skip-s` returns the first not-whitespace character it encounters while scanning the port. This character is left on the input stream.

— Function: ssax:read-ncname port

> Read a NCName starting from the current position in the port and return it as a symbol.

>               [4] NameChar ::= Letter | Digit | '.' | '-' | '_' | ':'
>                                | CombiningChar | Extender
>               [5] Name ::= (Letter | '_' | ':') (NameChar)*

> This code supports the XML Namespace Recommendation REC-xml-names, which modifies the above productions as follows:

>               [4] NCNameChar ::= Letter | Digit | '.' | '-' | '_'
>                                     | CombiningChar | Extender
>               [5] NCName ::= (Letter | '_') (NCNameChar)*

> As the Rec-xml-names says,

> > "An XML document conforms to this specification if all other tokens [other than element types and attribute names] in the document which are required, for XML conformance, to match the XML production for Name, match this specification's production for NCName."

> Element types and attribute names must match the production QName, defined below.

— Function: ssax:read-qname port

> Read a (namespace-) Qualified Name, QName, from the current position in port; and return an UNRES-NAME.

> From REC-xml-names:

>               [6] QName ::= (Prefix ':')? LocalPart
>               [7] Prefix ::= NCName
>               [8] LocalPart ::= NCName

— Function: ssax:read-markup-token port

> This procedure starts parsing of a markup token. The current position in the stream must be ``<`'. This procedure scans enough of the input stream to figure out what kind of a markup token it is seeing. The procedure returns an XML-TOKEN structure describing the token. Note, generally reading of the current markup is not finished! In particular, no attributes of the start-tag token are scanned.

> Here's a detailed break out of the return values and the position in the PORT when that particular value is returned:

> PI-token
>   only PI-target is read. To finish the Processing-Instruction and disregard it, call `ssax:skip-pi`. `ssax:read-attributes` may be useful as well (for PIs whose content is attribute-value pairs).
> END-token
>   The end tag is read completely; the current position is right after the terminating ``>`' character.
> COMMENT
>   is read and skipped completely. The current position is right after ``-->`' that terminates the comment.
> CDSECT
>   The current position is right after ``<!CDATA[`'. Use `ssax:read-cdata-body` to read the rest.
> DECL
>   We have read the keyword (the one that follows ``<!`') identifying this declaration markup. The current position is after the keyword (usually a whitespace character)
> START-token
>   We have read the keyword (GI) of this start tag. No attributes are scanned yet. We don't know if this tag has an empty content either. Use `ssax:complete-start-tag` to finish parsing of the token.

— Function: ssax:skip-pi port

> The current position is inside a PI. Skip till the rest of the PI

— Function: ssax:read-pi-body-as-string port

> The current position is right after reading the PITarget. We read the body of PI and return is as a string. The port will point to the character right after ``?>`' combination that terminates PI.

>               [16] PI ::= '<?' PITarget (S (Char* - (Char* '?>' Char*)))? '?>'

— Function: ssax:skip-internal-dtd port

> The current pos in the port is inside an internal DTD subset (e.g., after reading ``#\[`' that begins an internal DTD subset) Skip until the ``]>`' combination that terminates this DTD.

— Function: ssax:read-cdata-body port str-handler seed

> This procedure must be called after we have read a string ``<![CDATA[`' that begins a CDATA section. The current position must be the first position of the CDATA body. This function reads lines of the CDATA body and passes them to a str-handler, a character data consumer.

> str-handler is a procedure taking arguments: string1, string2, and seed. The first string1 argument to str-handler never contains a newline; the second string2 argument often will. On the first invocation of str-handler, seed is the one passed to `ssax:read-cdata-body` as the third argument. The result of this first invocation will be passed as the seed argument to the second invocation of the line consumer, and so on. The result of the last invocation of the str-handler is returned by the `ssax:read-cdata-body`. Note a similarity to the fundamental fold iterator.

> Within a CDATA section all characters are taken at their face value, with three exceptions:

> - CR, LF, and CRLF are treated as line delimiters, and passed as a single ``#\newline`' to str-handler
> - ``]]>`' combination is the end of the CDATA section. ``&gt;`' is treated as an embedded ``>`' character.
> - ``&lt;`' and ``&amp;`' are not specially recognized (and are not expanded)!

— Function: ssax:read-char-ref port

>               [66]  CharRef ::=  '&#' [0-9]+ ';'
>                                | '&#x' [0-9a-fA-F]+ ';'

> This procedure must be called after we we have read ``&#`' that introduces a char reference. The procedure reads this reference and returns the corresponding char. The current position in PORT will be after the ``;`' that terminates the char reference.

> Faults detected:
> WFC: XML-Spec.html#wf-Legalchar

> According to Section 4.1 Character and Entity References of the XML Recommendation:

> > "[Definition: A character reference refers to a specific character in the ISO/IEC 10646 character set, for example one not directly accessible from available input devices.]"

— Function: ssax:handle-parsed-entity port name entities content-handler str-handler seed

> Expands and handles a parsed-entity reference.

> name is a symbol, the name of the parsed entity to expand. content-handler is a procedure of arguments port, entities, and seed that returns a seed. str-handler is called if the entity in question is a pre-declared entity.

> `ssax:handle-parsed-entity` returns the result returned by content-handler or str-handler.

> Faults detected:
> WFC: XML-Spec.html#wf-entdeclared
> WFC: XML-Spec.html#norecursion

— Function: attlist-add attlist name-value

> Add a name-value pair to the existing attlist, preserving its sorted ascending order; and return the new list. Return #f if a pair with the same name already exists in attlist

— Function: attlist-remove-top attlist

> Given an non-null attlist, return a pair of values: the top and the rest.

— Function: ssax:read-attributes port entities

> This procedure reads and parses a production Attribute.

>               [41] Attribute ::= Name Eq AttValue
>               [10] AttValue ::=  '"' ([^<&"] | Reference)* '"'
>                               | "'" ([^<&'] | Reference)* "'"
>               [25] Eq ::= S? '=' S?

> The procedure returns an ATTLIST, of Name (as UNRES-NAME), Value (as string) pairs. The current character on the port is a non-whitespace character that is not an NCName-starting character.

> Note the following rules to keep in mind when reading an AttValue:

> > Before the value of an attribute is passed to the application or checked for validity, the XML processor must normalize it as follows:
> > - A character reference is processed by appending the referenced character to the attribute value.
> > - An entity reference is processed by recursively processing the replacement text of the entity. The named entities ``amp`', ``lt`', ``gt`', ``quot`', and ``apos`' are pre-declared.
> > - A whitespace character (#x20, #x0D, #x0A, #x09) is processed by appending #x20 to the normalized value, except that only a single #x20 is appended for a "#x0D#x0A" sequence that is part of an external parsed entity or the literal entity value of an internal parsed entity.
> > - Other characters are processed by appending them to the normalized value.

> Faults detected:
> WFC: XML-Spec.html#CleanAttrVals
> WFC: XML-Spec.html#uniqattspec

— Function: ssax:resolve-name port unres-name namespaces apply-default-ns?

> Convert an unres-name to a RES-NAME, given the appropriate namespaces declarations. The last parameter, apply-default-ns?, determines if the default namespace applies (for instance, it does not for attribute names).

> Per REC-xml-names/#nsc-NSDeclared, the "xml" prefix is considered pre-declared and bound to the namespace name "http://www.w3.org/XML/1998/namespace".

> `ssax:resolve-name` tests for the namespace constraints:
> http://www.w3.org/TR/REC-xml-names/#nsc-NSDeclared

— Function: ssax:complete-start-tag tag port elems entities namespaces

> Complete parsing of a start-tag markup. `ssax:complete-start-tag` must be called after the start tag token has been read. tag is an UNRES-NAME. elems is an instance of the ELEMS slot of XML-DECL; it can be #f to tell the function to do no validation of elements and their attributes.

> `ssax:complete-start-tag` returns several values:

> - ELEM-GI: a RES-NAME.
> - ATTRIBUTES: element's attributes, an ATTLIST of (RES-NAME . STRING) pairs. The list does NOT include xmlns attributes.
> - NAMESPACES: the input list of namespaces amended with namespace (re-)declarations contained within the start-tag under parsing
> - ELEM-CONTENT-MODEL

> On exit, the current position in port will be the first character after ``>`' that terminates the start-tag markup.

> Faults detected:
> VC: XML-Spec.html#enum
> VC: XML-Spec.html#RequiredAttr
> VC: XML-Spec.html#FixedAttr
> VC: XML-Spec.html#ValueType
> WFC: XML-Spec.html#uniqattspec (after namespaces prefixes are resolved)
> VC: XML-Spec.html#elementvalid
> WFC: REC-xml-names/#dt-NSName

> Note: although XML Recommendation does not explicitly say it, xmlns and xmlns: attributes don't have to be declared (although they can be declared, to specify their default value).

— Function: ssax:read-external-id port

> Parses an ExternalID production:

>               [75] ExternalID ::= 'SYSTEM' S SystemLiteral
>                                 | 'PUBLIC' S PubidLiteral S SystemLiteral
>               [11] SystemLiteral ::= ('"' [^"]* '"') | ("'" [^']* "'")
>               [12] PubidLiteral ::=  '"' PubidChar* '"'
>                                    | "'" (PubidChar - "'")* "'"
>               [13] PubidChar ::=  #x20 | #x0D | #x0A | [a-zA-Z0-9]
>                                        | [-'()+,./:=?;!*#@$_%]

> Call `ssax:read-external-id` when an ExternalID is expected; that is, the current character must be either #\S or #\P that starts correspondingly a SYSTEM or PUBLIC token. `ssax:read-external-id` returns the SystemLiteral as a string. A PubidLiteral is disregarded if present.

#### 4.11.5 Mid-Level Parsers and Scanners

These procedures parse productions corresponding to the whole (document) entity or its higher-level pieces (prolog, root element, etc).

— Function: ssax:scan-misc port

> Scan the Misc production in the context:

>               [1]  document ::=  prolog element Misc*
>               [22] prolog ::= XMLDecl? Misc* (doctypedec l Misc*)?
>               [27] Misc ::= Comment | PI |  S

> Call `ssax:scan-misc` in the prolog or epilog contexts. In these contexts, whitespaces are completely ignored. The return value from `ssax:scan-misc` is either a PI-token, a DECL-token, a START token, or *EOF*. Comments are ignored and not reported.

— Function: ssax:read-char-data port expect-eof? str-handler iseed

> Read the character content of an XML document or an XML element.

>               [43] content ::=
>               (element | CharData | Reference | CDSect | PI | Comment)*

> To be more precise, `ssax:read-char-data` reads CharData, expands CDSect and character entities, and skips comments. `ssax:read-char-data` stops at a named reference, EOF, at the beginning of a PI, or a start/end tag.

> expect-eof? is a boolean indicating if EOF is normal; i.e., the character data may be terminated by the EOF. EOF is normal while processing a parsed entity.

> iseed is an argument passed to the first invocation of str-handler.

> `ssax:read-char-data` returns two results: seed and token. The seed is the result of the last invocation of str-handler, or the original iseed if str-handler was never called.

> token can be either an eof-object (this can happen only if expect-eof? was #t), or:

> - an xml-token describing a START tag or an END-tag; For a start token, the caller has to finish reading it.
> - an xml-token describing the beginning of a PI. It's up to an application to read or skip through the rest of this PI;
> - an xml-token describing a named entity reference.

> CDATA sections and character references are expanded inline and never returned. Comments are silently disregarded.

> As the XML Recommendation requires, all whitespace in character data must be preserved. However, a CR character (#x0D) must be disregarded if it appears before a LF character (#x0A), or replaced by a #x0A character otherwise. See Secs. 2.10 and 2.11 of the XML Recommendation. See also the canonical XML Recommendation.

— Function: ssax:assert-token token kind gi error-cont

> Make sure that token is of anticipated kind and has anticipated gi. Note that the gi argument may actually be a pair of two symbols, Namespace-URI or the prefix, and of the localname. If the assertion fails, error-cont is evaluated by passing it three arguments: token kind gi. The result of error-cont is returned.

#### 4.11.6 High-level Parsers

These procedures are to instantiate a SSAX parser. A user can instantiate the parser to do the full validation, or no validation, or any particular validation. The user specifies which PI he wants to be notified about. The user tells what to do with the parsed character and element data. The latter handlers determine if the parsing follows a SAX or a DOM model.

— Function: ssax:make-pi-parser my-pi-handlers

> Create a parser to parse and process one Processing Element (PI).

> my-pi-handlers is an association list of pairs `(`pi-tag`.` pi-handler`)` where pi-tag is an NCName symbol, the PI target; and pi-handler is a procedure taking arguments port, pi-tag, and seed.

> pi-handler should read the rest of the PI up to and including the combination ``?>`' that terminates the PI. The handler should return a new seed. One of the pi-tags may be the symbol `*DEFAULT*`. The corresponding handler will handle PIs that no other handler will. If the *DEFAULT* pi-tag is not specified, `ssax:make-pi-parser` will assume the default handler that skips the body of the PI.

> `ssax:make-pi-parser` returns a procedure of arguments port, pi-tag, and seed; that will parse the current PI according to my-pi-handlers.

— Function: ssax:make-elem-parser my-new-level-seed my-finish-element my-char-data-handler my-pi-handlers

> Create a parser to parse and process one element, including its character content or children elements. The parser is typically applied to the root element of a document.

> my-new-level-seed
>   is a procedure taking arguments:

>   elem-gi attributes namespaces expected-content seed

>   where elem-gi is a RES-NAME of the element about to be processed.

>   my-new-level-seed is to generate the seed to be passed to handlers that process the content of the element.

> my-finish-element
>   is a procedure taking arguments:

>   elem-gi attributes namespaces parent-seed seed

>   my-finish-element is called when parsing of elem-gi is finished. The seed is the result from the last content parser (or from my-new-level-seed if the element has the empty content). parent-seed is the same seed as was passed to my-new-level-seed. my-finish-element is to generate a seed that will be the result of the element parser.

> my-char-data-handler
>   is a STR-HANDLER as described in Data Types above.
> my-pi-handlers
>   is as described for `ssax:make-pi-handler` above.

> The generated parser is a procedure taking arguments:

> start-tag-head port elems entities namespaces preserve-ws? seed

> The procedure must be called after the start tag token has been read. start-tag-head is an UNRES-NAME from the start-element tag. ELEMS is an instance of ELEMS slot of XML-DECL.

> Faults detected:
> VC: XML-Spec.html#elementvalid
> WFC: XML-Spec.html#GIMatch

— Function: ssax:make-parser user-handler-tag user-handler ...

> Create an XML parser, an instance of the XML parsing framework. This will be a SAX, a DOM, or a specialized parser depending on the supplied user-handlers.

> `ssax:make-parser` takes an even number of arguments; user-handler-tag is a symbol that identifies a procedure (or association list for `PROCESSING-INSTRUCTIONS`) (user-handler) that follows the tag. Given below are tags and signatures of the corresponding procedures. Not all tags have to be specified. If some are omitted, reasonable defaults will apply.

> ``DOCTYPE`'
>   handler-procedure: port docname systemid internal-subset? seed

>   If internal-subset? is #t, the current position in the port is right after we have read ``[`' that begins the internal DTD subset. We must finish reading of this subset before we return (or must call `skip-internal-dtd` if we aren't interested in reading it). port at exit must be at the first symbol after the whole DOCTYPE declaration.

>   The handler-procedure must generate four values:

>   > elems entities namespaces seed

>   elems is as defined for the ELEMS slot of XML-DECL. It may be #f to switch off validation. namespaces will typically contain user-prefixes for selected uri-symbs. The default handler-procedure skips the internal subset, if any, and returns `(values #f '() '() seed)`.

> ``UNDECL-ROOT`'
>   procedure: elem-gi seed

>   where elem-gi is an UNRES-NAME of the root element. This procedure is called when an XML document under parsing contains no DOCTYPE declaration.

>   The handler-procedure, as a DOCTYPE handler procedure above, must generate four values:

>   > elems entities namespaces seed

>   The default handler-procedure returns (values #f '() '() seed)

> ``DECL-ROOT`'
>   procedure: elem-gi seed

>   where elem-gi is an UNRES-NAME of the root element. This procedure is called when an XML document under parsing does contains the DOCTYPE declaration. The handler-procedure must generate a new seed (and verify that the name of the root element matches the doctype, if the handler so wishes). The default handler-procedure is the identity function.

> ``NEW-LEVEL-SEED`'
>   procedure: see ssax:make-elem-parser, my-new-level-seed
> ``FINISH-ELEMENT`'
>   procedure: see ssax:make-elem-parser, my-finish-element
> ``CHAR-DATA-HANDLER`'
>   procedure: see ssax:make-elem-parser, my-char-data-handler
> ``PROCESSING-INSTRUCTIONS`'
>   association list as is passed to `ssax:make-pi-parser`. The default value is '()

> The generated parser is a procedure of arguments port and seed.

> This procedure parses the document prolog and then exits to an element parser (created by `ssax:make-elem-parser`) to handle the rest.

>               [1]  document ::=  prolog element Misc*
>               [22] prolog ::= XMLDecl? Misc* (doctypedec | Misc*)?
>               [27] Misc ::= Comment | PI |  S
>               [28] doctypedecl ::=  '<!DOCTYPE' S Name (S ExternalID)? S?
>                             ('[' (markupdecl | PEReference | S)* ']' S?)? '>'
>               [29] markupdecl ::= elementdecl | AttlistDecl
>                                    | EntityDecl
>                                    | NotationDecl | PI
>                                    | Comment

#### 4.11.7 Parsing XML to SXML

— Function: ssax:xml->sxml port namespace-prefix-assig

> This is an instance of the SSAX parser that returns an SXML representation of the XML document to be read from port. namespace-prefix-assig is a list of `(`user-prefix`.` uri-string`)` that assigns user-prefixes to certain namespaces identified by particular uri-strings. It may be an empty list. `ssax:xml->sxml` returns an SXML tree. The port points out to the first character after the root element.

Next: Time and Date, Previous: Parsing XML, Up: Textual Conversion Packages

### 4.12 Printing Scheme

Next: Object-To-String, Previous: Printing Scheme, Up: Printing Scheme

#### 4.12.1 Generic-Write

`(require 'generic-write)` `generic-write` is a procedure that transforms a Scheme data value (or Scheme program expression) into its textual representation and prints it. The interface to the procedure is sufficiently general to easily implement other useful formatting procedures such as pretty printing, output to a string and truncated output.

— Procedure: generic-write obj display? width output

> obj
>   Scheme data value to transform.
> display?
>   Boolean, controls whether characters and strings are quoted.
> width
>   Extended boolean, selects format:
>   #f
>     single line format
>   integer > 0
>     pretty-print (value = max nb of chars per line)
> output
>   Procedure of 1 argument of string type, called repeatedly with successive substrings of the textual representation. This procedure can return `#f` to stop the transformation.

> The value returned by `generic-write` is undefined.

> Examples:

>               (write obj) == (generic-write obj #f #f display-string)
>               (display obj) == (generic-write obj #t #f display-string)

> where

>               display-string ==
>               (lambda (s) (for-each write-char (string->list s)) #t)

Next: Pretty-Print, Previous: Generic-Write, Up: Printing Scheme

#### 4.12.2 Object-To-String

`(require 'object->string)`

— Function: object->string obj

> Returns the textual representation of obj as a string.

— Function: object->limited-string obj limit

> Returns the textual representation of obj as a string of length at most limit.

Previous: Object-To-String, Up: Printing Scheme

#### 4.12.3 Pretty-Print

`(require 'pretty-print)`

— Procedure: pretty-print obj
— Procedure: pretty-print obj port

> `pretty-print`s obj on port. If port is not specified, `current-output-port` is used.

> Example:

>               (pretty-print '((1 2 3 4 5) (6 7 8 9 10) (11 12 13 14 15)
>                               (16 17 18 19 20) (21 22 23 24 25)))
>                  -| ((1 2 3 4 5)
>                  -|  (6 7 8 9 10)
>                  -|  (11 12 13 14 15)
>                  -|  (16 17 18 19 20)
>                  -|  (21 22 23 24 25))

— Procedure: pretty-print->string obj
— Procedure: pretty-print->string obj width

> Returns the string of obj `pretty-print`ed in width columns. If width is not specified, `(output-port-width)` is used.

> Example:

>               (pretty-print->string '((1 2 3 4 5) (6 7 8 9 10) (11 12 13 14 15)
>                                       (16 17 18 19 20) (21 22 23 24 25)))
>               =>
>               "((1 2 3 4 5)
>                (6 7 8 9 10)
>                (11 12 13 14 15)
>                (16 17 18 19 20)
>                (21 22 23 24 25))
>               "
>               (pretty-print->string '((1 2 3 4 5) (6 7 8 9 10) (11 12 13 14 15)
>                                       (16 17 18 19 20) (21 22 23 24 25))
>                                     16)
>               =>
>               "((1 2 3 4 5)
>                (6 7 8 9 10)
>                (11
>                 12
>                 13
>                 14
>                 15)
>                (16
>                 17
>                 18
>                 19
>                 20)
>                (21
>                 22
>                 23
>                 24
>                 25))
>               "

`(require 'pprint-file)`

— Procedure: pprint-file infile
— Procedure: pprint-file infile outfile

> Pretty-prints all the code in infile. If outfile is specified, the output goes to outfile, otherwise it goes to `(current-output-port)`.

— Function: pprint-filter-file infile proc outfile
— Function: pprint-filter-file infile proc

> infile is a port or a string naming an existing file. Scheme source code expressions and definitions are read from the port (or file) and proc is applied to them sequentially.

> outfile is a port or a string. If no outfile is specified then `current-output-port` is assumed. These expanded expressions are then `pretty-print`ed to this port.

> Whitepsace and comments (introduced by `;`) which are not part of scheme expressions are reproduced in the output. This procedure does not affect the values returned by `current-input-port` and `current-output-port`.

`pprint-filter-file` can be used to pre-compile macro-expansion and thus can reduce loading time. The following will write into `exp-code.scm` the result of expanding all defmacros in `code.scm`.

         (require 'pprint-file)
         (require 'defmacroexpand)
         (defmacro:load "my-macros.scm")
         (pprint-filter-file "code.scm" defmacro:expand* "exp-code.scm")

Next: NCBI-DNA, Previous: Printing Scheme, Up: Textual Conversion Packages

### 4.13 Time and Date

If `(provided? 'current-time)`:

The procedures `current-time`, `difftime`, and `offset-time` deal with a calendar time datatype which may or may not be disjoint from other Scheme datatypes.

— Function: current-time

> Returns the time since 00:00:00 GMT, January 1, 1970, measured in seconds. Note that the reference time is different from the reference time for `get-universal-time` in Common-Lisp Time.

— Function: difftime caltime1 caltime0

> Returns the difference (number of seconds) between twe calendar times: caltime1 - caltime0. caltime0 may also be a number.

— Function: offset-time caltime offset

> Returns the calendar time of caltime offset by offset number of seconds `(+ caltime offset)`.

Next: Posix Time, Previous: Time and Date, Up: Time and Date

#### 4.13.1 Time Zone

(require 'time-zone)

— Data Format: TZ-string

> POSIX standards specify several formats for encoding time-zone rules.

> `:`<pathname>
>   If the first character of <pathname> is ``/`', then <pathname> specifies the absolute pathname of a tzfile(5) format time-zone file. Otherwise, <pathname> is interpreted as a pathname within tzfile:vicinity (/usr/lib/zoneinfo/) naming a tzfile(5) format time-zone file.
> <std><offset>
>   The string <std> consists of 3 or more alphabetic characters. <offset> specifies the time difference from GMT. The <offset> is positive if the local time zone is west of the Prime Meridian and negative if it is east. <offset> can be the number of hours or hours and minutes (and optionally seconds) separated by ``:`'. For example, `-4:30`.
> <std><offset><dst>
>   <dst> is the at least 3 alphabetic characters naming the local daylight-savings-time.
> <std><offset><dst><doffset>
>   <doffset> specifies the offset from the Prime Meridian when daylight-savings-time is in effect.

> The non-tzfile formats can optionally be followed by transition times specifying the day and time when a zone changes from standard to daylight-savings and back again.

> `,`<date>`/`<time>`,`<date>`/`<time>
>   The <time>s are specified like the <offset>s above, except that leading ``+`' and ``-`' are not allowed.

>   Each <date> has one of the formats:

>   `J`<day>
>     specifies the Julian day with <day> between 1 and 365. February 29 is never counted and cannot be referenced.
>   <day>
>     This specifies the Julian day with n between 0 and 365. February 29 is counted in leap years and can be specified.
>   `M`<month>`.`<week>`.`<day>
>     This specifies day <day> (0 <= <day> <= 6) of week <week> (1 <= <week> <= 5) of month <month> (1 <= <month> <= 12). Week 1 is the first week in which day d occurs and week 5 is the last week in which day <day> occurs. Day 0 is a Sunday.

— Data Type: time-zone

> is a datatype encoding how many hours from Greenwich Mean Time the local time is, and the Daylight Savings Time rules for changing it.

— Function: time-zone TZ-string

> Creates and returns a time-zone object specified by the string TZ-string. If `time-zone` cannot interpret TZ-string, `#f` is returned.

— Function: tz:params caltime tz

> tz is a time-zone object. `tz:params` returns a list of three items:

> 0. An integer. 0 if standard time is in effect for timezone tz at caltime; 1 if daylight savings time is in effect for timezone tz at caltime.
> 1. The number of seconds west of the Prime Meridian timezone tz is at caltime.
> 2. The name for timezone tz at caltime.

> `tz:params` is unaffected by the default timezone; inquiries can be made of any timezone at any calendar time.

— Function: tz:std-offset tz

> tz is a time-zone object. `tz:std-offset` returns the number of seconds west of the Prime Meridian timezone tz is.

The rest of these procedures and variables are provided for POSIX compatability. Because of shared state they are not thread-safe.

— Function: tzset

> Returns the default time-zone. — Function: tzset tz

> > Sets (and returns) the default time-zone to tz. — Function: tzset TZ-string

> > > Sets (and returns) the default time-zone to that specified by TZ-string.

> > > `tzset` also sets the variables *timezone*, daylight?, and tzname. This function is automatically called by the time conversion procedures which depend on the time zone (see Time and Date).

— Variable: *timezone*

> Contains the difference, in seconds, between Greenwich Mean Time and local standard time (for example, in the U.S. Eastern time zone (EST), timezone is 5*60*60). `*timezone*` is initialized by `tzset`.

— Variable: daylight?

> is `#t` if the default timezone has rules for Daylight Savings Time. Note: daylight? does not tell you when Daylight Savings Time is in effect, just that the default zone sometimes has Daylight Savings Time.

— Variable: tzname

> is a vector of strings. Index 0 has the abbreviation for the standard timezone; If daylight?, then index 1 has the abbreviation for the Daylight Savings timezone.

Next: Common-Lisp Time, Previous: Time Zone, Up: Time and Date

#### 4.13.2 Posix Time

         (require 'posix-time)

— Data Type: Calendar-Time

> is a datatype encapsulating time.

— Data Type: Coordinated Universal Time

> (abbreviated UTC) is a vector of integers representing time:

> 0. seconds (0 - 61)
> 1. minutes (0 - 59)
> 2. hours since midnight (0 - 23)
> 3. day of month (1 - 31)
> 4. month (0 - 11). Note difference from `decode-universal-time`.
> 5. the number of years since 1900. Note difference from `decode-universal-time`.
> 6. day of week (0 - 6)
> 7. day of year (0 - 365)
> 8. 1 for daylight savings, 0 for regular time

— Function: gmtime caltime

> Converts the calendar time caltime to UTC and returns it. — Function: localtime caltime tz

> > Returns caltime converted to UTC relative to timezone tz. — Function: localtime caltime

> > > converts the calendar time caltime to a vector of integers expressed relative to the user's time zone. `localtime` sets the variable *timezone* with the difference between Coordinated Universal Time (UTC) and local standard time in seconds (see tzset).

— Function: gmktime univtime

> Converts a vector of integers in GMT Coordinated Universal Time (UTC) format to a calendar time. — Function: mktime univtime

> > Converts a vector of integers in local Coordinated Universal Time (UTC) format to a calendar time. — Function: mktime univtime tz

> > > Converts a vector of integers in Coordinated Universal Time (UTC) format (relative to time-zone tz) to calendar time.

— Function: asctime univtime

> Converts the vector of integers caltime in Coordinated Universal Time (UTC) format into a string of the form `"Wed Jun 30 21:49:08 1993"`.

— Function: gtime caltime
— Function: ctime caltime
— Function: ctime caltime tz

> Equivalent to `(asctime (gmtime` caltime`))`, `(asctime (localtime` caltime`))`, and `(asctime (localtime` caltime tz`))`, respectively.

Next: Time Infrastructure, Previous: Posix Time, Up: Time and Date

#### 4.13.3 Common-Lisp Time

— Function: get-decoded-time

> Equivalent to `(decode-universal-time (get-universal-time))`.

— Function: get-universal-time

> Returns the current time as Universal Time, number of seconds since 00:00:00 Jan 1, 1900 GMT. Note that the reference time is different from `current-time`.

— Function: decode-universal-time univtime

> Converts univtime to Decoded Time format. Nine values are returned:

> 0. seconds (0 - 61)
> 1. minutes (0 - 59)
> 2. hours since midnight
> 3. day of month
> 4. month (1 - 12). Note difference from `gmtime` and `localtime`.
> 5. year (A.D.). Note difference from `gmtime` and `localtime`.
> 6. day of week (0 - 6)
> 7. #t for daylight savings, #f otherwise
> 8. hours west of GMT (-24 - +24)

> Notice that the values returned by `decode-universal-time` do not match the arguments to `encode-universal-time`.

— Function: encode-universal-time second minute hour date month year
— Function: encode-universal-time second minute hour date month year time-zone

> Converts the arguments in Decoded Time format to Universal Time format. If time-zone is not specified, the returned time is adjusted for daylight saving time. Otherwise, no adjustment is performed.

> Notice that the values returned by `decode-universal-time` do not match the arguments to `encode-universal-time`.

Previous: Common-Lisp Time, Up: Time and Date

#### 4.13.4 Time Infrastructure

`(require 'time-core)`

— Function: time:gmtime tm
— Function: time:invert decoder target
— Function: time:split t tm_isdst tm_gmtoff tm_zone

`(require 'tzfile)`

— Function: tzfile:read path

Next: Schmooz, Previous: Time and Date, Up: Textual Conversion Packages

### 4.14 NCBI-DNA

`(require 'ncbi-dma)`

— Function: ncbi:read-dna-sequence port

> Reads the NCBI-format DNA sequence following the word ``ORIGIN`' from port.

— Function: ncbi:read-file file

> Reads the NCBI-format DNA sequence following the word ``ORIGIN`' from file.

— Function: mrna<-cdna str

> Replaces ``T`' with ``U`' in str

— Function: codons<-cdna cdna

> Returns a list of three-letter symbol codons comprising the protein sequence encoded by cdna starting with its first occurence of ``atg`'.

— Function: protein<-cdna cdna

> Returns a list of three-letter symbols for the protein sequence encoded by cdna starting with its first occurence of ``atg`'.

— Function: p<-cdna cdna

> Returns a string of one-letter amino acid codes for the protein sequence encoded by cdna starting with its first occurence of ``atg`'.

These cDNA count routines provide a means to check the nucleotide sequence with the ``BASE COUNT`' line preceding the sequence from NCBI.

— Function: cdna:base-count cdna

> Returns a list of counts of ``a`', ``c`', ``g`', and ``t`' occurrencing in cdna.

— Function: cdna:report-base-count cdna

> Prints the counts of ``a`', ``c`', ``g`', and ``t`' occurrencing in cdna.

Previous: NCBI-DNA, Up: Textual Conversion Packages

### 4.15 Schmooz

Schmooz is a simple, lightweight markup language for interspersing Texinfo documentation with Scheme source code. Schmooz does not create the top level Texinfo file; it creates ``txi`' files which can be imported into the documentation using the Texinfo command ``@include`'.

`(require 'schmooz)` defines the function `schmooz`, which is used to process files. Files containing schmooz documentation should not contain `(require 'schmooz)`.

— Procedure: schmooz filename.scm ...

> Filename.scm should be a string ending with ``.scm`' naming an existing file containing Scheme source code. `schmooz` extracts top-level comments containing schmooz commands from filename.scm and writes the converted Texinfo source to a file named filename.txi. — Procedure: schmooz filename.texi ...
> — Procedure: schmooz filename.tex ...
> — Procedure: schmooz filename.txi ...

> > Filename should be a string naming an existing file containing Texinfo source code. For every occurrence of the string ``@include filename.txi`' within that file, `schmooz` calls itself with the argument ``filename.scm`'.

Schmooz comments are distinguished (from non-schmooz comments) by their first line, which must start with an at-sign (@) preceded by one or more semicolons (`;`). A schmooz comment ends at the first subsequent line which does not start with a semicolon. Currently schmooz comments are recognized only at top level.

Schmooz comments are copied to the Texinfo output file with the leading contiguous semicolons removed. Certain character sequences starting with at-sign are treated specially. Others are copied unchanged.

A schmooz comment starting with ``@body`' must be followed by a Scheme definition. All comments between the ``@body`' line and the definition will be included in a Texinfo definition, either a ``@defun`' or a ``@defvar`', depending on whether a procedure or a variable is being defined.

Within the text of that schmooz comment, at-sign followed by ``0`' will be replaced by `@code{procedure-name}` if the following definition is of a procedure; or `@var{variable}` if defining a variable.

An at-sign followed by a non-zero digit will expand to the variable citation of that numbered argument: ``@var{argument-name}`'.

If more than one definition follows a ``@body`' comment line without an intervening blank or comment line, then those definitions will be included in the same Texinfo definition using ``@defvarx`' or ``@defunx`', depending on whether the first definition is of a variable or of a procedure.

Schmooz can figure out whether a definition is of a procedure if it is of the form:

``(define (<identifier> <arg> ...) <expression>)`'

or if the left hand side of the definition is some form ending in a lambda expression. Obviously, it can be fooled. In order to force recognition of a procedure definition, start the documentation with ``@args`' instead of ``@body`'. ``@args`' should be followed by the argument list of the function being defined, which may be enclosed in parentheses and delimited by whitespace, (as in Scheme), enclosed in braces and separated by commas, (as in Texinfo), or consist of the remainder of the line, separated by whitespace.

For example:

         ;;@args arg1 args ...
         ;;@0 takes argument @1 and any number of @2
         (define myfun (some-function-returning-magic))

Will result in:

         @defun myfun arg1 args @dots{}

         @code{myfun} takes argument @var{arg1} and any number of @var{args}
         @end defun

``@args`' may also be useful for indicating optional arguments by name. If ``@args`' occurs inside a schmooz comment section, rather than at the beginning, then it will generate a ``@defunx`' line with the arguments supplied.

If the first at-sign in a schmooz comment is immediately followed by whitespace, then the comment will be expanded to whatever follows that whitespace. If the at-sign is followed by a non-whitespace character then the at-sign will be included as the first character of the expansion. This feature is intended to make it easy to include Texinfo directives in schmooz comments.

Next: Database Packages, Previous: Textual Conversion Packages, Up: Top

## 5 Mathematical Packages

Next: Modular Arithmetic, Previous: Mathematical Packages, Up: Mathematical Packages

### 5.1 Bit-Twiddling

`(require 'logical)` or `(require 'srfi-60)` The bit-twiddling functions are made available through the use of the `logical` package. `logical` is loaded by inserting `(require 'logical)` before the code that uses these functions. These functions behave as though operating on integers in two's-complement representation.

#### 5.1.1 Bitwise Operations

— Function: logand n1 ...
— Function: bitwise-and n1 ...

> Returns the integer which is the bit-wise AND of the integer arguments.

> Example:

>               (number->string (logand #b1100 #b1010) 2)
>                  => "1000"

— Function: logior n1 ...
— Function: bitwise-ior n1 ...

> Returns the integer which is the bit-wise OR of the integer arguments.

> Example:

>               (number->string (logior #b1100 #b1010) 2)
>                  => "1110"

— Function: logxor n1 ...
— Function: bitwise-xor n1 ...

> Returns the integer which is the bit-wise XOR of the integer arguments.

> Example:

>               (number->string (logxor #b1100 #b1010) 2)
>                  => "110"

— Function: lognot n
— Function: bitwise-not n

> Returns the integer which is the one's-complement of the integer argument.

> Example:

>               (number->string (lognot #b10000000) 2)
>                  => "-10000001"
>               (number->string (lognot #b0) 2)
>                  => "-1"

— Function: bitwise-if mask n0 n1
— Function: bitwise-merge mask n0 n1

> Returns an integer composed of some bits from integer n0 and some from integer n1. A bit of the result is taken from n0 if the corresponding bit of integer mask is 1 and from n1 if that bit of mask is 0.

— Function: logtest j k
— Function: any-bits-set? j k

>               (logtest j k) == (not (zero? (logand j k)))

>               (logtest #b0100 #b1011) => #f
>               (logtest #b0100 #b0111) => #t

#### 5.1.2 Integer Properties

— Function: logcount n

> Returns the number of bits in integer n. If integer is positive, the 1-bits in its binary representation are counted. If negative, the 0-bits in its two's-complement binary representation are counted. If 0, 0 is returned.

> Example:

>               (logcount #b10101010)
>                  => 4
>               (logcount 0)
>                  => 0
>               (logcount -2)
>                  => 1

On `discuss@r6rs.org` Ben Harris credits Simon Tatham with the idea to have `bitwise-bit-count` return a negative count for negative inputs. Alan Bawden came up with the succinct invariant.

— Function: bitwise-bit-count n

> If n is non-negative, this procedure returns the number of 1 bits in the two's-complement representation of n. Otherwise it returns the result of the following computation:

>               (bitwise-not (bitwise-bit-count (bitwise-not n)))

— Function: integer-length n

> Returns the number of bits neccessary to represent n.

> Example:

>               (integer-length #b10101010)
>                  => 8
>               (integer-length 0)
>                  => 0
>               (integer-length #b1111)
>                  => 4

— Function: log2-binary-factors n
— Function: first-set-bit n

> Returns the number of factors of two of integer n. This value is also the bit-index of the least-significant ``1`' bit in n.

>               (require 'printf)
>               (do ((idx 0 (+ 1 idx)))
>                     ((> idx 16))
>                   (printf "%s(%3d) ==> %-5d %s(%2d) ==> %-5d\n"
>                           'log2-binary-factors
>                           (- idx) (log2-binary-factors (- idx))
>                           'log2-binary-factors
>                           idx (log2-binary-factors idx)))
>               -|
>               log2-binary-factors(  0) ==> -1    log2-binary-factors( 0) ==> -1
>               log2-binary-factors( -1) ==> 0     log2-binary-factors( 1) ==> 0
>               log2-binary-factors( -2) ==> 1     log2-binary-factors( 2) ==> 1
>               log2-binary-factors( -3) ==> 0     log2-binary-factors( 3) ==> 0
>               log2-binary-factors( -4) ==> 2     log2-binary-factors( 4) ==> 2
>               log2-binary-factors( -5) ==> 0     log2-binary-factors( 5) ==> 0
>               log2-binary-factors( -6) ==> 1     log2-binary-factors( 6) ==> 1
>               log2-binary-factors( -7) ==> 0     log2-binary-factors( 7) ==> 0
>               log2-binary-factors( -8) ==> 3     log2-binary-factors( 8) ==> 3
>               log2-binary-factors( -9) ==> 0     log2-binary-factors( 9) ==> 0
>               log2-binary-factors(-10) ==> 1     log2-binary-factors(10) ==> 1
>               log2-binary-factors(-11) ==> 0     log2-binary-factors(11) ==> 0
>               log2-binary-factors(-12) ==> 2     log2-binary-factors(12) ==> 2
>               log2-binary-factors(-13) ==> 0     log2-binary-factors(13) ==> 0
>               log2-binary-factors(-14) ==> 1     log2-binary-factors(14) ==> 1
>               log2-binary-factors(-15) ==> 0     log2-binary-factors(15) ==> 0
>               log2-binary-factors(-16) ==> 4     log2-binary-factors(16) ==> 4

#### 5.1.3 Bit Within Word

— Function: logbit? index n
— Function: bit-set? index n

>               (logbit? index n) == (logtest (expt 2 index) n)

>               (logbit? 0 #b1101) => #t
>               (logbit? 1 #b1101) => #f
>               (logbit? 2 #b1101) => #t
>               (logbit? 3 #b1101) => #t
>               (logbit? 4 #b1101) => #f

— Function: copy-bit index from bit

> Returns an integer the same as from except in the indexth bit, which is 1 if bit is `#t` and 0 if bit is `#f`.

> Example:

>               (number->string (copy-bit 0 0 #t) 2)       => "1"
>               (number->string (copy-bit 2 0 #t) 2)       => "100"
>               (number->string (copy-bit 2 #b1111 #f) 2)  => "1011"

#### 5.1.4 Field of Bits

— Function: bit-field n start end

> Returns the integer composed of the start (inclusive) through end (exclusive) bits of n. The startth bit becomes the 0-th bit in the result.

> Example:

>               (number->string (bit-field #b1101101010 0 4) 2)
>                  => "1010"
>               (number->string (bit-field #b1101101010 4 9) 2)
>                  => "10110"

— Function: copy-bit-field to from start end

> Returns an integer the same as to except possibly in the start (inclusive) through end (exclusive) bits, which are the same as those of from. The 0-th bit of from becomes the startth bit of the result.

> Example:

>               (number->string (copy-bit-field #b1101101010 0 0 4) 2)
>                       => "1101100000"
>               (number->string (copy-bit-field #b1101101010 -1 0 4) 2)
>                       => "1101101111"
>               (number->string (copy-bit-field #b110100100010000 -1 5 9) 2)
>                       => "110100111110000"

— Function: ash n count
— Function: arithmetic-shift n count

> Returns an integer equivalent to `(inexact->exact (floor (*` n`(expt 2` count`))))`.

> Example:

>               (number->string (ash #b1 3) 2)
>                  => "1000"
>               (number->string (ash #b1010 -1) 2)
>                  => "101"

— Function: rotate-bit-field n count start end

> Returns n with the bit-field from start to end cyclically permuted by count bits towards high-order.

> Example:

>               (number->string (rotate-bit-field #b0100 3 0 4) 2)
>                   => "10"
>               (number->string (rotate-bit-field #b0100 -1 0 4) 2)
>                   => "10"
>               (number->string (rotate-bit-field #b110100100010000 -1 5 9) 2)
>                   => "110100010010000"
>               (number->string (rotate-bit-field #b110100100010000 1 5 9) 2)
>                   => "110100000110000"

— Function: reverse-bit-field n start end

> Returns n with the order of bits start to end reversed.

>               (number->string (reverse-bit-field #xa7 0 8) 16)
>                 => "e5"

#### 5.1.5 Bits as Booleans

— Function: integer->list k len
— Function: integer->list k

> `integer->list` returns a list of len booleans corresponding to each bit of the given integer. #t is coded for each 1; #f for 0. The len argument defaults to `(integer-length` k`)`. — Function: list->integer list

> > `list->integer` returns an integer formed from the booleans in the list list, which must be a list of booleans. A 1 bit is coded for each #t; a 0 bit for #f.

> > `integer->list` and `list->integer` are inverses so far as `equal?` is concerned.

— Function: booleans->integer bool1 ...

> Returns the integer coded by the bool1 ... arguments.

Next: Irrational Integer Functions, Previous: Bit-Twiddling, Up: Mathematical Packages

### 5.2 Modular Arithmetic

`(require 'modular)`

— Function: extended-euclid n1 n2

> Returns a list of 3 integers `(d x y)` such that d = gcd(n1, n2) = n1 * x + n2 * y.

— Function: symmetric:modulus m

> For odd positive integer m, returns an object suitable for passing as the first argument to `modular:` procedures, directing them to return a symmetric modular number, ie. an n such that

>               (<= (quotient m -2) n (quotient m 2)

— Function: modular:characteristic modulus

> Returns the non-negative integer characteristic of the ring formed when modulus is used with `modular:` procedures.

— Function: modular:normalize modulus n

> Returns the integer `(modulo` n`(modular:characteristic` modulus`))` in the representation specified by modulus.

The rest of these functions assume normalized arguments; That is, the arguments are constrained by the following table:

For all of these functions, if the first argument (modulus) is:

`positive?`
  Integers mod modulus. The result is between 0 and modulus.
`zero?`
  The arguments are treated as integers. An integer is returned.

Otherwise, if modulus is a value returned by `(symmetric:modulus` radix`)`, then the arguments and result are treated as members of the integers modulo radix, but with symmetric representation; i.e.

         (<= (quotient radix 2) n (quotient (- -1 radix) 2)

If all the arguments are fixnums the computation will use only fixnums.

— Function: modular:invertable? modulus k

> Returns `#t` if there exists an integer n such that k * n == 1 mod modulus, and `#f` otherwise.

— Function: modular:invert modulus n2

> Returns an integer n such that 1 = (n * n2) mod modulus. If n2 has no inverse mod modulus an error is signaled.

— Function: modular:negate modulus n2

> Returns (−n2) mod modulus.

— Function: modular:+ modulus n2 n3

> Returns (n2 + n3) mod modulus.

— Function: modular:- modulus n2 n3

> Returns (n2 − n3) mod modulus.

— Function: modular:* modulus n2 n3

> Returns (n2 * n3) mod modulus.

> The Scheme code for `modular:*` with negative modulus is not completed for fixnum-only implementations.

— Function: modular:expt modulus n2 n3

> Returns (n2 ^ n3) mod modulus.

Next: Irrational Real Functions, Previous: Modular Arithmetic, Up: Mathematical Packages

### 5.3 Irrational Integer Functions

`(require 'math-integer)`

— Function: integer-expt n1 n2

> Returns n1 raised to the power n2 if that result is an exact integer; otherwise signals an error.

> `(integer-expt 0` n2`)`

> returns 1 for n2 equal to 0; returns 0 for positive integer n2; signals an error otherwise.

— Function: integer-log base k

> Returns the largest exact integer whose power of base is less than or equal to k. If base or k is not a positive exact integer, then `integer-log` signals an error.

— Function: integer-sqrt k

> For non-negative integer k returns the largest integer whose square is less than or equal to k; otherwise signals an error.

— Variable: quotient
— Variable: remainder
— Variable: modulo

> are redefined so that they accept only exact-integer arguments.

Next: Prime Numbers, Previous: Irrational Integer Functions, Up: Mathematical Packages

### 5.4 Irrational Real Functions

`(require 'math-real)` Although this package defines real and complex functions, it is safe to load into an integer-only implementation; those functions will be defined to #f.

— Function: real-exp x
— Function: real-ln x
— Function: real-log y x
— Function: real-sin x
— Function: real-cos x
— Function: real-tan x
— Function: real-asin x
— Function: real-acos x
— Function: real-atan x
— Function: atan y x

> These procedures are part of every implementation that supports general real numbers; they compute the usual transcendental functions. ``real-ln`' computes the natural logarithm of x; ``real-log`' computes the logarithm of x base y, which is `(/ (real-ln x) (real-ln y))`. If arguments x and y are not both real; or if the correct result would not be real, then these procedures signal an error.

— Function: real-sqrt x

> For non-negative real x the result will be its positive square root; otherwise an error will be signaled.

— Function: real-expt x1 x2

> Returns x1 raised to the power x2 if that result is a real number; otherwise signals an error.

> `(real-expt 0.0` x2`)`

> - returns 1.0 for x2 equal to 0.0;
> - returns 0.0 for positive real x2;
> - signals an error otherwise.

— Function: quo x1 x2
— Function: rem x1 x2
— Function: mod x1 x2

> x2 should be non-zero.

>                   (quo x1 x2)                     ==> n_q
>                   (rem x1 x2)                     ==> x_r
>                   (mod x1 x2)                     ==> x_m

> where n_q is x1/x2 rounded towards zero, 0 < |x_r| < |x2|, 0 < |x_m| < |x2|, x_r and x_m differ from x1 by a multiple of x2, x_r has the same sign as x1, and x_m has the same sign as x2.

> From this we can conclude that for x2 not equal to 0,

>                    (= x1 (+ (* x2 (quo x1 x2))
>                          (rem x1 x2)))
>                                                      ==>  #t

> provided all numbers involved in that computation are exact.

>                   (quo 2/3 1/5)                         ==>  3
>                   (mod 2/3 1/5)                         ==>  1/15

>                   (quo .666 1/5)                        ==>  3.0
>                   (mod .666 1/5)                        ==>  65.99999999999995e-3

— Function: ln z

> These procedures are part of every implementation that supports general real numbers. ``Ln`' computes the natural logarithm of z

> In general, the mathematical function ln is multiply defined. The value of ln z is defined to be the one whose imaginary part lies in the range from -pi (exclusive) to pi (inclusive).

— Function: abs x

> For real argument x, ``Abs`' returns the absolute value of x' otherwise it signals an error.

>     (abs -7)                               ==>  7

— Function: make-rectangular x1 x2
— Function: make-polar x3 x4

> These procedures are part of every implementation that supports general complex numbers. Suppose x1, x2, x3, and x4 are real numbers and z is a complex number such that

> z = x1 + x2i = x3 . e^i x4

> Then

>     (make-rectangular x1 x2)               ==> z
>          (make-polar x3 x4)                     ==> z

> where -pi < x_angle <= pi with x_angle = x4 + 2pi n for some integer n.

> If an argument is not real, then these procedures signal an error.

Next: Random Numbers, Previous: Irrational Real Functions, Up: Mathematical Packages

### 5.5 Prime Numbers

`(require 'factor)`

— Variable: prime:prngs

> prime:prngs is the random-state (see Random Numbers) used by these procedures. If you call these procedures from more than one thread (or from interrupt), `random` may complain about reentrant calls.

Note: The prime test and generation procedures implement (or use) the Solovay-Strassen primality test. See

- Robert Solovay and Volker Strassen, A Fast Monte-Carlo Test for Primality, SIAM Journal on Computing, 1977, pp 84-85.

— Function: jacobi-symbol p q

> Returns the value (+1, −1, or 0) of the Jacobi-Symbol of exact non-negative integer p and exact positive odd integer q.

— Variable: prime:trials

> prime:trials the maxinum number of iterations of Solovay-Strassen that will be done to test a number for primality.

— Function: prime? n

> Returns `#f` if n is composite; `#t` if n is prime. There is a slight chance `(expt 2 (- prime:trials))` that a composite will return `#t`.

— Function: primes< start count

> Returns a list of the first count prime numbers less than start. If there are fewer than count prime numbers less than start, then the returned list will have fewer than start elements.

— Function: primes> start count

> Returns a list of the first count prime numbers greater than start.

— Function: factor k

> Returns a list of the prime factors of k. The order of the factors is unspecified. In order to obtain a sorted list do `(sort! (factor` k`) <)`.

Next: Discrete Fourier Transform, Previous: Prime Numbers, Up: Mathematical Packages

### 5.6 Random Numbers

A pseudo-random number generator is only as good as the tests it passes. George Marsaglia of Florida State University developed a battery of tests named DIEHARD (http://stat.fsu.edu/~geo/diehard.html). `diehard.c` has a bug which the patch http://swiss.csail.mit.edu/ftpdir/users/jaffer/diehard.c.pat corrects.

SLIB's PRNG generates 8 bits at a time. With the degenerate seed ``0`', the numbers generated pass DIEHARD; but when bits are combined from sequential bytes, tests fail. With the seed ``http://swissnet.ai.mit.edu/~jaffer/SLIB.html`', all of those tests pass.

Next: Inexact Random Numbers, Previous: Random Numbers, Up: Random Numbers

#### 5.6.1 Exact Random Numbers

`(require 'random)`

— Function: random n state
— Function: random n

> n must be an exact positive integer. `random` returns an exact integer between zero (inclusive) and n (exclusive). The values returned by `random` are uniformly distributed from 0 to n.

> The optional argument state must be of the type returned by `(seed->random-state)` or `(make-random-state)`. It defaults to the value of the variable `*random-state*`. This object is used to maintain the state of the pseudo-random-number generator and is altered as a side effect of calls to `random`.

— Variable: *random-state*

> Holds a data structure that encodes the internal state of the random-number generator that `random` uses by default. The nature of this data structure is implementation-dependent. It may be printed out and successfully read back in, but may or may not function correctly as a random-number state object in another implementation.

— Function: copy-random-state state

> Returns a new copy of argument state. — Function: copy-random-state

> > Returns a new copy of `*random-state*`.

— Function: seed->random-state seed

> Returns a new object of type suitable for use as the value of the variable `*random-state*` or as a second argument to `random`. The number or string seed is used to initialize the state. If `seed->random-state` is called twice with arguments which are `equal?`, then the returned data structures will be `equal?`. Calling `seed->random-state` with unequal arguments will nearly always return unequal states.

— Function: make-random-state
— Function: make-random-state obj

> Returns a new object of type suitable for use as the value of the variable `*random-state*` or as a second argument to `random`. If the optional argument obj is given, it should be a printable Scheme object; the first 50 characters of its printed representation will be used as the seed. Otherwise the value of `*random-state*` is used as the seed.

Previous: Exact Random Numbers, Up: Random Numbers

#### 5.6.2 Inexact Random Numbers

`(require 'random-inexact)`

— Function: random:uniform
— Function: random:uniform state

> Returns an uniformly distributed inexact real random number in the range between 0 and 1.

— Function: random:exp
— Function: random:exp state

> Returns an inexact real in an exponential distribution with mean 1. For an exponential distribution with mean u use `(*` u`(random:exp))`.

— Function: random:normal
— Function: random:normal state

> Returns an inexact real in a normal distribution with mean 0 and standard deviation 1. For a normal distribution with mean m and standard deviation d use `(+` m`(*` d`(random:normal)))`.

— Procedure: random:normal-vector! vect
— Procedure: random:normal-vector! vect state

> Fills vect with inexact real random numbers which are independent and standard normally distributed (i.e., with mean 0 and variance 1).

— Procedure: random:hollow-sphere! vect
— Procedure: random:hollow-sphere! vect state

> Fills vect with inexact real random numbers the sum of whose squares is equal to 1.0. Thinking of vect as coordinates in space of dimension n = `(vector-length` vect`)`, the coordinates are uniformly distributed over the surface of the unit n-shere.

— Procedure: random:solid-sphere! vect
— Procedure: random:solid-sphere! vect state

> Fills vect with inexact real random numbers the sum of whose squares is less than 1.0. Thinking of vect as coordinates in space of dimension n = `(vector-length` vect`)`, the coordinates are uniformly distributed within the unit n-shere. The sum of the squares of the numbers is returned.

Next: Cyclic Checksum, Previous: Random Numbers, Up: Mathematical Packages

### 5.7 Discrete Fourier Transform

`(require 'dft)` or `(require 'Fourier-transform)` `fft` and `fft-1` compute the Fast-Fourier-Transforms (O(n*log(n))) of arrays whose dimensions are all powers of 2.

`sft` and `sft-1` compute the Discrete-Fourier-Transforms for all combinations of dimensions (O(n^2)).

— Function: sft array prot
— Function: sft array

> array is an array of positive rank. `sft` returns an array of type prot (defaulting to array) of complex numbers comprising the Discrete Fourier Transform of array.

— Function: sft-1 array prot
— Function: sft-1 array

> array is an array of positive rank. `sft-1` returns an array of type prot (defaulting to array) of complex numbers comprising the inverse Discrete Fourier Transform of array.

— Function: fft array prot
— Function: fft array

> array is an array of positive rank whose dimensions are all powers of 2. `fft` returns an array of type prot (defaulting to array) of complex numbers comprising the Discrete Fourier Transform of array.

— Function: fft-1 array prot
— Function: fft-1 array

> array is an array of positive rank whose dimensions are all powers of 2. `fft-1` returns an array of type prot (defaulting to array) of complex numbers comprising the inverse Discrete Fourier Transform of array.

`dft` and `dft-1` compute the discrete Fourier transforms using the best method for decimating each dimension.

— Function: dft array prot
— Function: dft array

> `dft` returns an array of type prot (defaulting to array) of complex numbers comprising the Discrete Fourier Transform of array.

— Function: dft-1 array prot
— Function: dft-1 array

> `dft-1` returns an array of type prot (defaulting to array) of complex numbers comprising the inverse Discrete Fourier Transform of array.

`(fft-1 (fft` array`))` will return an array of values close to array.

         (fft '#(1 0+i -1 0-i 1 0+i -1 0-i)) =>

         #(0.0 0.0 0.0+628.0783185208527e-18i 0.0
           0.0 0.0 8.0-628.0783185208527e-18i 0.0)

         (fft-1 '#(0 0 0 0 0 0 8 0)) =>

         #(1.0 -61.23031769111886e-18+1.0i -1.0 61.23031769111886e-18-1.0i
           1.0 -61.23031769111886e-18+1.0i -1.0 61.23031769111886e-18-1.0i)

Next: Graphing, Previous: Discrete Fourier Transform, Up: Mathematical Packages

### 5.8 Cyclic Checksum

`(require 'crc)` Cyclic Redundancy Checks using Galois field GF(2) polynomial arithmetic are used for error detection in many data transmission and storage applications.

The generator polynomials for various CRC protocols are availble from many sources. But the polynomial is just one of many parameters which must match in order for a CRC implementation to interoperate with existing systems:

- the byte-order and bit-order of the data stream;
- whether the CRC or its inverse is being calculated;
- the initial CRC value; and
- whether and where the CRC value is appended (inverted or non-inverted) to the data stream.

The performance of a particular CRC polynomial over packets of given sizes varies widely. In terms of the probability of undetected errors, some uses of extant CRC polynomials are suboptimal by several orders of magnitude.

If you are considering CRC for a new application, consult the following article to find the optimum CRC polynomial for your range of data lengths:

- Philip Koopman and Tridib Chakravarty,
  “Cyclic Redundancy Code (CRC) Polynomial Selection For Embedded Networks”,
  The International Conference on Dependable Systems and Networks, DSN-2004.

http://www.ece.cmu.edu/~koopman/roses/dsn04/koopman04_crc_poly_embedded.pdf

There is even some controversy over the polynomials themselves.

— Constant: crc-32-polynomial

> For CRC-32, http://www2.sis.pitt.edu/~jkabara/tele-2100/lect08.html gives x^32+x^26+x^23+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x^1+1.

> But http://www.cs.ncl.ac.uk/people/harry.whitfield/home.formal/CRCs.html, http://duchon.umuc.edu/Web_Pages/duchon/99_f_cm435/ShiftRegister.htm, http://spinroot.com/spin/Doc/Book91_PDF/ch3.pdf, http://www.erg.abdn.ac.uk/users/gorry/course/dl-pages/crc.html, http://www.rad.com/networks/1994/err_con/crc_most.htm, and http://www.gpfn.sk.ca/~rhg/csc8550s02/crc.html, http://www.nobugconsulting.ro/crc.php give x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x+1.

> SLIB `crc-32-polynomial` uses the latter definition.

— Constant: crc-ccitt-polynomial

> http://www.math.grin.edu/~rebelsky/Courses/CS364/2000S/Outlines/outline.12.html, http://duchon.umuc.edu/Web_Pages/duchon/99_f_cm435/ShiftRegister.htm, http://www.cs.ncl.ac.uk/people/harry.whitfield/home.formal/CRCs.html, http://www2.sis.pitt.edu/~jkabara/tele-2100/lect08.html, and http://www.gpfn.sk.ca/~rhg/csc8550s02/crc.html give CRC-CCITT: x^16+x^12+x^5+1.

— Constant: crc-16-polynomial

> http://www.math.grin.edu/~rebelsky/Courses/CS364/2000S/Outlines/outline.12.html, http://duchon.umuc.edu/Web_Pages/duchon/99_f_cm435/ShiftRegister.htm, http://www.cs.ncl.ac.uk/people/harry.whitfield/home.formal/CRCs.html, http://www.gpfn.sk.ca/~rhg/csc8550s02/crc.html, and http://www.usb.org/developers/data/crcdes.pdf give CRC-16: x^16+x^15+x^2+1.

— Constant: crc-12-polynomial

> http://www.math.grin.edu/~rebelsky/Courses/CS364/2000S/Outlines/outline.12.html, http://www.cs.ncl.ac.uk/people/harry.whitfield/home.formal/CRCs.html, http://www.it.iitb.ac.in/it605/lectures/link/node4.html, and http://spinroot.com/spin/Doc/Book91_PDF/ch3.pdf give CRC-12: x^12+x^11+x^3+x^2+1.

> But http://www.ffldusoe.edu/Faculty/Denenberg/Topics/Networks/Error_Detection_Correction/crc.html, http://duchon.umuc.edu/Web_Pages/duchon/99_f_cm435/ShiftRegister.htm, http://www.eng.uwi.tt/depts/elec/staff/kimal/errorcc.html, http://www.ee.uwa.edu.au/~roberto/teach/itc314/java/CRC/, http://www.gpfn.sk.ca/~rhg/csc8550s02/crc.html, and http://www.efg2.com/Lab/Mathematics/CRC.htm give CRC-12: x^12+x^11+x^3+x^2+x+1.

> These differ in bit 1 and calculations using them return different values. With citations near evenly split, it is hard to know which is correct. Thanks to Philip Koopman for breaking the tie in favor of the latter (#xC07).

— Constant: crc-10-polynomial

> http://www.math.grin.edu/~rebelsky/Courses/CS364/2000S/Outlines/outline.12.html gives CRC-10: x^10+x^9+x^5+x^4+1; but http://cell-relay.indiana.edu/cell-relay/publications/software/CRC/crc10.html, http://www.it.iitb.ac.in/it605/lectures/link/node4.html, http://www.gpfn.sk.ca/~rhg/csc8550s02/crc.html, http://www.techfest.com/networking/atm/atm.htm, http://www.protocols.com/pbook/atmcell2.htm, and http://www.nobugconsulting.ro/crc.php give CRC-10: x^10+x^9+x^5+x^4+x+1.

— Constant: crc-08-polynomial

> http://www.math.grin.edu/~rebelsky/Courses/CS364/2000S/Outlines/outline.12.html, http://www.cs.ncl.ac.uk/people/harry.whitfield/home.formal/CRCs.html, http://www.it.iitb.ac.in/it605/lectures/link/node4.html, and http://www.nobugconsulting.ro/crc.php give CRC-8: x^8+x^2+x^1+1

— Constant: atm-hec-polynomial

> http://cell-relay.indiana.edu/cell-relay/publications/software/CRC/32bitCRC.tutorial.html and http://www.gpfn.sk.ca/~rhg/csc8550s02/crc.html give ATM HEC: x^8+x^2+x+1.

— Constant: dowcrc-polynomial

> http://www.cs.ncl.ac.uk/people/harry.whitfield/home.formal/CRCs.html gives DOWCRC: x^8+x^5+x^4+1.

— Constant: usb-token-polynomial

> http://www.usb.org/developers/data/crcdes.pdf and http://www.nobugconsulting.ro/crc.php give USB-token: x^5+x^2+1.

Each of these polynomial constants is a string of ``1`'s and ``0`'s, the exponent of each power of x in descending order.

— Function: crc:make-table poly

> poly must be string of ``1`'s and ``0`'s beginning with ``1`' and having length greater than 8. `crc:make-table` returns a vector of 256 integers, such that:

>               (set! crc
>                     (logxor (ash (logand (+ -1 (ash 1 (- deg 8))) crc) 8)
>                             (vector-ref crc-table
>                                         (logxor (ash crc (- 8 deg)) byte))))

> will compute the crc with the 8 additional bits in byte; where crc is the previous accumulated CRC value, deg is the degree of poly, and crc-table is the vector returned by `crc:make-table`.

> If the implementation does not support deg-bit integers, then `crc:make-table` returns #f.

— Function: cksum file

> Computes the P1003.2/D11.2 (POSIX.2) 32-bit checksum of file.

>               (require 'crc)
>               (cksum (in-vicinity (library-vicinity) "ratize.scm"))
>               => 157103930

> — Function: cksum port

> > Computes the checksum of the bytes read from port until the end-of-file.

`cksum-string`, which returns the P1003.2/D11.2 (POSIX.2) 32-bit checksum of the bytes in str, can be defined as follows:

         (require 'string-port)
         (define (cksum-string str) (call-with-input-string str cksum))

— Function: crc16 file

> Computes the USB data-packet (16-bit) CRC of file. — Function: crc16 port

> > Computes the USB data-packet (16-bit) CRC of the bytes read from port until the end-of-file.

> > `crc16` calculates the same values as the crc16.pl program given in http://www.usb.org/developers/data/crcdes.pdf.

— Function: crc5 file

> Computes the USB token (5-bit) CRC of file. — Function: crc5 port

> > Computes the USB token (5-bit) CRC of the bytes read from port until the end-of-file.

> > `crc5` calculates the same values as the crc5.pl program given in http://www.usb.org/developers/data/crcdes.pdf.

Next: Solid Modeling, Previous: Cyclic Checksum, Up: Mathematical Packages

### 5.9 Graphing

Next: PostScript Graphing, Previous: Graphing, Up: Graphing

#### 5.9.1 Character Plotting

`(require 'charplot)`

— Variable: charplot:dimensions

> A list of the maximum height (number of lines) and maximum width (number of columns) for the graph, its scales, and labels.

> The default value for charplot:dimensions is the `output-port-height` and `output-port-width` of `current-output-port`.

— Procedure: plot coords x-label y-label

> coords is a list or vector of coordinates, lists of x and y coordinates. x-label and y-label are strings with which to label the x and y axes.

> Example:

>               (require 'charplot)
>               (set! charplot:dimensions '(20 55))

>               (define (make-points n)
>                 (if (zero? n)
>                     '()
>                     (cons (list (/ n 6) (sin (/ n 6))) (make-points (1- n)))))

>               (plot (make-points 40) "x" "Sin(x)")
>               -|
>                 Sin(x)   _________________________________________
>                        1|-       ****                             |
>                         |      **    **                           |
>                     0.75|-    *        *                          |
>                         |    *          *                         |
>                      0.5|-  *            *                        |
>                         |  *                                     *|
>                     0.25|-                *                     * |
>                         | *                *                      |
>                        0|-------------------*------------------*--|
>                         |                                     *   |
>                    -0.25|-                   *               *    |
>                         |                     *             *     |
>                     -0.5|-                     *                  |
>                         |                       *          *      |
>                    -0.75|-                       *        *       |
>                         |                         **    **        |
>                       -1|-                          ****          |
>                         |:_____._____:_____._____:_____._____:____|
>                    x                 2           4           6

— Procedure: plot func x1 x2
— Procedure: plot func x1 x2 npts

> Plots the function of one argument func over the range x1 to x2. If the optional integer argument npts is supplied, it specifies the number of points to evaluate func at.

>               (plot sin 0 (* 2 pi))
>               -|
>                          _________________________________________
>                        1|-:       ****                            |
>                         | :     **    **                          |
>                     0.75|-:    *        *                         |
>                         | :   *          *                        |
>                      0.5|-:  **          **                       |
>                         | : *             *                       |
>                     0.25|-:**              **                     |
>                         | :*                *                     |
>                        0|-*------------------*--------------------|
>                         | :                  *                 *  |
>                    -0.25|-:                   **              **  |
>                         | :                    *             *    |
>                     -0.5|-:                     *           **    |
>                         | :                      *          *     |
>                    -0.75|-:                       *       **      |
>                         | :                        **    **       |
>                       -1|-:                          ****         |
>                         |_:_____._____:_____._____:_____._____:___|
>                           0           2           4           6

— Procedure: histograph data label

> Creates and displays a histogram of the numerical values contained in vector or list data

>               (require 'random-inexact)
>               (histograph (do ((idx 99 (+ -1 idx))
>                                (lst '() (cons (* .02 (random:normal)) lst)))
>                               ((negative? idx) lst))
>                           "normal")
>               -|
>                          _________________________________________
>                        8|-                :    I                  |
>                         |                 :    I                  |
>                        7|-           I  I :    I                  |
>                         |            I  I :    I                  |
>                        6|-          III I :I   I                  |
>                         |           III I :I   I                  |
>                        5|-          IIIIIIIIII I                  |
>                         |           IIIIIIIIII I                  |
>                        4|-          IIIIIIIIIIII                  |
>                         |           IIIIIIIIIIII                  |
>                        3|-I    I I  IIIIIIIIIIII  II     I        |
>                         | I    I I  IIIIIIIIIIII  II     I        |
>                        2|-I    I I IIIIIIIIIIIIIIIII     I        |
>                         | I    I I IIIIIIIIIIIIIIIII     I        |
>                        1|-II I I IIIIIIIIIIIIIIIIIIIII   I I I    |
>                         | II I I IIIIIIIIIIIIIIIIIIIII   I I I    |
>                        0|-IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII----|
>                         |__.____:____.____:____.____:____.____:___|
>                 normal        -0.025      0       0.025      0.05

Previous: Character Plotting, Up: Graphing

#### 5.9.2 PostScript Graphing

`(require 'eps-graph)`

This is a graphing package creating encapsulated-PostScript files. Its motivations and design choice are described in http://swiss.csail.mit.edu/~jaffer/Docupage/grapheps

A dataset to be plotted is taken from a 2-dimensional array. Corresponding coordinates are in rows. Coordinates from any pair of columns can be plotted.

— Function: create-postscript-graph filename.eps size elt1 ...

> filename.eps should be a string naming an output file to be created. size should be an exact integer, a list of two exact integers, or #f. elt1, ... are values returned by graphing primitives described here.

> `create-postscript-graph` creates an Encapsulated-PostScript file named filename.eps containing graphs as directed by the elt1, ... arguments.

> The size of the graph is determined by the size argument. If a list of two integers, they specify the width and height. If one integer, then that integer is the width and the height is 3/4 of the width. If #f, the graph will be 800 by 600.

These graphing procedures should be called as arguments to `create-postscript-graph`. The order of these arguments is significant; PostScript graphics state is affected serially from the first elt argument to the last.

— Function: whole-page

> Pushes a rectangle for the whole encapsulated page onto the PostScript stack. This pushed rectangle is an implicit argument to `partition-page` or `setup-plot`.

Next: Drawing the Graph, Previous: PostScript Graphing, Up: PostScript Graphing

##### 5.9.2.1 Column Ranges

A range is a list of two numbers, the minimum and the maximum. Ranges can be given explicity or computed in PostScript by `column-range`.

— Function: column-range array k

> Returns the range of values in 2-dimensional array column k.

— Function: pad-range range p

> Expands range by p/100 on each end.

— Function: snap-range range

> Expands range to round number of ticks.

— Function: combine-ranges range1 range2 ...

> Returns the minimal range covering all range1, range2, ...

— Function: setup-plot x-range y-range pagerect
— Function: setup-plot x-range y-range

> x-range and y-range should each be a list of two numbers or the value returned by `pad-range`, `snap-range`, or `combine-range`. pagerect is the rectangle bounding the graph to be drawn; if missing, the rectangle from the top of the PostScript stack is popped and used.

> Based on the given ranges, `setup-plot` sets up scaling and margins for making a graph. The margins are sized proportional to the fontheight value at the time of the call to setup-plot. `setup-plot` sets two variables:

> plotrect
>   The region where data points will be plotted.
> graphrect
>   The pagerect argument to `setup-plot`. Includes plotrect, legends, etc.

Next: Graphics Context, Previous: Column Ranges, Up: PostScript Graphing

##### 5.9.2.2 Drawing the Graph

— Function: plot-column array x-column y-column proc3s

> Plots points with x coordinate in x-column of array and y coordinate y-column of array. The symbol proc3s specifies the type of glyph or drawing style for presenting these coordinates.

The glyphs and drawing styles available are:

`line`
  Draws line connecting points in order.
`mountain`
  Fill area below line connecting points.
`cloud`
  Fill area above line connecting points.
`impulse`
  Draw line from x-axis to each point.
`bargraph`
  Draw rectangle from x-axis to each point.
`disc`
  Solid round dot.
`point`
  Minimal point – invisible if linewidth is 0.
`square`
  Square box.
`diamond`
  Square box at 45.o
`plus`
  Plus sign.
`cross`
  X sign.
`triup`
  Triangle pointing upward
`tridown`
  Triangle pointing downward
`pentagon`
  Five sided polygon
`circle`
  Hollow circle

Next: Rectangles, Previous: Drawing the Graph, Up: PostScript Graphing

##### 5.9.2.3 Graphics Context

— Function: in-graphic-context arg ...

> Saves the current graphics state, executes args, then restores to saved graphics state.

— Function: set-color color

> color should be a string naming a Resene color, a saturate color, or a number between 0 and 100.

> `set-color` sets the PostScript color to the color of the given string, or a grey value between black (0) and white (100).

— Function: set-font name fontheight

> name should be a (case-sensitive) string naming a PostScript font. fontheight should be a positive real number.

> `set-font` Changes the current PostScript font to name with height equal to fontheight. The default font is Helvetica (12pt).

The base set of PostScript fonts is:

Times | Times-Italic | Times-Bold | Times-BoldItalic
Helvetica | Helvetica-Oblique | Helvetica-Bold | Helvetica-BoldOblique
Courier | Courier-Oblique | Courier-Bold | Courier-BoldOblique
Symbol

Line parameters do no affect fonts; they do effect glyphs.

— Function: set-linewidth w

> The default linewidth is 1. Setting it to 0 makes the lines drawn as skinny as possible. Linewidth must be much smaller than glyphsize for readable glyphs.

— Function: set-linedash j k

> Lines are drawn j-on k-off. — Function: set-linedash j

> > Lines are drawn j-on j-off. — Function: set-linedash

> > > Turns off dashing.

— Function: set-glyphsize w

> Sets the (PostScript) variable glyphsize to w. The default glyphsize is 6.

The effects of `clip-to-rect` are also part of the graphic context.

Next: Legending, Previous: Graphics Context, Up: PostScript Graphing

##### 5.9.2.4 Rectangles

A rectangle is a list of 4 numbers; the first two elements are the x and y coordinates of lower left corner of the rectangle. The other two elements are the width and height of the rectangle.

— Function: whole-page

> Pushes a rectangle for the whole encapsulated page onto the PostScript stack. This pushed rectangle is an implicit argument to `partition-page` or `setup-plot`.

— Function: partition-page xparts yparts

> Pops the rectangle currently on top of the stack and pushes xparts * yparts sub-rectangles onto the stack in decreasing y and increasing x order. If you are drawing just one graph, then you don't need `partition-page`.

— Variable: plotrect

> The rectangle where data points should be plotted. plotrect is set by `setup-plot`.

— Variable: graphrect

> The pagerect argument of the most recent call to `setup-plot`. Includes plotrect, legends, etc.

— Function: fill-rect rect

> fills rect with the current color.

— Function: outline-rect rect

> Draws the perimiter of rect in the current color.

— Function: clip-to-rect rect

> Modifies the current graphics-state so that nothing will be drawn outside of the rectangle rect. Use `in-graphic-context` to limit the extent of `clip-to-rect`.

Next: Legacy Plotting, Previous: Rectangles, Up: PostScript Graphing

##### 5.9.2.5 Legending

— Function: title-top title subtitle
— Function: title-top title

> Puts a title line and an optional subtitle line above the `graphrect`.

— Function: title-bottom title subtitle
— Function: title-bottom title

> Puts a title line and an optional subtitle line below the `graphrect`.

— Variable: topedge
— Variable: bottomedge

> These edge coordinates of `graphrect` are suitable for passing as the first argument to `rule-horizontal`.

— Variable: leftedge
— Variable: rightedge

> These edge coordinates of `graphrect` are suitable for passing as the first argument to `rule-vertical`.

— Function: set-margin-templates left right

> The margin-templates are strings whose displayed width is used to reserve space for the left and right side numerical legends. The default values are "-.0123456789".

— Function: rule-vertical x-coord text tick-width

> Draws a vertical ruler with X coordinate x-coord and labeled with string text. If tick-width is positive, then the ticks are tick-width long on the right side of x-coord; and text and numeric legends are on the left. If tick-width is negative, then the ticks are -tick-width long on the left side of x-coord; and text and numeric legends are on the right.

— Function: rule-horizontal y-coord text tick-height

> Draws a horizontal ruler with Y coordinate y-coord and labeled with string text. If tick-height is positive, then the ticks are tick-height long on the top side of y-coord; and text and numeric legends are on the bottom. If tick-height is negative, then the ticks are -tick-height long on the bottom side of y-coord; and text and numeric legends are on the top.

— Function: y-axis

> Draws the y-axis.

— Function: x-axis

> Draws the x-axis.

— Function: grid-verticals

> Draws vertical lines through `graphrect` at each tick on the vertical ruler.

— Function: grid-horizontals

> Draws horizontal lines through `graphrect` at each tick on the horizontal ruler.

Next: Example Graph, Previous: Legending, Up: PostScript Graphing

##### 5.9.2.6 Legacy Plotting

— Variable: graph:dimensions

> A list of the width and height of the graph to be plotted using `plot`.

— Function: plot func x1 x2 npts
— Function: plot func x1 x2

> Creates and displays using `(system "gv tmp.eps")` an encapsulated PostScript graph of the function of one argument func over the range x1 to x2. If the optional integer argument npts is supplied, it specifies the number of points to evaluate func at. — Function: x1 x2 npts func1 func2 ...

> > Creates and displays an encapsulated PostScript graph of the one-argument functions func1, func2, ... over the range x1 to x2 at npts points. — Function: plot coords x-label y-label

> > > coords is a list or vector of coordinates, lists of x and y coordinates. x-label and y-label are strings with which to label the x and y axes.

Previous: Legacy Plotting, Up: PostScript Graphing

##### 5.9.2.7 Example Graph

The file `am1.5.html`, a table of solar irradiance, is fetched with ``wget`' if it isn't already in the working directory. The file is read and stored into an array, irradiance.

`create-postscript-graph` is then called to create an encapsulated-PostScript file, `solarad.eps`. The size of the page is set to 600 by 300. `whole-page` is called and leaves the rectangle on the PostScript stack. `setup-plot` is called with a literal range for x and computes the range for column 1.

Two calls to `top-title` are made so a different font can be used for the lower half. `in-graphic-context` is used to limit the scope of the font change. The graphing area is outlined and a rule drawn on the left side.

Because the X range was intentionally reduced, `in-graphic-context` is called and `clip-to-rect` limits drawing to the plotting area. A black line is drawn from data column 1. That line is then overlayed with a mountain plot of the same column colored "Bright Sun".

After returning from the `in-graphic-context`, the bottom ruler is drawn. Had it been drawn earlier, all its ticks would have been painted over by the mountain plot.

The color is then changed to ``seagreen`' and the same graphrect is setup again, this time with a different Y scale, 0 to 1000. The graphic context is again clipped to plotrect, linedash is set, and column 2 is plotted as a dashed line. Finally the rightedge is ruled. Having the line and its scale both in green helps disambiguate the scales.

         (require 'eps-graph)
         (require 'line-i/o)
         (require 'string-port)

         (define irradiance
           (let ((url "http://www.pv.unsw.edu.au/am1.5.html")
                 (file "am1.5.html"))
             (define (read->list line)
               (define elts '())
               (call-with-input-string line
                 (lambda (iprt) (do ((elt (read iprt) (read iprt)))
                                    ((eof-object? elt) elts)
                                  (set! elts (cons elt elts))))))
             (if (not (file-exists? file))
                 (system (string-append "wget -c -O" file " " url)))
             (call-with-input-file file
               (lambda (iprt)
                 (define lines '())
                 (do ((line (read-line iprt) (read-line iprt)))
                     ((eof-object? line)
                      (let ((nra (make-array (A:floR64b)
                                               (length lines)
                                               (length (car lines)))))
                        (do ((lns lines (cdr lns))
                             (idx (+ -1 (length lines)) (+ -1 idx)))
                            ((null? lns) nra)
                          (do ((kdx (+ -1 (length (car lines))) (+ -1 kdx))
                               (lst (car lns) (cdr lst)))
                              ((null? lst))
                            (array-set! nra (car lst) idx kdx)))))
                   (if (and (positive? (string-length line))
                            (char-numeric? (string-ref line 0)))
                       (set! lines (cons (read->list line) lines))))))))

         (let ((xrange '(.25 2.5)))
           (create-postscript-graph
            "solarad.eps" '(600 300)
            (whole-page)
            (setup-plot xrange (column-range irradiance 1))
            (title-top
             "Solar Irradiance   http://www.pv.unsw.edu.au/am1.5.html")
            (in-graphic-context
             (set-font "Helvetica-Oblique" 12)
             (title-top
              ""
              "Key Centre for Photovoltaic Engineering UNSW - Air Mass 1.5 Global Spectrum"))
            (outline-rect plotrect)
            (rule-vertical leftedge "W/(m^2.um)" 10)
            (in-graphic-context (clip-to-rect plotrect)
                                (plot-column irradiance 0 1 'line)
                                (set-color "Bright Sun")
                                (plot-column irradiance 0 1 'mountain)
                                )
            (rule-horizontal bottomedge "Wavelength in .um" 5)
            (set-color 'seagreen)

            (setup-plot xrange '(0 1000) graphrect)
            (in-graphic-context (clip-to-rect plotrect)
                                (set-linedash 5 2)
                                (plot-column irradiance 0 2 'line))
            (rule-vertical rightedge "Integrated .W/(m^2)" -10)
            ))

         (system "gv solarad.eps")

Next: Color, Previous: Graphing, Up: Mathematical Packages

### 5.10 Solid Modeling

`(require 'solid)` http://swiss.csail.mit.edu/~jaffer/Solid/#Example gives an example use of this package.

— Function: vrml node ...

> Returns the VRML97 string (including header) of the concatenation of strings nodes, ....

— Function: vrml-append node1 node2 ...

> Returns the concatenation with interdigitated newlines of strings node1, node2, ....

— Function: vrml-to-file file node ...

> Writes to file named file the VRML97 string (including header) of the concatenation of strings nodes, ....

— Function: world:info title info ...

> Returns a VRML97 string setting the title of the file in which it appears to title. Additional strings info, ... are comments.

VRML97 strings passed to `vrml` and `vrml-to-file` as arguments will appear in the resulting VRML code. This string turns off the headlight at the viewpoint:

         " NavigationInfo {headlight FALSE}"

— Function: scene:panorama front right back left top bottom

> Specifies the distant images on the inside faces of the cube enclosing the virtual world.

— Function: scene:sphere colors angles

> colors is a list of color objects. Each may be of type color, a 24-bit sRGB integer, or a list of 3 numbers between 0.0 and 1.0.

> angles is a list of non-increasing angles the same length as colors. Each angle is between 90 and -90 degrees. If 90 or -90 are not elements of angles, then the color at the zenith and nadir are taken from the colors paired with the angles nearest them.

> `scene:sphere` fills horizontal bands with interpolated colors on the background sphere encasing the world.

— Function: scene:sky-and-dirt

> Returns a blue and brown background sphere encasing the world.

— Function: scene:sky-and-grass

> Returns a blue and green background sphere encasing the world.

— Function: scene:sun latitude julian-day hour turbidity strength
— Function: scene:sun latitude julian-day hour turbidity

> latitude is the virtual place's latitude in degrees. julian-day is an integer from 0 to 366, the day of the year. hour is a real number from 0 to 24 for the time of day; 12 is noon. turbidity is the degree of fogginess described in See turbidity.

> `scene:sun` returns a bright yellow, distant sphere where the sun would be at hour on julian-day at latitude. If strength is positive, included is a light source of strength (default 1).

— Function: scene:overcast latitude julian-day hour turbidity strength
— Function: scene:overcast latitude julian-day hour turbidity

> latitude is the virtual place's latitude in degrees. julian-day is an integer from 0 to 366, the day of the year. hour is a real number from 0 to 24 for the time of day; 12 is noon. turbidity is the degree of cloudiness described in See turbidity.

> `scene:overcast` returns an overcast sky as it might look at hour on julian-day at latitude. If strength is positive, included is an ambient light source of strength (default 1).

Viewpoints are objects in the virtual world, and can be transformed individually or with solid objects.

— Function: scene:viewpoint name distance compass pitch
— Function: scene:viewpoint name distance compass

> Returns a viewpoint named name facing the origin and placed distance from it. compass is a number from 0 to 360 giving the compass heading. pitch is a number from -90 to 90, defaulting to 0, specifying the angle from the horizontal.

— Function: scene:viewpoints proximity

> Returns 6 viewpoints, one at the center of each face of a cube with sides 2 * proximity, centered on the origin.

#### Light Sources

In VRML97, lights shine only on objects within the same children node and descendants of that node. Although it would have been convenient to let light direction be rotated by `solid:rotation`, this restricts a rotated light's visibility to objects rotated with it.

To workaround this limitation, these directional light source procedures accept either Cartesian or spherical coordinates for direction. A spherical coordinate is a list `(`theta azimuth`)`; where theta is the angle in degrees from the zenith, and azimuth is the angle in degrees due west of south.

It is sometimes useful for light sources to be brighter than ``1`'. When intensity arguments are greater than 1, these functions gang multiple sources to reach the desired strength.

— Function: light:ambient color intensity
— Function: light:ambient color

> Ambient light shines on all surfaces with which it is grouped.

> color is a an object of type color, a 24-bit sRGB integer, or a list of 3 numbers between 0.0 and 1.0. If color is #f, then the default color will be used. intensity is a real non-negative number defaulting to ``1`'.

> `light:ambient` returns a light source or sources of color with total strength of intensity (or 1 if omitted).

— Function: light:directional color direction intensity
— Function: light:directional color direction
— Function: light:directional color

> Directional light shines parallel rays with uniform intensity on all objects with which it is grouped.

> color is a an object of type color, a 24-bit sRGB integer, or a list of 3 numbers between 0.0 and 1.0. If color is #f, then the default color will be used.

> direction must be a list or vector of 2 or 3 numbers specifying the direction to this light. If direction has 2 numbers, then these numbers are the angle from zenith and the azimuth in degrees; if direction has 3 numbers, then these are taken as a Cartesian vector specifying the direction to the light source. The default direction is upwards; thus its light will shine down.

> intensity is a real non-negative number defaulting to ``1`'.

> `light:directional` returns a light source or sources of color with total strength of intensity, shining from direction.

— Function: light:beam attenuation radius aperture peak
— Function: light:beam attenuation radius aperture
— Function: light:beam attenuation radius
— Function: light:beam attenuation

> attenuation is a list or vector of three nonnegative real numbers specifying the reduction of intensity, the reduction of intensity with distance, and the reduction of intensity as the square of distance. radius is the distance beyond which the light does not shine. radius defaults to ``100`'.

> aperture is a real number between 0 and 180, the angle centered on the light's axis through which it sheds some light. peak is a real number between 0 and 90, the angle of greatest illumination.

— Function: light:point location color intensity beam
— Function: light:point location color intensity
— Function: light:point location color
— Function: light:point location

> Point light radiates from location, intensity decreasing with distance, towards all objects with which it is grouped.

> color is a an object of type color, a 24-bit sRGB integer, or a list of 3 numbers between 0.0 and 1.0. If color is #f, then the default color will be used. intensity is a real non-negative number defaulting to ``1`'. beam is a structure returned by `light:beam` or #f.

> `light:point` returns a light source or sources at location of color with total strength intensity and beam properties. Note that the pointlight itself is not visible. To make it so, place an object with emissive appearance at location.

— Function: light:spot location direction color intensity beam
— Function: light:spot location direction color intensity
— Function: light:spot location direction color
— Function: light:spot location direction
— Function: light:spot location

> Spot light radiates from location towards direction, intensity decreasing with distance, illuminating objects with which it is grouped.

> direction must be a list or vector of 2 or 3 numbers specifying the direction to this light. If direction has 2 numbers, then these numbers are the angle from zenith and the azimuth in degrees; if direction has 3 numbers, then these are taken as a Cartesian vector specifying the direction to the light source. The default direction is upwards; thus its light will shine down.

> color is a an object of type color, a 24-bit sRGB integer, or a list of 3 numbers between 0.0 and 1.0. If color is #f, then the default color will be used.

> intensity is a real non-negative number defaulting to ``1`'.

> `light:spot` returns a light source or sources at location of direction with total strength color. Note that the spotlight itself is not visible. To make it so, place an object with emissive appearance at location.

#### Object Primitives

— Function: solid:box geometry appearance
— Function: solid:box geometry

> geometry must be a number or a list or vector of three numbers. If geometry is a number, the `solid:box` returns a cube with sides of length geometry centered on the origin. Otherwise, `solid:box` returns a rectangular box with dimensions geometry centered on the origin. appearance determines the surface properties of the returned object.

— Function: solid:lumber geometry appearance

> Returns a box of the specified geometry, but with the y-axis of a texture specified in appearance being applied along the longest dimension in geometry.

— Function: solid:cylinder radius height appearance
— Function: solid:cylinder radius height

> Returns a right cylinder with dimensions `(abs` radius`)` and `(abs` height`)` centered on the origin. If height is positive, then the cylinder ends will be capped. If radius is negative, then only the ends will appear. appearance determines the surface properties of the returned object.

— Function: solid:disk radius thickness appearance
— Function: solid:disk radius thickness

> thickness must be a positive real number. `solid:disk` returns a circular disk with dimensions radius and thickness centered on the origin. appearance determines the surface properties of the returned object.

— Function: solid:cone radius height appearance
— Function: solid:cone radius height

> Returns an isosceles cone with dimensions radius and height centered on the origin. appearance determines the surface properties of the returned object.

— Function: solid:pyramid side height appearance
— Function: solid:pyramid side height

> Returns an isosceles pyramid with dimensions side and height centered on the origin. appearance determines the surface properties of the returned object.

— Function: solid:sphere radius appearance
— Function: solid:sphere radius

> Returns a sphere of radius radius centered on the origin. appearance determines the surface properties of the returned object.

— Function: solid:ellipsoid geometry appearance
— Function: solid:ellipsoid geometry

> geometry must be a number or a list or vector of three numbers. If geometry is a number, the `solid:ellipsoid` returns a sphere of diameter geometry centered on the origin. Otherwise, `solid:ellipsoid` returns an ellipsoid with diameters geometry centered on the origin. appearance determines the surface properties of the returned object.

— Function: solid:polyline coordinates appearance
— Function: solid:polyline coordinates

> coordinates must be a list or vector of coordinate lists or vectors specifying the x, y, and z coordinates of points. `solid:polyline` returns lines connecting successive pairs of points. If called with one argument, then the polyline will be white. If appearance is given, then the polyline will have its emissive color only; being black if appearance does not have an emissive color.

> The following code will return a red line between points at `(1 2 3)` and `(4 5 6)`:

>               (solid:polyline '((1 2 3) (4 5 6)) (solid:color #f 0 #f 0 '(1 0 0)))

— Function: solid:prism xz-array y appearance
— Function: solid:prism xz-array y

> xz-array must be an n-by-2 array holding a sequence of coordinates tracing a non-intersecting clockwise loop in the x-z plane. `solid:prism` will close the sequence if the first and last coordinates are not the same.

> `solid:prism` returns a capped prism y long.

— Function: solid:basrelief width height depth colorray appearance
— Function: solid:basrelief width height depth appearance
— Function: solid:basrelief width height depth

> One of width, height, or depth must be a 2-dimensional array; the others must be real numbers giving the length of the basrelief in those dimensions. The rest of this description assumes that height is an array of heights.

> `solid:basrelief` returns a width by depth basrelief solid with heights per array height with the buttom surface centered on the origin.

> If present, appearance determines the surface properties of the returned object. If present, colorray must be an array of objects of type color, 24-bit sRGB integers or lists of 3 numbers between 0.0 and 1.0.

> If colorray's dimensions match height, then each element of colorray paints its corresponding vertex of height. If colorray has all dimensions one smaller than height, then each element of colorray paints the corresponding face of height. Other dimensions for colorray are in error.

— Function: solid:text fontstyle str len appearance
— Function: solid:text fontstyle str len

> fontstyle must be a value returned by `solid:font`.

> str must be a string or list of strings.

> len must be #f, a nonnegative integer, or list of nonnegative integers.

> appearance, if given, determines the surface properties of the returned object.

> `solid:text` returns a two-sided, flat text object positioned in the Z=0 plane of the local coordinate system

#### Surface Attributes

— Function: solid:color diffuseColor ambientIntensity specularColor shininess emissiveColor transparency
— Function: solid:color diffuseColor ambientIntensity specularColor shininess emissiveColor
— Function: solid:color diffuseColor ambientIntensity specularColor shininess
— Function: solid:color diffuseColor ambientIntensity specularColor
— Function: solid:color diffuseColor ambientIntensity
— Function: solid:color diffuseColor

> Returns an appearance, the optical properties of the objects with which it is associated. ambientIntensity, shininess, and transparency must be numbers between 0 and 1. diffuseColor, specularColor, and emissiveColor are objects of type color, 24-bit sRGB integers or lists of 3 numbers between 0.0 and 1.0. If a color argument is omitted or #f, then the default color will be used.

— Function: solid:texture image color scale rotation center translation
— Function: solid:texture image color scale rotation center
— Function: solid:texture image color scale rotation
— Function: solid:texture image color scale
— Function: solid:texture image color
— Function: solid:texture image

> Returns an appearance, the optical properties of the objects with which it is associated. image is a string naming a JPEG or PNG image resource. color is #f, a color, or the string returned by `solid:color`. The rest of the optional arguments specify 2-dimensional transforms applying to the image.

> scale must be #f, a number, or list or vector of 2 numbers specifying the scale to apply to image. rotation must be #f or the number of degrees to rotate image. center must be #f or a list or vector of 2 numbers specifying the center of image relative to the image dimensions. translation must be #f or a list or vector of 2 numbers specifying the translation to apply to image.

— Function: solid:font family style justify size spacing language direction

> Returns a fontstyle object suitable for passing as an argument to `solid:text`. Any of the arguments may be #f, in which case its default value, which is first in each list of allowed values, is used.

> family is a case-sensitive string naming a font; ``SERIF`', ``SANS`', and ``TYPEWRITER`' are supported at the minimum.

> style is a case-sensitive string ``PLAIN`', ``BOLD`', ``ITALIC`', or ``BOLDITALIC`'.

> justify is a case-sensitive string ``FIRST`', ``BEGIN`', ``MIDDLE`', or ``END`'; or a list of one or two case-sensitive strings (same choices). The mechanics of justify get complicated; it is explained by tables 6.2 to 6.7 of http://www.web3d.org/x3d/specifications/vrml/ISO-IEC-14772-IS-VRML97WithAmendment1/part1/nodesRef.html#Table6.2

> size is the extent, in the non-advancing direction, of the text. size defaults to 1.

> spacing is the ratio of the line (or column) offset to size. spacing defaults to 1.

> language is the RFC-1766 language name.

> direction is a list of two numbers: `(`x`` y`)`. If `(> (abs` x`) (abs` y`))`, then the text will be arrayed horizontally; otherwise vertically. The direction in which characters are arrayed is determined by the sign of the major axis: positive x being left-to-right; positive y being top-to-bottom.

#### Aggregating Objects

— Function: solid:center-row-of number solid spacing

> Returns a row of number solid objects spaced evenly spacing apart.

— Function: solid:center-array-of number-a number-b solid spacing-a spacing-b

> Returns number-b rows, spacing-b apart, of number-a solid objects spacing-a apart.

— Function: solid:center-pile-of number-a number-b number-c solid spacing-a spacing-b spacing-c

> Returns number-c planes, spacing-c apart, of number-b rows, spacing-b apart, of number-a solid objects spacing-a apart.

— Function: solid:arrow center

> center must be a list or vector of three numbers. Returns an upward pointing metallic arrow centered at center. — Function: solid:arrow

> > Returns an upward pointing metallic arrow centered at the origin.

#### Spatial Transformations

— Function: solid:translation center solid ...

> center must be a list or vector of three numbers. `solid:translation` Returns an aggregate of solids, ... with their origin moved to center.

— Function: solid:scale scale solid ...

> scale must be a number or a list or vector of three numbers. `solid:scale` Returns an aggregate of solids, ... scaled per scale.

— Function: solid:rotation axis angle solid ...

> axis must be a list or vector of three numbers. `solid:rotation` Returns an aggregate of solids, ... rotated angle degrees around the axis axis.

Next: Root Finding, Previous: Solid Modeling, Up: Mathematical Packages

### 5.11 Color

http://swiss.csail.mit.edu/~jaffer/Color

The goals of this package are to provide methods to specify, compute, and transform colors in a core set of additive color spaces. The color spaces supported should be sufficient for working with the color data encountered in practice and the literature.

Next: Color Spaces, Previous: Color, Up: Color

#### 5.11.1 Color Data-Type

`(require 'color)`

— Function: color? obj

> Returns #t if obj is a color. — Function: color? obj typ

> > Returns #t if obj is a color of color-space typ. The symbol typ must be one of:

> > - CIEXYZ
> > - RGB709
> > - L*a*b*
> > - L*u*v*
> > - sRGB
> > - e-sRGB
> > - L*C*h

— Function: make-color space arg ...

> Returns a color of type space.

> - For space arguments `CIEXYZ`, `RGB709`, and `sRGB`, the sole arg is a list of three numbers.
> - For space arguments `L*a*b*`, `L*u*v*`, and `L*C*h`, arg is a list of three numbers optionally followed by a whitepoint.
> - For `xRGB`, arg is an integer.
> - For `e-sRGB`, the arguments are as for `e-sRGB->color`.

— Function: color-space color

> Returns the symbol for the color-space in which color is embedded.

— Function: color-precision color

> For colors in digital color-spaces, `color-precision` returns the number of bits used for each of the R, G, and B channels of the encoding. Otherwise, `color-precision` returns #f

— Function: color-white-point color

> Returns the white-point of color in all color-spaces except CIEXYZ.

— Function: convert-color color space white-point
— Function: convert-color color space
— Function: convert-color color e-sRGB precision

> Converts color into space at optional white-point.

##### 5.11.1.1 External Representation

Each color encoding has an external, case-insensitive representation. To ensure portability, the white-point for all color strings is D65. 5

Color Space | External Representation
CIEXYZ | CIEXYZ:<X>/<Y>/<Z>
RGB709 | RGBi:<R>/<G>/<B>
L*a*b* | CIELAB:<L>/<a>/<b>
L*u*v* | CIELuv:<L>/<u>/<v>
L*C*h | CIELCh:<L>/<C>/<h>

The X, Y, Z, L, a, b, u, v, C, h, R, G, and B fields are (Scheme) real numbers within the appropriate ranges.

Color Space | External Representation
sRGB | sRGB:<R>/<G>/<B>
e-sRGB10 | e-sRGB10:<R>/<G>/<B>
e-sRGB12 | e-sRGB12:<R>/<G>/<B>
e-sRGB16 | e-sRGB16:<R>/<G>/<B>

The R, G, and B, fields are non-negative exact decimal integers within the appropriate ranges.

Several additional syntaxes are supported by `string->color`:

Color Space | External Representation
sRGB | sRGB:<RRGGBB>
sRGB | #<RRGGBB>
sRGB | 0x<RRGGBB>
sRGB | #x<RRGGBB>

Where RRGGBB is a non-negative six-digit hexadecimal number.

— Function: color->string color

> Returns a string representation of color.

— Function: string->color string

> Returns the color represented by string. If string is not a syntactically valid notation for a color, then `string->color` returns #f.

##### 5.11.1.2 White

We experience color relative to the illumination around us. CIEXYZ coordinates, although subject to uniform scaling, are objective. Thus other color spaces are specified relative to a white point in CIEXYZ coordinates. The white point for digital color spaces is set to D65. For the other spaces a white-point argument can be specified. The default if none is specified is the white-point with which the color was created or last converted; and D65 if none has been specified.

— Constant: D65

> Is the color of 6500.K (blackbody) illumination. D65 is close to the average color of daylight.

— Constant: D50

> Is the color of 5000.K (blackbody) illumination. D50 is the color of indoor lighting by incandescent bulbs, whose filaments have temperatures around 5000.K.

Next: Spectra, Previous: Color Data-Type, Up: Color

#### 5.11.2 Color Spaces

##### Measurement-based Color Spaces

The tristimulus color spaces are those whose component values are proportional measurements of light intensity. The CIEXYZ(1931) system provides 3 sets of spectra to dot-product with a spectrum of interest. The result of those dot-products is coordinates in CIEXYZ space. All tristimuls color spaces are related to CIEXYZ by linear transforms, namely matrix multiplication. Of the color spaces listed here, CIEXYZ and RGB709 are tristimulus spaces.

— Color Space: CIEXYZ

> The CIEXYZ color space covers the full gamut. It is the basis for color-space conversions.

> CIEXYZ is a list of three inexact numbers between 0.0 and 1.1. '(0. 0. 0.) is black; '(1. 1. 1.) is white.

— Function: ciexyz->color xyz

> xyz must be a list of 3 numbers. If xyz is valid CIEXYZ coordinates, then `ciexyz->color` returns the color specified by xyz; otherwise returns #f.

— Function: color:ciexyz x y z

> Returns the CIEXYZ color composed of x, y, z. If the coordinates do not encode a valid CIEXYZ color, then an error is signaled.

— Function: color->ciexyz color

> Returns the list of 3 numbers encoding color in CIEXYZ.

— Color Space: RGB709

> BT.709-4 (03/00) Parameter values for the HDTV standards for production and international programme exchange specifies parameter values for chromaticity, sampling, signal format, frame rates, etc., of high definition television signals.

> An RGB709 color is represented by a list of three inexact numbers between 0.0 and 1.0. '(0. 0. 0.) is black '(1. 1. 1.) is white.

— Function: rgb709->color rgb

> rgb must be a list of 3 numbers. If rgb is valid RGB709 coordinates, then `rgb709->color` returns the color specified by rgb; otherwise returns #f.

— Function: color:rgb709 r g b

> Returns the RGB709 color composed of r, g, b. If the coordinates do not encode a valid RGB709 color, then an error is signaled.

— Function: color->rgb709 color

> Returns the list of 3 numbers encoding color in RGB709.

##### Perceptual Uniformity

Although properly encoding the chromaticity, tristimulus spaces do not match the logarithmic response of human visual systems to intensity. Minimum detectable differences between colors correspond to a smaller range of distances (6:1) in the L*a*b* and L*u*v* spaces than in tristimulus spaces (80:1). For this reason, color distances are computed in L*a*b* (or L*C*h).

— Color Space: L*a*b*

> Is a CIE color space which better matches the human visual system's perception of color. It is a list of three numbers:

> - 0 <= L* <= 100 (CIE Lightness)
> - -500 <= a* <= 500
> - -200 <= b* <= 200

— Function: l*a*b*->color L*a*b* white-point

> L*a*b* must be a list of 3 numbers. If L*a*b* is valid L*a*b* coordinates, then `l*a*b*->color` returns the color specified by L*a*b*; otherwise returns #f.

— Function: color:l*a*b* L* a* b* white-point

> Returns the L*a*b* color composed of L*, a*, b* with white-point. — Function: color:l*a*b* L* a* b*

> > Returns the L*a*b* color composed of L*, a*, b*. If the coordinates do not encode a valid L*a*b* color, then an error is signaled.

— Function: color->l*a*b* color white-point

> Returns the list of 3 numbers encoding color in L*a*b* with white-point. — Function: color->l*a*b* color

> > Returns the list of 3 numbers encoding color in L*a*b*.

— Color Space: L*u*v*

> Is another CIE encoding designed to better match the human visual system's perception of color.

— Function: l*u*v*->color L*u*v* white-point

> L*u*v* must be a list of 3 numbers. If L*u*v* is valid L*u*v* coordinates, then `l*u*v*->color` returns the color specified by L*u*v*; otherwise returns #f.

— Function: color:l*u*v* L* u* v* white-point

> Returns the L*u*v* color composed of L*, u*, v* with white-point. — Function: color:l*u*v* L* u* v*

> > Returns the L*u*v* color composed of L*, u*, v*. If the coordinates do not encode a valid L*u*v* color, then an error is signaled.

— Function: color->l*u*v* color white-point

> Returns the list of 3 numbers encoding color in L*u*v* with white-point. — Function: color->l*u*v* color

> > Returns the list of 3 numbers encoding color in L*u*v*.

##### Cylindrical Coordinates

HSL (Hue Saturation Lightness), HSV (Hue Saturation Value), HSI (Hue Saturation Intensity) and HCI (Hue Chroma Intensity) are cylindrical color spaces (with angle hue). But these spaces are all defined in terms device-dependent RGB spaces.

One might wonder if there is some fundamental reason why intuitive specification of color must be device-dependent. But take heart! A cylindrical system can be based on L*a*b* and is used for predicting how close colors seem to observers.

— Color Space: L*C*h

> Expresses the *a and b* of L*a*b* in polar coordinates. It is a list of three numbers:

> - 0 <= L* <= 100 (CIE Lightness)
> - C* (CIE Chroma) is the distance from the neutral (gray) axis.
> - 0 <= h <= 360 (CIE Hue) is the angle.

> The colors by quadrant of h are:

> 0 | red, orange, yellow | 90
> 90 | yellow, yellow-green, green | 180
> 180 | green, cyan (blue-green), blue | 270
> 270 | blue, purple, magenta | 360

— Function: l*c*h->color L*C*h white-point

> L*C*h must be a list of 3 numbers. If L*C*h is valid L*C*h coordinates, then `l*c*h->color` returns the color specified by L*C*h; otherwise returns #f.

— Function: color:l*c*h L* C* h white-point

> Returns the L*C*h color composed of L*, C*, h with white-point. — Function: color:l*c*h L* C* h

> > Returns the L*C*h color composed of L*, C*, h. If the coordinates do not encode a valid L*C*h color, then an error is signaled.

— Function: color->l*c*h color white-point

> Returns the list of 3 numbers encoding color in L*C*h with white-point. — Function: color->l*c*h color

> > Returns the list of 3 numbers encoding color in L*C*h.

##### Digital Color Spaces

The color spaces discussed so far are impractical for image data because of numerical precision and computational requirements. In 1998 the IEC adopted A Standard Default Color Space for the Internet - sRGB (http://www.w3.org/Graphics/Color/sRGB). sRGB was cleverly designed to employ the 24-bit (256x256x256) color encoding already in widespread use; and the 2.2 gamma intrinsic to CRT monitors.

Conversion from CIEXYZ to digital (sRGB) color spaces is accomplished by conversion first to a RGB709 tristimulus space with D65 white-point; then each coordinate is individually subjected to the same non-linear mapping. Inverse operations in the reverse order create the inverse transform.

— Color Space: sRGB

> Is "A Standard Default Color Space for the Internet". Most display monitors will work fairly well with sRGB directly. Systems using ICC profiles 6 should work very well with sRGB.

— Function: srgb->color rgb

> rgb must be a list of 3 numbers. If rgb is valid sRGB coordinates, then `srgb->color` returns the color specified by rgb; otherwise returns #f.

— Function: color:srgb r g b

> Returns the sRGB color composed of r, g, b. If the coordinates do not encode a valid sRGB color, then an error is signaled.

— Color Space: xRGB

> Represents the equivalent sRGB color with a single 24-bit integer. The most significant 8 bits encode red, the middle 8 bits blue, and the least significant 8 bits green.

— Function: color->srgb color

> Returns the list of 3 integers encoding color in sRGB.

— Function: color->xrgb color

> Returns the 24-bit integer encoding color in sRGB.

— Function: xrgb->color k

> Returns the sRGB color composed of the 24-bit integer k.

— Color Space: e-sRGB

> Is "Photography - Electronic still picture imaging - Extended sRGB color encoding" (PIMA 7667:2001). It extends the gamut of sRGB; and its higher precision numbers provide a larger dynamic range.

> A triplet of integers represent e-sRGB colors. Three precisions are supported:

> e-sRGB10
>   0 to 1023
> e-sRGB12
>   0 to 4095
> e-sRGB16
>   0 to 65535

— Function: e-srgb->color precision rgb

> precision must be the integer 10, 12, or 16. rgb must be a list of 3 numbers. If rgb is valid e-sRGB coordinates, then `e-srgb->color` returns the color specified by rgb; otherwise returns #f.

— Function: color:e-srgb 10 r g b

> Returns the e-sRGB10 color composed of integers r, g, b. — Function: color:e-srgb 12 r g b

> > Returns the e-sRGB12 color composed of integers r, g, b. — Function: color:e-srgb 16 r g b

> > > Returns the e-sRGB16 color composed of integers r, g, b. If the coordinates do not encode a valid e-sRGB color, then an error is signaled.

— Function: color->e-srgb precision color

> precision must be the integer 10, 12, or 16. `color->e-srgb` returns the list of 3 integers encoding color in sRGB10, sRGB12, or sRGB16.

Next: Color Difference Metrics, Previous: Color Spaces, Up: Color

#### 5.11.3 Spectra

The following functions compute colors from spectra, scale color luminance, and extract chromaticity. XYZ is used in the names of procedures for unnormalized colors; the coordinates of CIEXYZ colors are constrained as described in Color Spaces.

`(require 'color-space)`

A spectrum may be represented as:

- A procedure of one argument accepting real numbers from 380e-9 to 780e-9, the wavelength in meters; or
- A vector of real numbers representing intensity samples evenly spaced over some range of wavelengths overlapping the range 380e-9 to 780e-9.

CIEXYZ values are calculated as dot-product with the X, Y (Luminance), and Z Spectral Tristimulus Values. The files `cie1931.xyz` and `cie1964.xyz` in the distribution contain these CIE-defined values.

— Feature: cie1964

> Loads the Spectral Tristimulus Values CIE 1964 Supplementary Standard Colorimetric Observer, defining cie:x-bar, cie:y-bar, and cie:z-bar. — Feature: cie1931

> > Loads the Spectral Tristimulus Values CIE 1931 Supplementary Standard Colorimetric Observer, defining cie:x-bar, cie:y-bar, and cie:z-bar. — Feature: ciexyz

> > > Requires Spectral Tristimulus Values, defaulting to cie1931, defining cie:x-bar, cie:y-bar, and cie:z-bar.

`(require 'cie1964)` or `(require 'cie1931)` will `load-ciexyz` specific values used by the following spectrum conversion procedures. The spectrum conversion procedures `(require 'ciexyz)` to assure that a set is loaded.

— Function: read-cie-illuminant path

> path must be a string naming a file consisting of 107 numbers for 5.nm intervals from 300.nm to 830.nm. `read-cie-illuminant` reads (using Scheme `read`) these numbers and returns a length 107 vector filled with them.

         (define CIE:SI-D65
           (read-CIE-illuminant (in-vicinity (library-vicinity) "ciesid65.dat")))
         (spectrum->XYZ CIE:SI-D65 300e-9 830e-9)
         => (25.108569422374994 26.418013465625001 28.764075683374993)

— Function: read-normalized-illuminant path

> path must be a string naming a file consisting of 107 numbers for 5.nm intervals from 300.nm to 830.nm. `read-normalized-illuminant` reads (using Scheme `read`) these numbers and returns a length 107 vector filled with them, normalized so that `spectrum->XYZ` of the illuminant returns its whitepoint.

CIE Standard Illuminants A and D65 are included with SLIB:

         (define CIE:SI-A
           (read-normalized-illuminant (in-vicinity (library-vicinity) "ciesia.dat")))
         (define CIE:SI-D65
           (read-normalized-illuminant (in-vicinity (library-vicinity) "ciesid65.dat")))
         (spectrum->XYZ CIE:SI-A 300e-9 830e-9)
         => (1.098499460820401 999.9999999999998e-3 355.8173930654951e-3)
         (CIEXYZ->sRGB (spectrum->XYZ CIE:SI-A 300e-9 830e-9))
         => (255 234 133)
         (spectrum->XYZ CIE:SI-D65 300e-9 830e-9)
         => (950.4336673552745e-3 1.0000000000000002 1.0888053986649182)
         (CIEXYZ->sRGB (spectrum->XYZ CIE:SI-D65 300e-9 830e-9))
         => (255 255 255)

— Function: illuminant-map proc siv

> siv must be a one-dimensional array or vector of 107 numbers. `illuminant-map` returns a vector of length 107 containing the result of applying proc to each element of siv.

— Function: illuminant-map->XYZ proc siv

> `(spectrum->XYZ (illuminant-map` proc siv`) 300e-9 830e-9)`

— Function: spectrum->XYZ proc

> proc must be a function of one argument. `spectrum->XYZ` computes the CIEXYZ(1931) values for the spectrum returned by proc when called with arguments from 380e-9 to 780e-9, the wavelength in meters. — Function: spectrum->XYZ spectrum x1 x2

> > x1 and x2 must be positive real numbers specifying the wavelengths (in meters) corresponding to the zeroth and last elements of vector or list spectrum. `spectrum->XYZ` returns the CIEXYZ(1931) values for a light source with spectral values proportional to the elements of spectrum at evenly spaced wavelengths between x1 and x2.

> > Compute the colors of 6500.K and 5000.K blackbody radiation:

> >               (require 'color-space)
> >               (define xyz (spectrum->XYZ (blackbody-spectrum 6500)))
> >               (define y_n (cadr xyz))
> >               (map (lambda (x) (/ x y_n)) xyz)
> >                   => (0.9687111145512467 1.0 1.1210875945303613)

> >               (define xyz (spectrum->XYZ (blackbody-spectrum 5000)))
> >               (map (lambda (x) (/ x y_n)) xyz)
> >                   => (0.2933441826889158 0.2988931825387761 0.25783646831201573)

— Function: spectrum->chromaticity proc
— Function: spectrum->chromaticity spectrum x1 x2

> Computes the chromaticity for the given spectrum.

— Function: wavelength->XYZ w

> w must be a number between 380e-9 to 780e-9. `wavelength->XYZ` returns (unnormalized) XYZ values for a monochromatic light source with wavelength w.

— Function: wavelength->chromaticity w

> w must be a number between 380e-9 to 780e-9. `wavelength->chromaticity` returns the chromaticity for a monochromatic light source with wavelength w.

— Function: blackbody-spectrum temp
— Function: blackbody-spectrum temp span

> Returns a procedure of one argument (wavelength in meters), which returns the radiance of a black body at temp.

> The optional argument span is the wavelength analog of bandwidth. With the default span of 1.nm (1e-9.m), the values returned by the procedure correspond to the power of the photons with wavelengths w to w+1e-9.

— Function: temperature->XYZ x

> The positive number x is a temperature in degrees kelvin. `temperature->XYZ` computes the unnormalized CIEXYZ(1931) values for the spectrum of a black body at temperature x.

> Compute the chromaticities of 6500.K and 5000.K blackbody radiation:

>               (require 'color-space)
>               (XYZ->chromaticity (temperature->XYZ 6500))
>                   => (0.3135191660557008 0.3236456786200268)

>               (XYZ->chromaticity (temperature->XYZ 5000))
>                   => (0.34508082841161052 0.3516084965163377)

— Function: temperature->chromaticity x

> The positive number x is a temperature in degrees kelvin. `temperature->cromaticity` computes the chromaticity for the spectrum of a black body at temperature x.

> Compute the chromaticities of 6500.K and 5000.K blackbody radiation:

>               (require 'color-space)
>               (temperature->chromaticity 6500)
>                   => (0.3135191660557008 0.3236456786200268)

>               (temperature->chromaticity 5000)
>                   => (0.34508082841161052 0.3516084965163377)

— Function: XYZ->chromaticity xyz

> Returns a two element list: the x and y components of xyz normalized to 1 (= x + y + z).

— Function: chromaticity->CIEXYZ x y

> Returns the list of x, and y, 1 - y - x.

— Function: chromaticity->whitepoint x y

> Returns the CIEXYZ(1931) values having luminosity 1 and chromaticity x and y.

Many color datasets are expressed in xyY format; chromaticity with CIE luminance (Y). But xyY is not a CIE standard like CIEXYZ, CIELAB, and CIELUV. Although chrominance is well defined, the luminance component is sometimes scaled to 1, sometimes to 100, but usually has no obvious range. With no given whitepoint, the only reasonable course is to ascertain the luminance range of a dataset and normalize the values to lie from 0 to 1.

— Function: XYZ->xyY xyz

> Returns a three element list: the x and y components of XYZ normalized to 1, and CIE luminance Y.

— Function: xyY->XYZ xyY
— Function: xyY:normalize-colors colors

> colors is a list of xyY triples. `xyY:normalize-colors` scales each chromaticity so it sums to 1 or less; and divides the Y values by the maximum Y in the dataset, so all lie between 0 and 1. — Function: xyY:normalize-colors colors n

> > If n is positive real, then `xyY:normalize-colors` divides the Y values by n times the maximum Y in the dataset.

> > If n is an exact non-positive integer, then `xyY:normalize-colors` divides the Y values by the maximum of the Ys in the dataset excepting the -n largest Y values.

> > In all cases, returned Y values are limited to lie from 0 to 1.

Why would one want to normalize to other than 1? If the sun or its reflection is the brightest object in a scene, then normalizing to its luminance will tend to make the rest of the scene very dark. As with photographs, limiting the specular highlights looks better than darkening everything else.

The results of measurements being what they are, `xyY:normalize-colors` is extremely tolerant. Negative numbers are replaced with zero, and chromaticities with sums greater than one are scaled to sum to one.

Next: Color Conversions, Previous: Spectra, Up: Color

#### 5.11.4 Color Difference Metrics

`(require 'color-space)`

The low-level metric functions operate on lists of 3 numbers, lab1, lab2, lch1, or lch2.

`(require 'color)`

The wrapped functions operate on objects of type color, color1 and color2 in the function entries.

— Function: L*a*b*:DE* lab1 lab2

> Returns the Euclidean distance between lab1 and lab2. — Function: CIE:DE* color1 color2 white-point
> — Function: CIE:DE* color1 color2

> > Returns the Euclidean distance in L*a*b* space between color1 and color2.

— Function: L*C*h:DE*94 lch1 lch2 parametric-factors
— Function: L*C*h:DE*94 lch1 lch2
— Function: CIE:DE*94 color1 color2 parametric-factors
— Function: CIE:DE*94 color1 color2

> Measures distance in the L*C*h cylindrical color-space. The three axes are individually scaled (depending on C*) in their contributions to the total distance.

> The CIE has defined reference conditions under which the metric with default parameters can be expected to perform well. These are:

> - The specimens are homogeneous in colour.
> - The colour difference (CIELAB) is <= 5 units.
> - They are placed in direct edge contact.
> - Each specimen subtends an angle of >4 degrees to the assessor, whose colour vision is normal.
> - They are illuminated at 1000 lux, and viewed against a background of uniform grey, with L* of 50, under illumination simulating D65.

> The parametric-factors argument is a list of 3 quantities kL, kC and kH. parametric-factors independently adjust each colour-difference term to account for any deviations from the reference viewing conditions. Under the reference conditions explained above, the default is kL = kC = kH = 1.

The Color Measurement Committee of The Society of Dyers and Colorists in Great Britain created a more sophisticated color-distance function for use in judging the consistency of dye lots. With CMC:DE* it is possible to use a single value pass/fail tolerance for all shades.

— Function: CMC-DE lch1 lch2 parametric-factors
— Function: CMC-DE lch1 lch2 l c
— Function: CMC-DE lch1 lch2 l
— Function: CMC-DE lch1 lch2
— Function: CMC:DE* color1 color2 l c
— Function: CMC:DE* color1 color2

> `CMC:DE` is a L*C*h metric. The parametric-factors argument is a list of 2 numbers l and c. l and c parameterize this metric. 1 and 1 are recommended for perceptibility; the default, 2 and 1, for acceptability.

Next: Color Names, Previous: Color Difference Metrics, Up: Color

#### 5.11.5 Color Conversions

This package contains the low-level color conversion and color metric routines operating on lists of 3 numbers. There is no type or range checking.

`(require 'color-space)`

— Constant: CIEXYZ:D65

> Is the color of 6500.K (blackbody) illumination. D65 is close to the average color of daylight.

— Constant: CIEXYZ:D50

> Is the color of 5000.K (blackbody) illumination. D50 is the color of indoor lighting by incandescent bulbs.

— Constant: CIEXYZ:A
— Constant: CIEXYZ:B
— Constant: CIEXYZ:C
— Constant: CIEXYZ:E

> CIE 1931 illuminants normalized to 1 = y.

— Function: color:linear-transform matrix row
— Function: CIEXYZ->RGB709 xyz
— Function: RGB709->CIEXYZ srgb
— Function: CIEXYZ->L*u*v* xyz white-point
— Function: CIEXYZ->L*u*v* xyz
— Function: L*u*v*->CIEXYZ L*u*v* white-point
— Function: L*u*v*->CIEXYZ L*u*v*

> The white-point defaults to CIEXYZ:D65.

— Function: CIEXYZ->L*a*b* xyz white-point
— Function: CIEXYZ->L*a*b* xyz
— Function: L*a*b*->CIEXYZ L*a*b* white-point
— Function: L*a*b*->CIEXYZ L*a*b*

> The XYZ white-point defaults to CIEXYZ:D65.

— Function: L*a*b*->L*C*h L*a*b*
— Function: L*C*h->L*a*b* L*C*h
— Function: CIEXYZ->sRGB xyz
— Function: sRGB->CIEXYZ srgb
— Function: CIEXYZ->xRGB xyz
— Function: xRGB->CIEXYZ srgb
— Function: sRGB->xRGB xyz
— Function: xRGB->sRGB srgb
— Function: CIEXYZ->e-sRGB n xyz
— Function: e-sRGB->CIEXYZ n srgb
— Function: sRGB->e-sRGB n srgb
— Function: e-sRGB->sRGB n srgb

> The integer n must be 10, 12, or 16. Because sRGB and e-sRGB use the same RGB709 chromaticities, conversion between them is simpler than conversion through CIEXYZ.

Do not convert e-sRGB precision through `e-sRGB->sRGB` then `sRGB->e-sRGB` – values would be truncated to 8-bits!

— Function: e-sRGB->e-sRGB n1 srgb n2

> The integers n1 and n2 must be 10, 12, or 16. `e-sRGB->e-sRGB` converts srgb to e-sRGB of precision n2.

Next: Daylight, Previous: Color Conversions, Up: Color

#### 5.11.6 Color Names

`(require 'color-names)` Rather than ballast the color dictionaries with numbered grays, `file->color-dictionary` discards them. They are provided through the `grey` procedure:

— Function: grey k

> Returns `(inexact->exact (round (* k 2.55)))`, the X11 color grey<k>.

A color dictionary is a database table relating canonical color-names to color-strings (see External Representation).

The column names in a color dictionary are unimportant; the first field is the key, and the second is the color-string.

— Function: color-name:canonicalize name

> Returns a downcased copy of the string or symbol name with ``_`', ``-`', and whitespace removed.

— Function: color-name->color name table1 table2 ...

> table1, table2, ... must be color-dictionary tables. `color-name->color` searches for the canonical form of name in table1, table2, ... in order; returning the color-string of the first matching record; #f otherwise.

— Function: color-dictionaries->lookup table1 table2 ...

> table1, table2, ... must be color-dictionary tables. `color-dictionaries->lookup` returns a procedure which searches for the canonical form of its string argument in table1, table2, ...; returning the color-string of the first matching record; and #f otherwise.

— Function: color-dictionary name rdb base-table-type

> rdb must be a string naming a relational database file; and the symbol name a table therein. The database will be opened as base-table-type. `color-dictionary` returns the read-only table name in database name if it exists; #f otherwise. — Function: color-dictionary name rdb

> > rdb must be an open relational database or a string naming a relational database file; and the symbol name a table therein. `color-dictionary` returns the read-only table name in database name if it exists; #f otherwise.

— Function: load-color-dictionary name rdb base-table-type
— Function: load-color-dictionary name rdb

> rdb must be a string naming a relational database file; and the symbol name a table therein. If the symbol base-table-type is provided, the database will be opened as base-table-type. `load-color-dictionary` creates a top-level definition of the symbol name to a lookup procedure for the color dictionary name in rdb.

> The value returned by `load-color-dictionary` is unspecified.

##### Dictionary Creation

`(require 'color-database)`

— Function: file->color-dictionary file table-name rdb base-table-type
— Function: file->color-dictionary file table-name rdb

> rdb must be an open relational database or a string naming a relational database file, table-name a symbol, and the string file must name an existing file with colornames and their corresponding xRGB (6-digit hex) values. `file->color-dictionary` creates a table table-name in rdb and enters the associations found in file into it.

— Function: url->color-dictionary url table-name rdb base-table-type
— Function: url->color-dictionary url table-name rdb

> rdb must be an open relational database or a string naming a relational database file and table-name a symbol. `url->color-dictionary` retrieves the resource named by the string url using the wget program; then calls `file->color-dictionary` to enter its associations in table-name in url.

This section has detailed the procedures for creating and loading color dictionaries. So where are the dictionaries to load?

http://swiss.csail.mit.edu/~jaffer/Color/Dictionaries.html

Describes and evaluates several color-name dictionaries on the web. The following procedure creates a database containing two of these dictionaries.

— Function: make-slib-color-name-db

> Creates an alist-table relational database in library-vicinity containing the Resene and saturate color-name dictionaries.

> If the files `resenecolours.txt`, `nbs-iscc.txt`, and `saturate.txt` exist in the library-vicinity, then they used as the source of color-name data. Otherwise, `make-slib-color-name-db` calls url->color-dictionary with the URLs of appropriate source files.

##### The Short List

`(require 'saturate)`

— Function: saturate name

> Looks for name among the 19 saturated colors from Approximate Colors on CIE Chromaticity Diagram:

> reddish orange | orange | yellowish orange | yellow
> greenish yellow | yellow green | yellowish green | green
> bluish green | blue green | greenish blue | blue
> purplish blue | bluish purple | purple | reddish purple
> red purple | purplish red | red

> (http://swiss.csail.mit.edu/~jaffer/Color/saturate.pdf). If name is found, the corresponding color is returned. Otherwise #f is returned. Use saturate only for light source colors.

Resene Paints Limited, New Zealand's largest privately-owned and operated paint manufacturing company, has generously made their Resene RGB Values List available.

`(require 'resene)`

— Function: resene name

> Looks for name among the 1300 entries in the Resene color-name dictionary (http://swiss.csail.mit.edu/~jaffer/Color/resene.pdf). If name is found, the corresponding color is returned. Otherwise #f is returned. The Resene RGB Values List is an excellent source for surface colors.

If you include the Resene RGB Values List in binary form in a program, then you must include its license with your program:

> Resene RGB Values List
> For further information refer to http://www.resene.co.nz
> Copyright Resene Paints Ltd 2001

> Permission to copy this dictionary, to modify it, to redistribute it, to distribute modified versions, and to use it for any purpose is granted, subject to the following restrictions and understandings.

> 1. Any text copy made of this dictionary must include this copyright notice in full.
> 2. Any redistribution in binary form must reproduce this copyright notice in the documentation or other materials provided with the distribution.
> 3. Resene Paints Ltd makes no warranty or representation that this dictionary is error-free, and is under no obligation to provide any services, by way of maintenance, update, or otherwise.
> 4. There shall be no use of the name of Resene or Resene Paints Ltd in any advertising, promotional, or sales literature without prior written consent in each case.
> 5. These RGB colour formulations may not be used to the detriment of Resene Paints Ltd.

Previous: Color Names, Up: Color

#### 5.11.7 Daylight

`(require 'daylight)` This package calculates the colors of sky as detailed in:
http://www.cs.utah.edu/vissim/papers/sunsky/sunsky.pdf
A Practical Analytic Model for Daylight
A. J. Preetham, Peter Shirley, Brian Smits

— Function: solar-hour julian-day hour

> Returns the solar-time in hours given the integer julian-day in the range 1 to 366, and the local time in hours.

> To be meticulous, subtract 4 minutes for each degree of longitude west of the standard meridian of your time zone.

— Function: solar-declination julian-day
— Function: solar-polar declination latitude solar-hour

> Returns a list of theta_s, the solar angle from the zenith, and phi_s, the solar azimuth. 0 <= theta_s measured in degrees. phi_s is measured in degrees from due south; west of south being positive.

In the following procedures, the number 0 <= theta_s <= 90 is the solar angle from the zenith in degrees.

Turbidity is a measure of the fraction of scattering due to haze as opposed to molecules. This is a convenient quantity because it can be estimated based on visibility of distant objects. This model fails for turbidity values less than 1.3.

             _______________________________________________________________
         512|-:                                                             |
            | * pure-air                                                    |
         256|-:**                                                           |
            | : ** exceptionally-clear                                      |
         128|-:   *                                                         |
            | :    **                                                       |
          64|-:      *                                                      |
            | :       ** very-clear                                         |
          32|-:         **                                                  |
            | :           **                                                |
          16|-:             *** clear                                       |
            | :               ****                                          |
           8|-:                  ****                                       |
            | :                     **** light-haze                         |
           4|-:                         ****                                |
            | :                             ******                          |
           2|-:                                  ******** haze         thin-|
            | :                                          ***********    fog |
           1|-:----------------------------------------------------*******--|
            |_:____.____:____.____:____.____:____.____:____.____:____.____:_|
              1         2         4         8        16        32        64
                       Meterorological range (km) versus Turbidity

— Function: sunlight-spectrum turbidity theta_s

> Returns a vector of 41 values, the spectrum of sunlight from 380.nm to 790.nm for a given turbidity and theta_s.

— Function: sunlight-chromaticity turbidity theta_s

> Given turbidity and theta_s, `sunlight-chromaticity` returns the CIEXYZ triple for color of sunlight scaled to be just inside the RGB709 gamut.

— Function: zenith-xyy turbidity theta_s

> Returns the xyY (chromaticity and luminance) at the zenith. The Luminance has units kcd/m^2.

— Function: overcast-sky-color-xyy turbidity theta_s

> turbidity is a positive real number expressing the amount of light scattering. The real number theta_s is the solar angle from the zenith in degrees.

> `overcast-sky-color-xyy` returns a function of one angle theta, the angle from the zenith of the viewing direction (in degrees); and returning the xyY value for light coming from that elevation of the sky.

— Function: clear-sky-color-xyy turbidity theta_s phi_s
— Function: sky-color-xyy turbidity theta_s phi_s

> turbidity is a positive real number expressing the amount of light scattering. The real number theta_s is the solar angle from the zenith in degrees. The real number phi_s is the solar angle from south.

> `clear-sky-color-xyy` returns a function of two angles, theta and phi which specify the angles from the zenith and south meridian of the viewing direction (in degrees); returning the xyY value for light coming from that direction of the sky.

> `sky-color-xyY` calls `overcast-sky-color-xyY` for turbidity <= 20; otherwise the `clear-sky-color-xyy` function.

Next: Minimizing, Previous: Color, Up: Mathematical Packages

### 5.12 Root Finding

`(require 'root)`

— Function: newton:find-integer-root f df/dx x0

> Given integer valued procedure f, its derivative (with respect to its argument) df/dx, and initial integer value x0 for which df/dx(x0) is non-zero, returns an integer x for which f(x) is closer to zero than either of the integers adjacent to x; or returns `#f` if such an integer can't be found.

> To find the closest integer to a given integer's square root:

>               (define (integer-sqrt y)
>                 (newton:find-integer-root
>                  (lambda (x) (- (* x x) y))
>                  (lambda (x) (* 2 x))
>                  (ash 1 (quotient (integer-length y) 2))))

>               (integer-sqrt 15) => 4

— Function: newton:find-root f df/dx x0 prec

> Given real valued procedures f, df/dx of one (real) argument, initial real value x0 for which df/dx(x0) is non-zero, and positive real number prec, returns a real x for which `abs`(f(x)) is less than prec; or returns `#f` if such a real can't be found.

> If prec is instead a negative integer, `newton:find-root` returns the result of -prec iterations.

H. J. Orchard, The Laguerre Method for Finding the Zeros of Polynomials, IEEE Transactions on Circuits and Systems, Vol. 36, No. 11, November 1989, pp 1377-1381.

> There are 2 errors in Orchard's Table II. Line k=2 for starting value of 1000+j0 should have Z_k of 1.0475 + j4.1036 and line k=2 for starting value of 0+j1000 should have Z_k of 1.0988 + j4.0833.

— Function: laguerre:find-root f df/dz ddf/dz^2 z0 prec

> Given complex valued procedure f of one (complex) argument, its derivative (with respect to its argument) df/dx, its second derivative ddf/dz^2, initial complex value z0, and positive real number prec, returns a complex number z for which `magnitude`(f(z)) is less than prec; or returns `#f` if such a number can't be found.

> If prec is instead a negative integer, `laguerre:find-root` returns the result of -prec iterations.

— Function: laguerre:find-polynomial-root deg f df/dz ddf/dz^2 z0 prec

> Given polynomial procedure f of integer degree deg of one argument, its derivative (with respect to its argument) df/dx, its second derivative ddf/dz^2, initial complex value z0, and positive real number prec, returns a complex number z for which `magnitude`(f(z)) is less than prec; or returns `#f` if such a number can't be found.

> If prec is instead a negative integer, `laguerre:find-polynomial-root` returns the result of -prec iterations.

— Function: secant:find-root f x0 x1 prec
— Function: secant:find-bracketed-root f x0 x1 prec

> Given a real valued procedure f and two real valued starting points x0 and x1, returns a real x for which `(abs (f x))` is less than prec; or returns `#f` if such a real can't be found.

> If x0 and x1 are chosen such that they bracket a root, that is

>               (or (< (f x0) 0 (f x1))
>                   (< (f x1) 0 (f x0)))

> then the root returned will be between x0 and x1, and f will not be passed an argument outside of that interval.

> `secant:find-bracketed-root` will return `#f` unless x0 and x1 bracket a root.

> The secant method is used until a bracketing interval is found, at which point a modified regula falsi method is used.

> If prec is instead a negative integer, `secant:find-root` returns the result of -prec iterations.

> If prec is a procedure it should accept 5 arguments: x0 f0 x1 f1 and count, where f0 will be `(f x0)`, f1 `(f x1)`, and count the number of iterations performed so far. prec should return non-false if the iteration should be stopped.

Next: The Limit, Previous: Root Finding, Up: Mathematical Packages

### 5.13 Minimizing

`(require 'minimize)`

The Golden Section Search 7 algorithm finds minima of functions which are expensive to compute or for which derivatives are not available. Although optimum for the general case, convergence is slow, requiring nearly 100 iterations for the example (x^3-2x-5).

If the derivative is available, Newton-Raphson is probably a better choice. If the function is inexpensive to compute, consider approximating the derivative.

— Function: golden-section-search f x0 x1 prec

> x_0 are x_1 real numbers. The (single argument) procedure f is unimodal over the open interval (x_0, x_1). That is, there is exactly one point in the interval for which the derivative of f is zero.

> `golden-section-search` returns a pair (x . f(x)) where f(x) is the minimum. The prec parameter is the stop criterion. If prec is a positive number, then the iteration continues until x is within prec from the true value. If prec is a negative integer, then the procedure will iterate -prec times or until convergence. If prec is a procedure of seven arguments, x0, x1, a, b, fa, fb, and count, then the iterations will stop when the procedure returns `#t`.

> Analytically, the minimum of x^3-2x-5 is 0.816497.

>               (define func (lambda (x) (+ (* x (+ (* x x) -2)) -5)))
>               (golden-section-search func 0 1 (/ 10000))
>                     ==> (816.4883855245578e-3 . -6.0886621077391165)
>               (golden-section-search func 0 1 -5)
>                     ==> (819.6601125010515e-3 . -6.088637561916407)
>               (golden-section-search func 0 1
>                                      (lambda (a b c d e f g ) (= g 500)))
>                     ==> (816.4965933140557e-3 . -6.088662107903635)

Next: Commutative Rings, Previous: Minimizing, Up: Mathematical Packages

### 5.14 The Limit

— library procedure: limit proc x1 x2 k
— library procedure: limit proc x1 x2

> Proc must be a procedure taking a single inexact real argument. K is the number of points on which proc will be called; it defaults to 8.

> If x1 is finite, then Proc must be continuous on the half-open interval:

> ( x1 .. x1+x2 ]

> And x2 should be chosen small enough so that proc is expected to be monotonic or constant on arguments between x1 and x1 + x2.

> `Limit` computes the limit of proc as its argument approaches x1 from x1 + x2. `Limit` returns a real number or real infinity or ``#f`'.

> If x1 is not finite, then x2 must be a finite nonzero real with the same sign as x1; in which case `limit` returns:

> `(limit (lambda (x) (proc (/ x))) 0.0 (/` x2`)` k`)`

> `Limit` examines the magnitudes of the differences between successive values returned by proc called with a succession of numbers from x1+x2/k to x1.

> If the magnitudes of differences are monotonically decreasing, then then the limit is extrapolated from the degree n polynomial passing through the samples returned by proc.

> If the magnitudes of differences are increasing as fast or faster than a hyperbola matching at x1+x2, then a real infinity with sign the same as the differences is returned.

> If the magnitudes of differences are increasing more slowly than the hyperbola matching at x1+x2, then the limit is extrapolated from the quadratic passing through the three samples closest to x1.

> If the magnitudes of differences are not monotonic or are not completely within one of the above categories, then #f is returned.

         ;; constant
         (limit (lambda (x) (/ x x)) 0 1.0e-9)           ==> 1.0
         (limit (lambda (x) (expt 0 x)) 0 1.0e-9)        ==> 0.0
         (limit (lambda (x) (expt 0 x)) 0 -1.0e-9)       ==> +inf.0
         ;; linear
         (limit + 0 976.5625e-6)                         ==> 0.0
         (limit - 0 976.5625e-6)                         ==> 0.0
         ;; vertical point of inflection
         (limit sqrt 0 1.0e-18)                          ==> 0.0
         (limit (lambda (x) (* x (log x))) 0 1.0e-9)     ==> -102.70578127633066e-12
         (limit (lambda (x) (/ x (log x))) 0 1.0e-9)     ==> 96.12123142321669e-15
         ;; limits tending to infinity
         (limit + +inf.0 1.0e9)                          ==> +inf.0
         (limit + -inf.0 -1.0e9)                         ==> -inf.0
         (limit / 0 1.0e-9)                              ==> +inf.0
         (limit / 0 -1.0e-9)                             ==> -inf.0
         (limit (lambda (x) (/ (log x) x)) 0 1.0e-9)     ==> -inf.0
         (limit (lambda (x) (/ (magnitude (log x)) x)) 0 -1.0e-9)
                                                         ==> -inf.0
         ;; limit doesn't exist
         (limit sin +inf.0 1.0e9)                        ==> #f
         (limit (lambda (x) (sin (/ x))) 0 1.0e-9)       ==> #f
         (limit (lambda (x) (sin (/ x))) 0 -1.0e-9)      ==> #f
         (limit (lambda (x) (/ (log x) x)) 0 -1.0e-9)    ==> #f
         ;; conditionally convergent - return #f
         (limit (lambda (x) (/ (sin x) x)) +inf.0 1.0e222)
                                                         ==> #f
         ;; asymptotes
         (limit / -inf.0 -1.0e222)                       ==> 0.0
         (limit / +inf.0 1.0e222)                        ==> 0.0
         (limit (lambda (x) (expt x x)) 0 1.0e-18)       ==> 1.0
         (limit (lambda (x) (sin (/ x))) +inf.0 1.0e222) ==> 0.0
         (limit (lambda (x) (/ (+ (exp (/ x)) 1))) 0 1.0e-9)
                                                         ==> 0.0
         (limit (lambda (x) (/ (+ (exp (/ x)) 1))) 0 -1.0e-9)
                                                         ==> 1.0
         (limit (lambda (x) (real-part (expt (tan x) (cos x)))) (/ pi 2) 1.0e-9)
                                                         ==> 1.0
         ;; This example from the 1979 Macsyma manual grows so rapidly
         ;;  that x2 must be less than 41.  It correctly returns e^2.
         (limit (lambda (x) (expt (+ x (exp x) (exp (* 2 x))) (/ x))) +inf.0 40)
                                                         ==> 7.3890560989306504
         ;; LIMIT can calculate the proper answer when evaluation
         ;; of the function at the limit point does not:
         (tan (atan +inf.0))                             ==> 16.331778728383844e15
         (limit tan (atan +inf.0) -1.0e-15)              ==> +inf.0
         (tan (atan +inf.0))                             ==> 16.331778728383844e15
         (limit tan (atan +inf.0) 1.0e-15)               ==> -inf.0
         ((lambda (x) (expt (exp (/ -1 x)) x)) 0)        ==> 1.0
         (limit (lambda (x) (expt (exp (/ -1 x)) x)) 0 1.0e-9)
                                                         ==> 0.0

Next: Matrix Algebra, Previous: The Limit, Up: Mathematical Packages

### 5.15 Commutative Rings

Scheme provides a consistent and capable set of numeric functions. Inexacts implement a field; integers a commutative ring (and Euclidean domain). This package allows one to use basic Scheme numeric functions with symbols and non-numeric elements of commutative rings.

`(require 'commutative-ring)` The commutative-ring package makes the procedures `+`, `-`, `*`, `/`, and `^` careful in the sense that any non-numeric arguments they do not reduce appear in the expression output. In order to see what working with this package is like, self-set all the single letter identifiers (to their corresponding symbols).

         (define a 'a)
         ...
         (define z 'z)

Or just `(require 'self-set)`. Now try some sample expressions:

         (+ (+ a b) (- a b)) => (* a 2)
         (* (+ a b) (+ a b)) => (^ (+ a b) 2)
         (* (+ a b) (- a b)) => (* (+ a b) (- a b))
         (* (- a b) (- a b)) => (^ (- a b) 2)
         (* (- a b) (+ a b)) => (* (+ a b) (- a b))
         (/ (+ a b) (+ c d)) => (/ (+ a b) (+ c d))
         (^ (+ a b) 3) => (^ (+ a b) 3)
         (^ (+ a 2) 3) => (^ (+ 2 a) 3)

Associative rules have been applied and repeated addition and multiplication converted to multiplication and exponentiation.

We can enable distributive rules, thus expanding to sum of products form:

         (set! *ruleset* (combined-rulesets distribute* distribute/))

         (* (+ a b) (+ a b)) => (+ (* 2 a b) (^ a 2) (^ b 2))
         (* (+ a b) (- a b)) => (- (^ a 2) (^ b 2))
         (* (- a b) (- a b)) => (- (+ (^ a 2) (^ b 2)) (* 2 a b))
         (* (- a b) (+ a b)) => (- (^ a 2) (^ b 2))
         (/ (+ a b) (+ c d)) => (+ (/ a (+ c d)) (/ b (+ c d)))
         (/ (+ a b) (- c d)) => (+ (/ a (- c d)) (/ b (- c d)))
         (/ (- a b) (- c d)) => (- (/ a (- c d)) (/ b (- c d)))
         (/ (- a b) (+ c d)) => (- (/ a (+ c d)) (/ b (+ c d)))
         (^ (+ a b) 3) => (+ (* 3 a (^ b 2)) (* 3 b (^ a 2)) (^ a 3) (^ b 3))
         (^ (+ a 2) 3) => (+ 8 (* a 12) (* (^ a 2) 6) (^ a 3))

Use of this package is not restricted to simple arithmetic expressions:

         (require 'determinant)

         (determinant '((a b c) (d e f) (g h i))) =>
         (- (+ (* a e i) (* b f g) (* c d h)) (* a f h) (* b d i) (* c e g))

Currently, only `+`, `-`, `*`, `/`, and `^` support non-numeric elements. Expressions with `-` are converted to equivalent expressions without `-`, so behavior for `-` is not defined separately. `/` expressions are handled similarly.

This list might be extended to include `quotient`, `modulo`, `remainder`, `lcm`, and `gcd`; but these work only for the more restrictive Euclidean (Unique Factorization) Domain.

### 5.16 Rules and Rulesets

The commutative-ring package allows control of ring properties through the use of rulesets.

— Variable: *ruleset*

> Contains the set of rules currently in effect. Rules defined by `cring:define-rule` are stored within the value of *ruleset* at the time `cring:define-rule` is called. If *ruleset* is `#f`, then no rules apply.

— Function: make-ruleset rule1 ...
— Function: make-ruleset name rule1 ...

> Returns a new ruleset containing the rules formed by applying `cring:define-rule` to each 4-element list argument rule. If the first argument to `make-ruleset` is a symbol, then the database table created for the new ruleset will be named name. Calling `make-ruleset` with no rule arguments creates an empty ruleset.

— Function: combined-rulesets ruleset1 ...
— Function: combined-rulesets name ruleset1 ...

> Returns a new ruleset containing the rules contained in each ruleset argument ruleset. If the first argument to `combined-ruleset` is a symbol, then the database table created for the new ruleset will be named name. Calling `combined-ruleset` with no ruleset arguments creates an empty ruleset.

Two rulesets are defined by this package.

— Constant: distribute*

> Contains the ruleset to distribute multiplication over addition and subtraction.

— Constant: distribute/

> Contains the ruleset to distribute division over addition and subtraction.

> Take care when using both distribute* and distribute/ simultaneously. It is possible to put `/` into an infinite loop.

You can specify how sum and product expressions containing non-numeric elements simplify by specifying the rules for `+` or `*` for cases where expressions involving objects reduce to numbers or to expressions involving different non-numeric elements.

— Function: cring:define-rule op sub-op1 sub-op2 reduction

> Defines a rule for the case when the operation represented by symbol op is applied to lists whose `car`s are sub-op1 and sub-op2, respectively. The argument reduction is a procedure accepting 2 arguments which will be lists whose `car`s are sub-op1 and sub-op2. — Function: cring:define-rule op sub-op1 'identity reduction

> > Defines a rule for the case when the operation represented by symbol op is applied to a list whose `car` is sub-op1, and some other argument. Reduction will be called with the list whose `car` is sub-op1 and some other argument.

> > If reduction returns `#f`, the reduction has failed and other reductions will be tried. If reduction returns a non-false value, that value will replace the two arguments in arithmetic (`+`, `-`, and `*`) calculations involving non-numeric elements.

> > The operations `+` and `*` are assumed commutative; hence both orders of arguments to reduction will be tried if necessary.

> > The following rule is the definition for distributing `*` over `+`.

> >               (cring:define-rule
> >                '* '+ 'identity
> >                (lambda (exp1 exp2)
> >                  (apply + (map (lambda (trm) (* trm exp2)) (cdr exp1))))))

### 5.17 How to Create a Commutative Ring

The first step in creating your commutative ring is to write procedures to create elements of the ring. A non-numeric element of the ring must be represented as a list whose first element is a symbol or string. This first element identifies the type of the object. A convenient and clear convention is to make the type-identifying element be the same symbol whose top-level value is the procedure to create it.

         (define (n . list1)
           (cond ((and (= 2 (length list1))
                       (eq? (car list1) (cadr list1)))
                  0)
                 ((not (term< (first list1) (last1 list1)))
                  (apply n (reverse list1)))
                 (else (cons 'n list1))))

         (define (s x y) (n x y))

         (define (m . list1)
           (cond ((neq? (first list1) (term_min list1))
                  (apply m (cyclicrotate list1)))
                 ((term< (last1 list1) (cadr list1))
                  (apply m (reverse (cyclicrotate list1))))
                 (else (cons 'm list1))))

Define a procedure to multiply 2 non-numeric elements of the ring. Other multiplicatons are handled automatically. Objects for which rules have not been defined are not changed.

         (define (n*n ni nj)
           (let ((list1 (cdr ni)) (list2 (cdr nj)))
             (cond ((null? (intersection list1 list2)) #f)
                   ((and (eq? (last1 list1) (first list2))
                         (neq? (first list1) (last1 list2)))
                    (apply n (splice list1 list2)))
                   ((and (eq? (first list1) (first list2))
                         (neq? (last1 list1) (last1 list2)))
                    (apply n (splice (reverse list1) list2)))
                   ((and (eq? (last1 list1) (last1 list2))
                         (neq? (first list1) (first list2)))
                    (apply n (splice list1 (reverse list2))))
                   ((and (eq? (last1 list1) (first list2))
                         (eq? (first list1) (last1 list2)))
                    (apply m (cyclicsplice list1 list2)))
                   ((and (eq? (first list1) (first list2))
                         (eq? (last1 list1) (last1 list2)))
                    (apply m (cyclicsplice (reverse list1) list2)))
                   (else #f))))

Test the procedures to see if they work.

         ;;; where cyclicrotate(list) is cyclic rotation of the list one step
         ;;; by putting the first element at the end
         (define (cyclicrotate list1)
           (append (rest list1) (list (first list1))))
         ;;; and where term_min(list) is the element of the list which is
         ;;; first in the term ordering.
         (define (term_min list1)
           (car (sort list1 term<)))
         (define (term< sym1 sym2)
           (string<? (symbol->string sym1) (symbol->string sym2)))
         (define first car)
         (define rest cdr)
         (define (last1 list1) (car (last-pair list1)))
         (define (neq? obj1 obj2) (not (eq? obj1 obj2)))
         ;;; where splice is the concatenation of list1 and list2 except that their
         ;;; common element is not repeated.
         (define (splice list1 list2)
           (cond ((eq? (last1 list1) (first list2))
                  (append list1 (cdr list2)))
                 (else (slib:error 'splice list1 list2))))
         ;;; where cyclicsplice is the result of leaving off the last element of
         ;;; splice(list1,list2).
         (define (cyclicsplice list1 list2)
           (cond ((and (eq? (last1 list1) (first list2))
                       (eq? (first list1) (last1 list2)))
                  (butlast (splice list1 list2) 1))
                 (else (slib:error 'cyclicsplice list1 list2))))

         (N*N (S a b) (S a b)) => (m a b)

Then register the rule for multiplying type N objects by type N objects.

         (cring:define-rule '* 'N 'N N*N))

Now we are ready to compute!

         (define (t)
           (define detM
             (+ (* (S g b)
                   (+ (* (S f d)
                         (- (* (S a f) (S d g)) (* (S a g) (S d f))))
                      (* (S f f)
                         (- (* (S a g) (S d d)) (* (S a d) (S d g))))
                      (* (S f g)
                         (- (* (S a d) (S d f)) (* (S a f) (S d d))))))
                (* (S g d)
                   (+ (* (S f b)
                         (- (* (S a g) (S d f)) (* (S a f) (S d g))))
                      (* (S f f)
                         (- (* (S a b) (S d g)) (* (S a g) (S d b))))
                      (* (S f g)
                         (- (* (S a f) (S d b)) (* (S a b) (S d f))))))
                (* (S g f)
                   (+ (* (S f b)
                         (- (* (S a d) (S d g)) (* (S a g) (S d d))))
                      (* (S f d)
                         (- (* (S a g) (S d b)) (* (S a b) (S d g))))
                      (* (S f g)
                         (- (* (S a b) (S d d)) (* (S a d) (S d b))))))
                (* (S g g)
                   (+ (* (S f b)
                         (- (* (S a f) (S d d)) (* (S a d) (S d f))))
                      (* (S f d)
                         (- (* (S a b) (S d f)) (* (S a f) (S d b))))
                      (* (S f f)
                         (- (* (S a d) (S d b)) (* (S a b) (S d d))))))))
           (* (S b e) (S c a) (S e c)
              detM
              ))
         (pretty-print (t))
         -|
         (- (+ (m a c e b d f g)
               (m a c e b d g f)
               (m a c e b f d g)
               (m a c e b f g d)
               (m a c e b g d f)
               (m a c e b g f d))
            (* 2 (m a b e c) (m d f g))
            (* (m a c e b d) (m f g))
            (* (m a c e b f) (m d g))
            (* (m a c e b g) (m d f)))

Previous: Commutative Rings, Up: Mathematical Packages

### 5.18 Matrix Algebra

`(require 'determinant)` A Matrix can be either a list of lists (rows) or an array. Unlike linear-algebra texts, this package uses 0-based coordinates.

— Function: matrix->lists matrix

> Returns the list-of-lists form of matrix.

— Function: matrix->array matrix

> Returns the array form of matrix.

— Function: determinant matrix

> matrix must be a square matrix. `determinant` returns the determinant of matrix.

>               (require 'determinant)
>               (determinant '((1 2) (3 4))) => -2
>               (determinant '((1 2 3) (4 5 6) (7 8 9))) => 0

— Function: transpose matrix

> Returns a copy of matrix flipped over the diagonal containing the 1,1 element.

— Function: matrix:sum m1 m2

> Returns the element-wise sum of matricies m1 and m2.

— Function: matrix:difference m1 m2

> Returns the element-wise difference of matricies m1 and m2.

— Function: matrix:product m1 m2

> Returns the product of matrices m1 and m2. — Function: matrix:product m1 z

> > Returns matrix m1 times scalar z. — Function: matrix:product z m1

> > > Returns matrix m1 times scalar z.

— Function: matrix:inverse matrix

> matrix must be a square matrix. If matrix is singular, then `matrix:inverse` returns #f; otherwise `matrix:inverse` returns the `matrix:product` inverse of matrix.

Next: Other Packages, Previous: Mathematical Packages, Up: Top

## 6 Database Packages

Next: Relational Infrastructure, Previous: Database Packages, Up: Database Packages

### 6.1 Relational Database

`(require 'relational-database)` This package implements a database system inspired by the Relational Model (E. F. Codd, A Relational Model of Data for Large Shared Data Banks). An SLIB relational database implementation can be created from any Base Table implementation.

Why relational database? For motivations and design issues see
http://swiss.csail.mit.edu/~jaffer/DBManifesto.html.

Next: Table Operations, Previous: Relational Database, Up: Relational Database

#### 6.1.1 Using Databases

`(require 'databases)` This enhancement wraps a utility layer on `relational-database` which provides:

- Identification of open databases by filename.
- Automatic sharing of open (immutable) databases.
- Automatic loading of base-table package when creating a database.
- Detection and automatic loading of the appropriate base-table package when opening a database.
- Table and data definition from Scheme lists.

##### Database Sharing

Auto-sharing refers to a call to the procedure `open-database` returning an already open database (procedure), rather than opening the database file a second time.

> Note: Databases returned by `open-database` do not include wrappers applied by packages like Embedded Commands. But wrapped databases do work as arguments to these functions.

When a database is created, it is mutable by the creator and not auto-sharable. A database opened mutably is also not auto-sharable. But any number of readers can (open) share a non-mutable database file.

This next set of procedures mirror the whole-database methods in Database Operations. Except for `create-database`, each procedure will accept either a filename or database procedure for its first argument.

— Function: create-database filename base-table-type

> filename should be a string naming a file; or `#f`. base-table-type must be a symbol naming a feature which can be passed to `require`. `create-database` returns a new, open relational database (with base-table type base-table-type) associated with filename, or a new ephemeral database if filename is `#f`.

> `create-database` is the only run-time use of require in SLIB which crosses module boundaries. When base-table-type is `require`d by `create-database`; it adds an association of base-table-type with its relational-system procedure to mdbm:*databases*.

> alist-table is the default base-table type:

>               (require 'databases)
>               (define my-rdb (create-database "my.db" 'alist-table))

Only `alist-table` and base-table modules which have been `require`d will dispatch correctly from the `open-database` procedures. Therefore, either pass two arguments to `open-database`, or require the base-table of your database file uses before calling `open-database` with one argument.

— Procedure: open-database! rdb base-table-type

> Returns mutable open relational database or #f.

— Function: open-database rdb base-table-type

> Returns an open relational database associated with rdb. The database will be opened with base-table type base-table-type). — Function: open-database rdb

> > Returns an open relational database associated with rdb. `open-database` will attempt to deduce the correct base-table-type.

— Function: write-database rdb filename

> Writes the mutable relational-database rdb to filename.

— Function: sync-database rdb

> Writes the mutable relational-database rdb to the filename it was opened with.

— Function: solidify-database rdb

> Syncs rdb and makes it immutable.

— Function: close-database rdb

> rdb will only be closed when the count of `open-database` - `close-database` calls for rdb (and its filename) is 0. `close-database` returns #t if successful; and #f otherwise.

— Function: mdbm:report

> Prints a table of open database files. The columns are the base-table type, number of opens, ``!`' for mutable, the filename, and the lock certificate (if locked).

         (mdbm:report)
         -|
           alist-table 003   /usr/local/lib/slib/clrnamdb.scm
           alist-table 001 ! sdram.db jaffer@aubrey.jaffer.3166:1038628199

##### Opening Tables

— Function: open-table rdb table-name

> rdb must be a relational database and table-name a symbol.

> `open-table` returns a "methods" procedure for an existing relational table in rdb if it exists and can be opened for reading, otherwise returns `#f`.

— Procedure: open-table! rdb table-name

> rdb must be a relational database and table-name a symbol.

> `open-table!` returns a "methods" procedure for an existing relational table in rdb if it exists and can be opened in mutable mode, otherwise returns `#f`.

##### Defining Tables

— Function: define-domains rdb row5 ...

> Adds the domain rows row5 ... to the ``*domains-data*`' table in rdb. The format of the row is given in Catalog Representation.

>               (define-domains rdb '(permittivity #f complex? c64 #f))

— Function: add-domain rdb row5

> Use `define-domains` instead.

— Function: define-tables rdb spec-0 ...

> Adds tables as specified in spec-0 ... to the open relational-database rdb. Each spec has the form:

>               (<name> <descriptor-name> <descriptor-name> <rows>)

> or

>               (<name> <primary-key-fields> <other-fields> <rows>)

> where <name> is the table name, <descriptor-name> is the symbol name of a descriptor table, <primary-key-fields> and <other-fields> describe the primary keys and other fields respectively, and <rows> is a list of data rows to be added to the table.

> <primary-key-fields> and <other-fields> are lists of field descriptors of the form:

>               (<column-name> <domain>)

> or

>               (<column-name> <domain> <column-integrity-rule>)

> where <column-name> is the column name, <domain> is the domain of the column, and <column-integrity-rule> is an expression whose value is a procedure of one argument (which returns `#f` to signal an error).

> If <domain> is not a defined domain name and it matches the name of this table or an already defined (in one of spec-0 ...) single key field table, a foreign-key domain will be created for it.

##### Listing Tables

— Function: list-table-definition rdb table-name

> If symbol table-name exists in the open relational-database rdb, then returns a list of the table-name, its primary key names and domains, its other key names and domains, and the table's records (as lists). Otherwise, returns #f.

> The list returned by `list-table-definition`, when passed as an argument to `define-tables`, will recreate the table.

Next: Database Interpolation, Previous: Using Databases, Up: Relational Database

#### 6.1.2 Table Operations

These are the descriptions of the methods available from an open relational table. A method is retrieved from a table by calling the table with the symbol name of the operation. For example:

         ((plat 'get 'processor) 'djgpp) => i386

Some operations described below require primary key arguments. Primary keys arguments are denoted key1 key2 .... It is an error to call an operation for a table which takes primary key arguments with the wrong number of primary keys for that table.

— Operation on relational-table: get column-name

> Returns a procedure of arguments key1 key2 ... which returns the value for the column-name column of the row associated with primary keys key1, key2 ... if that row exists in the table, or `#f` otherwise.

>               ((plat 'get 'processor) 'djgpp) => i386
>               ((plat 'get 'processor) 'be-os) => #f

Next: Match-Keys, Previous: Table Operations, Up: Table Operations

##### 6.1.2.1 Single Row Operations

The term row used below refers to a Scheme list of values (one for each column) in the order specified in the descriptor (table) for this table. Missing values appear as `#f`. Primary keys must not be missing.

— Operation on relational-table: row:insert

> Adds the row row to this table. If a row for the primary key(s) specified by row already exists in this table an error is signaled. The value returned is unspecified.

         (define telephone-table-desc
                 ((my-database 'create-table) 'telephone-table-desc))
         (define ndrp (telephone-table-desc 'row:insert))
         (ndrp '(1 #t name #f string))
         (ndrp '(2 #f telephone
                   (lambda (d)
                     (and (string? d) (> (string-length d) 2)
                          (every
                           (lambda (c)
                             (memv c '(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9
                                           #\+ #\( #\space #\) #\-)))
                           (string->list d))))
                   string))

— Operation on relational-table: row:update

> Returns a procedure of one argument, row, which adds the row, row, to this table. If a row for the primary key(s) specified by row already exists in this table, it will be overwritten. The value returned is unspecified.

— Operation on relational-table: row:retrieve

> Returns a procedure of arguments key1 key2 ... which returns the row associated with primary keys key1, key2 ... if it exists, or `#f` otherwise.

         ((plat 'row:retrieve) 'linux) => (linux i386 linux gcc)
         ((plat 'row:retrieve) 'multics) => #f

— Operation on relational-table: row:remove

> Returns a procedure of arguments key1 key2 ... which removes and returns the row associated with primary keys key1, key2 ... if it exists, or `#f` otherwise.

— Operation on relational-table: row:delete

> Returns a procedure of arguments key1 key2 ... which deletes the row associated with primary keys key1, key2 ... if it exists. The value returned is unspecified.

Next: Multi-Row Operations, Previous: Single Row Operations, Up: Table Operations

##### 6.1.2.2 Match-Keys

The (optional) match-key1 ... arguments are used to restrict actions of a whole-table operation to a subset of that table. Those procedures (returned by methods) which accept match-key arguments will accept any number of match-key arguments between zero and the number of primary keys in the table. Any unspecified match-key arguments default to `#f`.

The match-key1 ... restrict the actions of the table command to those records whose primary keys each satisfy the corresponding match-key argument. The arguments and their actions are:

> `#f`
>   The false value matches any key in the corresponding position.
> an object of type procedure
>   This procedure must take a single argument, the key in the corresponding position. Any key for which the procedure returns a non-false value is a match; Any key for which the procedure returns a `#f` is not.
> other values
>   Any other value matches only those keys `equal?` to it.

— Operation on relational-table: get* column-name

> Returns a procedure of optional arguments match-key1 ... which returns a list of the values for the specified column for all rows in this table. The optional match-key1 ... arguments restrict actions to a subset of the table.

>               ((plat 'get* 'processor)) =>
>               (i386 i8086 i386 i8086 i386 i386 i8086 m68000
>                m68000 m68000 m68000 m68000 powerpc)

>               ((plat 'get* 'processor) #f) =>
>               (i386 i8086 i386 i8086 i386 i386 i8086 m68000
>                m68000 m68000 m68000 m68000 powerpc)

>               (define (a-key? key)
>                  (char=? #\a (string-ref (symbol->string key) 0)))

>               ((plat 'get* 'processor) a-key?) =>
>               (m68000 m68000 m68000 m68000 m68000 powerpc)

>               ((plat 'get* 'name) a-key?) =>
>               (atari-st-turbo-c atari-st-gcc amiga-sas/c-5.10
>                amiga-aztec amiga-dice-c aix)

Next: Indexed Sequential Access Methods, Previous: Match-Keys, Up: Table Operations

##### 6.1.2.3 Multi-Row Operations

— Operation on relational-table: row:retrieve*

> Returns a procedure of optional arguments match-key1 ... which returns a list of all rows in this table. The optional match-key1 ... arguments restrict actions to a subset of the table. For details see See Match-Keys.

         ((plat 'row:retrieve*) a-key?) =>
         ((atari-st-turbo-c m68000 atari turbo-c)
          (atari-st-gcc m68000 atari gcc)
          (amiga-sas/c-5.10 m68000 amiga sas/c)
          (amiga-aztec m68000 amiga aztec)
          (amiga-dice-c m68000 amiga dice-c)
          (aix powerpc aix -))

— Operation on relational-table: row:remove*

> Returns a procedure of optional arguments match-key1 ... which removes and returns a list of all rows in this table. The optional match-key1 ... arguments restrict actions to a subset of the table.

— Operation on relational-table: row:delete*

> Returns a procedure of optional arguments match-key1 ... which Deletes all rows from this table. The optional match-key1 ... arguments restrict deletions to a subset of the table. The value returned is unspecified. The descriptor table and catalog entry for this table are not affected.

— Operation on relational-table: for-each-row

> Returns a procedure of arguments proc match-key1 ... which calls proc with each row in this table. The optional match-key1 ... arguments restrict actions to a subset of the table. For details see See Match-Keys.

Note that `row:insert*` and `row:update*` do not use match-keys.

— Operation on relational-table: row:insert*

> Returns a procedure of one argument, rows, which adds each row in the list of rows, rows, to this table. If a row for the primary key specified by an element of rows already exists in this table, an error is signaled. The value returned is unspecified.

— Operation on relational-table: row:update*

> Returns a procedure of one argument, rows, which adds each row in the list of rows, rows, to this table. If a row for the primary key specified by an element of rows already exists in this table, it will be overwritten. The value returned is unspecified.

Next: Sequential Index Operations, Previous: Multi-Row Operations, Up: Table Operations

##### 6.1.2.4 Indexed Sequential Access Methods

Indexed Sequential Access Methods are a way of arranging database information so that records can be accessed both by key and by key sequence (ordering). ISAM is not part of Codd's relational model. Hardcore relational programmers might use some least-upper-bound join for every row to get them into an order.

Associative memory in B-Trees is an example of a database implementation which can support a native key ordering. SLIB's `alist-table` implementation uses `sort` to implement `for-each-row-in-order`, but does not support `isam-next` and `isam-prev`.

The multi-primary-key ordering employed by these operations is the lexicographic collation of those primary-key fields in their given order. For example:

         (12 a 34) < (12 a 36) < (12 b 1) < (13 a 0)

Next: Table Administration, Previous: Indexed Sequential Access Methods, Up: Table Operations

##### 6.1.2.5 Sequential Index Operations

The following procedures are individually optional depending on the base-table implememtation. If an operation is not supported, then calling the table with that operation symbol will return false.

— Operation on relational-table: for-each-row-in-order

> Returns a procedure of arguments proc match-key1 ... which calls proc with each row in this table in the (implementation-dependent) natural, repeatable ordering for rows. The optional match-key1 ... arguments restrict actions to a subset of the table. For details see See Match-Keys.

— Operation on relational-table: isam-next

> Returns a procedure of arguments key1 key2 ... which returns the key-list identifying the lowest record higher than key1 key2 ... which is stored in the relational-table; or false if no higher record is present. — Operation on relational-table: isam-next column-name

> > The symbol column-name names a key field. In the list returned by `isam-next`, that field, or a field to its left, will be changed. This allows one to skip over less significant key fields.

— Operation on relational-table: isam-prev

> Returns a procedure of arguments key1 key2 ... which returns the key-list identifying the highest record less than key1 key2 ... which is stored in the relational-table; or false if no lower record is present. — Operation on relational-table: isam-prev column-name

> > The symbol column-name names a key field. In the list returned by `isam-next`, that field, or a field to its left, will be changed. This allows one to skip over less significant key fields.

For example, if a table has key fields:

         (col1 col2)
         (9 5)
         (9 6)
         (9 7)
         (9 8)
         (12 5)
         (12 6)
         (12 7)

Then:

         ((table 'isam-next)       '(9 5))       => (9 6)
         ((table 'isam-next 'col2) '(9 5))       => (9 6)
         ((table 'isam-next 'col1) '(9 5))       => (12 5)
         ((table 'isam-prev)       '(12 7))      => (12 6)
         ((table 'isam-prev 'col2) '(12 7))      => (12 6)
         ((table 'isam-prev 'col1) '(12 7))      => (9 8)

Previous: Sequential Index Operations, Up: Table Operations

##### 6.1.2.6 Table Administration

— Operation on relational-table: column-names
— Operation on relational-table: column-foreigns
— Operation on relational-table: column-domains
— Operation on relational-table: column-types

> Return a list of the column names, foreign-key table names, domain names, or type names respectively for this table. These 4 methods are different from the others in that the list is returned, rather than a procedure to obtain the list. — Operation on relational-table: primary-limit

> > Returns the number of primary keys fields in the relations in this table.

— Operation on relational-table: close-table

> Subsequent operations to this table will signal an error.

Next: Embedded Commands, Previous: Table Operations, Up: Relational Database

#### 6.1.3 Database Interpolation

`(require 'database-interpolate)`

Indexed sequential access methods allow finding the keys (having associations) closest to a given value. This facilitates the interpolation of associations between those in the table.

— Function: interpolate-from-table table column

> Table should be a relational table with one numeric primary key field which supports the `isam-prev` and `isam-next` operations. column should be a symbol or exact positive integer designating a numerically valued column of table.

> `interpolate-from-table` calculates and returns a value proportionally intermediate between its values in the next and previous key records contained in table. For keys larger than all the stored keys the value associated with the largest stored key is used. For keys smaller than all the stored keys the value associated with the smallest stored key is used.

Next: Database Macros, Previous: Database Interpolation, Up: Relational Database

#### 6.1.4 Embedded Commands

`(require 'database-commands)`

This enhancement wraps a utility layer on `relational-database` which provides:

- Automatic execution of initialization commands stored in database.
- Transparent execution of database commands stored in `*commands*` table in database.

When an enhanced relational-database is called with a symbol which matches a name in the `*commands*` table, the associated procedure expression is evaluated and applied to the enhanced relational-database. A procedure should then be returned which the user can invoke on (optional) arguments.

The command `*initialize*` is special. If present in the `*commands*` table, `open-database` or `open-database!` will return the value of the `*initialize*` command. Notice that arbitrary code can be run when the `*initialize*` procedure is automatically applied to the enhanced relational-database.

Note also that if you wish to shadow or hide from the user relational-database methods described in Database Operations, this can be done by a dispatch in the closure returned by the `*initialize*` expression rather than by entries in the `*commands*` table if it is desired that the underlying methods remain accessible to code in the `*commands*` table.

Next: Command Intrinsics, Previous: Embedded Commands, Up: Embedded Commands

##### 6.1.4.1 Database Extension

— Function: wrap-command-interface rdb

> Returns relational database rdb wrapped with additional commands defined in its *commands* table.

— Function: add-command-tables rdb

> The relational database rdb must be mutable. add-command-tables adds a *command* table to rdb; then returns `(wrap-command-interface` rdb`)`.

— Function: define-*commands* rdb spec-0 ...

> Adds commands to the `*commands*` table as specified in spec-0 ... to the open relational-database rdb. Each spec has the form:

>               ((<name> <rdb>) "comment" <expression1> <expression2> ...)

> or

>               ((<name> <rdb>) <expression1> <expression2> ...)

> where <name> is the command name, <rdb> is a formal passed the calling relational database, "comment" describes the command, and <expression1>, <expression1>, ... are the body of the procedure.

> `define-*commands*` adds to the `*commands*` table a command <name>:

>               (lambda (<name> <rdb>) <expression1> <expression2> ...)

— Function: open-command-database filename
— Function: open-command-database filename base-table-type

> Returns an open enhanced relational database associated with filename. The database will be opened with base-table type base-table-type) if supplied. If base-table-type is not supplied, `open-command-database` will attempt to deduce the correct base-table-type. If the database can not be opened or if it lacks the `*commands*` table, `#f` is returned. — Function: open-command-database! filename
> — Function: open-command-database! filename base-table-type

> > Returns mutable open enhanced relational database ... — Function: open-command-database database

> > > Returns database if it is an immutable relational database; #f otherwise. — Function: open-command-database! database

> > > > Returns database if it is a mutable relational database; #f otherwise.

Next: Define-tables Example, Previous: Database Extension, Up: Embedded Commands

##### 6.1.4.2 Command Intrinsics

Some commands are defined in all extended relational-databases. The are called just like Database Operations.

— Operation on relational-database: add-domain domain-row

> Adds domain-row to the domains table if there is no row in the domains table associated with key `(car` domain-row`)` and returns `#t`. Otherwise returns `#f`.

> For the fields and layout of the domain table, See Catalog Representation. Currently, these fields are

> - domain-name
> - foreign-table
> - domain-integrity-rule
> - type-id
> - type-param

> The following example adds 3 domains to the ``build`' database. ``Optstring`' is either a string or `#f`. `filename` is a string and `build-whats` is a symbol.

>               (for-each (build 'add-domain)
>                         '((optstring #f
>                                      (lambda (x) (or (not x) (string? x)))
>                                      string
>                                      #f)
>                           (filename #f #f string #f)
>                           (build-whats #f #f symbol #f)))

— Operation on relational-database: delete-domain domain-name

> Removes and returns the domain-name row from the domains table.

— Operation on relational-database: domain-checker domain

> Returns a procedure to check an argument for conformance to domain domain.

Next: The *commands* Table, Previous: Command Intrinsics, Up: Embedded Commands

##### 6.1.4.3 Define-tables Example

The following example shows a new database with the name of `foo.db` being created with tables describing processor families and processor/os/compiler combinations. The database is then solidified; saved and changed to immutable.

         (require 'databases)
         (define my-rdb (create-database "foo.db" 'alist-table))
         (define-tables my-rdb
           '(processor-family
             ((family    atom))
             ((also-ran  processor-family))
             ((m68000           #f)
              (m68030           m68000)
              (i386             i8086)
              (i8086            #f)
              (powerpc          #f)))

           '(platform
             ((name      symbol))
             ((processor processor-family)
              (os        symbol)
              (compiler  symbol))
             ((aix              powerpc aix     -)
              (amiga-dice-c     m68000  amiga   dice-c)
              (amiga-aztec      m68000  amiga   aztec)
              (amiga-sas/c-5.10 m68000  amiga   sas/c)
              (atari-st-gcc     m68000  atari   gcc)
              (atari-st-turbo-c m68000  atari   turbo-c)
              (borland-c-3.1    i8086   ms-dos  borland-c)
              (djgpp            i386    ms-dos  gcc)
              (linux            i386    linux   gcc)
              (microsoft-c      i8086   ms-dos  microsoft-c)
              (os/2-emx         i386    os/2    gcc)
              (turbo-c-2        i8086   ms-dos  turbo-c)
              (watcom-9.0       i386    ms-dos  watcom))))

         (solidify-database my-rdb)

Next: Command Service, Previous: Define-tables Example, Up: Embedded Commands

##### 6.1.4.4 The *commands* Table

The table `*commands*` in an enhanced relational-database has the fields (with domains):

         PRI name        symbol
             parameters  parameter-list
             procedure   expression
             documentation string

The `parameters` field is a foreign key (domain `parameter-list`) of the `*catalog-data*` table and should have the value of a table described by `*parameter-columns*`. This `parameter-list` table describes the arguments suitable for passing to the associated command. The intent of this table is to be of a form such that different user-interfaces (for instance, pull-down menus or plain-text queries) can operate from the same table. A `parameter-list` table has the following fields:

         PRI index       ordinal
             name        symbol
             arity       parameter-arity
             domain      domain
             defaulter   expression
             expander    expression
             documentation string

The `arity` field can take the values:

`single`
  Requires a single parameter of the specified domain.
`optional`
  A single parameter of the specified domain or zero parameters is acceptable.
`boolean`
  A single boolean parameter or zero parameters (in which case `#f` is substituted) is acceptable.
`nary`
  Any number of parameters of the specified domain are acceptable. The argument passed to the command function is always a list of the parameters.
`nary1`
  One or more of parameters of the specified domain are acceptable. The argument passed to the command function is always a list of the parameters.

The `domain` field specifies the domain which a parameter or parameters in the `index`th field must satisfy.

The `defaulter` field is an expression whose value is either `#f` or a procedure of one argument (the parameter-list) which returns a list of the default value or values as appropriate. Note that since the `defaulter` procedure is called every time a default parameter is needed for this column, sticky defaults can be implemented using shared state with the domain-integrity-rule.

Next: Command Example, Previous: The *commands* Table, Up: Embedded Commands

##### 6.1.4.5 Command Service

— Function: make-command-server rdb table-name

> Returns a procedure of 2 arguments, a (symbol) command and a call-back procedure. When this returned procedure is called, it looks up command in table table-name and calls the call-back procedure with arguments:

> command
>   The command
> command-value
>   The result of evaluating the expression in the procedure field of table-name and calling it with rdb.
> parameter-name
>   A list of the official name of each parameter. Corresponds to the `name` field of the command's parameter-table.
> positions
>   A list of the positive integer index of each parameter. Corresponds to the `index` field of the command's parameter-table.
> arities
>   A list of the arities of each parameter. Corresponds to the `arity` field of the command's parameter-table. For a description of `arity` see table above.
> types
>   A list of the type name of each parameter. Correspnds to the `type-id` field of the contents of the `domain` of the command's parameter-table.
> defaulters
>   A list of the defaulters for each parameter. Corresponds to the `defaulters` field of the command's parameter-table.
> domain-integrity-rules
>   A list of procedures (one for each parameter) which tests whether a value for a parameter is acceptable for that parameter. The procedure should be called with each datum in the list for `nary` arity parameters.
> aliases
>   A list of lists of `(`alias parameter-name`)`. There can be more than one alias per parameter-name.

For information about parameters, See Parameter lists.

Previous: Command Service, Up: Embedded Commands

##### 6.1.4.6 Command Example

Here is an example of setting up a command with arguments and parsing those arguments from a `getopt` style argument list (see Getopt).

         (require 'database-commands)
         (require 'databases)
         (require 'getopt-parameters)
         (require 'parameters)
         (require 'getopt)
         (require 'fluid-let)
         (require 'printf)

         (define my-rdb (add-command-tables (create-database #f 'alist-table)))

         (define-tables my-rdb
           '(foo-params
             *parameter-columns*
             *parameter-columns*
             ((1 single-string single string
                 (lambda (pl) '("str")) #f "single string")
              (2 nary-symbols nary symbol
                 (lambda (pl) '()) #f "zero or more symbols")
              (3 nary1-symbols nary1 symbol
                 (lambda (pl) '(symb)) #f "one or more symbols")
              (4 optional-number optional ordinal
                 (lambda (pl) '()) #f "zero or one number")
              (5 flag boolean boolean
                 (lambda (pl) '(#f)) #f "a boolean flag")))
           '(foo-pnames
             ((name string))
             ((parameter-index ordinal))
             (("s" 1)
              ("single-string" 1)
              ("n" 2)
              ("nary-symbols" 2)
              ("N" 3)
              ("nary1-symbols" 3)
              ("o" 4)
              ("optional-number" 4)
              ("f" 5)
              ("flag" 5)))
           '(my-commands
             ((name symbol))
             ((parameters parameter-list)
              (parameter-names parameter-name-translation)
              (procedure expression)
              (documentation string))
             ((foo
               foo-params
               foo-pnames
               (lambda (rdb) (lambda args (print args)))
               "test command arguments"))))

         (define (dbutil:serve-command-line rdb command-table command argv)
           (set! *argv* (if (vector? argv) (vector->list argv) argv))
           ((make-command-server rdb command-table)
            command
            (lambda (comname comval options positions
                             arities types defaulters dirs aliases)
              (apply comval (getopt->arglist options positions
                             arities types defaulters dirs aliases)))))

         (define (cmd . opts)
           (fluid-let ((*optind* 1))
             (printf "%-34s => "
                     (call-with-output-string
                      (lambda (pt) (write (cons 'cmd opts) pt))))
             (set! opts (cons "cmd" opts))
             (force-output)
             (dbutil:serve-command-line
              my-rdb 'my-commands 'foo (length opts) opts)))

         (cmd)                              => ("str" () (symb) () #f)
         (cmd "-f")                         => ("str" () (symb) () #t)
         (cmd "--flag")                     => ("str" () (symb) () #t)
         (cmd "-o177")                      => ("str" () (symb) (177) #f)
         (cmd "-o" "177")                   => ("str" () (symb) (177) #f)
         (cmd "--optional" "621")           => ("str" () (symb) (621) #f)
         (cmd "--optional=621")             => ("str" () (symb) (621) #f)
         (cmd "-s" "speciality")            => ("speciality" () (symb) () #f)
         (cmd "-sspeciality")               => ("speciality" () (symb) () #f)
         (cmd "--single" "serendipity")     => ("serendipity" () (symb) () #f)
         (cmd "--single=serendipity")       => ("serendipity" () (symb) () #f)
         (cmd "-n" "gravity" "piety")       => ("str" () (piety gravity) () #f)
         (cmd "-ngravity" "piety")          => ("str" () (piety gravity) () #f)
         (cmd "--nary" "chastity")          => ("str" () (chastity) () #f)
         (cmd "--nary=chastity" "")         => ("str" () ( chastity) () #f)
         (cmd "-N" "calamity")              => ("str" () (calamity) () #f)
         (cmd "-Ncalamity")                 => ("str" () (calamity) () #f)
         (cmd "--nary1" "surety")           => ("str" () (surety) () #f)
         (cmd "--nary1=surety")             => ("str" () (surety) () #f)
         (cmd "-N" "levity" "fealty")       => ("str" () (fealty levity) () #f)
         (cmd "-Nlevity" "fealty")          => ("str" () (fealty levity) () #f)
         (cmd "--nary1" "surety" "brevity") => ("str" () (brevity surety) () #f)
         (cmd "--nary1=surety" "brevity")   => ("str" () (brevity surety) () #f)
         (cmd "-?")
         -|
         Usage: cmd [OPTION ARGUMENT ...] ...

           -f, --flag
           -o, --optional[=]<number>
           -n, --nary[=]<symbols> ...
           -N, --nary1[=]<symbols> ...
           -s, --single[=]<string>

         ERROR: getopt->parameter-list "unrecognized option" "-?"

Next: Database Browser, Previous: Embedded Commands, Up: Relational Database

#### 6.1.5 Database Macros

`(require 'within-database)`

The object-oriented programming interface to SLIB relational databases has failed to support clear, understandable, and modular code-writing for database applications.

This seems to be a failure of the object-oriented paradigm where the type of an object is not manifest (or even traceable) in source code.

`within-database`, along with the ``databases`' package, reorganizes high-level database functions toward a more declarative style. Using this package, one can tag database table and command declarations for emacs:

         etags -lscheme -r'/ *(define-\(command\|table\) (\([^; \t]+\)/\2/' \
               source1.scm ...

Next: Within-database Example, Previous: Database Macros, Up: Database Macros

##### 6.1.5.1 Within-database

— Function: within-database database statement-1 ...

> `within-database` creates a lexical scope in which the commands `define-table` and `define-command` create tables and `*commands*`-table entries respectively in open relational database database. The expressions in `within-database' form are executed in order.

> `within-database` Returns database.

— Syntax: define-command (<name> <rdb>) "comment" <expression1> <expression2> ...
— Syntax: define-command (<name> <rdb>) <expression1> <expression2> ...

> Adds to the `*commands*` table a command <name>:

>               (lambda (<name> <rdb>) <expression1> <expression2> ...)

— Syntax: define-table <name> <descriptor-name> <descriptor-name> <rows>
— Syntax: define-table <name> <primary-key-fields> <other-fields> <rows>

> where <name> is the table name, <descriptor-name> is the symbol name of a descriptor table, <primary-key-fields> and <other-fields> describe the primary keys and other fields respectively, and <rows> is a list of data rows to be added to the table.

> <primary-key-fields> and <other-fields> are lists of field descriptors of the form:

>               (<column-name> <domain>)

> or

>               (<column-name> <domain> <column-integrity-rule>)

> where <column-name> is the column name, <domain> is the domain of the column, and <column-integrity-rule> is an expression whose value is a procedure of one argument (which returns `#f` to signal an error).

> If <domain> is not a defined domain name and it matches the name of this table or an already defined (in one of spec-0 ...) single key field table, a foreign-key domain will be created for it.

— Function: add-macro-support database

> The relational database database must be mutable. `add-macro-support` adds a `*macros*` table and `define-macro` macro to database; then database is returned.

— Syntax: define-macro (<name> arg1 ...) "comment" <expression1> <expression2> ...
— Syntax: define-macro (<name> arg1 ...) <expression1> <expression2> ...

> Adds a macro <name> to the `*macros*`.

> Note: `within-database` creates lexical scope where not only `define-command` and `define-table`, but every command and macro are defined, ie.:

>               (within-database my-rdb
>                 (define-command (message rdb)
>                   (lambda (msg)
>                     (display "message: ")
>                     (display msg)
>                     (newline)))
>                 (message "Defining FOO...")
>                 ;; ... defining FOO ...
>                 (message "Defining BAR...")
>                 ;; ... defining BAR ...
>                 )

Previous: Within-database, Up: Database Macros

##### 6.1.5.2 Within-database Example

Here is an example of `within-database` macros:

         (require 'within-database)

         (define my-rdb
           (add-command-tables
            (create-database "foo.db" 'alist-table)))

         (within-database my-rdb
           (define-command (*initialize* rdb)
             "Print Welcome"
             (display "Welcome")
             (newline)
             rdb)
           (define-command (without-documentation rdb)
             (display "without-documentation called")
             (newline))
           (define-table (processor-family
                          ((family   atom))
                          ((also-ran processor-family)))
             (m68000  #f)
             (m68030  m68000)
             (i386    i8086)
             (i8086   #f)
             (powerpc #f))
           (define-table (platform
                          ((name symbol))
                          ((processor processor-family)
                           (os        symbol)
                           (compiler  symbol)))
             (aix              powerpc aix     -)
             ;; ...
             (amiga-aztec      m68000  amiga   aztec)
             (amiga-sas/c-5.10 m68000  amiga   sas/c)
             (atari-st-gcc     m68000  atari   gcc)
             ;; ...
             (watcom-9.0       i386    ms-dos  watcom))
           (define-command (get-processor rdb)
             "Get processor for given platform."
             (((rdb 'open-table) 'platform #f) 'get 'processor)))

         (close-database my-rdb)

         (set! my-rdb (open-command-database! "foo.db"))
         -|
         Welcome

         (my-rdb 'without-documentation)
         -|
         without-documentation called

         ((my-rdb 'get-processor) 'amiga-sas/c-5.10)
         => m68000

         (close-database my-rdb)

Previous: Database Macros, Up: Relational Database

#### 6.1.6 Database Browser

(require 'database-browse)

— Procedure: browse database

> Prints the names of all the tables in database and sets browse's default to database. — Procedure: browse

> > Prints the names of all the tables in the default database. — Procedure: browse table-name

> > > For each record of the table named by the symbol table-name, prints a line composed of all the field values. — Procedure: browse pathname

> > > > Opens the database named by the string pathname, prints the names of all its tables, and sets browse's default to the database. — Procedure: browse database table-name

> > > > > Sets browse's default to database and prints the records of the table named by the symbol table-name. — Procedure: browse pathname table-name

> > > > > > Opens the database named by the string pathname and sets browse's default to it; `browse` prints the records of the table named by the symbol table-name.

Next: Weight-Balanced Trees, Previous: Relational Database, Up: Database Packages

### 6.2 Relational Infrastructure

Next: Catalog Representation, Previous: Relational Infrastructure, Up: Relational Infrastructure

#### 6.2.1 Base Table

A base-table is the primitive database layer upon which SLIB relational databases are built. At the minimum, it must support the types integer, symbol, string, and boolean. The base-table may restrict the size of integers, symbols, and strings it supports.

A base table implementation is available as the value of the identifier naming it (eg. alist-table) after requiring the symbol of that name.

— Feature: alist-table

> `(require 'alist-table)` Association-list base tables support all Scheme types and are suitable for small databases. In order to be retrieved after being written to a file, the data stored should include only objects which are readable and writeable in the Scheme implementation.

> The alist-table base-table implementation is included in the SLIB distribution.

WB is a B-tree database package with SCM interfaces. Being disk-based, WB databases readily store and access hundreds of megabytes of data. WB comes with two base-table embeddings.

— Feature: wb-table

> `(require 'wb-table)` `wb-table` supports scheme expressions for keys and values whose text representations are less than 255 characters in length. See wb-table.

— Feature: rwb-isam

> `(require 'rwb-isam)` rwb-isam is a sophisticated base-table implementation built on WB and SCM which uses binary numerical formats for key and non-key fields. It supports IEEE floating-point and fixed-precision integer keys with the correct numerical collation order.

This rest of this section documents the interface for a base table implementation from which the Relational Database package constructs a Relational system. It will be of interest primarily to those wishing to port or write new base-table implementations.

— Variable: *base-table-implementations*

> To support automatic dispatch for `open-database`, each base-table module adds an association to *base-table-implementations* when loaded. This association is the list of the base-table symbol and the value returned by `(make-relational-system` base-table`)`.

Next: Base Tables, Previous: Base Table, Up: Base Table

##### 6.2.1.1 The Base

All of these functions are accessed through a single procedure by calling that procedure with the symbol name of the operation. A procedure will be returned if that operation is supported and `#f` otherwise. For example:

         (require 'alist-table)
         (define my-base (alist-table 'make-base))
         my-base         => *a procedure*
         (define foo (alist-table 'foo))
         foo             => #f

— Operation on base-table: make-base filename key-dimension column-types

> Returns a new, open, low-level database (collection of tables) associated with filename. This returned database has an empty table associated with catalog-id. The positive integer key-dimension is the number of keys composed to make a primary-key for the catalog table. The list of symbols column-types describes the types of each column for that table. If the database cannot be created as specified, `#f` is returned.

> Calling the `close-base` method on this database and possibly other operations will cause filename to be written to. If filename is `#f` a temporary, non-disk based database will be created if such can be supported by the base table implelentation.

— Operation on base-table: open-base filename mutable

> Returns an open low-level database associated with filename. If mutable is `#t`, this database will have methods capable of effecting change to the database. If mutable is `#f`, only methods for inquiring the database will be available. If the database cannot be opened as specified `#f` is returned.

> Calling the `close-base` (and possibly other) method on a mutable database will cause filename to be written to.

— Operation on base-table: write-base lldb filename

> Causes the low-level database lldb to be written to filename. If the write is successful, also causes lldb to henceforth be associated with filename. Calling the `close-database` (and possibly other) method on lldb may cause filename to be written to. If filename is `#f` this database will be changed to a temporary, non-disk based database if such can be supported by the underlying base table implelentation. If the operations completed successfully, `#t` is returned. Otherwise, `#f` is returned.

— Operation on base-table: sync-base lldb

> Causes the file associated with the low-level database lldb to be updated to reflect its current state. If the associated filename is `#f`, no action is taken and `#f` is returned. If this operation completes successfully, `#t` is returned. Otherwise, `#f` is returned.

— Operation on base-table: close-base lldb

> Causes the low-level database lldb to be written to its associated file (if any). If the write is successful, subsequent operations to lldb will signal an error. If the operations complete successfully, `#t` is returned. Otherwise, `#f` is returned.

Next: Base Field Types, Previous: The Base, Up: Base Table

##### 6.2.1.2 Base Tables

— Operation on base-table: make-table lldb key-dimension column-types

> Returns the ordinal base-id for a new base table, otherwise returns `#f`. The base table can then be opened using `(open-table` lldb base-id`)`. The positive integer key-dimension is the number of keys composed to make a primary-key for this table. The list of symbols column-types describes the types of each column.

— Operation on base-table: open-table lldb base-id key-dimension column-types

> Returns a handle for an existing base table in the low-level database lldb if that table exists and can be opened in the mode indicated by mutable, otherwise returns `#f`.

> As with `make-table`, the positive integer key-dimension is the number of keys composed to make a primary-key for this table. The list of symbols column-types describes the types of each column.

— Operation on base-table: kill-table lldb base-id key-dimension column-types

> Returns `#t` if the base table associated with base-id was removed from the low level database lldb, and `#f` otherwise.

— Operation on base-table: catalog-id

> A constant base-id ordinal suitable for passing as a parameter to `open-table`. catalog-id will be used as the base table for the system catalog.

Next: Composite Keys, Previous: Base Tables, Up: Base Table

##### 6.2.1.3 Base Field Types

— Operation on base-table: supported-type? symbol

> Returns `#t` if symbol names a type allowed as a column value by the implementation, and `#f` otherwise. At a minimum, an implementation must support the types `integer`, `ordinal`, `symbol`, `string`, and `boolean`.

— Operation on base-table: supported-key-type? symbol

> Returns `#t` if symbol names a type allowed as a key value by the implementation, and `#f` otherwise. At a minimum, an implementation must support the types `ordinal`, and `symbol`.

An ordinal is an exact positive integer. The other types are standard Scheme.

Next: Base Record Operations, Previous: Base Field Types, Up: Base Table

##### 6.2.1.4 Composite Keys

— Operation on base-table: make-keyifier-1 type

> Returns a procedure which accepts a single argument which must be of type type. This returned procedure returns an object suitable for being a key argument in the functions whose descriptions follow.

> Any 2 arguments of the supported type passed to the returned function which are not `equal?` must result in returned values which are not `equal?`.

— Operation on base-table: make-list-keyifier key-dimension types

> The list of symbols types must have at least key-dimension elements. Returns a procedure which accepts a list of length key-dimension and whose types must corresopond to the types named by types. This returned procedure combines the elements of its list argument into an object suitable for being a key argument in the functions whose descriptions follow.

> Any 2 lists of supported types (which must at least include symbols and non-negative integers) passed to the returned function which are not `equal?` must result in returned values which are not `equal?`.

— Operation on base-table: make-key-extractor key-dimension types column-number

> Returns a procedure which accepts objects produced by application of the result of `(make-list-keyifier` key-dimension types`)`. This procedure returns a key which is `equal?` to the column-numberth element of the list which was passed to create composite-key. The list types must have at least key-dimension elements.

— Operation on base-table: make-key->list key-dimension types

> Returns a procedure which accepts objects produced by application of the result of `(make-list-keyifier` key-dimension types`)`. This procedure returns a list of keys which are elementwise `equal?` to the list which was passed to create composite-key.

Next: Match Keys, Previous: Composite Keys, Up: Base Table

##### 6.2.1.5 Base Record Operations

In the following functions, the key argument can always be assumed to be the value returned by a call to a keyify routine.

— Operation on base-table: present? handle key

> Returns a non-`#f` value if there is a row associated with key in the table opened in handle and `#f` otherwise.

— Operation on base-table: make-getter key-dimension types

> Returns a procedure which takes arguments handle and key. This procedure returns a list of the non-primary values of the relation (in the base table opened in handle) whose primary key is key if it exists, and `#f` otherwise.

`make-getter-1` is a new operation. The relational-database module works with older base-table implementations by using `make-getter`.

— Operation on base-table: make-getter-1 key-dimension types index

> Returns a procedure which takes arguments handle and key. This procedure returns the value of the indexth field (in the base table opened in handle) whose primary key is key if it exists, and `#f` otherwise.

> index must be larger than key-dimension.

— Operation on base-table: make-putter key-dimension types

> Returns a procedure which takes arguments handle and key and value-list. This procedure associates the primary key key with the values in value-list (in the base table opened in handle) and returns an unspecified value.

— Operation on base-table: delete handle key

> Removes the row associated with key from the table opened in handle. An unspecified value is returned.

Next: Aggregate Base Operations, Previous: Base Record Operations, Up: Base Table

##### 6.2.1.6 Match Keys

A match-keys argument is a list of length equal to the number of primary keys. The match-keys restrict the actions of the table command to those records whose primary keys all satisfy the corresponding element of the match-keys list. The elements and their actions are:

> `#f`
>   The false value matches any key in the corresponding position.
> an object of type procedure
>   This procedure must take a single argument, the key in the corresponding position. Any key for which the procedure returns a non-false value is a match; Any key for which the procedure returns a `#f` is not.
> other values
>   Any other value matches only those keys `equal?` to it.

Next: Base ISAM Operations, Previous: Match Keys, Up: Base Table

##### 6.2.1.7 Aggregate Base Operations

The key-dimension and column-types arguments are needed to decode the composite-keys for matching with match-keys.

— Operation on base-table: delete* handle key-dimension column-types match-keys

> Removes all rows which satisfy match-keys from the table opened in handle. An unspecified value is returned.

— Operation on base-table: for-each-key handle procedure key-dimension column-types match-keys

> Calls procedure once with each key in the table opened in handle which satisfy match-keys in an unspecified order. An unspecified value is returned.

— Operation on base-table: map-key handle procedure key-dimension column-types match-keys

> Returns a list of the values returned by calling procedure once with each key in the table opened in handle which satisfy match-keys in an unspecified order.

Previous: Aggregate Base Operations, Up: Base Table

##### 6.2.1.8 Base ISAM Operations

These operations are optional for a Base-Table implementation.

— Operation on base-table: ordered-for-each-key handle procedure key-dimension column-types match-keys

> Calls procedure once with each key in the table opened in handle which satisfy match-keys in the natural order for the types of the primary key fields of that table. An unspecified value is returned.

— Operation on base-table: make-nexter handle key-dimension column-types index

> Returns a procedure of arguments key1 key2 ... which returns the key-list identifying the lowest record higher than key1 key2 ... which is stored in the base-table and which differs in column index or a lower indexed key; or false if no higher record is present.

— Operation on base-table: make-prever handle key-dimension column-types index

> Returns a procedure of arguments key1 key2 ... which returns the key-list identifying the highest record less than key1 key2 ... which is stored in the base-table and which differs in column index or a lower indexed key; or false if no higher record is present.

Next: Relational Database Objects, Previous: Base Table, Up: Relational Infrastructure

#### 6.2.2 Catalog Representation

Each database (in an implementation) has a system catalog which describes all the user accessible tables in that database (including itself).

The system catalog base table has the following fields. `PRI` indicates a primary key for that table.

         PRI table-name
             column-limit            the highest column number
             coltab-name             descriptor table name
             bastab-id               data base table identifier
             user-integrity-rule
             view-procedure          A scheme thunk which, when called,
                                     produces a handle for the view.  coltab
                                     and bastab are specified if and only if
                                     view-procedure is not.

Descriptors for base tables (not views) are tables (pointed to by system catalog). Descriptor (base) tables have the fields:

         PRI column-number           sequential integers from 1
             primary-key?            boolean TRUE for primary key components
             column-name
             column-integrity-rule
             domain-name

A primary key is any column marked as `primary-key?` in the corresponding descriptor table. All the `primary-key?` columns must have lower column numbers than any non-`primary-key?` columns. Every table must have at least one primary key. Primary keys must be sufficient to distinguish all rows from each other in the table. All of the system defined tables have a single primary key.

A domain is a category describing the allowable values to occur in a column. It is described by a (base) table with the fields:

         PRI domain-name
             foreign-table
             domain-integrity-rule
             type-id
             type-param

The type-id field value is a symbol. This symbol may be used by the underlying base table implementation in storing that field.

If the `foreign-table` field is non-`#f` then that field names a table from the catalog. The values for that domain must match a primary key of the table referenced by the type-param (or `#f`, if allowed). This package currently does not support composite foreign-keys.

The types for which support is planned are:

             atom
             symbol
             string                  [<length>]
             number                  [<base>]
             money                   <currency>
             date-time
             boolean

             foreign-key             <table-name>
             expression
             virtual                 <expression>

Next: Database Operations, Previous: Catalog Representation, Up: Relational Infrastructure

#### 6.2.3 Relational Database Objects

This object-oriented interface is deprecated for typical database applications; Using Databases provides an application programmer interface which is easier to understand and use.

— Function: make-relational-system base-table-implementation

> Returns a procedure implementing a relational database using the base-table-implementation.

> All of the operations of a base table implementation are accessed through a procedure defined by `require`ing that implementation. Similarly, all of the operations of the relational database implementation are accessed through the procedure returned by `make-relational-system`. For instance, a new relational database could be created from the procedure returned by `make-relational-system` by:

>               (require 'alist-table)
>               (define relational-alist-system
>                       (make-relational-system alist-table))
>               (define create-alist-database
>                       (relational-alist-system 'create-database))
>               (define my-database
>                       (create-alist-database "mydata.db"))

What follows are the descriptions of the methods available from relational system returned by a call to `make-relational-system`.

— Operation on relational-system: create-database filename

> Returns an open, nearly empty relational database associated with filename. The only tables defined are the system catalog and domain table. Calling the `close-database` method on this database and possibly other operations will cause filename to be written to. If filename is `#f` a temporary, non-disk based database will be created if such can be supported by the underlying base table implelentation. If the database cannot be created as specified `#f` is returned. For the fields and layout of descriptor tables, Catalog Representation

— Operation on relational-system: open-database filename mutable?

> Returns an open relational database associated with filename. If mutable? is `#t`, this database will have methods capable of effecting change to the database. If mutable? is `#f`, only methods for inquiring the database will be available. Calling the `close-database` (and possibly other) method on a mutable? database will cause filename to be written to. If the database cannot be opened as specified `#f` is returned.

Previous: Relational Database Objects, Up: Relational Infrastructure

#### 6.2.4 Database Operations

This object-oriented interface is deprecated for typical database applications; Using Databases provides an application programmer interface which is easier to understand and use.

These are the descriptions of the methods available from an open relational database. A method is retrieved from a database by calling the database with the symbol name of the operation. For example:

         (define my-database
                 (create-alist-database "mydata.db"))
         (define telephone-table-desc
                 ((my-database 'create-table) 'telephone-table-desc))

— Operation on relational-database: close-database

> Causes the relational database to be written to its associated file (if any). If the write is successful, subsequent operations to this database will signal an error. If the operations completed successfully, `#t` is returned. Otherwise, `#f` is returned.

— Operation on relational-database: write-database filename

> Causes the relational database to be written to filename. If the write is successful, also causes the database to henceforth be associated with filename. Calling the `close-database` (and possibly other) method on this database will cause filename to be written to. If filename is `#f` this database will be changed to a temporary, non-disk based database if such can be supported by the underlying base table implelentation. If the operations completed successfully, `#t` is returned. Otherwise, `#f` is returned.

— Operation on relational-database: sync-database

> Causes any pending updates to the database file to be written out. If the operations completed successfully, `#t` is returned. Otherwise, `#f` is returned.

— Operation on relational-database: solidify-database

> Causes any pending updates to the database file to be written out. If the writes completed successfully, then the database is changed to be immutable and `#t` is returned. Otherwise, `#f` is returned.

— Operation on relational-database: table-exists? table-name

> Returns `#t` if table-name exists in the system catalog, otherwise returns `#f`.

— Operation on relational-database: open-table table-name mutable?

> Returns a methods procedure for an existing relational table in this database if it exists and can be opened in the mode indicated by mutable?, otherwise returns `#f`.

These methods will be present only in mutable databases.

— Operation on relational-database: delete-table table-name

> Removes and returns the table-name row from the system catalog if the table or view associated with table-name gets removed from the database, and `#f` otherwise.

— Operation on relational-database: create-table table-desc-name

> Returns a methods procedure for a new (open) relational table for describing the columns of a new base table in this database, otherwise returns `#f`. For the fields and layout of descriptor tables, See Catalog Representation. — Operation on relational-database: create-table table-name table-desc-name

> > Returns a methods procedure for a new (open) relational table with columns as described by table-desc-name, otherwise returns `#f`.

— Operation on relational-database: create-view ??
— Operation on relational-database: project-table ??
— Operation on relational-database: restrict-table ??
— Operation on relational-database: cart-prod-tables ??

> Not yet implemented.

Previous: Relational Infrastructure, Up: Database Packages

### 6.3 Weight-Balanced Trees

`(require 'wt-tree)` Balanced binary trees are a useful data structure for maintaining large sets of ordered objects or sets of associations whose keys are ordered. MIT Scheme has an comprehensive implementation of weight-balanced binary trees which has several advantages over the other data structures for large aggregates:

- In addition to the usual element-level operations like insertion, deletion and lookup, there is a full complement of collection-level operations, like set intersection, set union and subset test, all of which are implemented with good orders of growth in time and space. This makes weight balanced trees ideal for rapid prototyping of functionally derived specifications.
- An element in a tree may be indexed by its position under the ordering of the keys, and the ordinal position of an element may be determined, both with reasonable efficiency.
- Operations to find and remove minimum element make weight balanced trees simple to use for priority queues.
- The implementation is functional rather than imperative. This means that operations like `inserting' an association in a tree do not destroy the old tree, in much the same way that `(+ 1 x)` modifies neither the constant 1 nor the value bound to `x`. The trees are referentially transparent thus the programmer need not worry about copying the trees. Referential transparency allows space efficiency to be achieved by sharing subtrees.

These features make weight-balanced trees suitable for a wide range of applications, especially those that require large numbers of sets or discrete maps. Applications that have a few global databases and/or concentrate on element-level operations like insertion and lookup are probably better off using hash-tables or red-black trees.

The size of a tree is the number of associations that it contains. Weight balanced binary trees are balanced to keep the sizes of the subtrees of each node within a constant factor of each other. This ensures logarithmic times for single-path operations (like lookup and insertion). A weight balanced tree takes space that is proportional to the number of associations in the tree. For the current implementation, the constant of proportionality is six words per association.

Weight balanced trees can be used as an implementation for either discrete sets or discrete maps (associations). Sets are implemented by ignoring the datum that is associated with the key. Under this scheme if an associations exists in the tree this indicates that the key of the association is a member of the set. Typically a value such as `()`, `#t` or `#f` is associated with the key.

Many operations can be viewed as computing a result that, depending on whether the tree arguments are thought of as sets or maps, is known by two different names. An example is `wt-tree/member?`, which, when regarding the tree argument as a set, computes the set membership operation, but, when regarding the tree as a discrete map, `wt-tree/member?` is the predicate testing if the map is defined at an element in its domain. Most names in this package have been chosen based on interpreting the trees as sets, hence the name `wt-tree/member?` rather than `wt-tree/defined-at?`.

The weight balanced tree implementation is a run-time-loadable option. To use weight balanced trees, execute

         (load-option 'wt-tree)

once before calling any of the procedures defined here.

Next: Basic Operations on Weight-Balanced Trees, Previous: Weight-Balanced Trees, Up: Weight-Balanced Trees

#### 6.3.1 Construction of Weight-Balanced Trees

Binary trees require there to be a total order on the keys used to arrange the elements in the tree. Weight balanced trees are organized by types, where the type is an object encapsulating the ordering relation. Creating a tree is a two-stage process. First a tree type must be created from the predicate which gives the ordering. The tree type is then used for making trees, either empty or singleton trees or trees from other aggregate structures like association lists. Once created, a tree `knows' its type and the type is used to test compatibility between trees in operations taking two trees. Usually a small number of tree types are created at the beginning of a program and used many times throughout the program's execution.

— procedure+: make-wt-tree-type key<?

> This procedure creates and returns a new tree type based on the ordering predicate key<?. Key<? must be a total ordering, having the property that for all key values `a`, `b` and `c`:

>               (key<? a a)                         => #f
>               (and (key<? a b) (key<? b a))       => #f
>               (if (and (key<? a b) (key<? b c))
>                   (key<? a c)
>                   #t)                             => #t

> Two key values are assumed to be equal if neither is less than the other by key<?.

> Each call to `make-wt-tree-type` returns a distinct value, and trees are only compatible if their tree types are `eq?`. A consequence is that trees that are intended to be used in binary tree operations must all be created with a tree type originating from the same call to `make-wt-tree-type`.

— variable+: number-wt-type

> A standard tree type for trees with numeric keys. `Number-wt-type` could have been defined by

>               (define number-wt-type (make-wt-tree-type  <))

— variable+: string-wt-type

> A standard tree type for trees with string keys. `String-wt-type` could have been defined by

>               (define string-wt-type (make-wt-tree-type  string<?))

— procedure+: make-wt-tree wt-tree-type

> This procedure creates and returns a newly allocated weight balanced tree. The tree is empty, i.e. it contains no associations. Wt-tree-type is a weight balanced tree type obtained by calling `make-wt-tree-type`; the returned tree has this type.

— procedure+: singleton-wt-tree wt-tree-type key datum

> This procedure creates and returns a newly allocated weight balanced tree. The tree contains a single association, that of datum with key. Wt-tree-type is a weight balanced tree type obtained by calling `make-wt-tree-type`; the returned tree has this type.

— procedure+: alist->wt-tree tree-type alist

> Returns a newly allocated weight-balanced tree that contains the same associations as alist. This procedure is equivalent to:

>               (lambda (type alist)
>                 (let ((tree (make-wt-tree type)))
>                   (for-each (lambda (association)
>                               (wt-tree/add! tree
>                                             (car association)
>                                             (cdr association)))
>                             alist)
>                   tree))

Next: Advanced Operations on Weight-Balanced Trees, Previous: Construction of Weight-Balanced Trees, Up: Weight-Balanced Trees

#### 6.3.2 Basic Operations on Weight-Balanced Trees

This section describes the basic tree operations on weight balanced trees. These operations are the usual tree operations for insertion, deletion and lookup, some predicates and a procedure for determining the number of associations in a tree.

— procedure+: wt-tree/empty? wt-tree

> Returns `#t` if wt-tree contains no associations, otherwise returns `#f`.

— procedure+: wt-tree/size wt-tree

> Returns the number of associations in wt-tree, an exact non-negative integer. This operation takes constant time.

— procedure+: wt-tree/add wt-tree key datum

> Returns a new tree containing all the associations in wt-tree and the association of datum with key. If wt-tree already had an association for key, the new association overrides the old. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in wt-tree.

— procedure+: wt-tree/add! wt-tree key datum

> Associates datum with key in wt-tree and returns an unspecified value. If wt-tree already has an association for key, that association is replaced. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in wt-tree.

— procedure+: wt-tree/member? key wt-tree

> Returns `#t` if wt-tree contains an association for key, otherwise returns `#f`. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in wt-tree.

— procedure+: wt-tree/lookup wt-tree key default

> Returns the datum associated with key in wt-tree. If wt-tree doesn't contain an association for key, default is returned. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in wt-tree.

— procedure+: wt-tree/delete wt-tree key

> Returns a new tree containing all the associations in wt-tree, except that if wt-tree contains an association for key, it is removed from the result. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in wt-tree.

— procedure+: wt-tree/delete! wt-tree key

> If wt-tree contains an association for key the association is removed. Returns an unspecified value. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in wt-tree.

Next: Indexing Operations on Weight-Balanced Trees, Previous: Basic Operations on Weight-Balanced Trees, Up: Weight-Balanced Trees

#### 6.3.3 Advanced Operations on Weight-Balanced Trees

In the following the size of a tree is the number of associations that the tree contains, and a smaller tree contains fewer associations.

— procedure+: wt-tree/split< wt-tree bound

> Returns a new tree containing all and only the associations in wt-tree which have a key that is less than bound in the ordering relation of the tree type of wt-tree. The average and worst-case times required by this operation are proportional to the logarithm of the size of wt-tree.

— procedure+: wt-tree/split> wt-tree bound

> Returns a new tree containing all and only the associations in wt-tree which have a key that is greater than bound in the ordering relation of the tree type of wt-tree. The average and worst-case times required by this operation are proportional to the logarithm of size of wt-tree.

— procedure+: wt-tree/union wt-tree-1 wt-tree-2

> Returns a new tree containing all the associations from both trees. This operation is asymmetric: when both trees have an association for the same key, the returned tree associates the datum from wt-tree-2 with the key. Thus if the trees are viewed as discrete maps then `wt-tree/union` computes the map override of wt-tree-1 by wt-tree-2. If the trees are viewed as sets the result is the set union of the arguments. The worst-case time required by this operation is proportional to the sum of the sizes of both trees. If the minimum key of one tree is greater than the maximum key of the other tree then the time required is at worst proportional to the logarithm of the size of the larger tree.

— procedure+: wt-tree/intersection wt-tree-1 wt-tree-2

> Returns a new tree containing all and only those associations from wt-tree-1 which have keys appearing as the key of an association in wt-tree-2. Thus the associated data in the result are those from wt-tree-1. If the trees are being used as sets the result is the set intersection of the arguments. As a discrete map operation, `wt-tree/intersection` computes the domain restriction of wt-tree-1 to (the domain of) wt-tree-2. The time required by this operation is never worse that proportional to the sum of the sizes of the trees.

— procedure+: wt-tree/difference wt-tree-1 wt-tree-2

> Returns a new tree containing all and only those associations from wt-tree-1 which have keys that do not appear as the key of an association in wt-tree-2. If the trees are viewed as sets the result is the asymmetric set difference of the arguments. As a discrete map operation, it computes the domain restriction of wt-tree-1 to the complement of (the domain of) wt-tree-2. The time required by this operation is never worse that proportional to the sum of the sizes of the trees.

— procedure+: wt-tree/subset? wt-tree-1 wt-tree-2

> Returns `#t` iff the key of each association in wt-tree-1 is the key of some association in wt-tree-2, otherwise returns `#f`. Viewed as a set operation, `wt-tree/subset?` is the improper subset predicate. A proper subset predicate can be constructed:

>               (define (proper-subset? s1 s2)
>                 (and (wt-tree/subset? s1 s2)
>                      (< (wt-tree/size s1) (wt-tree/size s2))))

> As a discrete map operation, `wt-tree/subset?` is the subset test on the domain(s) of the map(s). In the worst-case the time required by this operation is proportional to the size of wt-tree-1.

— procedure+: wt-tree/set-equal? wt-tree-1 wt-tree-2

> Returns `#t` iff for every association in wt-tree-1 there is an association in wt-tree-2 that has the same key, and vice versa.

> Viewing the arguments as sets `wt-tree/set-equal?` is the set equality predicate. As a map operation it determines if two maps are defined on the same domain.

> This procedure is equivalent to

>               (lambda (wt-tree-1 wt-tree-2)
>                 (and (wt-tree/subset? wt-tree-1 wt-tree-2
>                      (wt-tree/subset? wt-tree-2 wt-tree-1)))

> In the worst-case the time required by this operation is proportional to the size of the smaller tree.

— procedure+: wt-tree/fold combiner initial wt-tree

> This procedure reduces wt-tree by combining all the associations, using an reverse in-order traversal, so the associations are visited in reverse order. Combiner is a procedure of three arguments: a key, a datum and the accumulated result so far. Provided combiner takes time bounded by a constant, `wt-tree/fold` takes time proportional to the size of wt-tree.

> A sorted association list can be derived simply:

>               (wt-tree/fold  (lambda (key datum list)
>                                (cons (cons key datum) list))
>                              '()
>                              wt-tree))

> The data in the associations can be summed like this:

>               (wt-tree/fold  (lambda (key datum sum) (+ sum datum))
>                              0
>                              wt-tree)

— procedure+: wt-tree/for-each action wt-tree

> This procedure traverses the tree in-order, applying action to each association. The associations are processed in increasing order of their keys. Action is a procedure of two arguments which take the key and datum respectively of the association. Provided action takes time bounded by a constant, `wt-tree/for-each` takes time proportional to in the size of wt-tree. The example prints the tree:

>               (wt-tree/for-each (lambda (key value)
>                                   (display (list key value)))
>                                 wt-tree))

Previous: Advanced Operations on Weight-Balanced Trees, Up: Weight-Balanced Trees

#### 6.3.4 Indexing Operations on Weight-Balanced Trees

Weight balanced trees support operations that view the tree as sorted sequence of associations. Elements of the sequence can be accessed by position, and the position of an element in the sequence can be determined, both in logarthmic time.

— procedure+: wt-tree/index wt-tree index
— procedure+: wt-tree/index-datum wt-tree index
— procedure+: wt-tree/index-pair wt-tree index

> Returns the 0-based indexth association of wt-tree in the sorted sequence under the tree's ordering relation on the keys. `wt-tree/index` returns the indexth key, `wt-tree/index-datum` returns the datum associated with the indexth key and `wt-tree/index-pair` returns a new pair `(`key`.` datum`)` which is the `cons` of the indexth key and its datum. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in the tree.

> These operations signal an error if the tree is empty, if index`<0`, or if index is greater than or equal to the number of associations in the tree.

> Indexing can be used to find the median and maximum keys in the tree as follows:

         median:  (wt-tree/index wt-tree (quotient (wt-tree/size wt-tree) 2))

         maximum: (wt-tree/index wt-tree (-1+ (wt-tree/size wt-tree)))

— procedure+: wt-tree/rank wt-tree key

> Determines the 0-based position of key in the sorted sequence of the keys under the tree's ordering relation, or `#f` if the tree has no association with for key. This procedure returns either an exact non-negative integer or `#f`. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in the tree.

— procedure+: wt-tree/min wt-tree
— procedure+: wt-tree/min-datum wt-tree
— procedure+: wt-tree/min-pair wt-tree

> Returns the association of wt-tree that has the least key under the tree's ordering relation. `wt-tree/min` returns the least key, `wt-tree/min-datum` returns the datum associated with the least key and `wt-tree/min-pair` returns a new pair `(key . datum)` which is the `cons` of the minimum key and its datum. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in the tree.

> These operations signal an error if the tree is empty. They could be written

>               (define (wt-tree/min tree)        (wt-tree/index tree 0))
>               (define (wt-tree/min-datum tree)  (wt-tree/index-datum tree 0))
>               (define (wt-tree/min-pair tree)   (wt-tree/index-pair tree 0))

— procedure+: wt-tree/delete-min wt-tree

> Returns a new tree containing all of the associations in wt-tree except the association with the least key under the wt-tree's ordering relation. An error is signalled if the tree is empty. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in the tree. This operation is equivalent to

>               (wt-tree/delete wt-tree (wt-tree/min wt-tree))

— procedure+: wt-tree/delete-min! wt-tree

> Removes the association with the least key under the wt-tree's ordering relation. An error is signalled if the tree is empty. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in the tree. This operation is equivalent to

>               (wt-tree/delete! wt-tree (wt-tree/min wt-tree))

Next: About SLIB, Previous: Database Packages, Up: Top

## 7 Other Packages

Next: Sorting and Searching, Previous: Other Packages, Up: Other Packages

### 7.1 Data Structures

Next: Subarrays, Previous: Data Structures, Up: Data Structures

#### 7.1.1 Arrays

`(require 'array)` or `(require 'srfi-63)`

— Function: array? obj

> Returns `#t` if the obj is an array, and `#f` if not.

Note: Arrays are not disjoint from other Scheme types. Vectors and possibly strings also satisfy `array?`. A disjoint array predicate can be written:

         (define (strict-array? obj)
           (and (array? obj) (not (string? obj)) (not (vector? obj))))

— Function: equal? obj1 obj2

> Returns `#t` if obj1 and obj2 have the same rank and dimensions and the corresponding elements of obj1 and obj2 are `equal?`.

> `equal?` recursively compares the contents of pairs, vectors, strings, and arrays, applying `eqv?` on other objects such as numbers and symbols. A rule of thumb is that objects are generally `equal?` if they print the same. `equal?` may fail to terminate if its arguments are circular data structures.

>               (equal? 'a 'a)                             =>  #t
>               (equal? '(a) '(a))                         =>  #t
>               (equal? '(a (b) c)
>                       '(a (b) c))                        =>  #t
>               (equal? "abc" "abc")                       =>  #t
>               (equal? 2 2)                               =>  #t
>               (equal? (make-vector 5 'a)
>                       (make-vector 5 'a))                =>  #t
>               (equal? (make-array (A:fixN32b 4) 5 3)
>                       (make-array (A:fixN32b 4) 5 3))    =>  #t
>               (equal? (make-array '#(foo) 3 3)
>                       (make-array '#(foo) 3 3))          =>  #t
>               (equal? (lambda (x) x)
>                       (lambda (y) y))                    =>  unspecified

— Function: array-rank obj

> Returns the number of dimensions of obj. If obj is not an array, 0 is returned.

— Function: array-dimensions array

> Returns a list of dimensions.

>               (array-dimensions (make-array '#() 3 5))
>                  => (3 5)

— Function: make-array prototype k1 ...

> Creates and returns an array of type prototype with dimensions k1, ... and filled with elements from prototype. prototype must be an array, vector, or string. The implementation-dependent type of the returned array will be the same as the type of prototype; except if that would be a vector or string with rank not equal to one, in which case some variety of array will be returned.

> If the prototype has no elements, then the initial contents of the returned array are unspecified. Otherwise, the returned array will be filled with the element at the origin of prototype.

— Function: create-array prototype k1 ...

> `create-array` is an alias for `make-array`.

— Function: make-shared-array array mapper k1 ...

> `make-shared-array` can be used to create shared subarrays of other arrays. The mapper is a function that translates coordinates in the new array into coordinates in the old array. A mapper must be linear, and its range must stay within the bounds of the old array, but it can be otherwise arbitrary. A simple example:

>               (define fred (make-array '#(#f) 8 8))
>               (define freds-diagonal
>                 (make-shared-array fred (lambda (i) (list i i)) 8))
>               (array-set! freds-diagonal 'foo 3)
>               (array-ref fred 3 3)
>                  => FOO
>               (define freds-center
>                 (make-shared-array fred (lambda (i j) (list (+ 3 i) (+ 3 j)))
>                                    2 2))
>               (array-ref freds-center 0 0)
>                  => FOO

— Function: list->array rank proto list

> list must be a rank-nested list consisting of all the elements, in row-major order, of the array to be created.

> `list->array` returns an array of rank rank and type proto consisting of all the elements, in row-major order, of list. When rank is 0, list is the lone array element; not necessarily a list.

>               (list->array 2 '#() '((1 2) (3 4)))
>                               => #2A((1 2) (3 4))
>               (list->array 0 '#() 3)
>                               => #0A 3

— Function: array->list array

> Returns a rank-nested list consisting of all the elements, in row-major order, of array. In the case of a rank-0 array, `array->list` returns the single element.

>               (array->list #2A((ho ho ho) (ho oh oh)))
>                               => ((ho ho ho) (ho oh oh))
>               (array->list #0A ho)
>                               => ho

— Function: vector->array vect proto dim1 ...

> vect must be a vector of length equal to the product of exact nonnegative integers dim1, ....

> `vector->array` returns an array of type proto consisting of all the elements, in row-major order, of vect. In the case of a rank-0 array, vect has a single element.

>               (vector->array #(1 2 3 4) #() 2 2)
>                               => #2A((1 2) (3 4))
>               (vector->array '#(3) '#())
>                               => #0A 3

— Function: array->vector array

> Returns a new vector consisting of all the elements of array in row-major order.

>               (array->vector #2A ((1 2)( 3 4)))
>                               => #(1 2 3 4)
>               (array->vector #0A ho)
>                               => #(ho)

— Function: array-in-bounds? array index1 ...

> Returns `#t` if its arguments would be acceptable to `array-ref`.

— Function: array-ref array k1 ...

> Returns the (k1, ...) element of array.

— Procedure: array-set! array obj k1 ...

> Stores obj in the (k1, ...) element of array. The value returned by `array-set!` is unspecified.

These functions return a prototypical uniform-array enclosing the optional argument (which must be of the correct type). If the uniform-array type is supported by the implementation, then it is returned; defaulting to the next larger precision type; resorting finally to vector.

— Function: A:floC128b z
— Function: A:floC128b

> Returns an inexact 128.bit flonum complex uniform-array prototype.

— Function: A:floC64b z
— Function: A:floC64b

> Returns an inexact 64.bit flonum complex uniform-array prototype.

— Function: A:floC32b z
— Function: A:floC32b

> Returns an inexact 32.bit flonum complex uniform-array prototype.

— Function: A:floC16b z
— Function: A:floC16b

> Returns an inexact 16.bit flonum complex uniform-array prototype.

— Function: A:floR128b x
— Function: A:floR128b

> Returns an inexact 128.bit flonum real uniform-array prototype.

— Function: A:floR64b x
— Function: A:floR64b

> Returns an inexact 64.bit flonum real uniform-array prototype.

— Function: A:floR32b x
— Function: A:floR32b

> Returns an inexact 32.bit flonum real uniform-array prototype.

— Function: A:floR16b x
— Function: A:floR16b

> Returns an inexact 16.bit flonum real uniform-array prototype.

— Function: A:floR128d q
— Function: A:floR128d

> Returns an exact 128.bit decimal flonum rational uniform-array prototype.

— Function: A:floR64d q
— Function: A:floR64d

> Returns an exact 64.bit decimal flonum rational uniform-array prototype.

— Function: A:floR32d q
— Function: A:floR32d

> Returns an exact 32.bit decimal flonum rational uniform-array prototype.

— Function: A:fixZ64b n
— Function: A:fixZ64b

> Returns an exact binary fixnum uniform-array prototype with at least 64 bits of precision.

— Function: A:fixZ32b n
— Function: A:fixZ32b

> Returns an exact binary fixnum uniform-array prototype with at least 32 bits of precision.

— Function: A:fixZ16b n
— Function: A:fixZ16b

> Returns an exact binary fixnum uniform-array prototype with at least 16 bits of precision.

— Function: A:fixZ8b n
— Function: A:fixZ8b

> Returns an exact binary fixnum uniform-array prototype with at least 8 bits of precision.

— Function: A:fixN64b k
— Function: A:fixN64b

> Returns an exact non-negative binary fixnum uniform-array prototype with at least 64 bits of precision.

— Function: A:fixN32b k
— Function: A:fixN32b

> Returns an exact non-negative binary fixnum uniform-array prototype with at least 32 bits of precision.

— Function: A:fixN16b k
— Function: A:fixN16b

> Returns an exact non-negative binary fixnum uniform-array prototype with at least 16 bits of precision.

— Function: A:fixN8b k
— Function: A:fixN8b

> Returns an exact non-negative binary fixnum uniform-array prototype with at least 8 bits of precision.

— Function: A:bool bool
— Function: A:bool

> Returns a boolean uniform-array prototype.

Next: Array Mapping, Previous: Arrays, Up: Data Structures

#### 7.1.2 Subarrays

`(require 'subarray)`

— Function: subarray array select ...

> selects a subset of an array. For array of rank n, there must be at least n selects arguments. For 0 <= j < n, selectsj is either an integer, a list of two integers within the range for the jth index, or #f.

> When selectsj is a list of two integers, then the jth index is restricted to that subrange in the returned array.

> When selectsj is #f, then the full range of the jth index is accessible in the returned array. An elided argument is equivalent to #f.

> When selectsj is an integer, then the rank of the returned array is less than array, and only elements whose jth index equals selectsj are shared.

>               > (define ra '#2A((a b c) (d e f)))
>               #<unspecified>
>               > (subarray ra 0 #f)
>               #1A(a b c)
>               > (subarray ra 1 #f)
>               #1A(d e f)
>               > (subarray ra #f 1)
>               #1A(b e)
>               > (subarray ra '(0 1) #f)
>               #2A((a b c) (d e f))
>               > (subarray ra #f '(0 1))
>               #2A((a b) (d e))
>               > (subarray ra #f '(1 2))
>               #2A((b c) (e f))
>               > (subarray ra #f '(2 1))
>               #2A((c b) (f e))

> Arrays can be reflected (reversed) using `subarray`:

>               > (subarray '#1A(a b c d e) '(4 0))
>               #1A(e d c b a)

— Function: array-trim array trim ...

> Returns a subarray sharing contents with array except for slices removed from either side of each dimension. Each of the trims is an exact integer indicating how much to trim. A positive s trims the data from the lower end and reduces the upper bound of the result; a negative s trims from the upper end and increases the lower bound.

> For example:

>               (array-trim '#(0 1 2 3 4) 1)  => #1A(1 2 3 4)
>               (array-trim '#(0 1 2 3 4) -1) => #1A(0 1 2 3)

>               (require 'array-for-each)
>               (define (centered-difference ra)
>                 (array-map ra - (array-trim ra 1) (array-trim ra -1)))

>               (centered-difference '#(0 1 3 5 9 22))
>                 => #(1 2 2 4 13)

Next: Array Interpolation, Previous: Subarrays, Up: Data Structures

#### 7.1.3 Array Mapping

`(require 'array-for-each)`

— Procedure: array-map! array0 proc array1 ...

> array1, ... must have the same number of dimensions as array0 and have a range for each index which includes the range for the corresponding index in array0. proc is applied to each tuple of elements of array1 ... and the result is stored as the corresponding element in array0. The value returned is unspecified. The order of application is unspecified.

— Function: array-map prototype proc array1 array2 ...

> array2, ... must have the same number of dimensions as array1 and have a range for each index which includes the range for the corresponding index in array1. proc is applied to each tuple of elements of array1, array2, ... and the result is stored as the corresponding element in a new array of type prototype. The new array is returned. The order of application is unspecified.

— Function: array-for-each proc array0 ...

> proc is applied to each tuple of elements of array0 ... in row-major order. The value returned is unspecified.

— Function: array-indexes array

> Returns an array of lists of indexes for array such that, if li is a list of indexes for which array is defined, (equal? li (apply array-ref (array-indexes array) li)).

— Function: array-index-for-each array proc

> applies proc to the indices of each element of array in turn. The value returned and the order of application are unspecified.

> One can implement array-index-map! as

>               (define (array-index-map! ra fun)
>                 (array-index-for-each
>                  ra
>                  (lambda is (apply array-set! ra (apply fun is) is))))

— Procedure: array-index-map! array proc

> applies proc to the indices of each element of array in turn, storing the result in the corresponding element. The value returned and the order of application are unspecified.

> One can implement array-indexes as

>               (define (array-indexes array)
>                   (let ((ra (apply make-array '#() (array-dimensions array))))
>                     (array-index-map! ra (lambda x x))
>                     ra))

> Another example:

>               (define (apl:index-generator n)
>                   (let ((v (make-vector n 1)))
>                     (array-index-map! v (lambda (i) i))
>                     v))

— Procedure: array:copy! destination source

> Copies every element from vector or array source to the corresponding element of destination. destination must have the same rank as source, and be at least as large in each dimension. The order of copying is unspecified.

Next: Association Lists, Previous: Array Mapping, Up: Data Structures

#### 7.1.4 Array Interpolation

`(require 'array-interpolate)`

— Function: interpolate-array-ref ra x1 ... xj

> ra must be an array of rank j containing numbers. `interpolate-array-ref` returns a value interpolated from the nearest j-dimensional cube of elements of ra.

>               (interpolate-array-ref '#2A:fixZ32b((1 2 3) (4 5 6)) 1 0.1)
>                                             ==> 4.1
>               (interpolate-array-ref '#2A:fixZ32b((1 2 3) (4 5 6)) 0.5 0.25)
>                                             ==> 2.75

— Procedure: resample-array! ra1 ra2

> ra1 and ra2 must be numeric arrays of equal rank. `resample-array!` sets ra1 to values interpolated from ra2 such that the values of elements at the corners of ra1 and ra2 are equal.

>               (define ra (make-array (A:fixZ32b) 2 2))
>               (resample-array! ra '#2A:fixZ32b((1 2 3) (4 5 6)))
>               ra              ==>  #2A:fixZ32b((1 3) (4 6))
>               (define ra (make-array (A:floR64b) 3 2))
>               (resample-array! ra '#2A:fixZ32b((1 2 3) (4 5 6)))
>               ra              ==>  #2A:floR64b((1.0 3.0) (2.5 4.5) (4.0 6.0))

Next: Byte, Previous: Array Interpolation, Up: Data Structures

#### 7.1.5 Association Lists

`(require 'alist)` Alist functions provide utilities for treating a list of key-value pairs as an associative database. These functions take an equality predicate, pred, as an argument. This predicate should be repeatable, symmetric, and transitive.

Alist functions can be used with a secondary index method such as hash tables for improved performance.

— Function: predicate->asso pred

> Returns an association function (like `assq`, `assv`, or `assoc`) corresponding to pred. The returned function returns a key-value pair whose key is `pred`-equal to its first argument or `#f` if no key in the alist is pred-equal to the first argument.

— Function: alist-inquirer pred

> Returns a procedure of 2 arguments, alist and key, which returns the value associated with key in alist or `#f` if key does not appear in alist.

— Function: alist-associator pred

> Returns a procedure of 3 arguments, alist, key, and value, which returns an alist with key and value associated. Any previous value associated with key will be lost. This returned procedure may or may not have side effects on its alist argument. An example of correct usage is:

>               (define put (alist-associator string-ci=?))
>               (define alist '())
>               (set! alist (put alist "Foo" 9))

— Function: alist-remover pred

> Returns a procedure of 2 arguments, alist and key, which returns an alist with an association whose key is key removed. This returned procedure may or may not have side effects on its alist argument. An example of correct usage is:

>               (define rem (alist-remover string-ci=?))
>               (set! alist (rem alist "foo"))

— Function: alist-map proc alist

> Returns a new association list formed by mapping proc over the keys and values of alist. proc must be a function of 2 arguments which returns the new value part.

— Function: alist-for-each proc alist

> Applies proc to each pair of keys and values of alist. proc must be a function of 2 arguments. The returned value is unspecified.

Next: Byte/Number Conversions, Previous: Association Lists, Up: Data Structures

#### 7.1.6 Byte

`(require 'byte)` Some algorithms are expressed in terms of arrays of small integers. Using Scheme strings to implement these arrays is not portable vis-a-vis the correspondence between integers and characters and non-ascii character sets. These functions abstract the notion of a byte.

— Function: byte-ref bytes k

> k must be a valid index of bytes. `byte-ref` returns byte k of bytes using zero-origin indexing.

— Procedure: byte-set! bytes k byte

> k must be a valid index of bytes, and byte must be a small nonnegative integer. `byte-set!` stores byte in element k of bytes and returns an unspecified value.

— Function: make-bytes k byte
— Function: make-bytes k

> `make-bytes` returns a newly allocated byte-array of length k. If byte is given, then all elements of the byte-array are initialized to byte, otherwise the contents of the byte-array are unspecified.

— Function: bytes-length bytes

> `bytes-length` returns length of byte-array bytes.

— Function: bytes byte ...

> Returns a newly allocated byte-array composed of the small nonnegative arguments.

— Function: list->bytes bytes

> `list->bytes` returns a newly allocated byte-array formed from the small nonnegative integers in the list bytes.

— Function: bytes->list bytes

> `bytes->list` returns a newly allocated list of the bytes that make up the given byte-array.

`Bytes->list` and `list->bytes` are inverses so far as `equal?` is concerned.

— Function: bytes->string bytes

> Returns a new string formed from applying `integer->char` to each byte in `bytes->string`. Note that this may signal an error for bytes having values between 128 and 255.

— Function: string->bytes string

> Returns a new byte-array formed from applying `char->integer` to each character in `string->bytes`. Note that this may signal an error if an integer is larger than 255.

— Function: bytes-copy bytes

> Returns a newly allocated copy of the given bytes.

— Function: subbytes bytes start end

> bytes must be a bytes, and start and end must be exact integers satisfying

> 0 <= start <= end <= `(bytes-length` bytes`)`.

> `subbytes` returns a newly allocated bytes formed from the bytes of bytes beginning with index start (inclusive) and ending with index end (exclusive).

— Procedure: bytes-reverse! bytes

> Reverses the order of byte-array bytes.

— Function: bytes-reverse bytes

> Returns a newly allocated bytes-array consisting of the elements of bytes in reverse order.

Input and output of bytes should be with ports opened in binary mode (see Input/Output). Calling `open-file` with 'rb or 'wb modes argument will return a binary port if the Scheme implementation supports it.

— Function: write-byte byte port
— Function: write-byte byte

> Writes the byte byte (not an external representation of the byte) to the given port and returns an unspecified value. The port argument may be omitted, in which case it defaults to the value returned by `current-output-port`.

— Function: read-byte port
— Function: read-byte

> Returns the next byte available from the input port, updating the port to point to the following byte. If no more bytes are available, an end-of-file object is returned. port may be omitted, in which case it defaults to the value returned by `current-input-port`.

When reading and writing binary numbers with `read-bytes` and `write-bytes`, the sign of the length argument determines the endianness (order) of bytes. Positive treats them as big-endian, the first byte input or output is highest order. Negative treats them as little-endian, the first byte input or output is the lowest order.

Once read in, SLIB treats byte sequences as big-endian. The multi-byte sequences produced and used by number conversion routines see Byte/Number Conversions are always big-endian.

— Function: read-bytes n port
— Function: read-bytes n

> `read-bytes` returns a newly allocated bytes-array filled with `(abs` n`)` bytes read from port. If n is positive, then the first byte read is stored at index 0; otherwise the last byte read is stored at index 0. Note that the length of the returned byte-array will be less than `(abs` n`)` if port reaches end-of-file.

> port may be omitted, in which case it defaults to the value returned by `current-input-port`.

— Function: write-bytes bytes n port
— Function: write-bytes bytes n

> `write-bytes` writes `(abs` n`)` bytes to output-port port. If n is positive, then the first byte written is index 0 of bytes; otherwise the last byte written is index 0 of bytes. `write-bytes` returns an unspecified value.

> port may be omitted, in which case it defaults to the value returned by `current-output-port`.

`subbytes-read!` and `subbytes-write` provide lower-level procedures for reading and writing blocks of bytes. The relative size of start and end determines the order of writing.

— Procedure: subbytes-read! bts start end port
— Procedure: subbytes-read! bts start end

> Fills bts with up to `(abs (-` start end`))` bytes read from port. The first byte read is stored at index bts. `subbytes-read!` returns the number of bytes read.

> port may be omitted, in which case it defaults to the value returned by `current-input-port`.

— Function: subbytes-write bts start end port
— Function: subbytes-write bts start end

> `subbytes-write` writes `(abs (-` start end`))` bytes to output-port port. The first byte written is index start of bts. `subbytes-write` returns the number of bytes written.

> port may be omitted, in which case it defaults to the value returned by `current-output-port`.

Next: MAT-File Format, Previous: Byte, Up: Data Structures

#### 7.1.7 Byte/Number Conversions

`(require 'byte-number)` The multi-byte sequences produced and used by numeric conversion routines are always big-endian. Endianness can be changed during reading and writing bytes using `read-bytes` and `write-bytes` See read-bytes.

The sign of the length argument to bytes/integer conversion procedures determines the signedness of the number.

— Function: bytes->integer bytes n

> Converts the first `(abs` n`)` bytes of big-endian bytes array to an integer. If n is negative then the integer coded by the bytes are treated as two's-complement (can be negative).

>               (bytes->integer (bytes   0   0   0  15) -4)   =>          15
>               (bytes->integer (bytes   0   0   0  15)  4)   =>          15
>               (bytes->integer (bytes 255 255 255 255) -4)   =>          -1
>               (bytes->integer (bytes 255 255 255 255)  4)   =>  4294967295
>               (bytes->integer (bytes 128   0   0   0) -4)   => -2147483648
>               (bytes->integer (bytes 128   0   0   0)  4)   =>  2147483648

— Function: integer->bytes n len

> Converts the integer n to a byte-array of `(abs` n`)` bytes. If n and len are both negative, then the bytes in the returned array are coded two's-complement.

>               (bytes->list (integer->bytes          15 -4))   => (0 0 0 15)
>               (bytes->list (integer->bytes          15  4))   => (0 0 0 15)
>               (bytes->list (integer->bytes          -1 -4))   => (255 255 255 255)
>               (bytes->list (integer->bytes  4294967295  4))   => (255 255 255 255)
>               (bytes->list (integer->bytes -2147483648 -4))   => (128 0 0 0)
>               (bytes->list (integer->bytes  2147483648  4))   => (128 0 0 0)

— Function: bytes->ieee-float bytes

> bytes must be a 4-element byte-array. `bytes->ieee-float` calculates and returns the value of bytes interpreted as a big-endian IEEE 4-byte (32-bit) number.

         (bytes->ieee-float (bytes    0    0 0 0))  =>  0.0
         (bytes->ieee-float (bytes #x80    0 0 0))  => -0.0
         (bytes->ieee-float (bytes #x40    0 0 0))  =>  2.0
         (bytes->ieee-float (bytes #x40 #xd0 0 0))  =>  6.5
         (bytes->ieee-float (bytes #xc0 #xd0 0 0))  => -6.5

         (bytes->ieee-float (bytes    0 #x80 0 0))  => 11.754943508222875e-39
         (bytes->ieee-float (bytes    0 #x40 0 0))  =>  5.877471754111437e-39
         (bytes->ieee-float (bytes    0    0 0 1))  =>  1.401298464324817e-45

         (bytes->ieee-float (bytes #xff #x80 0 0))  => -inf.0
         (bytes->ieee-float (bytes #x7f #x80 0 0))  => +inf.0
         (bytes->ieee-float (bytes #x7f #x80 0 1))  =>  0/0
         (bytes->ieee-float (bytes #x7f #xc0 0 0))  =>  0/0

— Function: bytes->ieee-double bytes

> bytes must be a 8-element byte-array. `bytes->ieee-double` calculates and returns the value of bytes interpreted as a big-endian IEEE 8-byte (64-bit) number.

         (bytes->ieee-double (bytes    0    0 0 0 0 0 0 0))  =>  0.0
         (bytes->ieee-double (bytes #x80    0 0 0 0 0 0 0))  => -0.0
         (bytes->ieee-double (bytes #x40    0 0 0 0 0 0 0))  =>  2.0
         (bytes->ieee-double (bytes #x40 #x1A 0 0 0 0 0 0))  =>  6.5
         (bytes->ieee-double (bytes #xC0 #x1A 0 0 0 0 0 0))  => -6.5

         (bytes->ieee-double (bytes 0 8 0 0 0 0 0 0)) => 11.125369292536006e-309
         (bytes->ieee-double (bytes 0 4 0 0 0 0 0 0)) =>  5.562684646268003e-309
         (bytes->ieee-double (bytes 0 0 0 0 0 0 0 1)) =>  4.0e-324

         (bytes->ieee-double (bytes #xFF #xF0 0 0 0 0 0 0))  => -inf.0
         (bytes->ieee-double (bytes #x7F #xF0 0 0 0 0 0 0))  => +inf.0
         (bytes->ieee-double (bytes #x7F #xF8 0 0 0 0 0 0))  =>  0/0

— Function: ieee-float->bytes x

> Returns a 4-element byte-array encoding the IEEE single-precision floating-point of x.

         (bytes->list (ieee-float->bytes  0.0))                    => (0     0 0 0)
         (bytes->list (ieee-float->bytes -0.0))                    => (128   0 0 0)
         (bytes->list (ieee-float->bytes  2.0))                    => (64    0 0 0)
         (bytes->list (ieee-float->bytes  6.5))                    => (64  208 0 0)
         (bytes->list (ieee-float->bytes -6.5))                    => (192 208 0 0)

         (bytes->list (ieee-float->bytes 11.754943508222875e-39))  => (  0 128 0 0)
         (bytes->list (ieee-float->bytes  5.877471754111438e-39))  => (  0  64 0 0)
         (bytes->list (ieee-float->bytes  1.401298464324817e-45))  => (  0   0 0 1)

         (bytes->list (ieee-float->bytes -inf.0))                  => (255 128 0 0)
         (bytes->list (ieee-float->bytes +inf.0))                  => (127 128 0 0)
         (bytes->list (ieee-float->bytes  0/0))                    => (127 192 0 0)

— Function: ieee-double->bytes x

> Returns a 8-element byte-array encoding the IEEE double-precision floating-point of x.

         (bytes->list (ieee-double->bytes  0.0)) => (0     0 0 0 0 0 0 0)
         (bytes->list (ieee-double->bytes -0.0)) => (128   0 0 0 0 0 0 0)
         (bytes->list (ieee-double->bytes  2.0)) => (64    0 0 0 0 0 0 0)
         (bytes->list (ieee-double->bytes  6.5)) => (64   26 0 0 0 0 0 0)
         (bytes->list (ieee-double->bytes -6.5)) => (192  26 0 0 0 0 0 0)

         (bytes->list (ieee-double->bytes 11.125369292536006e-309))
                                                 => (  0   8 0 0 0 0 0 0)
         (bytes->list (ieee-double->bytes  5.562684646268003e-309))
                                                 => (  0   4 0 0 0 0 0 0)
         (bytes->list (ieee-double->bytes  4.0e-324))
                                                 => (  0   0 0 0 0 0 0 1)

         (bytes->list (ieee-double->bytes -inf.0)) => (255 240 0 0 0 0 0 0)
         (bytes->list (ieee-double->bytes +inf.0)) => (127 240 0 0 0 0 0 0)
         (bytes->list (ieee-double->bytes  0/0)) => (127 248 0 0 0 0 0 0)

##### Byte Collation Order

The `string<?` ordering of big-endian byte-array representations of fixed and IEEE floating-point numbers agrees with the numerical ordering only when those numbers are non-negative.

Straighforward modification of these formats can extend the byte-collating order to work for their entire ranges. This agreement enables the full range of numbers as keys in indexed-sequential-access-method databases.

— Procedure: integer-byte-collate! byte-vector

> Modifies sign bit of byte-vector so that `string<?` ordering of two's-complement byte-vectors matches numerical order. `integer-byte-collate!` returns byte-vector and is its own functional inverse.

— Function: integer-byte-collate byte-vector

> Returns copy of byte-vector with sign bit modified so that `string<?` ordering of two's-complement byte-vectors matches numerical order. `integer-byte-collate` is its own functional inverse.

— Procedure: ieee-byte-collate! byte-vector

> Modifies byte-vector so that `string<?` ordering of IEEE floating-point byte-vectors matches numerical order. `ieee-byte-collate!` returns byte-vector.

— Procedure: ieee-byte-decollate! byte-vector

> Given byte-vector modified by `ieee-byte-collate!`, reverses the byte-vector modifications.

— Function: ieee-byte-collate byte-vector

> Returns copy of byte-vector encoded so that `string<?` ordering of IEEE floating-point byte-vectors matches numerical order.

— Function: ieee-byte-decollate byte-vector

> Given byte-vector returned by `ieee-byte-collate`, reverses the byte-vector modifications.

Next: Portable Image Files, Previous: Byte/Number Conversions, Up: Data Structures

#### 7.1.8 MAT-File Format

`(require 'matfile)` http://www.mathworks.com/access/helpdesk/help/pdf_doc/matlab/matfile_format.pdf

This package reads MAT-File Format version 4 (MATLAB) binary data files. MAT-files written from big-endian or little-endian computers having IEEE format numbers are currently supported. Support for files written from VAX or Cray machines could also be added.

The numeric and text matrix types handled; support for sparse matrices awaits a sample file.

— Function: matfile:read filename

> filename should be a string naming an existing file containing a MATLAB Version 4 MAT-File. The `matfile:read` procedure reads matrices from the file and returns a list of the results; a list of the name string and array for each matrix.

— Function: matfile:load filename

> filename should be a string naming an existing file containing a MATLAB Version 4 MAT-File. The `matfile:load` procedure reads matrices from the file and defines the `string-ci->symbol` for each matrix to its corresponding array. `matfile:load` returns a list of the symbols defined.

Next: Collections, Previous: MAT-File Format, Up: Data Structures

#### 7.1.9 Portable Image Files

`(require 'pnm)`

— Function: pnm:type-dimensions path

> The string path must name a portable bitmap graphics file. `pnm:type-dimensions` returns a list of 4 items:

> 1. A symbol describing the type of the file named by path.
> 2. The image width in pixels.
> 3. The image height in pixels.
> 4. The maximum value of pixels assume in the file.

> The current set of file-type symbols is:

> pbm
> pbm-raw
>   Black-and-White image; pixel values are 0 or 1.
> pgm
> pgm-raw
>   Gray (monochrome) image; pixel values are from 0 to maxval specified in file header.
> ppm
> ppm-raw
>   RGB (full color) image; red, green, and blue interleaved pixel values are from 0 to maxval

— Function: pnm:image-file->array path array

> Reads the portable bitmap graphics file named by path into array. array must be the correct size and type for path. array is returned. — Function: pnm:image-file->array path

> > `pnm:image-file->array` creates and returns an array with the portable bitmap graphics file named by path read into it.

— Function: pnm:array-write type array maxval path comment ...

> Writes the contents of array to a type image file named path. The file will have pixel values between 0 and maxval, which must be compatible with type. For ``pbm`' files, maxval must be ``1`'. comments are included in the file header.

Next: Dynamic Data Type, Previous: Portable Image Files, Up: Data Structures

#### 7.1.10 Collections

`(require 'collect)` Routines for managing collections. Collections are aggregate data structures supporting iteration over their elements, similar to the Dylan(TM) language, but with a different interface. They have elements indexed by corresponding keys, although the keys may be implicit (as with lists).

New types of collections may be defined as YASOS objects (see Yasos). They must support the following operations:

- `(collection?` self`)` (always returns `#t`);
- `(size` self`)` returns the number of elements in the collection;
- `(print` self port`)` is a specialized print operation for the collection which prints a suitable representation on the given port or returns it as a string if port is `#t`;
- `(gen-elts` self`)` returns a thunk which on successive invocations yields elements of self in order or gives an error if it is invoked more than `(size` self`)` times;
- `(gen-keys` self`)` is like `gen-elts`, but yields the collection's keys in order.

They might support specialized `for-each-key` and `for-each-elt` operations.

— Function: collection? obj

> A predicate, true initially of lists, vectors and strings. New sorts of collections must answer `#t` to `collection?`.

— Procedure: map-elts proc collection1 ...
— Procedure: do-elts proc collection1 ...

> proc is a procedure taking as many arguments as there are collections (at least one). The collections are iterated over in their natural order and proc is applied to the elements yielded by each iteration in turn. The order in which the arguments are supplied corresponds to te order in which the collections appear. `do-elts` is used when only side-effects of proc are of interest and its return value is unspecified. `map-elts` returns a collection (actually a vector) of the results of the applications of proc.

> Example:

>               (map-elts + (list 1 2 3) (vector 1 2 3))
>                  => #(2 4 6)

— Procedure: map-keys proc collection1 ...
— Procedure: do-keys proc collection1 ...

> These are analogous to `map-elts` and `do-elts`, but each iteration is over the collections' keys rather than their elements.

> Example:

>               (map-keys + (list 1 2 3) (vector 1 2 3))
>                  => #(0 2 4)

— Procedure: for-each-key collection proc
— Procedure: for-each-elt collection proc

> These are like `do-keys` and `do-elts` but only for a single collection; they are potentially more efficient.

— Function: reduce proc seed collection1 ...

> A generalization of the list-based `reduce-init` (see Lists as sequences) to collections.

> Examples:

>               (reduce + 0 (vector 1 2 3))
>                  => 6
>               (reduce union '() '((a b c) (b c d) (d a)))
>                  => (c b d a).

> `Reduce` called with two arguments will work as does the procedure of the same name from See Common List Functions).

— Function: any? pred collection1 ...

> A generalization of the list-based `some` (see Lists as sequences) to collections.

> Example:

>               (any? odd? (list 2 3 4 5))
>                  => #t

— Function: every? pred collection1 ...

> A generalization of the list-based `every` (see Lists as sequences) to collections.

> Example:

>               (every? collection? '((1 2) #(1 2)))
>                  => #t

— Function: empty? collection

> Returns `#t` iff there are no elements in collection.

> `(empty?` collection`) == (zero? (size` collection`))`

— Function: size collection

> Returns the number of elements in collection.

— Function: Setter list-ref

> See Setters for a definition of setter. N.B. `(setter list-ref)` doesn't work properly for element 0 of a list.

Here is a sample collection: `simple-table` which is also a `table`.

         (define-predicate TABLE?)
         (define-operation (LOOKUP table key failure-object))
         (define-operation (ASSOCIATE! table key value)) ;; returns key
         (define-operation (REMOVE! table key))          ;; returns value

         (define (MAKE-SIMPLE-TABLE)
           (let ( (table (list)) )
             (object
              ;; table behaviors
              ((TABLE? self) #t)
              ((SIZE self) (size table))
              ((PRINT self port) (format port "#<SIMPLE-TABLE>"))
              ((LOOKUP self key failure-object)
               (cond
                ((assq key table) => cdr)
                (else failure-object)
                ))
              ((ASSOCIATE! self key value)
               (cond
                ((assq key table)
                 => (lambda (bucket) (set-cdr! bucket value) key))
                (else
                 (set! table (cons (cons key value) table))
                 key)
                ))
              ((REMOVE! self key);; returns old value
               (cond
                ((null? table) (slib:error "TABLE:REMOVE! Key not found: " key))
                ((eq? key (caar table))
                 (let ( (value (cdar table)) )
                   (set! table (cdr table))
                   value)
                 )
                (else
                 (let loop ( (last table) (this (cdr table)) )
                   (cond
                    ((null? this)
                     (slib:error "TABLE:REMOVE! Key not found: " key))
                    ((eq? key (caar this))
                     (let ( (value (cdar this)) )
                       (set-cdr! last (cdr this))
                       value)
                     )
                    (else
                     (loop (cdr last) (cdr this)))
                    ) ) )
                ))
              ;; collection behaviors
              ((COLLECTION? self) #t)
              ((GEN-KEYS self) (collect:list-gen-elts (map car table)))
              ((GEN-ELTS self) (collect:list-gen-elts (map cdr table)))
              ((FOR-EACH-KEY self proc)
               (for-each (lambda (bucket) (proc (car bucket))) table)
               )
              ((FOR-EACH-ELT self proc)
               (for-each (lambda (bucket) (proc (cdr bucket))) table)
               ) ) ) )

Next: Hash Tables, Previous: Collections, Up: Data Structures

#### 7.1.11 Dynamic Data Type

`(require 'dynamic)`

— Function: make-dynamic obj

> Create and returns a new dynamic whose global value is obj.

— Function: dynamic? obj

> Returns true if and only if obj is a dynamic. No object satisfying `dynamic?` satisfies any of the other standard type predicates.

— Function: dynamic-ref dyn

> Return the value of the given dynamic in the current dynamic environment.

— Procedure: dynamic-set! dyn obj

> Change the value of the given dynamic to obj in the current dynamic environment. The returned value is unspecified.

— Function: call-with-dynamic-binding dyn obj thunk

> Invoke and return the value of the given thunk in a new, nested dynamic environment in which the given dynamic has been bound to a new location whose initial contents are the value obj. This dynamic environment has precisely the same extent as the invocation of the thunk and is thus captured by continuations created within that invocation and re-established by those continuations when they are invoked.

The `dynamic-bind` macro is not implemented.

Next: Object, Previous: Dynamic Data Type, Up: Data Structures

#### 7.1.12 Hash Tables

`(require 'hash-table)`

— Function: predicate->hash pred

> Returns a hash function (like `hashq`, `hashv`, or `hash`) corresponding to the equality predicate pred. pred should be `eq?`, `eqv?`, `equal?`, `=`, `char=?`, `char-ci=?`, `string=?`, or `string-ci=?`.

A hash table is a vector of association lists.

— Function: make-hash-table k

> Returns a vector of k empty (association) lists.

Hash table functions provide utilities for an associative database. These functions take an equality predicate, pred, as an argument. pred should be `eq?`, `eqv?`, `equal?`, `=`, `char=?`, `char-ci=?`, `string=?`, or `string-ci=?`.

— Function: predicate->hash-asso pred

> Returns a hash association function of 2 arguments, key and hashtab, corresponding to pred. The returned function returns a key-value pair whose key is pred-equal to its first argument or `#f` if no key in hashtab is pred-equal to the first argument.

— Function: hash-inquirer pred

> Returns a procedure of 2 arguments, hashtab and key, which returns the value associated with key in hashtab or `#f` if key does not appear in hashtab.

— Function: hash-associator pred

> Returns a procedure of 3 arguments, hashtab, key, and value, which modifies hashtab so that key and value associated. Any previous value associated with key will be lost.

— Function: hash-remover pred

> Returns a procedure of 2 arguments, hashtab and key, which modifies hashtab so that the association whose key is key is removed.

— Function: hash-map proc hash-table

> Returns a new hash table formed by mapping proc over the keys and values of hash-table. proc must be a function of 2 arguments which returns the new value part.

— Function: hash-for-each proc hash-table

> Applies proc to each pair of keys and values of hash-table. proc must be a function of 2 arguments. The returned value is unspecified.

— Function: hash-rehasher pred

> `hash-rehasher` accepts a hash table predicate and returns a function of two arguments hashtab and new-k which is specialized for that predicate.

> This function is used for nondestrutively resizing a hash table. hashtab should be an existing hash-table using pred, new-k is the size of a new hash table to be returned. The new hash table will have all of the associations of the old hash table.

Next: Priority Queues, Previous: Hash Tables, Up: Data Structures

#### 7.1.13 Macroless Object System

`(require 'object)` This is the Macroless Object System written by Wade Humeniuk (whumeniu@datap.ca). Conceptual Tributes: Yasos, MacScheme's %object, CLOS, Lack of R4RS macros.

#### 7.1.14 Concepts

OBJECT
  An object is an ordered association-list (by `eq?`) of methods (procedures). Methods can be added (`make-method!`), deleted (`unmake-method!`) and retrieved (`get-method`). Objects may inherit methods from other objects. The object binds to the environment it was created in, allowing closures to be used to hide private procedures and data.
GENERIC-METHOD
  A generic-method associates (in terms of `eq?`) object's method. This allows scheme function style to be used for objects. The calling scheme for using a generic method is `(generic-method object param1 param2 ...)`.
METHOD
  A method is a procedure that exists in the object. To use a method get-method must be called to look-up the method. Generic methods implement the get-method functionality. Methods may be added to an object associated with any scheme obj in terms of eq?
GENERIC-PREDICATE
  A generic method that returns a boolean value for any scheme obj.
PREDICATE
  A object's method asscociated with a generic-predicate. Returns `#t`.

#### 7.1.15 Procedures

— Function: make-object ancestor ...

> Returns an object. Current object implementation is a tagged vector. ancestors are optional and must be objects in terms of object?. ancestors methods are included in the object. Multiple ancestors might associate the same generic-method with a method. In this case the method of the ancestor first appearing in the list is the one returned by `get-method`.

— Function: object? obj

> Returns boolean value whether obj was created by make-object.

— Function: make-generic-method exception-procedure

> Returns a procedure which be associated with an object's methods. If exception-procedure is specified then it is used to process non-objects.

— Function: make-generic-predicate

> Returns a boolean procedure for any scheme object.

— Function: make-method! object generic-method method

> Associates method to the generic-method in the object. The method overrides any previous association with the generic-method within the object. Using `unmake-method!` will restore the object's previous association with the generic-method. method must be a procedure.

— Function: make-predicate! object generic-preciate

> Makes a predicate method associated with the generic-predicate.

— Function: unmake-method! object generic-method

> Removes an object's association with a generic-method .

— Function: get-method object generic-method

> Returns the object's method associated (if any) with the generic-method. If no associated method exists an error is flagged.

#### 7.1.16 Examples

         (require 'object)

         (define instantiate (make-generic-method))

         (define (make-instance-object . ancestors)
           (define self (apply make-object
                               (map (lambda (obj) (instantiate obj)) ancestors)))
           (make-method! self instantiate (lambda (self) self))
           self)

         (define who (make-generic-method))
         (define imigrate! (make-generic-method))
         (define emigrate! (make-generic-method))
         (define describe (make-generic-method))
         (define name (make-generic-method))
         (define address (make-generic-method))
         (define members (make-generic-method))

         (define society
           (let ()
             (define self (make-instance-object))
             (define population '())
             (make-method! self imigrate!
                           (lambda (new-person)
                             (if (not (eq? new-person self))
                                 (set! population (cons new-person population)))))
             (make-method! self emigrate!
                           (lambda (person)
                             (if (not (eq? person self))
                                 (set! population
                                       (comlist:remove-if (lambda (member)
                                                            (eq? member person))
                                                          population)))))
             (make-method! self describe
                           (lambda (self)
                             (map (lambda (person) (describe person)) population)))
             (make-method! self who
                           (lambda (self) (map (lambda (person) (name person))
                                               population)))
             (make-method! self members (lambda (self) population))
             self))

         (define (make-person %name %address)
           (define self (make-instance-object society))
           (make-method! self name (lambda (self) %name))
           (make-method! self address (lambda (self) %address))
           (make-method! self who (lambda (self) (name self)))
           (make-method! self instantiate
                         (lambda (self)
                           (make-person (string-append (name self) "-son-of")
                                        %address)))
           (make-method! self describe
                         (lambda (self) (list (name self) (address self))))
           (imigrate! self)
           self)

##### 7.1.16.1 Inverter Documentation

Inheritance:

                 <inverter>::(<number> <description>)

Generic-methods

                 <inverter>::value      => <number>::value
                 <inverter>::set-value! => <number>::set-value!
                 <inverter>::describe   => <description>::describe
                 <inverter>::help
                 <inverter>::invert
                 <inverter>::inverter?

##### 7.1.16.2 Number Documention

Inheritance

                 <number>::()

Slots

                 <number>::<x>

Generic Methods

                 <number>::value
                 <number>::set-value!

##### 7.1.16.3 Inverter code

         (require 'object)

         (define value (make-generic-method (lambda (val) val)))
         (define set-value! (make-generic-method))
         (define invert (make-generic-method
                         (lambda (val)
                           (if (number? val)
                               (/ 1 val)
                               (error "Method not supported:" val)))))
         (define noop (make-generic-method))
         (define inverter? (make-generic-predicate))
         (define describe (make-generic-method))
         (define help (make-generic-method))

         (define (make-number x)
           (define self (make-object))
           (make-method! self value (lambda (this) x))
           (make-method! self set-value!
                         (lambda (this new-value) (set! x new-value)))
           self)

         (define (make-description str)
           (define self (make-object))
           (make-method! self describe (lambda (this) str))
           (make-method! self help (lambda (this) "Help not available"))
           self)

         (define (make-inverter)
           (let* ((self (make-object
                         (make-number 1)
                         (make-description "A number which can be inverted")))
                  (<value> (get-method self value)))
             (make-method! self invert (lambda (self) (/ 1 (<value> self))))
             (make-predicate! self inverter?)
             (unmake-method! self help)
             (make-method! self help
                           (lambda (self)
                             (display "Inverter Methods:") (newline)
                             (display "  (value inverter) ==> n") (newline)))
             self))

         ;;;; Try it out

         (define invert! (make-generic-method))

         (define x (make-inverter))

         (make-method! x invert! (lambda (x) (set-value! x (/ 1 (value x)))))

         (value x)                       => 1
         (set-value! x 33)               => undefined
         (invert! x)                     => undefined
         (value x)                       => 1/33

         (unmake-method! x invert!)      => undefined

         (invert! x)                     error-->  ERROR: Method not supported: x

Next: Queues, Previous: Object, Up: Data Structures

#### 7.1.17 Priority Queues

`(require 'priority-queue)` This algorithm for priority queues is due to Introduction to Algorithms by T. Cormen, C. Leiserson, R. Rivest. 1989 MIT Press.

— Function: make-heap pred<?

> Returns a binary heap suitable which can be used for priority queue operations.

— Function: heap-length heap

> Returns the number of elements in heap.

— Procedure: heap-insert! heap item

> Inserts item into heap. item can be inserted multiple times. The value returned is unspecified.

— Procedure: heap-extract-max! heap

> Returns the item which is larger than all others according to the pred<? argument to `make-heap`. If there are no items in heap, an error is signaled.

Next: Records, Previous: Priority Queues, Up: Data Structures

#### 7.1.18 Queues

`(require 'queue)` A queue is a list where elements can be added to both the front and rear, and removed from the front (i.e., they are what are often called dequeues). A queue may also be used like a stack.

— Function: make-queue

> Returns a new, empty queue.

— Function: queue? obj

> Returns `#t` if obj is a queue.

— Function: queue-empty? q

> Returns `#t` if the queue q is empty.

— Procedure: queue-push! q datum

> Adds datum to the front of queue q.

— Procedure: enqueue! q datum

> Adds datum to the rear of queue q.

— Procedure: dequeue! q
— Procedure: queue-pop! q

> Both of these procedures remove and return the datum at the front of the queue. `queue-pop!` is used to suggest that the queue is being used like a stack.

All of the following functions raise an error if the queue q is empty.

— Procedure: dequeue-all! q

> Removes and returns (the list) of all contents of queue q.

— Function: queue-front q

> Returns the datum at the front of the queue q.

— Function: queue-rear q

> Returns the datum at the rear of the queue q.

Previous: Queues, Up: Data Structures

#### 7.1.19 Records

`(require 'record)` The Record package provides a facility for user to define their own record data types.

— Function: make-record-type type-name field-names

> Returns a record-type descriptor, a value representing a new data type disjoint from all others. The type-name argument must be a string, but is only used for debugging purposes (such as the printed representation of a record of the new type). The field-names argument is a list of symbols naming the fields of a record of the new type. It is an error if the list contains any duplicates. It is unspecified how record-type descriptors are represented.

— Function: record-constructor rtd [field-names]

> Returns a procedure for constructing new members of the type represented by rtd. The returned procedure accepts exactly as many arguments as there are symbols in the given list, field-names; these are used, in order, as the initial values of those fields in a new record, which is returned by the constructor procedure. The values of any fields not named in that list are unspecified. The field-names argument defaults to the list of field names in the call to `make-record-type` that created the type represented by rtd; if the field-names argument is provided, it is an error if it contains any duplicates or any symbols not in the default list.

— Function: record-predicate rtd

> Returns a procedure for testing membership in the type represented by rtd. The returned procedure accepts exactly one argument and returns a true value if the argument is a member of the indicated record type; it returns a false value otherwise.

— Function: record-accessor rtd field-name

> Returns a procedure for reading the value of a particular field of a member of the type represented by rtd. The returned procedure accepts exactly one argument which must be a record of the appropriate type; it returns the current value of the field named by the symbol field-name in that record. The symbol field-name must be a member of the list of field-names in the call to `make-record-type` that created the type represented by rtd.

— Function: record-modifier rtd field-name

> Returns a procedure for writing the value of a particular field of a member of the type represented by rtd. The returned procedure accepts exactly two arguments: first, a record of the appropriate type, and second, an arbitrary Scheme value; it modifies the field named by the symbol field-name in that record to contain the given value. The returned value of the modifier procedure is unspecified. The symbol field-name must be a member of the list of field-names in the call to `make-record-type` that created the type represented by rtd.

In May of 1996, as a product of discussion on the `rrrs-authors` mailing list, I rewrote `record.scm` to portably implement type disjointness for record data types.

As long as an implementation's procedures are opaque and the `record` code is loaded before other programs, this will give disjoint record types which are unforgeable and incorruptible by R4RS procedures.

As a consequence, the procedures `record?`, `record-type-descriptor`, `record-type-name`.and `record-type-field-names` are no longer supported.

Next: Procedures, Previous: Data Structures, Up: Other Packages

### 7.2 Sorting and Searching

Next: Tree Operations, Previous: Sorting and Searching, Up: Sorting and Searching

#### 7.2.1 Common List Functions

`(require 'common-list-functions)` The procedures below follow the Common LISP equivalents apart from optional arguments in some cases.

Next: Lists as sets, Previous: Common List Functions, Up: Common List Functions

##### 7.2.1.1 List construction

— Function: make-list k
— Function: make-list k init

> `make-list` creates and returns a list of k elements. If init is included, all elements in the list are initialized to init.

> Example:

>               (make-list 3)
>                  => (#<unspecified> #<unspecified> #<unspecified>)
>               (make-list 5 'foo)
>                  => (foo foo foo foo foo)

— Function: list* obj1 obj2 ...

> Works like `list` except that the cdr of the last pair is the last argument unless there is only one argument, when the result is just that argument. Sometimes called `cons*`. E.g.:

>               (list* 1)
>                  => 1
>               (list* 1 2 3)
>                  => (1 2 . 3)
>               (list* 1 2 '(3 4))
>                  => (1 2 3 4)
>               (list* args '())
>                  == (list args)

— Function: copy-list lst

> `copy-list` makes a copy of lst using new pairs and returns it. Only the top level of the list is copied, i.e., pairs forming elements of the copied list remain `eq?` to the corresponding elements of the original; the copy is, however, not `eq?` to the original, but is `equal?` to it.

> Example:

>               (copy-list '(foo foo foo))
>                  => (foo foo foo)
>               (define q '(foo bar baz bang))
>               (define p q)
>               (eq? p q)
>                  => #t
>               (define r (copy-list q))
>               (eq? q r)
>                  => #f
>               (equal? q r)
>                  => #t
>               (define bar '(bar))
>               (eq? bar (car (copy-list (list bar 'foo))))
>               => #t

Next: Lists as sequences, Previous: List construction, Up: Common List Functions

##### 7.2.1.2 Lists as sets

`eqv?` is used to test for membership by procedures which treat lists as sets.

— Function: adjoin e l

> `adjoin` returns the adjoint of the element e and the list l. That is, if e is in l, `adjoin` returns l, otherwise, it returns `(cons` e l`)`.

> Example:

>               (adjoin 'baz '(bar baz bang))
>                  => (bar baz bang)
>               (adjoin 'foo '(bar baz bang))
>                  => (foo bar baz bang)

— Function: union l1 l2

> `union` returns a list of all elements that are in l1 or l2. Duplicates between l1 and l2 are culled. Duplicates within l1 or within l2 may or may not be removed.

> Example:

>               (union '(1 2 3 4) '(5 6 7 8))
>                  => (1 2 3 4 5 6 7 8)
>               (union '(0 1 2 3 4) '(3 4 5 6))
>                  => (5 6 0 1 2 3 4)

— Function: intersection l1 l2

> `intersection` returns a list of all elements that are in both l1 and l2.

> Example:

>               (intersection '(1 2 3 4) '(3 4 5 6))
>                  => (3 4)
>               (intersection '(1 2 3 4) '(5 6 7 8))
>                  => ()

— Function: set-difference l1 l2

> `set-difference` returns a list of all elements that are in l1 but not in l2.

> Example:

>               (set-difference '(1 2 3 4) '(3 4 5 6))
>                  => (1 2)
>               (set-difference '(1 2 3 4) '(1 2 3 4 5 6))
>                  => ()

— Function: subset? list1 list2

> Returns `#t` if every element of list1 is `eqv?` an element of list2; otherwise returns `#f`.

> Example:

>               (subset? '(1 2 3 4) '(3 4 5 6))
>                  => #f
>               (subset? '(1 2 3 4) '(6 5 4 3 2 1 0))
>                  => #t

— Function: member-if pred lst

> `member-if` returns the list headed by the first element of lst to satisfy `(`pred element`)`. `Member-if` returns `#f` if pred returns `#f` for every element in lst.

> Example:

>               (member-if vector? '(a 2 b 4))
>                  => #f
>               (member-if number? '(a 2 b 4))
>                  => (2 b 4)

— Function: some pred lst1 lst2 ...

> pred is a boolean function of as many arguments as there are list arguments to `some` i.e., lst plus any optional arguments. pred is applied to successive elements of the list arguments in order. `some` returns `#t` as soon as one of these applications returns `#t`, and is `#f` if none returns `#t`. All the lists should have the same length.

> Example:

>               (some odd? '(1 2 3 4))
>                  => #t

>               (some odd? '(2 4 6 8))
>                  => #f

>               (some > '(1 3) '(2 4))
>                  => #f

— Function: every pred lst1 lst2 ...

> `every` is analogous to `some` except it returns `#t` if every application of pred is `#t` and `#f` otherwise.

> Example:

>               (every even? '(1 2 3 4))
>                  => #f

>               (every even? '(2 4 6 8))
>                  => #t

>               (every > '(2 3) '(1 4))
>                  => #f

— Function: notany pred lst1 ...

> `notany` is analogous to `some` but returns `#t` if no application of pred returns `#t` or `#f` as soon as any one does.

— Function: notevery pred lst1 ...

> `notevery` is analogous to `some` but returns `#t` as soon as an application of pred returns `#f`, and `#f` otherwise.

> Example:

>               (notevery even? '(1 2 3 4))
>                  => #t

>               (notevery even? '(2 4 6 8))
>                  => #f

— Function: list-of?? predicate

> Returns a predicate which returns true if its argument is a list every element of which satisfies predicate. — Function: list-of?? predicate low-bound high-bound

> > low-bound and high-bound are non-negative integers. `list-of??` returns a predicate which returns true if its argument is a list of length between low-bound and high-bound (inclusive); every element of which satisfies predicate. — Function: list-of?? predicate bound

> > > bound is an integer. If bound is negative, `list-of??` returns a predicate which returns true if its argument is a list of length greater than `(-` bound`)`; every element of which satisfies predicate. Otherwise, `list-of??` returns a predicate which returns true if its argument is a list of length less than or equal to bound; every element of which satisfies predicate.

— Function: find-if pred lst

> `find-if` searches for the first element in lst such that `(`pred element`)` returns `#t`. If it finds any such element in lst, element is returned. Otherwise, `#f` is returned.

> Example:

>               (find-if number? '(foo 1 bar 2))
>                  => 1

>               (find-if number? '(foo bar baz bang))
>                  => #f

>               (find-if symbol? '(1 2 foo bar))
>                  => foo

— Function: remove elt lst

> `remove` removes all occurrences of elt from lst using `eqv?` to test for equality and returns everything that's left. N.B.: other implementations (Chez, Scheme->C and T, at least) use `equal?` as the equality test.

> Example:

>               (remove 1 '(1 2 1 3 1 4 1 5))
>                  => (2 3 4 5)

>               (remove 'foo '(bar baz bang))
>                  => (bar baz bang)

— Function: remove-if pred lst

> `remove-if` removes all elements from lst where `(`pred element`)` is `#t` and returns everything that's left.

> Example:

>               (remove-if number? '(1 2 3 4))
>                  => ()

>               (remove-if even? '(1 2 3 4 5 6 7 8))
>                  => (1 3 5 7)

— Function: remove-if-not pred lst

> `remove-if-not` removes all elements from lst for which `(`pred element`)` is `#f` and returns everything that's left.

> Example:

>               (remove-if-not number? '(foo bar baz))
>                  => ()
>               (remove-if-not odd? '(1 2 3 4 5 6 7 8))
>                  => (1 3 5 7)

— Function: has-duplicates? lst

> returns `#t` if 2 members of lst are `equal?`, `#f` otherwise.

> Example:

>               (has-duplicates? '(1 2 3 4))
>                  => #f

>               (has-duplicates? '(2 4 3 4))
>                  => #t

The procedure `remove-duplicates` uses `member` (rather than `memv`).

— Function: remove-duplicates lst

> returns a copy of lst with its duplicate members removed. Elements are considered duplicate if they are `equal?`.

> Example:

>               (remove-duplicates '(1 2 3 4))
>                  => (1 2 3 4)

>               (remove-duplicates '(2 4 3 4))
>                  => (2 4 3)

Next: Destructive list operations, Previous: Lists as sets, Up: Common List Functions

##### 7.2.1.3 Lists as sequences

— Function: position obj lst

> `position` returns the 0-based position of obj in lst, or `#f` if obj does not occur in lst.

> Example:

>               (position 'foo '(foo bar baz bang))
>                  => 0
>               (position 'baz '(foo bar baz bang))
>                  => 2
>               (position 'oops '(foo bar baz bang))
>                  => #f

— Function: reduce p lst

> `reduce` combines all the elements of a sequence using a binary operation (the combination is left-associative). For example, using `+`, one can add up all the elements. `reduce` allows you to apply a function which accepts only two arguments to more than 2 objects. Functional programmers usually refer to this as foldl. `collect:reduce` (see Collections) provides a version of `collect` generalized to collections.

> Example:

>               (reduce + '(1 2 3 4))
>                  => 10
>               (define (bad-sum . l) (reduce + l))
>               (bad-sum 1 2 3 4)
>                  == (reduce + (1 2 3 4))
>                  == (+ (+ (+ 1 2) 3) 4)
>               => 10
>               (bad-sum)
>                  == (reduce + ())
>                  => ()
>               (reduce string-append '("hello" "cruel" "world"))
>                  == (string-append (string-append "hello" "cruel") "world")
>                  => "hellocruelworld"
>               (reduce anything '())
>                  => ()
>               (reduce anything '(x))
>                  => x

> What follows is a rather non-standard implementation of `reverse` in terms of `reduce` and a combinator elsewhere called C.

>               ;;; Contributed by Jussi Piitulainen (jpiitula @ ling.helsinki.fi)

>               (define commute
>                 (lambda (f)
>                   (lambda (x y)
>                     (f y x))))

>               (define reverse
>                 (lambda (args)
>                   (reduce-init (commute cons) '() args)))

— Function: reduce-init p init lst

> `reduce-init` is the same as reduce, except that it implicitly inserts init at the start of the list. `reduce-init` is preferred if you want to handle the null list, the one-element, and lists with two or more elements consistently. It is common to use the operator's idempotent as the initializer. Functional programmers usually call this foldl.

> Example:

>               (define (sum . l) (reduce-init + 0 l))
>               (sum 1 2 3 4)
>                  == (reduce-init + 0 (1 2 3 4))
>                  == (+ (+ (+ (+ 0 1) 2) 3) 4)
>                  => 10
>               (sum)
>                  == (reduce-init + 0 '())
>                  => 0

>               (reduce-init string-append "@" '("hello" "cruel" "world"))
>               ==
>               (string-append (string-append (string-append "@" "hello")
>                                              "cruel")
>                              "world")
>               => "@hellocruelworld"

> Given a differentiation of 2 arguments, `diff`, the following will differentiate by any number of variables.

>               (define (diff* exp . vars)
>                 (reduce-init diff exp vars))

> Example:

>               ;;; Real-world example:  Insertion sort using reduce-init.

>               (define (insert l item)
>                 (if (null? l)
>                     (list item)
>                     (if (< (car l) item)
>                         (cons (car l) (insert (cdr l) item))
>                         (cons item l))))
>               (define (insertion-sort l) (reduce-init insert '() l))

>               (insertion-sort '(3 1 4 1 5)
>                  == (reduce-init insert () (3 1 4 1 5))
>                  == (insert (insert (insert (insert (insert () 3) 1) 4) 1) 5)
>                  == (insert (insert (insert (insert (3)) 1) 4) 1) 5)
>                  == (insert (insert (insert (1 3) 4) 1) 5)
>                  == (insert (insert (1 3 4) 1) 5)
>                  == (insert (1 1 3 4) 5)
>                  => (1 1 3 4 5)

— Function: last lst n

> `last` returns the last n elements of lst. n must be a non-negative integer.

> Example:

>               (last '(foo bar baz bang) 2)
>                  => (baz bang)
>               (last '(1 2 3) 0)
>                  => 0

— Function: butlast lst n

> `butlast` returns all but the last n elements of lst.

> Example:

>               (butlast '(a b c d) 3)
>                  => (a)
>               (butlast '(a b c d) 4)
>                  => ()

`last` and `butlast` split a list into two parts when given identical arguments.

         (last '(a b c d e) 2)
            => (d e)
         (butlast '(a b c d e) 2)
            => (a b c)

— Function: nthcdr n lst

> `nthcdr` takes n `cdr`s of lst and returns the result. Thus `(nthcdr 3` lst`)` == `(cdddr` lst`)`

> Example:

>               (nthcdr 2 '(a b c d))
>                  => (c d)
>               (nthcdr 0 '(a b c d))
>                  => (a b c d)

— Function: butnthcdr n lst

> `butnthcdr` returns all but the nthcdr n elements of lst.

> Example:

>               (butnthcdr 3 '(a b c d))
>                  => (a b c)
>               (butnthcdr 4 '(a b c d))
>                  => (a b c d)

`nthcdr` and `butnthcdr` split a list into two parts when given identical arguments.

         (nthcdr 2 '(a b c d e))
            => (c d e)
         (butnthcdr 2 '(a b c d e))
            => (a b)

Next: Non-List functions, Previous: Lists as sequences, Up: Common List Functions

##### 7.2.1.4 Destructive list operations

These procedures may mutate the list they operate on, but any such mutation is undefined.

— Procedure: nconc args

> `nconc` destructively concatenates its arguments. (Compare this with `append`, which copies arguments rather than destroying them.) Sometimes called `append!` (see Rev2 Procedures).

> Example: You want to find the subsets of a set. Here's the obvious way:

>               (define (subsets set)
>                 (if (null? set)
>                     '(())
>                     (append (map (lambda (sub) (cons (car set) sub))
>                                  (subsets (cdr set)))
>                             (subsets (cdr set)))))

> But that does way more consing than you need. Instead, you could replace the `append` with `nconc`, since you don't have any need for all the intermediate results.

> Example:

>               (define x '(a b c))
>               (define y '(d e f))
>               (nconc x y)
>                  => (a b c d e f)
>               x
>                  => (a b c d e f)

> `nconc` is the same as `append!` in `sc2.scm`.

— Procedure: nreverse lst

> `nreverse` reverses the order of elements in lst by mutating `cdr`s of the list. Sometimes called `reverse!`.

> Example:

>               (define foo '(a b c))
>               (nreverse foo)
>                  => (c b a)
>               foo
>                  => (a)

> Some people have been confused about how to use `nreverse`, thinking that it doesn't return a value. It needs to be pointed out that

>               (set! lst (nreverse lst))

> is the proper usage, not

>               (nreverse lst)

> The example should suffice to show why this is the case.

— Procedure: delete elt lst
— Procedure: delete-if pred lst
— Procedure: delete-if-not pred lst

> Destructive versions of `remove` `remove-if`, and `remove-if-not`.

> Example:

>               (define lst (list 'foo 'bar 'baz 'bang))
>               (delete 'foo lst)
>                  => (bar baz bang)
>               lst
>                  => (foo bar baz bang)

>               (define lst (list 1 2 3 4 5 6 7 8 9))
>               (delete-if odd? lst)
>                  => (2 4 6 8)
>               lst
>                  => (1 2 4 6 8)

> Some people have been confused about how to use `delete`, `delete-if`, and `delete-if`, thinking that they don't return a value. It needs to be pointed out that

>               (set! lst (delete el lst))

> is the proper usage, not

>               (delete el lst)

> The examples should suffice to show why this is the case.

Previous: Destructive list operations, Up: Common List Functions

##### 7.2.1.5 Non-List functions

— Function: and? arg1 ...

> `and?` checks to see if all its arguments are true. If they are, `and?` returns `#t`, otherwise, `#f`. (In contrast to `and`, this is a function, so all arguments are always evaluated and in an unspecified order.)

> Example:

>               (and? 1 2 3)
>                  => #t
>               (and #f 1 2)
>                  => #f

— Function: or? arg1 ...

> `or?` checks to see if any of its arguments are true. If any is true, `or?` returns `#t`, and `#f` otherwise. (To `or` as `and?` is to `and`.)

> Example:

>               (or? 1 2 #f)
>                  => #t
>               (or? #f #f #f)
>                  => #f

— Function: atom? object

> Returns `#t` if object is not a pair and `#f` if it is pair. (Called `atom` in Common LISP.)

>               (atom? 1)
>                  => #t
>               (atom? '(1 2))
>                  => #f
>               (atom? #(1 2))   ; dubious!
>                  => #t

Next: Chapter Ordering, Previous: Common List Functions, Up: Sorting and Searching

#### 7.2.2 Tree operations

`(require 'tree)` These are operations that treat lists a representations of trees.

— Function: subst new old tree
— Function: substq new old tree
— Function: substv new old tree
— Function: subst new old tree equ?

> `subst` makes a copy of tree, substituting new for every subtree or leaf of tree which is `equal?` to old and returns a modified tree. The original tree is unchanged, but may share parts with the result.

> `substq` and `substv` are similar, but test against old using `eq?` and `eqv?` respectively. If `subst` is called with a fourth argument, equ? is the equality predicate.

> Examples:

>               (substq 'tempest 'hurricane '(shakespeare wrote (the hurricane)))
>                  => (shakespeare wrote (the tempest))
>               (substq 'foo '() '(shakespeare wrote (twelfth night)))
>                  => (shakespeare wrote (twelfth night . foo) . foo)
>               (subst '(a . cons) '(old . pair)
>                      '((old . spice) ((old . shoes) old . pair) (old . pair)))
>                  => ((old . spice) ((old . shoes) a . cons) (a . cons))

— Function: copy-tree tree

> Makes a copy of the nested list structure tree using new pairs and returns it. All levels are copied, so that none of the pairs in the tree are `eq?` to the original ones – only the leaves are.

> Example:

>               (define bar '(bar))
>               (copy-tree (list bar 'foo))
>                  => ((bar) foo)
>               (eq? bar (car (copy-tree (list bar 'foo))))
>                  => #f

Next: Sorting, Previous: Tree Operations, Up: Sorting and Searching

#### 7.2.3 Chapter Ordering

`(require 'chapter-order)` The ``chap:`' functions deal with strings which are ordered like chapter numbers (or letters) in a book. Each section of the string consists of consecutive numeric or consecutive aphabetic characters of like case.

— Function: chap:string<? string1 string2

> Returns #t if the first non-matching run of alphabetic upper-case or the first non-matching run of alphabetic lower-case or the first non-matching run of numeric characters of string1 is `string<?` than the corresponding non-matching run of characters of string2.

>               (chap:string<? "a.9" "a.10")                    => #t
>               (chap:string<? "4c" "4aa")                      => #t
>               (chap:string<? "Revised^{3.99}" "Revised^{4}")  => #t

— Function: chap:string>? string1 string2
— Function: chap:string<=? string1 string2
— Function: chap:string>=? string1 string2

> Implement the corresponding chapter-order predicates.

— Function: chap:next-string string

> Returns the next string in the chapter order. If string has no alphabetic or numeric characters, `(string-append` string`"0")` is returnd. The argument to chap:next-string will always be `chap:string<?` than the result.

>               (chap:next-string "a.9")                => "a.10"
>               (chap:next-string "4c")                 => "4d"
>               (chap:next-string "4z")                 => "4aa"
>               (chap:next-string "Revised^{4}")        => "Revised^{5}"

Next: Topological Sort, Previous: Chapter Ordering, Up: Sorting and Searching

#### 7.2.4 Sorting

`(require 'sort)` or `(require 'srfi-95)` [by Richard A. O'Keefe, 1991]

I am providing this source code with no restrictions at all on its use (but please retain D.H.D.Warren's credit for the original idea).

The code of `merge` and `merge!` could have been quite a bit simpler, but they have been coded to reduce the amount of work done per iteration. (For example, we only have one `null?` test per iteration.)

I gave serious consideration to producing Common-LISP-compatible functions. However, Common LISP's `sort` is our `sort!` (well, in fact Common LISP's `stable-sort` is our `sort!`; merge sort is fast as well as stable!) so adapting CL code to Scheme takes a bit of work anyway. I did, however, appeal to CL to determine the order of the arguments.

The standard functions `<`, `>`, `char<?`, `char>?`, `char-ci<?`, `char-ci>?`, `string<?`, `string>?`, `string-ci<?`, and `string-ci>?` are suitable for use as comparison functions. Think of `(less? x y)` as saying when `x` must not precede `y`.

[Addendum by Aubrey Jaffer, 2006]

These procedures are stable when called with predicates which return `#f` when applied to identical arguments.

The `sorted?`, `merge`, and `merge!` procedures consume asymptotic time and space no larger than O(N), where N is the sum of the lengths of the sequence arguments. The `sort` and `sort!` procedures consume asymptotic time and space no larger than O(N*log(N)), where N is the length of the sequence argument.

All five functions take an optional key argument corresponding to a CL-style ``&key`' argument. A less? predicate with a key argument behaves like:

         (lambda (x y) (less? (key x) (key y)))

All five functions will call the key argument at most once per element.

The ``!`' variants sort in place; `sort!` returns its sequence argument.

— Function: sorted? sequence less?
— Function: sorted? sequence less? key

> Returns `#t` when the sequence argument is in non-decreasing order according to less? (that is, there is no adjacent pair `... x y ...` for which `(less? y x)`).

> Returns `#f` when the sequence contains at least one out-of-order pair. It is an error if the sequence is not a list or array (including vectors and strings).

— Function: merge list1 list2 less?
— Function: merge list1 list2 less? key

> Merges two sorted lists, returning a freshly allocated list as its result.

— Function: merge! list1 list2 less?
— Function: merge! list1 list2 less? key

> Merges two sorted lists, re-using the pairs of list1 and list2 to build the result. The result will be either list1 or list2.

— Function: sort sequence less?
— Function: sort sequence less? key

> Accepts a list or array (including vectors and strings) for sequence; and returns a completely new sequence which is sorted according to less?. The returned sequence is the same type as the argument sequence. Given valid arguments, it is always the case that:

>               (sorted? (sort sequence less?) less?) => #t

— Function: sort! sequence less?
— Function: sort! sequence less? key

> Returns list, array, vector, or string sequence which has been mutated to order its elements according to less?. Given valid arguments, it is always the case that:

>               (sorted? (sort! sequence less?) less?) => #t

Next: Hashing, Previous: Sorting, Up: Sorting and Searching

#### 7.2.5 Topological Sort

`(require 'topological-sort)` or `(require 'tsort)` The algorithm is inspired by Cormen, Leiserson and Rivest (1990) Introduction to Algorithms, chapter 23.

— Function: tsort dag pred
— Function: topological-sort dag pred

> where

> dag
>   is a list of sublists. The car of each sublist is a vertex. The cdr is the adjacency list of that vertex, i.e. a list of all vertices to which there exists an edge from the car vertex.
> pred
>   is one of `eq?`, `eqv?`, `equal?`, `=`, `char=?`, `char-ci=?`, `string=?`, or `string-ci=?`.

> Sort the directed acyclic graph dag so that for every edge from vertex u to v, u will come before v in the resulting list of vertices.

> Time complexity: O (|V| + |E|)

> Example (from Cormen):

> > Prof. Bumstead topologically sorts his clothing when getting dressed. The first argument to `tsort` describes which garments he needs to put on before others. (For example, Prof Bumstead needs to put on his shirt before he puts on his tie or his belt.) `tsort` gives the correct order of dressing:

>               (require 'tsort)
>               (tsort '((shirt tie belt)
>                        (tie jacket)
>                        (belt jacket)
>                        (watch)
>                        (pants shoes belt)
>                        (undershorts pants shoes)
>                        (socks shoes))
>                      eq?)
>               =>
>               (socks undershorts pants shoes watch shirt belt tie jacket)

Next: Space-Filling Curves, Previous: Topological Sort, Up: Sorting and Searching

#### 7.2.6 Hashing

`(require 'hash)` These hashing functions are for use in quickly classifying objects. Hash tables use these functions.

— Function: hashq obj k
— Function: hashv obj k
— Function: hash obj k

> Returns an exact non-negative integer less than k. For each non-negative integer less than k there are arguments obj for which the hashing functions applied to obj and k returns that integer.

> For `hashq`, `(eq? obj1 obj2)` implies `(= (hashq obj1 k) (hashq obj2))`.

> For `hashv`, `(eqv? obj1 obj2)` implies `(= (hashv obj1 k) (hashv obj2))`.

> For `hash`, `(equal? obj1 obj2)` implies `(= (hash obj1 k) (hash obj2))`.

> `hash`, `hashv`, and `hashq` return in time bounded by a constant. Notice that items having the same `hash` implies the items have the same `hashv` implies the items have the same `hashq`.

Next: Soundex, Previous: Hashing, Up: Sorting and Searching

#### 7.2.7 Space-Filling Curves

Next: Peano Space-Filling Curve, Previous: Space-Filling Curves, Up: Space-Filling Curves

##### 7.2.7.1 Hilbert Space-Filling Curve

`(require 'hilbert-fill)` The Hilbert Space-Filling Curve is a one-to-one mapping between a unit line segment and an n-dimensional unit cube. This implementation treats the nonnegative integers either as fractional bits of a given width or as nonnegative integers.

The integer procedures map the non-negative integers to an arbitrarily large n-dimensional cube with its corner at the origin and all coordinates are non-negative.

For any exact nonnegative integer scalar and exact integer rank > 2,

         (= scalar (hilbert-coordinates->integer
                    (integer->hilbert-coordinates scalar rank)))
                                                => #t

When treating integers as k fractional bits,

         (= scalar (hilbert-coordinates->integer
                    (integer->hilbert-coordinates scalar rank k)) k)
                                                => #t

— Function: integer->hilbert-coordinates scalar rank

> Returns a list of rank integer coordinates corresponding to exact non-negative integer scalar. The lists returned by `integer->hilbert-coordinates` for scalar arguments 0 and 1 will differ in the first element. — Function: integer->hilbert-coordinates scalar rank k

> > scalar must be a nonnegative integer of no more than rank`*`k bits.

> > `integer->hilbert-coordinates` Returns a list of rank k-bit nonnegative integer coordinates corresponding to exact non-negative integer scalar. The curves generated by `integer->hilbert-coordinates` have the same alignment independent of k.

— Function: hilbert-coordinates->integer coords
— Function: hilbert-coordinates->integer coords k

> Returns an exact non-negative integer corresponding to coords, a list of non-negative integer coordinates.

##### 7.2.7.2 Gray code

A Gray code is an ordering of non-negative integers in which exactly one bit differs between each pair of successive elements. There are multiple Gray codings. An n-bit Gray code corresponds to a Hamiltonian cycle on an n-dimensional hypercube.

Gray codes find use communicating incrementally changing values between asynchronous agents. De-laminated Gray codes comprise the coordinates of Hilbert space-filling curves.

— Function: integer->gray-code k

> Converts k to a Gray code of the same `integer-length` as k. — Function: gray-code->integer k

> > Converts the Gray code k to an integer of the same `integer-length` as k.

> > For any non-negative integer k,

> >               (eqv? k (gray-code->integer (integer->gray-code k)))

— Function: = k1 k2
— Function: gray-code<? k1 k2
— Function: gray-code>? k1 k2
— Function: gray-code<=? k1 k2
— Function: gray-code>=? k1 k2

> These procedures return #t if their Gray code arguments are (respectively): equal, monotonically increasing, monotonically decreasing, monotonically nondecreasing, or monotonically nonincreasing.

> For any non-negative integers k1 and k2, the Gray code predicate of `(integer->gray-code k1)` and `(integer->gray-code k2)` will return the same value as the corresponding predicate of k1 and k2.

##### 7.2.7.3 Bitwise Lamination

— Function: delaminate-list count ks

> Returns a list of count integers comprised of the jth bit of the integers ks where j ranges from count-1 to 0.

>               (map (lambda (k) (number->string k 2))
>                    (delaminate-list 4 '(7 6 5 4 0 0 0 0)))
>                   => ("0" "11110000" "11000000" "10100000")

> `delaminate-list` is its own inverse:

>               (delaminate-list 8 (delaminate-list 4 '(7 6 5 4 0 0 0 0)))
>                   => (7 6 5 4 0 0 0 0)

Next: Sierpinski Curve, Previous: Hilbert Space-Filling Curve, Up: Space-Filling Curves

##### 7.2.7.4 Peano Space-Filling Curve

`(require 'peano-fill)`

— Function: natural->peano-coordinates scalar rank

> Returns a list of rank nonnegative integer coordinates corresponding to exact nonnegative integer scalar. The lists returned by `natural->peano-coordinates` for scalar arguments 0 and 1 will differ in the first element.

— Function: peano-coordinates->natural coords

> Returns an exact nonnegative integer corresponding to coords, a list of nonnegative integer coordinates.

— Function: integer->peano-coordinates scalar rank

> Returns a list of rank integer coordinates corresponding to exact integer scalar. The lists returned by `integer->peano-coordinates` for scalar arguments 0 and 1 will differ in the first element.

— Function: peano-coordinates->integer coords

> Returns an exact integer corresponding to coords, a list of integer coordinates.

Previous: Peano Space-Filling Curve, Up: Space-Filling Curves

##### 7.2.7.5 Sierpinski Curve

`(require 'sierpinski)`

— Function: make-sierpinski-indexer max-coordinate

> Returns a procedure (eg hash-function) of 2 numeric arguments which preserves nearness in its mapping from NxN to N.

> max-coordinate is the maximum coordinate (a positive integer) of a population of points. The returned procedures is a function that takes the x and y coordinates of a point, (non-negative integers) and returns an integer corresponding to the relative position of that point along a Sierpinski curve. (You can think of this as computing a (pseudo-) inverse of the Sierpinski spacefilling curve.)

> Example use: Make an indexer (hash-function) for integer points lying in square of integer grid points [0,99]x[0,99]:

>               (define space-key (make-sierpinski-indexer 100))

> Now let's compute the index of some points:

>               (space-key 24 78)               => 9206
>               (space-key 23 80)               => 9172

> Note that locations (24, 78) and (23, 80) are near in index and therefore, because the Sierpinski spacefilling curve is continuous, we know they must also be near in the plane. Nearness in the plane does not, however, necessarily correspond to nearness in index, although it tends to be so.

> Example applications:

> - Sort points by Sierpinski index to get heuristic solution to travelling salesman problem. For details of performance, see L. Platzman and J. Bartholdi, "Spacefilling curves and the Euclidean travelling salesman problem", JACM 36(4):719–737 (October 1989) and references therein.
> - Use Sierpinski index as key by which to store 2-dimensional data in a 1-dimensional data structure (such as a table). Then locations that are near each other in 2-d space will tend to be near each other in 1-d data structure; and locations that are near in 1-d data structure will be near in 2-d space. This can significantly speed retrieval from secondary storage because contiguous regions in the plane will tend to correspond to contiguous regions in secondary storage. (This is a standard technique for managing CAD/CAM or geographic data.)

Next: String Search, Previous: Space-Filling Curves, Up: Sorting and Searching

#### 7.2.8 Soundex

`(require 'soundex)`

— Function: soundex name

> Computes the soundex hash of name. Returns a string of an initial letter and up to three digits between 0 and 6. Soundex supposedly has the property that names that sound similar in normal English pronunciation tend to map to the same key.

> Soundex was a classic algorithm used for manual filing of personal records before the advent of computers. It performs adequately for English names but has trouble with other languages.

> See Knuth, Vol. 3 Sorting and searching, pp 391–2

> To manage unusual inputs, `soundex` omits all non-alphabetic characters. Consequently, in this implementation:

>               (soundex <string of blanks>)    => ""
>               (soundex "")                    => ""

> Examples from Knuth:

>               (map soundex '("Euler" "Gauss" "Hilbert" "Knuth"
>                                      "Lloyd" "Lukasiewicz"))
>                       => ("E460" "G200" "H416" "K530" "L300" "L222")

>               (map soundex '("Ellery" "Ghosh" "Heilbronn" "Kant"
>                                       "Ladd" "Lissajous"))
>                       => ("E460" "G200" "H416" "K530" "L300" "L222")

> Some cases in which the algorithm fails (Knuth):

>               (map soundex '("Rogers" "Rodgers"))     => ("R262" "R326")

>               (map soundex '("Sinclair" "St. Clair")) => ("S524" "S324")

>               (map soundex '("Tchebysheff" "Chebyshev")) => ("T212" "C121")

Next: Sequence Comparison, Previous: Soundex, Up: Sorting and Searching

#### 7.2.9 String Search

`(require 'string-search)`

— Procedure: string-index string char
— Procedure: string-index-ci string char

> Returns the index of the first occurence of char within string, or `#f` if the string does not contain a character char.

— Procedure: string-reverse-index string char
— Procedure: string-reverse-index-ci string char

> Returns the index of the last occurence of char within string, or `#f` if the string does not contain a character char.

— Procedure: substring? pattern string
— Procedure: substring-ci? pattern string

> Searches string to see if some substring of string is equal to pattern. `substring?` returns the index of the first character of the first substring of string that is equal to pattern; or `#f` if string does not contain pattern.

>               (substring? "rat" "pirate") =>  2
>               (substring? "rat" "outrage") =>  #f
>               (substring? "" any-string) =>  0

— Procedure: find-string-from-port? str in-port max-no-chars

> Looks for a string str within the first max-no-chars chars of the input port in-port. — Procedure: find-string-from-port? str in-port

> > When called with two arguments, the search span is limited by the end of the input stream. — Procedure: find-string-from-port? str in-port char

> > > Searches up to the first occurrence of character char in str. — Procedure: find-string-from-port? str in-port proc

> > > > Searches up to the first occurrence of the procedure proc returning non-false when called with a character (from in-port) argument.

> > > > When the str is found, `find-string-from-port?` returns the number of characters it has read from the port, and the port is set to read the first char after that (that is, after the str) The function returns `#f` when the str isn't found.

> > > > `find-string-from-port?` reads the port strictly sequentially, and does not perform any buffering. So `find-string-from-port?` can be used even if the in-port is open to a pipe or other communication channel.

— Function: string-subst txt old1 new1 ...

> Returns a copy of string txt with all occurrences of string old1 in txt replaced with new1; then old2 replaced with new2 .... Matches are found from the left. Matches do not overlap.

— Function: count-newlines str

> Returns the number of ``#\newline`' characters in string str.

Previous: String Search, Up: Sorting and Searching

#### 7.2.10 Sequence Comparison

`(require 'diff)`

`diff:edit-length` implements the algorithm:

The values returned by `diff:edit-length` can be used to gauge the degree of match between two sequences.

`diff:edits` and `diff:longest-common-subsequence` combine the algorithm with the divide-and-conquer method outlined in:

If the items being sequenced are text lines, then the computed edit-list is equivalent to the output of the diff utility program. If the items being sequenced are words, then it is like the lesser known spiff program.

— Function: diff:longest-common-subsequence array1 array2 p-lim
— Function: diff:longest-common-subsequence array1 array2

> array1 and array2 are one-dimensional arrays.

> The non-negative integer p-lim, if provided, is maximum number of deletions of the shorter sequence to allow. `diff:longest-common-subsequence` will return `#f` if more deletions would be necessary.

> `diff:longest-common-subsequence` returns a one-dimensional array of length `(quotient (- (+ len1 len2) (diff:edit-length` array1 array2`)) 2)` holding the longest sequence common to both arrays.

— Function: diff:edits array1 array2 p-lim
— Function: diff:edits array1 array2

> array1 and array2 are one-dimensional arrays.

> The non-negative integer p-lim, if provided, is maximum number of deletions of the shorter sequence to allow. `diff:edits` will return `#f` if more deletions would be necessary.

> `diff:edits` returns a vector of length `(diff:edit-length` array1 array2`)` composed of a shortest sequence of edits transformaing array1 to array2.

> Each edit is an integer:

> k > 0
>   Inserts `(array-ref` array1`(+ -1` j`))` into the sequence.
> k < 0
>   Deletes `(array-ref` array2`(- -1` k`))` from the sequence.

— Function: diff:edit-length array1 array2 p-lim
— Function: diff:edit-length array1 array2

> array1 and array2 are one-dimensional arrays.

> The non-negative integer p-lim, if provided, is maximum number of deletions of the shorter sequence to allow. `diff:edit-length` will return `#f` if more deletions would be necessary.

> `diff:edit-length` returns the length of the shortest sequence of edits transformaing array1 to array2.

         (diff:longest-common-subsequence "fghiejcklm" "fgehijkpqrlm")
         => "fghijklm"

         (diff:edit-length "fghiejcklm" "fgehijkpqrlm")
         => 6

         (diff:edits "fghiejcklm" "fgehijkpqrlm")
         => #A:fixZ32b(3 -5 -7 8 9 10)
                ; e  c  h p q  r

Next: Standards Support, Previous: Sorting and Searching, Up: Other Packages

### 7.3 Procedures

Anything that doesn't fall neatly into any of the other categories winds up here.

Next: String-Case, Previous: Procedures, Up: Procedures

#### 7.3.1 Type Coercion

`(require 'coerce)`

— Function: type-of obj

> Returns a symbol name for the type of obj.

— Function: coerce obj result-type

> Converts and returns obj of type `char`, `number`, `string`, `symbol`, `list`, or `vector` to result-type (which must be one of these symbols).

Next: String Ports, Previous: Type Coercion, Up: Procedures

#### 7.3.2 String-Case

`(require 'string-case)`

— Procedure: string-upcase str
— Procedure: string-downcase str
— Procedure: string-capitalize str

> The obvious string conversion routines. These are non-destructive.

— Function: string-upcase! str
— Function: string-downcase! str
— Function: string-capitalize! str

> The destructive versions of the functions above.

— Function: string-ci->symbol str

> Converts string str to a symbol having the same case as if the symbol had been `read`.

— Function: symbol-append obj1 ...

> Converts obj1 ... to strings, appends them, and converts to a symbol which is returned. Strings and numbers are converted to read's symbol case; the case of symbol characters is not changed. #f is converted to the empty string (symbol).

— Function: StudlyCapsExpand str delimiter
— Function: StudlyCapsExpand str

> delimiter must be a string or character. If absent, delimiter defaults to ``-`'. `StudlyCapsExpand` returns a copy of str where delimiter is inserted between each lower-case character immediately followed by an upper-case character; and between two upper-case characters immediately followed by a lower-case character.

>               (StudlyCapsExpand "aX" " ")   => "a X"
>               (StudlyCapsExpand "aX" "..")  => "a..X"
>               (StudlyCapsExpand "AX")       => "AX"
>               (StudlyCapsExpand "Ax")       => "Ax"
>               (StudlyCapsExpand "AXLE")     => "AXLE"
>               (StudlyCapsExpand "aAXACz")   => "a-AXA-Cz"
>               (StudlyCapsExpand "AaXACz")   => "Aa-XA-Cz"
>               (StudlyCapsExpand "AAaXACz")  => "A-Aa-XA-Cz"
>               (StudlyCapsExpand "AAaXAC")   => "A-Aa-XAC"

Next: Line I/O, Previous: String-Case, Up: Procedures

#### 7.3.3 String Ports

`(require 'string-port)`

— Procedure: call-with-output-string proc

> proc must be a procedure of one argument. This procedure calls proc with one argument: a (newly created) output port. When the function returns, the string composed of the characters written into the port is returned.

— Procedure: call-with-input-string string proc

> proc must be a procedure of one argument. This procedure calls proc with one argument: an (newly created) input port from which string's contents may be read. When proc returns, the port is closed and the value yielded by the procedure proc is returned.

Next: Multi-Processing, Previous: String Ports, Up: Procedures

#### 7.3.4 Line I/O

`(require 'line-i/o)`

— Function: read-line
— Function: read-line port

> Returns a string of the characters up to, but not including a newline or end of file, updating port to point to the character following the newline. If no characters are available, an end of file object is returned. The port argument may be omitted, in which case it defaults to the value returned by `current-input-port`.

— Procedure: read-line! string
— Procedure: read-line! string port

> Fills string with characters up to, but not including a newline or end of file, updating the port to point to the last character read or following the newline if it was read. If no characters are available, an end of file object is returned. If a newline or end of file was found, the number of characters read is returned. Otherwise, `#f` is returned. The port argument may be omitted, in which case it defaults to the value returned by `current-input-port`.

— Function: write-line string
— Function: write-line string port

> Writes string followed by a newline to the given port and returns an unspecified value. The Port argument may be omitted, in which case it defaults to the value returned by `current-input-port`.

— Function: system->line command tmp
— Function: system->line command

> command must be a string. The string tmp, if supplied, is a path to use as a temporary file. `system->line` calls `system` with command as argument, redirecting stdout to file tmp. `system->line` returns a string containing the first line of output from tmp.

> `system->line` is intended to be a portable method for getting one-line results from programs like `pwd`, `whoami`, `hostname`, `which`, `identify`, and `cksum`. Its behavior when called with programs which generate lots of output is unspecified.

Next: Metric Units, Previous: Line I/O, Up: Procedures

#### 7.3.5 Multi-Processing

`(require 'process)` This module implements asynchronous (non-polled) time-sliced multi-processing in the SCM Scheme implementation using procedures `alarm` and `alarm-interrupt`. Until this is ported to another implementation, consider it an example of writing schedulers in Scheme.

— Procedure: add-process! proc

> Adds proc, which must be a procedure (or continuation) capable of accepting accepting one argument, to the `process:queue`. The value returned is unspecified. The argument to proc should be ignored. If proc returns, the process is killed.

— Procedure: process:schedule!

> Saves the current process on `process:queue` and runs the next process from `process:queue`. The value returned is unspecified.

— Procedure: kill-process!

> Kills the current process and runs the next process from `process:queue`. If there are no more processes on `process:queue`, `(slib:exit)` is called (see System).

Previous: Multi-Processing, Up: Procedures

#### 7.3.6 Metric Units

`(require 'metric-units)` http://swiss.csail.mit.edu/~jaffer/MIXF

Metric Interchange Format is a character string encoding for numerical values and units which:

- is unambiguous in all locales;
- uses only [TOG] "Portable Character Set" characters matching "Basic Latin" characters in Plane 0 of the Universal Character Set [UCS];
- is transparent to [UTF-7] and [UTF-8] UCS transformation formats;
- is human readable and writable;
- is machine readable and writable;
- incorporates SI prefixes and units;
- incorporates [ISO 6093] numbers; and
- incorporates [IEC 60027-2] binary prefixes.

In the expression for the value of a quantity, the unit symbol is placed after the numerical value. A dot (PERIOD, ``.`') is placed between the numerical value and the unit symbol.

Within a compound unit, each of the base and derived symbols can optionally have an attached SI prefix.

Unit symbols formed from other unit symbols by multiplication are indicated by means of a dot (PERIOD, ``.`') placed between them.

Unit symbols formed from other unit symbols by division are indicated by means of a SOLIDUS (``/`') or negative exponents. The SOLIDUS must not be repeated in the same compound unit unless contained within a parenthesized subexpression.

The grouping formed by a prefix symbol attached to a unit symbol constitutes a new inseparable symbol (forming a multiple or submultiple of the unit concerned) which can be raised to a positive or negative power and which can be combined with other unit symbols to form compound unit symbols.

The grouping formed by surrounding compound unit symbols with parentheses (``(`' and ``)`') constitutes a new inseparable symbol which can be raised to a positive or negative power and which can be combined with other unit symbols to form compound unit symbols.

Compound prefix symbols, that is, prefix symbols formed by the juxtaposition of two or more prefix symbols, are not permitted.

Prefix symbols are not used with the time-related unit symbols min (minute), h (hour), d (day). No prefix symbol may be used with dB (decibel). Only submultiple prefix symbols may be used with the unit symbols L (liter), Np (neper), o (degree), oC (degree Celsius), rad (radian), and sr (steradian). Submultiple prefix symbols may not be used with the unit symbols t (metric ton), r (revolution), or Bd (baud).

A unit exponent follows the unit, separated by a CIRCUMFLEX (``^`'). Exponents may be positive or negative. Fractional exponents must be parenthesized.

##### 7.3.6.1 SI Prefixes

                Factor     Name    Symbol  |  Factor     Name    Symbol
                ======     ====    ======  |  ======     ====    ======
                 1e24      yotta      Y    |   1e-1      deci       d
                 1e21      zetta      Z    |   1e-2      centi      c
                 1e18      exa        E    |   1e-3      milli      m
                 1e15      peta       P    |   1e-6      micro      u
                 1e12      tera       T    |   1e-9      nano       n
                 1e9       giga       G    |   1e-12     pico       p
                 1e6       mega       M    |   1e-15     femto      f
                 1e3       kilo       k    |   1e-18     atto       a
                 1e2       hecto      h    |   1e-21     zepto      z
                 1e1       deka       da   |   1e-24     yocto      y

##### 7.3.6.2 Binary Prefixes

These binary prefixes are valid only with the units B (byte) and bit. However, decimal prefixes can also be used with bit; and decimal multiple (not submultiple) prefixes can also be used with B (byte).

                         Factor       (power-of-2)  Name  Symbol
                         ======       ============  ====  ======
                1.152921504606846976e18  (2^60)     exbi    Ei
                   1.125899906842624e15  (2^50)     pebi    Pi
                      1.099511627776e12  (2^40)     tebi    Ti
                         1.073741824e9   (2^30)     gibi    Gi
                            1.048576e6   (2^20)     mebi    Mi
                               1.024e3   (2^10)     kibi    Ki

##### 7.3.6.3 Unit Symbols

             Type of Quantity      Name          Symbol   Equivalent
             ================      ====          ======   ==========
         time                      second           s
         time                      minute           min = 60.s
         time                      hour             h   = 60.min
         time                      day              d   = 24.h
         frequency                 hertz            Hz    s^-1
         signaling rate            baud             Bd    s^-1
         length                    meter            m
         volume                    liter            L     dm^3
         plane angle               radian           rad
         solid angle               steradian        sr    rad^2
         plane angle               revolution     * r   = 6.283185307179586.rad
         plane angle               degree         * o   = 2.777777777777778e-3.r
         information capacity      bit              bit
         information capacity      byte, octet      B   = 8.bit
         mass                      gram             g
         mass                      ton              t     Mg
         mass              unified atomic mass unit u   = 1.66053873e-27.kg
         amount of substance       mole             mol
         catalytic activity        katal            kat   mol/s
         thermodynamic temperature kelvin           K
         centigrade temperature    degree Celsius   oC
         luminous intensity        candela          cd
         luminous flux             lumen            lm    cd.sr
         illuminance               lux              lx    lm/m^2
         force                     newton           N     m.kg.s^-2
         pressure, stress          pascal           Pa    N/m^2
         energy, work, heat        joule            J     N.m
         energy                    electronvolt     eV  = 1.602176462e-19.J
         power, radiant flux       watt             W     J/s
         logarithm of power ratio  neper            Np
         logarithm of power ratio  decibel        * dB  = 0.1151293.Np
         electric current          ampere           A
         electric charge           coulomb          C     s.A
         electric potential, EMF   volt             V     W/A
         capacitance               farad            F     C/V
         electric resistance       ohm              Ohm   V/A
         electric conductance      siemens          S     A/V
         magnetic flux             weber            Wb    V.s
         magnetic flux density     tesla            T     Wb/m^2
         inductance                henry            H     Wb/A
         radionuclide activity     becquerel        Bq    s^-1
         absorbed dose energy      gray             Gy    m^2.s^-2
         dose equivalent           sievert          Sv    m^2.s^-2

* The formulas are:

- r/rad = 8 * atan(1)
- o/r = 1 / 360
- db/Np = ln(10) / 20

— Function: si:conversion-factor to-unit from-unit

> If the strings from-unit and to-unit express valid unit expressions for quantities of the same unit-dimensions, then the value returned by `si:conversion-factor` will be such that multiplying a numerical value expressed in from-units by the returned conversion factor yields the numerical value expressed in to-units.

> Otherwise, `si:conversion-factor` returns:

> -3
>   if neither from-unit nor to-unit is a syntactically valid unit.
> -2
>   if from-unit is not a syntactically valid unit.
> -1
>   if to-unit is not a syntactically valid unit.
> 0
>   if linear conversion (by a factor) is not possible.

         (si:conversion-factor "km/s" "m/s" ) => 0.001
         (si:conversion-factor "N"    "m/s" ) => 0
         (si:conversion-factor "moC"  "oC"  ) => 1000
         (si:conversion-factor "mK"   "oC"  ) => 0
         (si:conversion-factor "rad"  "o"   ) => 0.0174533
         (si:conversion-factor "K"    "o"   ) => 0
         (si:conversion-factor "K"    "K"   ) => 1
         (si:conversion-factor "oK"   "oK"  ) => -3
         (si:conversion-factor ""     "s/s" ) => 1
         (si:conversion-factor "km/h" "mph" ) => -2

Next: Session Support, Previous: Procedures, Up: Other Packages

### 7.4 Standards Support

Next: With-File, Previous: Standards Support, Up: Standards Support

#### 7.4.1 RnRS

The `r2rs`, `r3rs`, `r4rs`, and `r5rs` features attempt to provide procedures and macros to bring a Scheme implementation to the desired version of Scheme.

— Feature: r2rs

> Requires features implementing procedures and optional procedures specified by Revised^2 Report on the Algorithmic Language Scheme; namely `rev3-procedures` and `rev2-procedures`.

— Feature: r3rs

> Requires features implementing procedures and optional procedures specified by Revised^3 Report on the Algorithmic Language Scheme; namely `rev3-procedures`.

> Note: SLIB already mandates the `r3rs` procedures which can be portably implemented in `r4rs` implementations.

— Feature: r4rs

> Requires features implementing procedures and optional procedures specified by Revised^4 Report on the Algorithmic Language Scheme; namely `rev4-optional-procedures`.

— Feature: r5rs

> Requires features implementing procedures and optional procedures specified by Revised^5 Report on the Algorithmic Language Scheme; namely `values`, `macro`, and `eval`.

Next: Transcripts, Previous: RnRS, Up: Standards Support

#### 7.4.2 With-File

`(require 'with-file)`

— Function: with-input-from-file file thunk
— Function: with-output-to-file file thunk

> Description found in R4RS.

Next: Rev2 Procedures, Previous: With-File, Up: Standards Support

#### 7.4.3 Transcripts

`(require 'transcript)`

— Function: transcript-on filename
— Function: transcript-off filename

> Redefines `read-char`, `read`, `write-char`, `write`, `display`, and `newline`.

Next: Rev4 Optional Procedures, Previous: Transcripts, Up: Standards Support

#### 7.4.4 Rev2 Procedures

`(require 'rev2-procedures)` The procedures below were specified in the Revised^2 Report on Scheme. N.B.: The symbols `1+` and `-1+` are not R4RS syntax. Scheme->C, for instance, chokes on this module.

— Procedure: substring-move-left! string1 start1 end1 string2 start2
— Procedure: substring-move-right! string1 start1 end1 string2 start2

> string1 and string2 must be a strings, and start1, start2 and end1 must be exact integers satisfying

>               0 <= start1 <= end1 <= (string-length string1)
>               0 <= start2 <= end1 - start1 + start2 <= (string-length string2)

> `substring-move-left!` and `substring-move-right!` store characters of string1 beginning with index start1 (inclusive) and ending with index end1 (exclusive) into string2 beginning with index start2 (inclusive).

> `substring-move-left!` stores characters in time order of increasing indices. `substring-move-right!` stores characters in time order of increasing indeces.

— Procedure: substring-fill! string start end char

> Fills the elements start–end of string with the character char.

— Function: string-null? str

> == `(= 0 (string-length` str`))`

— Procedure: append! pair1 ...

> Destructively appends its arguments. Equivalent to `nconc`.

— Function: 1+ n

> Adds 1 to n.

— Function: -1+ n

> Subtracts 1 from n.

— Function: <?
— Function: <=?
— Function: =?
— Function: >?
— Function: >=?

> These are equivalent to the procedures of the same name but without the trailing ``?`'.

Next: Multi-argument / and -, Previous: Rev2 Procedures, Up: Standards Support

#### 7.4.5 Rev4 Optional Procedures

`(require 'rev4-optional-procedures)` For the specification of these optional procedures, See Standard procedures.

— Function: list-tail l p
— Function: string-copy
— Procedure: string-fill! s obj
— Procedure: vector-fill! s obj

Next: Multi-argument Apply, Previous: Rev4 Optional Procedures, Up: Standards Support

#### 7.4.6 Multi-argument / and -

`(require 'multiarg/and-)` For the specification of these optional forms, See Numerical operations.

— Function: / dividend divisor1 ...
— Function: - minuend subtrahend1 ...

Next: Rationalize, Previous: Multi-argument / and -, Up: Standards Support

#### 7.4.7 Multi-argument Apply

`(require 'multiarg-apply)` For the specification of this optional form, See Control features.

— Function: apply proc arg1 ...

Next: Promises, Previous: Multi-argument Apply, Up: Standards Support

#### 7.4.8 Rationalize

`(require 'rationalize)`

— Function: rationalize x e

> Computes the correct result for exact arguments (provided the implementation supports exact rational numbers of unlimited precision); and produces a reasonable answer for inexact arguments when inexact arithmetic is implemented using floating-point.

`Rationalize` has limited use in implementations lacking exact (non-integer) rational numbers. The following procedures return a list of the numerator and denominator.

— Function: find-ratio x e

> `find-ratio` returns the list of the simplest numerator and denominator whose quotient differs from x by no more than e.

>     (find-ratio 3/97 .0001)             => (3 97)
>          (find-ratio 3/97 .001)              => (1 32)

— Function: find-ratio-between x y

> `find-ratio-between` returns the list of the simplest numerator and denominator between x and y.

>     (find-ratio-between 2/7 3/5)        => (1 2)
>          (find-ratio-between -3/5 -2/7)      => (-1 2)

Next: Dynamic-Wind, Previous: Rationalize, Up: Standards Support

#### 7.4.9 Promises

`(require 'promise)`

— Function: make-promise proc
— Function: force promise

`(require 'delay)` provides `force` and `delay`:

— Macro: delay obj

> Change occurrences of `(delay` expression`)` to

>               (make-promise (lambda () expression))

(see Control features).

Next: Eval, Previous: Promises, Up: Standards Support

#### 7.4.10 Dynamic-Wind

`(require 'dynamic-wind)` This facility is a generalization of Common LISP `unwind-protect`, designed to take into account the fact that continuations produced by `call-with-current-continuation` may be reentered.

— Procedure: dynamic-wind thunk1 thunk2 thunk3

> The arguments thunk1, thunk2, and thunk3 must all be procedures of no arguments (thunks).

> `dynamic-wind` calls thunk1, thunk2, and then thunk3. The value returned by thunk2 is returned as the result of `dynamic-wind`. thunk3 is also called just before control leaves the dynamic context of thunk2 by calling a continuation created outside that context. Furthermore, thunk1 is called before reentering the dynamic context of thunk2 by calling a continuation created inside that context. (Control is inside the context of thunk2 if thunk2 is on the current return stack).

> Warning: There is no provision for dealing with errors or interrupts. If an error or interrupt occurs while using `dynamic-wind`, the dynamic environment will be that in effect at the time of the error or interrupt.

Next: Values, Previous: Dynamic-Wind, Up: Standards Support

#### 7.4.11 Eval

`(require 'eval)`

— Function: eval expression environment-specifier

> Evaluates expression in the specified environment and returns its value. Expression must be a valid Scheme expression represented as data, and environment-specifier must be a value returned by one of the three procedures described below. Implementations may extend `eval` to allow non-expression programs (definitions) as the first argument and to allow other values as environments, with the restriction that `eval` is not allowed to create new bindings in the environments associated with `null-environment` or `scheme-report-environment`.

>               (eval '(* 7 3) (scheme-report-environment 5))
>                                                                  =>  21

>               (let ((f (eval '(lambda (f x) (f x x))
>                              (null-environment))))
>                 (f + 10))
>                                                                  =>  20

— Function: scheme-report-environment version
— Function: null-environment version
— Function: null-environment

> Version must be an exact non-negative integer n corresponding to a version of one of the Revised^n Reports on Scheme. `Scheme-report-environment` returns a specifier for an environment that contains the set of bindings specified in the corresponding report that the implementation supports. `Null-environment` returns a specifier for an environment that contains only the (syntactic) bindings for all the syntactic keywords defined in the given version of the report.

> Not all versions may be available in all implementations at all times. However, an implementation that conforms to version n of the Revised^n Reports on Scheme must accept version n. An error is signalled if the specified version is not available.

> The effect of assigning (through the use of `eval`) a variable bound in a `scheme-report-environment` (for example `car`) is unspecified. Thus the environments specified by `scheme-report-environment` may be immutable.

— Function: interaction-environment

> This optional procedure returns a specifier for the environment that contains implementation-defined bindings, typically a superset of those listed in the report. The intent is that this procedure will return the environment in which the implementation would evaluate expressions dynamically typed by the user.

Here are some more `eval` examples:

         (require 'eval)
         => #<unspecified>
         (define car 'volvo)
         => #<unspecified>
         car
         => volvo
         (eval 'car (interaction-environment))
         => volvo
         (eval 'car (scheme-report-environment 5))
         => #<primitive-procedure car>
         (eval '(eval 'car (interaction-environment))
               (scheme-report-environment 5))
         => volvo
         (eval '(eval '(set! car 'buick) (interaction-environment))
               (scheme-report-environment 5))
         => #<unspecified>
         car
         => buick
         (eval 'car (scheme-report-environment 5))
         => #<primitive-procedure car>
         (eval '(eval 'car (interaction-environment))
               (scheme-report-environment 5))
         => buick

Next: SRFI, Previous: Eval, Up: Standards Support

#### 7.4.12 Values

`(require 'values)`

— Function: values obj ...

> `values` takes any number of arguments, and passes (returns) them to its continuation.

— Function: call-with-values thunk proc

> thunk must be a procedure of no arguments, and proc must be a procedure. `call-with-values` calls thunk with a continuation that, when passed some values, calls proc with those values as arguments.

> Except for continuations created by the `call-with-values` procedure, all continuations take exactly one value, as now; the effect of passing no value or more than one value to continuations that were not created by the `call-with-values` procedure is unspecified.

Previous: Values, Up: Standards Support

#### 7.4.13 SRFI

`(require 'srfi)` Implements Scheme Request For Implementation (SRFI) as described at http://srfi.schemers.org/

— Macro: cond-expand <clause1> <clause2> ...

> Syntax: Each <clause> should be of the form

>     (<feature> <expression1> ...)

> where <feature> is a boolean expression composed of symbols and `and', `or', and `not' of boolean expressions. The last <clause> may be an “else clause,” which has the form

>     (else <expression1> <expression2> ...).

> The first clause whose feature expression is satisfied is expanded. If no feature expression is satisfied and there is no else clause, an error is signaled.

> SLIB `cond-expand` is an extension of SRFI-0, http://srfi.schemers.org/srfi-0/srfi-0.html.

- SRFI-2 Guarded LET* special form
- SRFI-8 Binding to multiple values
- SRFI-9 Define-Record-Type
- SRFI-11 Binding to multiple values
- SRFI-23 `(define error slib:error)`
- SRFI-28 Format
- SRFI-47 Arrays
- SRFI-59 Vicinity
- SRFI-60 Bit-Twiddling
- SRFI-61 Guarded COND Clause
- SRFI-63 Arrays
- SRFI-94 Irrational Integer Functions and Irrational Real Functions
- SRFI-95 Sorting
- SRFI-96 Universal SLIB Procedures

Previous: SRFI, Up: SRFI

##### 7.4.13.1 SRFI-1

`(require 'srfi-1)` Implements the SRFI-1 list-processing library as described at http://srfi.schemers.org/srfi-1/srfi-1.html

#### Constructors

— Function: xcons d a

> `(define (xcons d a) (cons a d))`.

— Function: list-tabulate len proc

> Returns a list of length len. Element i is `(`proc i`)` for 0 <= i < len.

— Function: cons* obj1 obj2
— Function: list-copy flist
— Function: iota count start step
— Function: iota count start
— Function: iota count

> Returns a list of count numbers: (start, start+step, ..., start+(count-1)*step).

— Function: circular-list obj1 obj2 ...

> Returns a circular list of obj1, obj2, ....

#### Predicates

— Function: proper-list? obj
— Function: circular-list? x
— Function: dotted-list? obj
— Function: null-list? obj
— Function: not-pair? obj
— Function: list= =pred list ...

#### Selectors

— Function: first pair
— Function: second pair
— Function: third pair
— Function: fourth pair
— Function: fifth pair
— Function: sixth pair
— Function: seventh pair
— Function: eighth pair
— Function: ninth pair
— Function: tenth pair
— Function: car+cdr pair
— Function: drop lst k
— Function: take lst k
— Function: take! lst k
— Function: take-right lst k
— Function: drop-right lst k
— Procedure: drop-right! lst k
— Function: split-at lst k
— Function: split-at! lst k
— Function: last lst k ...

#### Miscellaneous

— Function: length+ clist
— Function: concatenate lists
— Function: concatenate! lists
— Procedure: reverse! lst
— Function: append-reverse rev-head tail
— Function: append-reverse! rev-head tail
— Function: zip list1 list2 ...
— Function: unzip1 lst
— Function: unzip2 lst
— Function: unzip3 lst
— Function: unzip4 lst
— Function: unzip5 lst
— Function: count pred list1 list2 ...

#### Fold and Unfold

— Function: fold kons knil clist1 clist2 ...
— Function: fold-right kons knil clist1 clist2 ...
— Function: pair-fold kons knil clist1 clist2 ...
— Function: pair-fold-right kons knil clist1 clist2 ...
— Function: reduce arg ...
— Procedure: map! f clist1 clist2 ...
— Function: pair-for-each f clist1 clist2 ...

#### Filtering and Partitioning

— Function: filter pred list
— Procedure: filter! pred list
— Function: partition pred list
— Function: remove pred list
— Procedure: partition! pred list
— Procedure: remove! pred list

#### Searching

— Function: find pred clist
— Function: find-tail pred clist
— Function: span pred list
— Procedure: span! pred list
— Function: break pred list
— Procedure: break! pred list
— Function: any pred clist1 clist2 ...
— Function: list-index pred clist1 clist2 ...
— Function: member obj list =
— Function: member obj list

#### Deleting

— Function: delete-duplicates x list =
— Function: delete-duplicates x list
— Procedure: delete-duplicates! x list =
— Procedure: delete-duplicates! x list

#### Association lists

— Function: assoc obj alist pred
— Function: assoc obj alist
— Function: alist-cons key datum alist
— Function: alist-copy alist
— Function: alist-delete key alist =
— Function: alist-delete key alist
— Procedure: alist-delete! key alist =
— Procedure: alist-delete! key alist

#### Set operations

— Function: lset<= = list1 ...

> Determine if a transitive subset relation exists between the lists list1 ..., using = to determine equality of list members.

— Function: lset= = list1 list2 ...
— Function: lset-adjoin list elt1 ...
— Function: lset-union = list1 ...
— Function: lset-intersection = list1 list2 ...
— Function: lset-difference = list1 list2 ...
— Function: lset-xor = list1 ...
— Function: lset-diff+intersection = list1 list2 ...

These are linear-update variants. They are allowed, but not required, to use the cons cells in their first list parameter to construct their answer. `lset-union!` is permitted to recycle cons cells from any of its list arguments.

— Procedure: lset-intersection! = list1 list2 ...
— Procedure: lset-difference! = list1 list2 ...
— Procedure: lset-union! = list1 ...
— Procedure: lset-xor! = list1 ...
— Procedure: lset-diff+intersection! = list1 list2 ...

Next: System Interface, Previous: Standards Support, Up: Other Packages

### 7.5 Session Support

If `(provided? 'abort)`:

— Function: abort

> Resumes the top level Read-Eval-Print loop. If provided, `abort` is used by the `break` and `debug` packages.

Next: Quick Print, Previous: Session Support, Up: Session Support

#### 7.5.1 Repl

`(require 'repl)` Here is a read-eval-print-loop which, given an eval, evaluates forms.

— Procedure: repl:top-level repl:eval

> `read`s, `repl:eval`s and `write`s expressions from `(current-input-port)` to `(current-output-port)` until an end-of-file is encountered. `load`, `slib:eval`, `slib:error`, and `repl:quit` dynamically bound during `repl:top-level`.

— Procedure: repl:quit

> Exits from the invocation of `repl:top-level`.

The `repl:` procedures establish, as much as is possible to do portably, a top level environment supporting macros. `repl:top-level` uses `dynamic-wind` to catch error conditions and interrupts. If your implementation supports this you are all set.

Otherwise, if there is some way your implementation can catch error conditions and interrupts, then have them call `slib:error`. It will display its arguments and reenter `repl:top-level`. `slib:error` dynamically bound by `repl:top-level`.

To have your top level loop always use macros, add any interrupt catching lines and the following lines to your Scheme init file:

         (require 'macro)
         (require 'repl)
         (repl:top-level macro:eval)

Next: Debug, Previous: Repl, Up: Session Support

#### 7.5.2 Quick Print

`(require 'qp)` When displaying error messages and warnings, it is paramount that the output generated for circular lists and large data structures be limited. This section supplies a procedure to do this. It could be much improved.

> Notice that the neccessity for truncating output eliminates Common-Lisp's Format from consideration; even when variables `*print-level*` and `*print-level*` are set, huge strings and bit-vectors are not limited.

— Procedure: qp arg1 ...
— Procedure: qpn arg1 ...
— Procedure: qpr arg1 ...

> `qp` writes its arguments, separated by spaces, to `(current-output-port)`. `qp` compresses printing by substituting ``...`' for substructure it does not have sufficient room to print. `qpn` is like `qp` but outputs a newline before returning. `qpr` is like `qpn` except that it returns its last argument.

— Variable: *qp-width*

> *qp-width* is the largest number of characters that `qp` should use. If *qp-width* is #f, then all items will be `write`n. If *qp-width* is 0, then all items except procedures will be `write`n; procedures will be indicated by ``#[proc]`'.

Next: Breakpoints, Previous: Quick Print, Up: Session Support

#### 7.5.3 Debug

`(require 'debug)` Requiring `debug` automatically requires `trace` and `break`.

An application with its own datatypes may want to substitute its own printer for `qp`. This example shows how to do this:

         (define qpn (lambda args) ...)
         (provide 'qp)
         (require 'debug)

— Procedure: trace-all file ...

> Traces (see Trace) all procedures `define`d at top-level in `file` .... — Procedure: track-all file ...

> > Tracks (see Trace) all procedures `define`d at top-level in `file` .... — Procedure: stack-all file ...

> > > Stacks (see Trace) all procedures `define`d at top-level in `file` ....

— Procedure: break-all file ...

> Breakpoints (see Breakpoints) all procedures `define`d at top-level in `file` ....

Next: Trace, Previous: Debug, Up: Session Support

#### 7.5.4 Breakpoints

`(require 'break)`

— Function: init-debug

> If your Scheme implementation does not support `break` or `abort`, a message will appear when you `(require 'break)` or `(require 'debug)` telling you to type `(init-debug)`. This is in order to establish a top-level continuation. Typing `(init-debug)` at top level sets up a continuation for `break`.

— Function: breakpoint arg1 ...

> Returns from the top level continuation and pushes the continuation from which it was called on a continuation stack.

— Function: continue

> Pops the topmost continuation off of the continuation stack and returns an unspecified value to it. — Function: continue arg1 ...

> > Pops the topmost continuation off of the continuation stack and returns arg1 ... to it.

— Macro: break proc1 ...

> Redefines the top-level named procedures given as arguments so that `breakpoint` is called before calling proc1 .... — Macro: break

> > With no arguments, makes sure that all the currently broken identifiers are broken (even if those identifiers have been redefined) and returns a list of the broken identifiers.

— Macro: unbreak proc1 ...

> Turns breakpoints off for its arguments. — Macro: unbreak

> > With no arguments, unbreaks all currently broken identifiers and returns a list of these formerly broken identifiers.

These are procedures for breaking. If defmacros are not natively supported by your implementation, these might be more convenient to use.

— Function: breakf proc
— Function: breakf proc name

> To break, type

>               (set! symbol (breakf symbol))

> or

>               (set! symbol (breakf symbol 'symbol))

> or

>               (define symbol (breakf function))

> or

>               (define symbol (breakf function 'symbol))

— Function: unbreakf proc

> To unbreak, type

>               (set! symbol (unbreakf symbol))

Previous: Breakpoints, Up: Session Support

#### 7.5.5 Tracing

`(require 'trace)` This feature provides three ways to monitor procedure invocations:

stack
  Pushes the procedure-name when the procedure is called; pops when it returns.
track
  Pushes the procedure-name and arguments when the procedure is called; pops when it returns.
trace
  Pushes the procedure-name and prints ``CALL procedure-name arg1 ...`' when the procdure is called; pops and prints ``RETN procedure-name value`' when the procedure returns.

— Variable: debug:max-count

> If a traced procedure calls itself or untraced procedures which call it, stack, track, and trace will limit the number of stack pushes to debug:max-count.

— Function: print-call-stack
— Function: print-call-stack port

> Prints the call-stack to port or the current-error-port.

— Macro: trace proc1 ...

> Traces the top-level named procedures given as arguments. — Macro: trace

> > With no arguments, makes sure that all the currently traced identifiers are traced (even if those identifiers have been redefined) and returns a list of the traced identifiers.

— Macro: track proc1 ...

> Traces the top-level named procedures given as arguments. — Macro: track

> > With no arguments, makes sure that all the currently tracked identifiers are tracked (even if those identifiers have been redefined) and returns a list of the tracked identifiers.

— Macro: stack proc1 ...

> Traces the top-level named procedures given as arguments. — Macro: stack

> > With no arguments, makes sure that all the currently stacked identifiers are stacked (even if those identifiers have been redefined) and returns a list of the stacked identifiers.

— Macro: untrace proc1 ...

> Turns tracing, tracking, and off for its arguments. — Macro: untrace

> > With no arguments, untraces all currently traced identifiers and returns a list of these formerly traced identifiers.

— Macro: untrack proc1 ...

> Turns tracing, tracking, and off for its arguments. — Macro: untrack

> > With no arguments, untracks all currently tracked identifiers and returns a list of these formerly tracked identifiers.

— Macro: unstack proc1 ...

> Turns tracing, stacking, and off for its arguments. — Macro: unstack

> > With no arguments, unstacks all currently stacked identifiers and returns a list of these formerly stacked identifiers.

These are procedures for tracing. If defmacros are not natively supported by your implementation, these might be more convenient to use.

— Function: tracef proc
— Function: tracef proc name
— Function: trackf proc
— Function: trackf proc name
— Function: stackf proc
— Function: stackf proc name

> To trace, type

>               (set! symbol (tracef symbol))

> or

>               (set! symbol (tracef symbol 'symbol))

> or

>               (define symbol (tracef function))

> or

>               (define symbol (tracef function 'symbol))

— Function: untracef proc

> Removes tracing, tracking, or stacking for proc. To untrace, type

>               (set! symbol (untracef symbol))

Next: Extra-SLIB Packages, Previous: Session Support, Up: Other Packages

### 7.6 System Interface

If `(provided? 'getenv)`:

— Function: getenv name

> Looks up name, a string, in the program environment. If name is found a string of its value is returned. Otherwise, `#f` is returned.

If `(provided? 'system)`:

— Function: system command-string

> Executes the command-string on the computer and returns the integer status code.

If `(provided? 'program-arguments)`:

— Function: program-arguments

> Returns a list of strings, the first of which is the program name followed by the command-line arguments.

Next: Transactions, Previous: System Interface, Up: System Interface

#### 7.6.1 Directories

`(require 'directory)`

— Function: current-directory

> `current-directory` returns a string containing the absolute file name representing the current working directory. If this string cannot be obtained, #f is returned.

> If `current-directory` cannot be supported by the platform, then #f is returned.

— Function: make-directory name

> Creates a sub-directory name of the current-directory. If successful, `make-directory` returns #t; otherwise #f.

— Function: directory-for-each proc directory

> proc must be a procedure taking one argument. ``Directory-For-Each`' applies proc to the (string) name of each file in directory. The dynamic order in which proc is applied to the filenames is unspecified. The value returned by ``directory-for-each`' is unspecified. — Function: directory-for-each proc directory pred

> > Applies proc only to those filenames for which the procedure pred returns a non-false value. — Function: directory-for-each proc directory match

> > > Applies proc only to those filenames for which `(filename:match??` match`)` would return a non-false value (see Filenames).

> > >               (require 'directory)
> > >               (directory-for-each print "." "[A-Z]*.scm")
> > >               -|
> > >               "Bev2slib.scm"
> > >               "Template.scm"

Next: CVS, Previous: Directories, Up: System Interface

#### 7.6.2 Transactions

If `system` is provided by the Scheme implementation, the transact package provides functions for file-locking and file-replacement transactions.

`(require 'transact)`

##### File Locking

Unix file-locking is focussed on write permissions for segments of a existing file. While this might be employed for (binary) database access, it is not used for everyday contention (between users) for text files.

Microsoft has several file-locking protocols. Their model denies write access to a file if any reader has it open. This is too restrictive. Write access is denied even when the reader has reached end-of-file. And tracking read access (which is much more common than write access) causes havoc when remote hosts crash or disconnect.

It is bizarre that the concept of multi-user contention for modifying files has not been adequately addressed by either of the large operating system development efforts. There is further irony that both camps support contention detection and resolution only through weak conventions of some their document editing programs.

The file-lock procedures implement a transaction method for file replacement compatible with the methods used by the GNU emacs text editor on Unix systems and the Microsoft Word editor. Both protocols employ what I term a certificate containing the user, hostname, time, and (on Unix) process-id. Intent to replace file is indicated by adding to file's directory a certificate object whose name is derived from file.

The Microsoft Word certificate is contained in a 162 byte file named for the visited file with a ``~$`' prefix. Emacs/Unix creates a symbolic link to a certificate named for the visited file prefixed with ``.#`'. Because Unix systems can import Microsoft file systems, these routines maintain and check both Emacs and Word certificates.

— Function: file-lock-owner path

> Returns the string ``user@hostname`' associated with the lock owner of file path if locked; and #f otherwise.

— Procedure: file-lock! path email
— Procedure: file-lock! path

> path must be a string naming the file to be locked. If supplied, email must be a string formatted as ``user@hostname`'. If absent, email defaults to the value returned by `user-email-address`.

> If path is already locked, then `file-lock!` returns ``#f`'. If path is unlocked, then `file-lock!` returns the certificate string associated with the new lock for file path.

— Procedure: file-unlock! path certificate

> path must be a string naming the file to be unlocked. certificate must be the string returned by `file-lock!` for path.

> If path is locked with certificate, then `file-unlock!` removes the locks and returns ``#t`'. Otherwise, `file-unlock!` leaves the file system unaltered and returns ``#f`'.

— Function: describe-file-lock path prefix
— Function: describe-file-lock path

> path must be a string naming a file. Optional argument prefix is a string printed before each line of the message. `describe-file-lock` prints to `(current-error-port)` that path is locked for writing and lists its lock-files.

>               (describe-file-lock "my.txt" ">> ")
>               -|
>               >> "my.txt" is locked for writing by 'luser@no.com.4829:1200536423'
>               >> (lock files are "~$my.txt" and ".#my.txt")

##### File Transactions

— Function: emacs:backup-name path backup-style

> path must be a string. backup-style must be a symbol. Depending on backup-style, `emacs:backup-name` returns:

> none
>   #f
> simple
>   the string "path~"
> numbered
>   the string "path.~n~", where n is one greater than the highest number appearing in a filename matching "path.~*~". n defauls to 1 when no filename matches.
> existing
>   the string "path.~n~" if a numbered backup already exists in this directory; otherwise. "path~"
> orig
>   the string "path.orig"
> bak
>   the string "path.bak"

— Function: transact-file-replacement proc path backup-style certificate
— Function: transact-file-replacement proc path backup-style
— Function: transact-file-replacement proc path

> path must be a string naming an existing file. backup-style is one of the symbols none, simple, numbered, existing, orig, bak or #f; with meanings described above; or a string naming the location of a backup file. backup-style defaults to #f. If supplied, certificate is the certificate with which path is locked.

> proc must be a procedure taking two string arguments:

> - path, the original filename (to be read); and
> - a temporary file-name.

> If path is locked by other than certificate, or if certificate is supplied and path is not locked, then `transact-file-replacement` returns #f. If certificate is not supplied, then, `transact-file-replacement` creates temporary (Emacs and Word) locks for path during the transaction. The lock status of path will be restored before `transact-file-replacement` returns.

> `transact-file-replacement` calls proc with path (which should not be modified) and a temporary file path to be written. If proc returns any value other than #t, then the file named by path is not altered and `transact-file-replacement` returns #f. Otherwise, `emacs:backup-name` is called with path and backup-style. If it returns a string, then path is renamed to it.

> Finally, the temporary file is renamed path. `transact-file-replacement` returns #t if path was successfully replaced; and #f otherwise.

##### Identification

— Function: user-email-address

> `user-email-address` returns a string of the form ``username@hostname`'. If this e-mail address cannot be obtained, #f is returned.

Previous: Transactions, Up: System Interface

#### 7.6.3 CVS

`(require 'cvs)`

— Function: cvs-files directory/

> Returns a list of the local pathnames (with prefix directory/) of all CVS controlled files in directory/ and in directory/'s subdirectories.

— Function: cvs-directories directory/

> Returns a list of all of directory/ and all directory/'s CVS controlled subdirectories.

— Function: cvs-root path/

> Returns the (string) contents of path/CVS/Root; or `(getenv "CVSROOT")` if Root doesn't exist.

— Function: cvs-repository directory/

> Returns the (string) contents of directory/CVS/Root appended with directory/CVS/Repository; or #f if directory/CVS/Repository doesn't exist.

— Procedure: cvs-set-root! new-root directory/

> Writes new-root to file CVS/Root of directory/.

— Procedure: cvs-set-roots! new-root directory/

> Writes new-root to file CVS/Root of directory/ and all its CVS subdirectories.

— Function: cvs-vet directory/

> Signals an error if CVS/Repository or CVS/Root files in directory/ or any subdirectory do not match.

Previous: System Interface, Up: Other Packages

### 7.7 Extra-SLIB Packages

Several Scheme packages have been written using SLIB. There are several reasons why a package might not be included in the SLIB distribution:

- Because it requires special hardware or software which is not universal.
- Because it is large and of limited interest to most Scheme users.
- Because it has copying terms different enough from the other SLIB packages that its inclusion would cause confusion.
- Because it is an application program, rather than a library module.
- Because I have been too busy to integrate it.

Once an optional package is installed (and an entry added to `*catalog*`), the `require` mechanism allows it to be called up and used as easily as any other SLIB package. Some optional packages (for which `*catalog*` already has entries) available from SLIB sites are:

SLIB-PSD
  is a portable debugger for Scheme (requires emacs editor).

  http://swiss.csail.mit.edu/ftpdir/scm/slib-psd1-3.tar.gz

  swiss.csail.mit.edu:/pub/scm/slib-psd1-3.tar.gz

  ftp.maths.tcd.ie:pub/bosullvn/jacal/slib-psd1-3.tar.gz

  ftp.cs.indiana.edu:/pub/scheme-repository/utl/slib-psd1-3.tar.gz

  With PSD, you can run a Scheme program in an Emacs buffer, set breakpoints, single step evaluation and access and modify the program's variables. It works by instrumenting the original source code, so it should run with any R4RS compliant Scheme. It has been tested with SCM, Elk 1.5, and the sci interpreter in the Scheme->C system, but should work with other Schemes with a minimal amount of porting, if at all. Includes documentation and user's manual. Written by Pertti Kellom\"aki, pk @ cs.tut.fi. The Lisp Pointers article describing PSD (Lisp Pointers VI(1):15-23, January-March 1993) is available as http://www.cs.tut.fi/staff/pk/scheme/psd/article/article.html

SCHELOG
  is an embedding of Prolog in Scheme.
  http://www.ccs.neu.edu/~dorai/schelog/schelog.html

JFILTER
  is a Scheme program which converts text among the JIS, EUC, and Shift-JIS Japanese character sets.
  http://www.sci.toyama-u.ac.jp/~iwao/Scheme/Jfilter/index.html

Next: Index, Previous: Other Packages, Up: Top

## 8 About SLIB

More people than I can name have contributed to SLIB. Thanks to all of you!

> SLIB 3b1, released July 2008.
> Aubrey Jaffer <agj @ alum.mit.edu>

Current information about SLIB can be found on SLIB's WWW home page:

http://swiss.csail.mit.edu/~jaffer/SLIB

SLIB is part of the GNU project.

Next: The SLIB script, Previous: About SLIB, Up: About SLIB

### 8.1 Installation

There are five parts to installation:

- Unpack the SLIB distribution.
- Install documentation and `slib` script.
- Configure the Scheme implementation(s) to locate the SLIB directory and implementation directories.
- Arrange for Scheme implementation to load its SLIB initialization file.
- Build the SLIB catalog for the Scheme implementation.

#### 8.1.1 Unpacking the SLIB Distribution

If the SLIB distribution is a GNU/Linux RPM, it will create the SLIB directory `/usr/share/slib`.

If the SLIB distribution is a ZIP file, unzip the distribution to create the SLIB directory. Locate this `slib` directory either in your home directory (if only you will use this SLIB installation); or put it in a location where libraries reside on your system. On unix systems this might be `/usr/share/slib`, `/usr/local/lib/slib`, or `/usr/lib/slib`. If you know where SLIB should go on other platforms, please inform agj @ alum.mit.edu.

#### 8.1.2 Install documentation and slib script

         make infoz
         make install

#### 8.1.3 Configure Scheme Implementation to Locate SLIB

If the Scheme implementation supports `getenv`, then the value of the shell environment variable SCHEME_LIBRARY_PATH will be used for `(library-vicinity)` if it is defined. Currently, Bigloo, Chez, Elk, Gambit, Guile, Jscheme, Larceny, MITScheme, MzScheme, RScheme, STk, VSCM, and SCM support `getenv`. Scheme48 supports `getenv` but does not use it for determining `library-vicinity`. (That is done from the Makefile.)

The `(library-vicinity)` can also be set from the SLIB initialization file or by implementation-specific means.

Support for locating an implementation's auxiliary directory is uneven among implementations. Also, the person installing SLIB may not have write permission to some of these directories (necessary for writing slibcat). Therefore, those implementations supporting `getenv` (except SCM and Scheme48) provide a means for specifying the `implementation-vicinity` through environment variables. Define the indicated environment variable to the pathname (with trailing slash or backslash) of the desired directory. Do not use `slib/` as an implementation-vicinity!

Bigloo | BIGLOO_IMPLEMENTATION_PATH
Chez | CHEZ_IMPLEMENTATION_PATH
ELK | ELK_IMPLEMENTATION_PATH
Gambit | GAMBIT_IMPLEMENTATION_PATH
Guile | GUILE_IMPLEMENTATION_PATH
Jscheme | JSCHEME_IMPLEMENTATION_PATH
MIT-Scheme | MITSCHEME_IMPLEMENTATION_PATH
MzScheme | MZSCHEME_IMPLEMENTATION_PATH
RScheme | RSCHEME_IMPLEMENTATION_PATH
STk | STK_IMPLEMENTATION_PATH
Vscm | VSCM_IMPLEMENTATION_PATH

#### 8.1.4 Loading SLIB Initialization File

Check the manifest in `README` to find a configuration file for your Scheme implementation. Initialization files for most IEEE P1178 compliant Scheme Implementations are included with this distribution.

You should check the definitions of `software-type`, `scheme-implementation-version`, `implementation-vicinity`, and `library-vicinity` in the initialization file. There are comments in the file for how to configure it.

Once this is done, modify the startup file for your Scheme implementation to `load` this initialization file.

#### 8.1.5 Build New SLIB Catalog for Implementation

When SLIB is first used from an implementation, a file named `slibcat` is written to the `implementation-vicinity` for that implementation. Because users may lack permission to write in `implementation-vicinity`, it is good practice to build the new catalog when installing SLIB.

To build (or rebuild) the catalog, start the Scheme implementation (with SLIB), then:

         (require 'new-catalog)

The catalog also supports color-name dictionaries. With an SLIB-installed scheme implementation, type:

         (require 'color-names)
         (make-slib-color-name-db)
         (require 'new-catalog)
         (slib:exit)

#### 8.1.6 Implementation-specific Instructions

Multiple implementations of Scheme can all use the same SLIB directory. Simply configure each implementation's initialization file as outlined above.

— Implementation: SCM

> The SCM implementation does not require any initialization file as SLIB support is already built into SCM. See the documentation with SCM for installation instructions.

— Implementation: Larceny

> Starting with version 0.96, Larceny contains its own SLIB initialization file, loaded by `(require 'srfi-96)`. If SCHEME_LIBRARY_PATH is not set, then Larceny looks for an `slib` subdirectory of a directory in the list returned by `(current-require-path)`

>               larceny -- -e "(require 'srfi-96)"

— Implementation: ELK

>               elk -i -l ${SCHEME_LIBRARY_PATH}elk.init

— Implementation: PLT Scheme
— Implementation: DrScheme
— Implementation: MzScheme

> The `init.ss` file in the _slibinit_ collection is an SLIB initialization file. To run SLIB in MzScheme:

>               mzscheme -f ${SCHEME_LIBRARY_PATH}mzscheme.init

— Implementation: MIT Scheme

>               scheme -load ${SCHEME_LIBRARY_PATH}mitscheme.init

— Implementation: Gambit-C 3.0

>               gsi -:s ${SCHEME_LIBRARY_PATH}gambit.init -

— Implementation: SISC

>               sisc -e "(load \"${SCHEME_LIBRARY_PATH}sisc.init\")" --

— Implementation: Kawa

>               kawa -f ${SCHEME_LIBRARY_PATH}kawa.init --

— Implementation: Guile

> Guile versions 1.6 and earlier link to an archaic SLIB version. In RedHat or Fedora installations:

>               rm /usr/share/guile/slib
>               ln -s ${SCHEME_LIBRARY_PATH} /usr/share/guile/slib

> In Debian installations:

>               rm /usr/share/guile/1.6/slib
>               ln -s ${SCHEME_LIBRARY_PATH} /usr/share/guile/1.6/slib

> `${SCHEME_LIBRARY_PATH}` is where SLIB gets installed.

> Guile with SLIB can then be started thus:

>               guile -l ${SCHEME_LIBRARY_PATH}guile.init

— Implementation: Scheme48

> To make a Scheme48 image for an installation under `<prefix>`,

> 1. `cd` to the SLIB directory
> 2. type `make prefix=<prefix> slib48`.
> 3. To install the image, type `make prefix=<prefix> install48`. This will also create a shell script with the name `slib48` which will invoke the saved image.

— Implementation: VSCM

>     From: Matthias Blume <blume @ cs.Princeton.EDU>
>          Date: Tue, 1 Mar 1994 11:42:31 -0500

> Disclaimer: The code below is only a quick hack. If I find some time to spare I might get around to make some more things work.

> You have to provide `vscm.init` as an explicit command line argument. Since this is not very nice I would recommend the following installation procedure:

> 1. run scheme
> 2. `(load "vscm.init")`
> 3. `(slib:dump "dumpfile")`
> 4. mv dumpfile place-where-vscm-standard-bootfile-resides. For example:

>    `mv dumpfile /usr/local/vscm/lib/scheme-boot`

>    In this case vscm should have been compiled with flag:

>    -DDEFAULT_BOOTFILE='"/usr/local/vscm/lib/scheme-boot"'

>    See Makefile (definition of DDP) for details.

Next: Porting, Previous: Installation, Up: About SLIB

### 8.2 The SLIB script

SLIB comes with shell script for Unix platforms.

          slib  [ scheme | scm | gsi | mzscheme | guile
                | scheme48 | scmlit | elk | sisc | kawa ]

Starts an interactive Scheme-with-SLIB session.

The optional argument to the `slib` script is the Scheme implementation to run. Absent the argument, it searches for implementations in the above order.

Next: Coding Guidelines, Previous: The SLIB script, Up: About SLIB

### 8.3 Porting

If there is no initialization file for your Scheme implementation, you will have to create one. Your Scheme implementation must be largely compliant with

         IEEE Std 1178-1990,
         Revised^4 Report on the Algorithmic Language Scheme, or
         Revised^5 Report on the Algorithmic Language Scheme

in order to support SLIB. 8

`Template.scm` is an example configuration file. The comments inside will direct you on how to customize it to reflect your system. Give your new initialization file the implementation's name with `.init` appended. For instance, if you were porting `foo-scheme` then the initialization file might be called `foo.init`.

Your customized version should then be loaded as part of your scheme implementation's initialization. It will load `require.scm` from the library; this will allow the use of `provide`, `provided?`, and `require` along with the vicinity functions (these functions are documented in the sections Feature and Require). The rest of the library will then be accessible in a system independent fashion.

Please mail new working configuration files to `agj @ alum.mit.edu` so that they can be included in the SLIB distribution.

Next: Copyrights, Previous: Porting, Up: About SLIB

### 8.4 Coding Guidelines

All library packages are written in IEEE P1178 Scheme and assume that a configuration file and `require.scm` package have already been loaded. Other versions of Scheme can be supported in library packages as well by using, for example, `(provided? 'r3rs)` or `(require 'r3rs)` (see Require). If a procedure defined in a module is called by other procedures in that module, then those procedures should instead call an alias defined in that module:

         (define module-name:foo foo)

The module name and ``:`' should prefix that symbol for the internal name. Do not export internal aliases.

A procedure is exported from a module by putting Schmooz-style comments (see Schmooz) or ``;@`' at the beginning of the line immediately preceding the definition (`define`, `define-syntax`, or `defmacro`). Modules, exports and other relevant issues are discussed in Compiling Scheme.

Code submitted for inclusion in SLIB should not duplicate (more than one) routines already in SLIB files. Use `require` to force those library routines to be used by your package.

Documentation should be provided in Emacs Texinfo format if possible, but documentation must be provided.

Your package will be released sooner with SLIB if you send me a file which tests your code. Please run this test before you send me the code!

#### 8.4.1 Modifications

Please document your changes. A line or two for `ChangeLog` is sufficient for simple fixes or extensions. Look at the format of `ChangeLog` to see what information is desired. Please send me `diff` files from the latest SLIB distribution (remember to send `diff`s of `slib.texi` and `ChangeLog`). This makes for less email traffic and makes it easier for me to integrate when more than one person is changing a file (this happens a lot with `slib.texi` and ``*.init`' files).

If someone else wrote a package you want to significantly modify, please try to contact the author, who may be working on a new version. This will insure against wasting effort on obsolete versions.

Please do not reformat the source code with your favorite beautifier, make 10 fixes, and send me the resulting source code. I do not have the time to fish through 10000 diffs to find your 10 real fixes.

Next: About this manual, Previous: Coding Guidelines, Up: About SLIB

### 8.5 Copyrights

This section has instructions for SLIB authors regarding copyrights. Each package in SLIB must either be in the public domain, or come with a statement of terms permitting users to copy, redistribute and modify it. The comments at the beginning of `require.scm` and `macwork.scm` illustrate copyright and appropriate terms.

If your code or changes amount to less than about 10 lines, you do not need to add your copyright or send a disclaimer.

#### 8.5.1 Putting code into the Public Domain

In order to put code in the public domain you should sign a copyright disclaimer and send it to the SLIB maintainer. Contact agj @ alum.mit.edu for the address to mail the disclaimer to.

> I, <my-name>, hereby affirm that I have placed the software package <name> in the public domain.

> I affirm that I am the sole author and sole copyright holder for the software package, that I have the right to place this software package in the public domain, and that I will do nothing to undermine this status in the future.

> signature and date

This wording assumes that you are the sole author. If you are not the sole author, the wording needs to be different. If you don't want to be bothered with sending a letter every time you release or modify a module, make your letter say that it also applies to your future revisions of that module.

Make sure no employer has any claim to the copyright on the work you are submitting. If there is any doubt, create a copyright disclaimer and have your employer sign it. Mail the signed disclaimer to the SLIB maintainer. Contact agj @ alum.mit.edu for the address to mail the disclaimer to. An example disclaimer follows.

#### 8.5.2 Explicit copying terms

If you submit more than about 10 lines of code which you are not placing into the Public Domain (by sending me a disclaimer) you need to:

- Arrange that your name appears in a copyright line for the appropriate year. Multiple copyright lines are acceptable.
- With your copyright line, specify any terms you require to be different from those already in the file.
- Make sure no employer has any claim to the copyright on the work you are submitting. If there is any doubt, create a copyright disclaimer and have your employer sign it. Mail the signed disclaim to the SLIB maintainer. Contact agj @ alum.mit.edu for the address to mail the disclaimer to.

#### 8.5.3 Example: Company Copyright Disclaimer

This disclaimer should be signed by a vice president or general manager of the company. If you can't get at them, anyone else authorized to license out software produced there will do. Here is a sample wording:

> <employer> Corporation hereby disclaims all copyright interest in the program <program> written by <name>.

> <employer> Corporation affirms that it has no other intellectual property interest that would undermine this release, and will do nothing to undermine it in the future.

> <signature and date>, <name>, <title>, <employer> Corporation

Previous: Copyrights, Up: About SLIB

### 8.6 About this manual

- Entries that are labeled as Functions are called for their return values. Entries that are labeled as Procedures are called primarily for their side effects.
- Examples in this text were produced using the `scm` Scheme implementation.
- At the beginning of each section, there is a line that looks like:

                (require 'feature)

  Include this line in your code prior to using the package.

Previous: About this manual, Up: About this manual

#### 8.6.1 GNU Free Documentation License

Version 1.2, November 2002

         Copyright © 2000,2001,2002 Free Software Foundation, Inc.
         51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA

         Everyone is permitted to copy and distribute verbatim copies
         of this license document, but changing it is not allowed.

0. PREAMBLE

   The purpose of this License is to make a manual, textbook, or other functional and useful document free in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

   This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

   We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

1. APPLICABILITY AND DEFINITIONS

   This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”. You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

   A “Modified Version” of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

   A “Secondary Section” is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

   The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.

   The “Cover Texts” are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.

   A “Transparent” copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not “Transparent” is called “Opaque”.

   Examples of suitable formats for Transparent copies include plain ascii without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only.

   The “Title Page” means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, “Title Page” means the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text.

   A section “Entitled XYZ” means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as “Acknowledgements”, “Dedications”, “Endorsements”, or “History”.) To “Preserve the Title” of such a section when you modify the Document means that it remains a section “Entitled XYZ” according to this definition.

   The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.

2. VERBATIM COPYING

   You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

   You may also lend copies, under the same conditions stated above, and you may publicly display copies.

3. COPYING IN QUANTITY

   If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document's license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

   If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

   If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

   It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.

4. MODIFICATIONS

   You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

   1. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.
   2. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement.
   3. State on the Title page the name of the publisher of the Modified Version, as the publisher.
   4. Preserve all the copyright notices of the Document.
   5. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.
   6. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.
   7. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document's license notice.
   8. Include an unaltered copy of this License.
   9. Preserve the section Entitled “History”, Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled “History” in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.
   10. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the “History” section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.
   11. For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
   12. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
   13. Delete any section Entitled “Endorsements”. Such a section may not be included in the Modified Version.
   14. Do not retitle any existing section to be Entitled “Endorsements” or to conflict in title with any Invariant Section.
   15. Preserve any Warranty Disclaimers.

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Next: Procedure and Macro Index, Previous: About SLIB, Up: Top

## Index

Next: Variable Index, Previous: Index, Up: Index

## Procedure and Macro Index

- `-`: Multi-argument / and -
- `-1+`: Rev2 Procedures
- `/`: Multi-argument / and -
- `1+`: Rev2 Procedures
- `<=?`: Rev2 Procedures
- `<?`: Rev2 Procedures
- `=`: Hilbert Space-Filling Curve
- `=?`: Rev2 Procedures
- `>=?`: Rev2 Procedures
- `>?`: Rev2 Procedures
- `A:bool`: Arrays
- `A:fixN16b`: Arrays
- `A:fixN32b`: Arrays
- `A:fixN64b`: Arrays
- `A:fixN8b`: Arrays
- `A:fixZ16b`: Arrays
- `A:fixZ32b`: Arrays
- `A:fixZ64b`: Arrays
- `A:fixZ8b`: Arrays
- `A:floC128b`: Arrays
- `A:floC16b`: Arrays
- `A:floC32b`: Arrays
- `A:floC64b`: Arrays
- `A:floR128b`: Arrays
- `A:floR128d`: Arrays
- `A:floR16b`: Arrays
- `A:floR32b`: Arrays
- `A:floR32d`: Arrays
- `A:floR64b`: Arrays
- `A:floR64d`: Arrays
- `abort`: Session Support
- `abs`: Irrational Real Functions
- `absolute-path?`: URI
- `absolute-uri?`: URI
- `add-command-tables`: Database Extension
- `add-domain`: Using Databases
- `add-domain on relational-database`: Command Intrinsics
- `add-macro-support`: Within-database
- `add-process!`: Multi-Processing
- `add-setter`: Setters
- `adjoin`: Lists as sets
- `adjoin-parameters!`: Parameter lists
- `alist->wt-tree`: Construction of Weight-Balanced Trees
- `alist-associator`: Association Lists
- `alist-cons`: SRFI-1
- `alist-copy`: SRFI-1
- `alist-delete`: SRFI-1
- `alist-delete!`: SRFI-1
- `alist-for-each`: Association Lists
- `alist-inquirer`: Association Lists
- `alist-map`: Association Lists
- `alist-remover`: Association Lists
- `alist-table`: The Base
- `and-let*`: Guarded LET* special form
- `and?`: Non-List functions
- `any`: SRFI-1
- `any-bits-set?`: Bit-Twiddling
- `any?`: Collections
- `append!`: Rev2 Procedures
- `append-reverse`: SRFI-1
- `append-reverse!`: SRFI-1
- `apply`: Multi-argument Apply
- `arithmetic-shift`: Bit-Twiddling
- `array->list`: Arrays
- `array->vector`: Arrays
- `array-dimensions`: Arrays
- `array-for-each`: Array Mapping
- `array-in-bounds?`: Arrays
- `array-index-for-each`: Array Mapping
- `array-index-map!`: Array Mapping
- `array-indexes`: Array Mapping
- `array-map`: Array Mapping
- `array-map!`: Array Mapping
- `array-rank`: Arrays
- `array-ref`: Arrays
- `array-set!`: Arrays
- `array-trim`: Subarrays
- `array:copy!`: Array Mapping
- `array?`: Arrays
- `asctime`: Posix Time
- `ash`: Bit-Twiddling
- `assoc`: SRFI-1
- `atan`: Irrational Real Functions
- `atom?`: Non-List functions
- `attlist-add`: Parsing XML
- `attlist-remove-top`: Parsing XML
- `batch:call-with-output-script`: Batch
- `batch:command`: Batch
- `batch:comment`: Batch
- `batch:delete-file`: Batch
- `batch:initialize!`: Batch
- `batch:lines->file`: Batch
- `batch:rename-file`: Batch
- `batch:run-script`: Batch
- `batch:try-chopped-command`: Batch
- `batch:try-command`: Batch
- `bit-field`: Bit-Twiddling
- `bit-set?`: Bit-Twiddling
- `bitwise-and`: Bit-Twiddling
- `bitwise-bit-count`: Bit-Twiddling
- `bitwise-if`: Bit-Twiddling
- `bitwise-ior`: Bit-Twiddling
- `bitwise-merge`: Bit-Twiddling
- `bitwise-not`: Bit-Twiddling
- `bitwise-xor`: Bit-Twiddling
- `blackbody-spectrum`: Spectra
- `booleans->integer`: Bit-Twiddling
- `break`: Breakpoints
- `break`: SRFI-1
- `break!`: SRFI-1
- `break-all`: Debug
- `breakf`: Breakpoints
- `breakpoint`: Breakpoints
- `browse`: Database Browser
- `browse-url`: System
- `butlast`: Lists as sequences
- `butnthcdr`: Lists as sequences
- `byte-ref`: Byte
- `byte-set!`: Byte
- `bytes`: Byte
- `bytes->ieee-double`: Byte/Number Conversions
- `bytes->ieee-float`: Byte/Number Conversions
- `bytes->integer`: Byte/Number Conversions
- `bytes->list`: Byte
- `bytes->string`: Byte
- `bytes-copy`: Byte
- `bytes-length`: Byte
- `bytes-reverse`: Byte
- `bytes-reverse!`: Byte
- `call-with-dynamic-binding`: Dynamic Data Type
- `call-with-input-string`: String Ports
- `call-with-open-ports`: Input/Output
- `call-with-output-string`: String Ports
- `call-with-tmpnam`: Filenames
- `call-with-values`: Values
- `capture-syntactic-environment`: Syntactic Closures
- `car+cdr`: SRFI-1
- `cart-prod-tables on relational-database`: Database Operations
- `catalog->html`: HTML Tables
- `catalog-id on base-table`: Base Tables
- `catalog:read`: Catalog Vicinities
- `cdna:base-count`: NCBI-DNA
- `cdna:report-base-count`: NCBI-DNA
- `cgi:serve-query`: HTTP and CGI
- `chap:next-string`: Chapter Ordering
- `chap:string<=?`: Chapter Ordering
- `chap:string<?`: Chapter Ordering
- `chap:string>=?`: Chapter Ordering
- `chap:string>?`: Chapter Ordering
- `check-parameters`: Parameter lists
- `chromaticity->CIEXYZ`: Spectra
- `chromaticity->whitepoint`: Spectra
- `CIE:DE*`: Color Difference Metrics
- `CIE:DE*94`: Color Difference Metrics
- `ciexyz->color`: Color Spaces
- `CIEXYZ->e-sRGB`: Color Conversions
- `CIEXYZ->L*a*b*`: Color Conversions
- `CIEXYZ->L*u*v*`: Color Conversions
- `CIEXYZ->RGB709`: Color Conversions
- `CIEXYZ->sRGB`: Color Conversions
- `CIEXYZ->xRGB`: Color Conversions
- `circular-list`: SRFI-1
- `circular-list?`: SRFI-1
- `cksum`: Cyclic Checksum
- `clear-sky-color-xyy`: Daylight
- `clip-to-rect`: Rectangles
- `close-base on base-table`: The Base
- `close-database`: Using Databases
- `close-database on relational-database`: Database Operations
- `close-port`: Input/Output
- `close-table on relational-table`: Table Administration
- `CMC-DE`: Color Difference Metrics
- `CMC:DE*`: Color Difference Metrics
- `codons<-cdna`: NCBI-DNA
- `coerce`: Type Coercion
- `collection?`: Collections
- `color->ciexyz`: Color Spaces
- `color->e-srgb`: Color Spaces
- `color->l*a*b*`: Color Spaces
- `color->l*c*h`: Color Spaces
- `color->l*u*v*`: Color Spaces
- `color->rgb709`: Color Spaces
- `color->srgb`: Color Spaces
- `color->string`: Color Data-Type
- `color->xrgb`: Color Spaces
- `color-dictionaries->lookup`: Color Names
- `color-dictionary`: Color Names
- `color-name->color`: Color Names
- `color-name:canonicalize`: Color Names
- `color-precision`: Color Data-Type
- `color-space`: Color Data-Type
- `color-white-point`: Color Data-Type
- `color:ciexyz`: Color Spaces
- `color:e-srgb`: Color Spaces
- `color:l*a*b*`: Color Spaces
- `color:l*c*h`: Color Spaces
- `color:l*u*v*`: Color Spaces
- `color:linear-transform`: Color Conversions
- `color:rgb709`: Color Spaces
- `color:srgb`: Color Spaces
- `color?`: Color Data-Type
- `column-domains on relational-table`: Table Administration
- `column-foreigns on relational-table`: Table Administration
- `column-names on relational-table`: Table Administration
- `column-range`: Column Ranges
- `column-types on relational-table`: Table Administration
- `combine-ranges`: Column Ranges
- `combined-rulesets`: Commutative Rings
- `command->p-specs`: HTML
- `command:make-editable-table`: HTML Tables
- `command:modify-table`: HTML Tables
- `concatenate`: SRFI-1
- `concatenate!`: SRFI-1
- `cond`: Guarded COND Clause
- `cond-expand`: SRFI
- `cons*`: SRFI-1
- `continue`: Breakpoints
- `convert-color`: Color Data-Type
- `copy-bit`: Bit-Twiddling
- `copy-bit-field`: Bit-Twiddling
- `copy-list`: List construction
- `copy-random-state`: Exact Random Numbers
- `copy-tree`: Tree Operations
- `count`: SRFI-1
- `count-newlines`: String Search
- `crc16`: Cyclic Checksum
- `crc5`: Cyclic Checksum
- `crc:make-table`: Cyclic Checksum
- `create-array`: Arrays
- `create-database`: Using Databases
- `create-database on relational-system`: Relational Database Objects
- `create-postscript-graph`: PostScript Graphing
- `create-table on relational-database`: Database Operations
- `create-view on relational-database`: Database Operations
- `cring:define-rule`: Commutative Rings
- `ctime`: Posix Time
- `current-directory`: Directories
- `current-error-port`: Input/Output
- `current-input-port`: Byte
- `current-input-port`: Ruleset Definition and Use
- `current-output-port`: Byte
- `current-time`: Time and Date
- `cvs-directories`: CVS
- `cvs-files`: CVS
- `cvs-repository`: CVS
- `cvs-root`: CVS
- `cvs-set-root!`: CVS
- `cvs-set-roots!`: CVS
- `cvs-vet`: CVS
- `db->html-directory`: HTML Tables
- `db->html-files`: HTML Tables
- `db->netscape`: HTML Tables
- `decode-universal-time`: Common-Lisp Time
- `define-*commands*`: Database Extension
- `define-access-operation`: Setters
- `define-command`: Within-database
- `define-domains`: Using Databases
- `define-macro`: Within-database
- `define-operation`: Yasos interface
- `define-predicate`: Yasos interface
- `define-record-type`: Define-Record-Type
- `define-structure`: Define-Structure
- `define-syntax`: Macro by Example
- `define-table`: Within-database
- `define-tables`: Using Databases
- `defmacro`: Defmacro
- `defmacro:eval`: Defmacro
- `defmacro:expand*`: Defmacro
- `defmacro:load`: Defmacro
- `defmacro?`: Defmacro
- `delaminate-list`: Hilbert Space-Filling Curve
- `delay`: Promises
- `delete`: Destructive list operations
- `delete on base-table`: Base Record Operations
- `delete* on base-table`: Aggregate Base Operations
- `delete-domain on relational-database`: Command Intrinsics
- `delete-duplicates`: SRFI-1
- `delete-duplicates!`: SRFI-1
- `delete-file`: Input/Output
- `delete-if`: Destructive list operations
- `delete-if-not`: Destructive list operations
- `delete-table on relational-database`: Database Operations
- `dequeue!`: Queues
- `dequeue-all!`: Queues
- `describe-file-lock`: Transactions
- `determinant`: Matrix Algebra
- `dft`: Discrete Fourier Transform
- `dft-1`: Discrete Fourier Transform
- `diff:edit-length`: Sequence Comparison
- `diff:edits`: Sequence Comparison
- `diff:longest-common-subsequence`: Sequence Comparison
- `difftime`: Time and Date
- `directory-for-each`: Directories
- `do-elts`: Collections
- `do-keys`: Collections
- `domain-checker on relational-database`: Command Intrinsics
- `dotted-list?`: SRFI-1
- `drop`: SRFI-1
- `drop-right`: SRFI-1
- `drop-right!`: SRFI-1
- `dynamic-ref`: Dynamic Data Type
- `dynamic-set!`: Dynamic Data Type
- `dynamic-wind`: Dynamic-Wind
- `dynamic?`: Dynamic Data Type
- `e-sRGB->CIEXYZ`: Color Conversions
- `e-srgb->color`: Color Spaces
- `e-sRGB->e-sRGB`: Color Conversions
- `e-sRGB->sRGB`: Color Conversions
- `eighth`: SRFI-1
- `emacs:backup-name`: Transactions
- `empty?`: Collections
- `encode-universal-time`: Common-Lisp Time
- `enqueue!`: Queues
- `equal?`: Byte
- `equal?`: Arrays
- `eval`: Eval
- `every`: Lists as sets
- `every?`: Collections
- `exports<-info-index`: Top-level Variable References
- `extended-euclid`: Modular Arithmetic
- `factor`: Prime Numbers
- `feature->export-alist`: Module Manifests
- `feature->exports`: Module Manifests
- `feature->requires`: Module Manifests
- `feature->requires*`: Module Manifests
- `feature-eval`: Feature
- `fft`: Discrete Fourier Transform
- `fft-1`: Discrete Fourier Transform
- `fifth`: SRFI-1
- `file->color-dictionary`: Color Names
- `file->definitions`: Module Manifests
- `file->exports`: Module Manifests
- `file->loads`: Module Manifests
- `file->requires`: Module Manifests
- `file->requires*`: Module Manifests
- `file-exists?`: Input/Output
- `file-lock!`: Transactions
- `file-lock-owner`: Transactions
- `file-position`: Input/Output
- `file-unlock!`: Transactions
- `filename:match-ci??`: Filenames
- `filename:match??`: Filenames
- `filename:substitute-ci??`: Filenames
- `filename:substitute??`: Filenames
- `fill-empty-parameters`: Parameter lists
- `fill-rect`: Rectangles
- `filter`: SRFI-1
- `filter!`: SRFI-1
- `find`: SRFI-1
- `find-if`: Lists as sets
- `find-ratio`: Rationalize
- `find-ratio-between`: Rationalize
- `find-string-from-port?`: String Search
- `find-tail`: SRFI-1
- `first`: SRFI-1
- `first-set-bit`: Bit-Twiddling
- `fluid-let`: Fluid-Let
- `fold`: SRFI-1
- `fold-right`: SRFI-1
- `for-each-elt`: Collections
- `for-each-key`: Collections
- `for-each-key on base-table`: Aggregate Base Operations
- `for-each-row on relational-table`: Multi-Row Operations
- `for-each-row-in-order on relational-table`: Sequential Index Operations
- `force`: Promises
- `force-output`: Input/Output
- `form:delimited`: HTML
- `form:element`: HTML
- `form:image`: HTML
- `form:reset`: HTML
- `form:submit`: HTML
- `format`: Format Interface
- `fourth`: SRFI-1
- `fprintf`: Standard Formatted Output
- `fscanf`: Standard Formatted Input
- `gen-elts`: Collections
- `gen-keys`: Collections
- `generic-write`: Generic-Write
- `gentemp`: Defmacro
- `get on relational-table`: Table Operations
- `get* on relational-table`: Match-Keys
- `get-decoded-time`: Common-Lisp Time
- `get-foreign-choices`: HTML
- `get-method`: Object
- `get-universal-time`: Common-Lisp Time
- `getenv`: System Interface
- `getopt`: Getopt
- `getopt--`: Getopt
- `getopt->arglist`: Getopt Parameter lists
- `getopt->parameter-list`: Getopt Parameter lists
- `glob-pattern?`: URI
- `gmktime`: Posix Time
- `gmtime`: Posix Time
- `golden-section-search`: Minimizing
- `gray-code->integer`: Hilbert Space-Filling Curve
- `gray-code<=?`: Hilbert Space-Filling Curve
- `gray-code<?`: Hilbert Space-Filling Curve
- `gray-code>=?`: Hilbert Space-Filling Curve
- `gray-code>?`: Hilbert Space-Filling Curve
- `grey`: Color Names
- `grid-horizontals`: Legending
- `grid-verticals`: Legending
- `gtime`: Posix Time
- `has-duplicates?`: Lists as sets
- `hash`: Hashing
- `hash-associator`: Hash Tables
- `hash-for-each`: Hash Tables
- `hash-inquirer`: Hash Tables
- `hash-map`: Hash Tables
- `hash-rehasher`: Hash Tables
- `hash-remover`: Hash Tables
- `hashq`: Hashing
- `hashv`: Hashing
- `heap-extract-max!`: Priority Queues
- `heap-insert!`: Priority Queues
- `heap-length`: Priority Queues
- `hilbert-coordinates->integer`: Hilbert Space-Filling Curve
- `histograph`: Character Plotting
- `home-vicinity`: Vicinity
- `htm-fields`: Parsing HTML
- `html-for-each`: Parsing HTML
- `html:anchor`: URI
- `html:atval`: HTML
- `html:base`: URI
- `html:body`: HTML
- `html:buttons`: HTML
- `html:caption`: HTML Tables
- `html:checkbox`: HTML
- `html:comment`: HTML
- `html:delimited-list`: HTML
- `html:editable-row-converter`: HTML Tables
- `html:form`: HTML
- `html:head`: HTML
- `html:heading`: HTML Tables
- `html:hidden`: HTML
- `html:href-heading`: HTML Tables
- `html:http-equiv`: HTML
- `html:isindex`: URI
- `html:link`: URI
- `html:linked-row-converter`: HTML Tables
- `html:meta`: HTML
- `html:meta-refresh`: HTML
- `html:plain`: HTML
- `html:pre`: HTML
- `html:read-title`: Parsing HTML
- `html:select`: HTML
- `html:table`: HTML Tables
- `html:text`: HTML
- `html:text-area`: HTML
- `http:content`: HTTP and CGI
- `http:error-page`: HTTP and CGI
- `http:forwarding-page`: HTTP and CGI
- `http:header`: HTTP and CGI
- `http:serve-query`: HTTP and CGI
- `identifier=?`: Syntactic Closures
- `identifier?`: Syntactic Closures
- `identity`: Miscellany
- `ieee-byte-collate`: Byte/Number Conversions
- `ieee-byte-collate!`: Byte/Number Conversions
- `ieee-byte-decollate`: Byte/Number Conversions
- `ieee-byte-decollate!`: Byte/Number Conversions
- `ieee-double->bytes`: Byte/Number Conversions
- `ieee-float->bytes`: Byte/Number Conversions
- `illuminant-map`: Spectra
- `illuminant-map->XYZ`: Spectra
- `implementation-vicinity`: Vicinity
- `in-graphic-context`: Graphics Context
- `in-vicinity`: Vicinity
- `init-debug`: Breakpoints
- `integer->bytes`: Byte/Number Conversions
- `integer->gray-code`: Hilbert Space-Filling Curve
- `integer->hilbert-coordinates`: Hilbert Space-Filling Curve
- `integer->list`: Bit-Twiddling
- `integer->peano-coordinates`: Peano Space-Filling Curve
- `integer-byte-collate`: Byte/Number Conversions
- `integer-byte-collate!`: Byte/Number Conversions
- `integer-expt`: Irrational Integer Functions
- `integer-length`: Bit-Twiddling
- `integer-log`: Irrational Integer Functions
- `integer-sqrt`: Irrational Integer Functions
- `interaction-environment`: Eval
- `interpolate-array-ref`: Array Interpolation
- `interpolate-from-table`: Database Interpolation
- `intersection`: Lists as sets
- `iota`: SRFI-1
- `isam-next on relational-table`: Sequential Index Operations
- `isam-prev on relational-table`: Sequential Index Operations
- `jacobi-symbol`: Prime Numbers
- `kill-process!`: Multi-Processing
- `kill-table on base-table`: Base Tables
- `L*a*b*->CIEXYZ`: Color Conversions
- `l*a*b*->color`: Color Spaces
- `L*a*b*->L*C*h`: Color Conversions
- `L*a*b*:DE*`: Color Difference Metrics
- `l*c*h->color`: Color Spaces
- `L*C*h->L*a*b*`: Color Conversions
- `L*C*h:DE*94`: Color Difference Metrics
- `L*u*v*->CIEXYZ`: Color Conversions
- `l*u*v*->color`: Color Spaces
- `laguerre:find-polynomial-root`: Root Finding
- `laguerre:find-root`: Root Finding
- `last`: SRFI-1
- `last`: Lists as sequences
- `last-pair`: Miscellany
- `length+`: SRFI-1
- `let-values`: Binding to multiple values
- `let-values*`: Binding to multiple values
- `library-vicinity`: Vicinity
- `light:ambient`: Solid Modeling
- `light:beam`: Solid Modeling
- `light:directional`: Solid Modeling
- `light:point`: Solid Modeling
- `light:spot`: Solid Modeling
- `limit`: The Limit
- `list*`: List construction
- `list->array`: Arrays
- `list->bytes`: Byte
- `list->integer`: Bit-Twiddling
- `list-copy`: SRFI-1
- `list-index`: SRFI-1
- `list-of??`: Lists as sets
- `list-table-definition`: Using Databases
- `list-tabulate`: SRFI-1
- `list-tail`: Rev4 Optional Procedures
- `list=`: SRFI-1
- `ln`: Irrational Real Functions
- `load->path`: Module Manifests
- `load-ciexyz`: Spectra
- `load-color-dictionary`: Color Names
- `localtime`: Posix Time
- `log2-binary-factors`: Bit-Twiddling
- `logand`: Bit-Twiddling
- `logbit?`: Bit-Twiddling
- `logcount`: Bit-Twiddling
- `logior`: Bit-Twiddling
- `lognot`: Bit-Twiddling
- `logtest`: Bit-Twiddling
- `logxor`: Bit-Twiddling
- `lset-adjoin`: SRFI-1
- `lset-diff+intersection`: SRFI-1
- `lset-diff+intersection!`: SRFI-1
- `lset-difference`: SRFI-1
- `lset-difference!`: SRFI-1
- `lset-intersection`: SRFI-1
- `lset-intersection!`: SRFI-1
- `lset-union`: SRFI-1
- `lset-union!`: SRFI-1
- `lset-xor`: SRFI-1
- `lset-xor!`: SRFI-1
- `lset<=`: SRFI-1
- `lset=`: SRFI-1
- `macro:eval`: Syntax-Case Macros
- `macro:eval`: Syntactic Closures
- `macro:eval`: Macros That Work
- `macro:eval`: R4RS Macros
- `macro:expand`: Syntax-Case Macros
- `macro:expand`: Syntactic Closures
- `macro:expand`: Macros That Work
- `macro:expand`: R4RS Macros
- `macro:load`: Syntax-Case Macros
- `macro:load`: Syntactic Closures
- `macro:load`: Macros That Work
- `macro:load`: R4RS Macros
- `macroexpand`: Defmacro
- `macroexpand-1`: Defmacro
- `macwork:eval`: Macros That Work
- `macwork:expand`: Macros That Work
- `macwork:load`: Macros That Work
- `make-array`: Arrays
- `make-base on base-table`: The Base
- `make-bytes`: Byte
- `make-color`: Color Data-Type
- `make-command-server`: Command Service
- `make-directory`: Directories
- `make-dynamic`: Dynamic Data Type
- `make-exchanger`: Miscellany
- `make-generic-method`: Object
- `make-generic-predicate`: Object
- `make-getter on base-table`: Base Record Operations
- `make-getter-1 on base-table`: Base Record Operations
- `make-hash-table`: Hash Tables
- `make-heap`: Priority Queues
- `make-key->list on base-table`: Composite Keys
- `make-key-extractor on base-table`: Composite Keys
- `make-keyifier-1 on base-table`: Composite Keys
- `make-list`: List construction
- `make-list-keyifier on base-table`: Composite Keys
- `make-method!`: Object
- `make-nexter on base-table`: Base ISAM Operations
- `make-object`: Object
- `make-parameter-list`: Parameter lists
- `make-polar`: Irrational Real Functions
- `make-predicate!`: Object
- `make-prever on base-table`: Base ISAM Operations
- `make-promise`: Promises
- `make-putter on base-table`: Base Record Operations
- `make-query-alist-command-server`: HTTP and CGI
- `make-queue`: Queues
- `make-random-state`: Exact Random Numbers
- `make-record-type`: Records
- `make-rectangular`: Irrational Real Functions
- `make-relational-system`: Relational Database Objects
- `make-ruleset`: Commutative Rings
- `make-shared-array`: Arrays
- `make-sierpinski-indexer`: Sierpinski Curve
- `make-slib-color-name-db`: Color Names
- `make-syntactic-closure`: Syntactic Closures
- `make-table on base-table`: Base Tables
- `make-uri`: URI
- `make-vicinity`: Vicinity
- `make-wt-tree`: Construction of Weight-Balanced Trees
- `make-wt-tree-type`: Construction of Weight-Balanced Trees
- `map!`: SRFI-1
- `map-elts`: Collections
- `map-key on base-table`: Aggregate Base Operations
- `map-keys`: Collections
- `matfile:load`: MAT-File Format
- `matfile:read`: MAT-File Format
- `matrix->array`: Matrix Algebra
- `matrix->lists`: Matrix Algebra
- `matrix:difference`: Matrix Algebra
- `matrix:inverse`: Matrix Algebra
- `matrix:product`: Matrix Algebra
- `matrix:sum`: Matrix Algebra
- `mdbm:report`: Using Databases
- `member`: SRFI-1
- `member-if`: Lists as sets
- `merge`: Sorting
- `merge!`: Sorting
- `mktime`: Posix Time
- `mod`: Irrational Real Functions
- `modular:*`: Modular Arithmetic
- `modular:+`: Modular Arithmetic
- `modular:-`: Modular Arithmetic
- `modular:characteristic`: Modular Arithmetic
- `modular:expt`: Modular Arithmetic
- `modular:invert`: Modular Arithmetic
- `modular:invertable?`: Modular Arithmetic
- `modular:negate`: Modular Arithmetic
- `modular:normalize`: Modular Arithmetic
- `mrna<-cdna`: NCBI-DNA
- `must-be-first`: Batch
- `must-be-last`: Batch
- `natural->peano-coordinates`: Peano Space-Filling Curve
- `ncbi:read-dna-sequence`: NCBI-DNA
- `ncbi:read-file`: NCBI-DNA
- `nconc`: Destructive list operations
- `newton:find-integer-root`: Root Finding
- `newton:find-root`: Root Finding
- `ninth`: SRFI-1
- `not-pair?`: SRFI-1
- `notany`: Lists as sets
- `notevery`: Lists as sets
- `nreverse`: Destructive list operations
- `nthcdr`: Lists as sequences
- `null-directory?`: URI
- `null-environment`: Eval
- `null-list?`: SRFI-1
- `object`: Yasos interface
- `object->limited-string`: Object-To-String
- `object->string`: Object-To-String
- `object-with-ancestors`: Yasos interface
- `object?`: Object
- `offset-time`: Time and Date
- `open-base on base-table`: The Base
- `open-command-database`: Database Extension
- `open-command-database!`: Database Extension
- `open-database`: Using Databases
- `open-database on relational-system`: Relational Database Objects
- `open-database!`: Using Databases
- `open-file`: Byte
- `open-file`: Input/Output
- `open-table`: Using Databases
- `open-table on base-table`: Base Tables
- `open-table on relational-database`: Database Operations
- `open-table!`: Using Databases
- `operate-as`: Yasos interface
- `or?`: Non-List functions
- `ordered-for-each-key on base-table`: Base ISAM Operations
- `os->batch-dialect`: Batch
- `outline-rect`: Rectangles
- `output-port-height`: Input/Output
- `output-port-width`: Input/Output
- `overcast-sky-color-xyy`: Daylight
- `p<-cdna`: NCBI-DNA
- `pad-range`: Column Ranges
- `pair-fold`: SRFI-1
- `pair-fold-right`: SRFI-1
- `pair-for-each`: SRFI-1
- `parameter-list->arglist`: Parameter lists
- `parameter-list-expand`: Parameter lists
- `parameter-list-ref`: Parameter lists
- `parse-ftp-address`: URI
- `partition`: SRFI-1
- `partition!`: SRFI-1
- `partition-page`: Rectangles
- `path->uri`: URI
- `pathname->vicinity`: Vicinity
- `peano-coordinates->integer`: Peano Space-Filling Curve
- `peano-coordinates->natural`: Peano Space-Filling Curve
- `plot`: Legacy Plotting
- `plot`: Character Plotting
- `plot-column`: Drawing the Graph
- `pnm:array-write`: Portable Image Files
- `pnm:image-file->array`: Portable Image Files
- `pnm:type-dimensions`: Portable Image Files
- `port?`: Input/Output
- `position`: Lists as sequences
- `pprint-file`: Pretty-Print
- `pprint-filter-file`: Pretty-Print
- `prec:commentfix`: Grammar Rule Definition
- `prec:define-grammar`: Ruleset Definition and Use
- `prec:delim`: Grammar Rule Definition
- `prec:infix`: Grammar Rule Definition
- `prec:inmatchfix`: Grammar Rule Definition
- `prec:make-led`: Nud and Led Definition
- `prec:make-nud`: Nud and Led Definition
- `prec:matchfix`: Grammar Rule Definition
- `prec:nary`: Grammar Rule Definition
- `prec:nofix`: Grammar Rule Definition
- `prec:parse`: Ruleset Definition and Use
- `prec:postfix`: Grammar Rule Definition
- `prec:prefix`: Grammar Rule Definition
- `prec:prestfix`: Grammar Rule Definition
- `predicate->asso`: Association Lists
- `predicate->hash`: Hash Tables
- `predicate->hash-asso`: Hash Tables
- `present? on base-table`: Base Record Operations
- `pretty-print`: Pretty-Print
- `pretty-print->string`: Pretty-Print
- `primary-limit on relational-table`: Table Administration
- `prime?`: Prime Numbers
- `primes<`: Prime Numbers
- `primes>`: Prime Numbers
- `print`: Yasos interface
- `print-call-stack`: Trace
- `printf`: Standard Formatted Output
- `process:schedule!`: Multi-Processing
- `program-arguments`: System Interface
- `program-vicinity`: Vicinity
- `project-table on relational-database`: Database Operations
- `proper-list?`: SRFI-1
- `protein<-cdna`: NCBI-DNA
- `provide`: Feature
- `provided?`: Feature
- `qp`: Quick Print
- `qpn`: Quick Print
- `qpr`: Quick Print
- `queue-empty?`: Queues
- `queue-front`: Queues
- `queue-pop!`: Queues
- `queue-push!`: Queues
- `queue-rear`: Queues
- `queue?`: Queues
- `quo`: Irrational Real Functions
- `random`: Exact Random Numbers
- `random:exp`: Inexact Random Numbers
- `random:hollow-sphere!`: Inexact Random Numbers
- `random:normal`: Inexact Random Numbers
- `random:normal-vector!`: Inexact Random Numbers
- `random:solid-sphere!`: Inexact Random Numbers
- `random:uniform`: Inexact Random Numbers
- `rationalize`: Rationalize
- `read-byte`: Byte
- `read-bytes`: Byte
- `read-cie-illuminant`: Spectra
- `read-command`: Command Line
- `read-line`: Line I/O
- `read-line!`: Line I/O
- `read-normalized-illuminant`: Spectra
- `read-options-file`: Command Line
- `real-acos`: Irrational Real Functions
- `real-asin`: Irrational Real Functions
- `real-atan`: Irrational Real Functions
- `real-cos`: Irrational Real Functions
- `real-exp`: Irrational Real Functions
- `real-expt`: Irrational Real Functions
- `real-ln`: Irrational Real Functions
- `real-log`: Irrational Real Functions
- `real-sin`: Irrational Real Functions
- `real-sqrt`: Irrational Real Functions
- `real-tan`: Irrational Real Functions
- `receive`: Binding to multiple values
- `record-accessor`: Records
- `record-constructor`: Records
- `record-modifier`: Records
- `record-predicate`: Records
- `reduce`: SRFI-1
- `reduce`: Lists as sequences
- `reduce`: Collections
- `reduce-init`: Lists as sequences
- `rem`: Irrational Real Functions
- `remove`: SRFI-1
- `remove`: Lists as sets
- `remove!`: SRFI-1
- `remove-duplicates`: Lists as sets
- `remove-if`: Lists as sets
- `remove-if-not`: Lists as sets
- `remove-parameter`: Parameter lists
- `remove-setter-for`: Setters
- `repl:quit`: Repl
- `repl:top-level`: Repl
- `replace-suffix`: Filenames
- `require`: Catalog Creation
- `require`: Require
- `require-if`: Require
- `resample-array!`: Array Interpolation
- `resene`: Color Names
- `restrict-table on relational-database`: Database Operations
- `reverse!`: SRFI-1
- `reverse-bit-field`: Bit-Twiddling
- `RGB709->CIEXYZ`: Color Conversions
- `rgb709->color`: Color Spaces
- `rotate-bit-field`: Bit-Twiddling
- `row:delete on relational-table`: Single Row Operations
- `row:delete* on relational-table`: Multi-Row Operations
- `row:insert on relational-table`: Single Row Operations
- `row:insert* on relational-table`: Multi-Row Operations
- `row:remove on relational-table`: Single Row Operations
- `row:remove* on relational-table`: Multi-Row Operations
- `row:retrieve on relational-table`: Single Row Operations
- `row:retrieve* on relational-table`: Multi-Row Operations
- `row:update on relational-table`: Single Row Operations
- `row:update* on relational-table`: Multi-Row Operations
- `rule-horizontal`: Legending
- `rule-vertical`: Legending
- `saturate`: Color Names
- `scanf`: Standard Formatted Input
- `scanf-read-list`: Standard Formatted Input
- `scene:overcast`: Solid Modeling
- `scene:panorama`: Solid Modeling
- `scene:sky-and-dirt`: Solid Modeling
- `scene:sky-and-grass`: Solid Modeling
- `scene:sphere`: Solid Modeling
- `scene:sun`: Solid Modeling
- `scene:viewpoint`: Solid Modeling
- `scene:viewpoints`: Solid Modeling
- `scheme-report-environment`: Eval
- `schmooz`: Schmooz
- `secant:find-bracketed-root`: Root Finding
- `secant:find-root`: Root Finding
- `second`: SRFI-1
- `seed->random-state`: Exact Random Numbers
- `set`: Setters
- `set-color`: Graphics Context
- `set-difference`: Lists as sets
- `set-font`: Graphics Context
- `set-glyphsize`: Graphics Context
- `set-linedash`: Graphics Context
- `set-linewidth`: Graphics Context
- `set-margin-templates`: Legending
- `Setter`: Collections
- `setter`: Setters
- `setup-plot`: Column Ranges
- `seventh`: SRFI-1
- `sft`: Discrete Fourier Transform
- `sft-1`: Discrete Fourier Transform
- `si:conversion-factor`: Metric Units
- `singleton-wt-tree`: Construction of Weight-Balanced Trees
- `sixth`: SRFI-1
- `size`: Collections
- `size`: Yasos interface
- `sky-color-xyy`: Daylight
- `slib:error`: System
- `slib:eval`: System
- `slib:eval-load`: System
- `slib:exit`: System
- `slib:in-catalog?`: Require
- `slib:load`: System
- `slib:load-compiled`: System
- `slib:load-source`: System
- `slib:report`: Configuration
- `slib:report-version`: Configuration
- `slib:warn`: System
- `snap-range`: Column Ranges
- `software-type`: Configuration
- `solar-declination`: Daylight
- `solar-hour`: Daylight
- `solar-polar`: Daylight
- `solid:arrow`: Solid Modeling
- `solid:basrelief`: Solid Modeling
- `solid:box`: Solid Modeling
- `solid:center-array-of`: Solid Modeling
- `solid:center-pile-of`: Solid Modeling
- `solid:center-row-of`: Solid Modeling
- `solid:color`: Solid Modeling
- `solid:cone`: Solid Modeling
- `solid:cylinder`: Solid Modeling
- `solid:disk`: Solid Modeling
- `solid:ellipsoid`: Solid Modeling
- `solid:font`: Solid Modeling
- `solid:lumber`: Solid Modeling
- `solid:polyline`: Solid Modeling
- `solid:prism`: Solid Modeling
- `solid:pyramid`: Solid Modeling
- `solid:rotation`: Solid Modeling
- `solid:scale`: Solid Modeling
- `solid:sphere`: Solid Modeling
- `solid:text`: Solid Modeling
- `solid:texture`: Solid Modeling
- `solid:translation`: Solid Modeling
- `solidify-database`: Using Databases
- `solidify-database on relational-database`: Database Operations
- `some`: Lists as sets
- `sort`: Sorting
- `sort!`: Sorting
- `sorted?`: Sorting
- `soundex`: Soundex
- `span`: SRFI-1
- `span!`: SRFI-1
- `spectrum->chromaticity`: Spectra
- `spectrum->XYZ`: Spectra
- `split-at`: SRFI-1
- `split-at!`: SRFI-1
- `sprintf`: Standard Formatted Output
- `sRGB->CIEXYZ`: Color Conversions
- `srgb->color`: Color Spaces
- `sRGB->e-sRGB`: Color Conversions
- `sRGB->xRGB`: Color Conversions
- `ssax:assert-current-char`: Parsing XML
- `ssax:assert-token`: Parsing XML
- `ssax:complete-start-tag`: Parsing XML
- `ssax:handle-parsed-entity`: Parsing XML
- `ssax:init-buffer`: Parsing XML
- `ssax:make-elem-parser`: Parsing XML
- `ssax:make-parser`: Parsing XML
- `ssax:make-pi-parser`: Parsing XML
- `ssax:next-token`: Parsing XML
- `ssax:next-token-of`: Parsing XML
- `ssax:read-attributes`: Parsing XML
- `ssax:read-cdata-body`: Parsing XML
- `ssax:read-char-data`: Parsing XML
- `ssax:read-char-ref`: Parsing XML
- `ssax:read-external-id`: Parsing XML
- `ssax:read-markup-token`: Parsing XML
- `ssax:read-ncname`: Parsing XML
- `ssax:read-pi-body-as-string`: Parsing XML
- `ssax:read-qname`: Parsing XML
- `ssax:read-string`: Parsing XML
- `ssax:resolve-name`: Parsing XML
- `ssax:reverse-collect-str`: Parsing XML
- `ssax:reverse-collect-str-drop-ws`: Parsing XML
- `ssax:scan-misc`: Parsing XML
- `ssax:skip-internal-dtd`: Parsing XML
- `ssax:skip-pi`: Parsing XML
- `ssax:skip-s`: Parsing XML
- `ssax:skip-while`: Parsing XML
- `ssax:xml->sxml`: Parsing XML
- `sscanf`: Standard Formatted Input
- `stack`: Trace
- `stack-all`: Debug
- `stackf`: Trace
- `string->bytes`: Byte
- `string->color`: Color Data-Type
- `string-capitalize`: String-Case
- `string-capitalize!`: String-Case
- `string-ci->symbol`: String-Case
- `string-copy`: Rev4 Optional Procedures
- `string-downcase`: String-Case
- `string-downcase!`: String-Case
- `string-fill!`: Rev4 Optional Procedures
- `string-index`: String Search
- `string-index-ci`: String Search
- `string-join`: Batch
- `string-null?`: Rev2 Procedures
- `string-reverse-index`: String Search
- `string-reverse-index-ci`: String Search
- `string-subst`: String Search
- `string-upcase`: String-Case
- `string-upcase!`: String-Case
- `StudlyCapsExpand`: String-Case
- `sub-vicinity`: Vicinity
- `subarray`: Subarrays
- `subbytes`: Byte
- `subbytes-read!`: Byte
- `subbytes-write`: Byte
- `subset?`: Lists as sets
- `subst`: Tree Operations
- `substq`: Tree Operations
- `substring-ci?`: String Search
- `substring-fill!`: Rev2 Procedures
- `substring-move-left!`: Rev2 Procedures
- `substring-move-right!`: Rev2 Procedures
- `substring?`: String Search
- `substv`: Tree Operations
- `sunlight-chromaticity`: Daylight
- `sunlight-spectrum`: Daylight
- `supported-key-type? on base-table`: Base Field Types
- `supported-type? on base-table`: Base Field Types
- `symbol-append`: String-Case
- `symmetric:modulus`: Modular Arithmetic
- `sync-base on base-table`: The Base
- `sync-database`: Using Databases
- `sync-database on relational-database`: Database Operations
- `syncase:eval`: Syntax-Case Macros
- `syncase:expand`: Syntax-Case Macros
- `syncase:load`: Syntax-Case Macros
- `syncase:sanity-check`: Syntax-Case Macros
- `synclo:eval`: Syntactic Closures
- `synclo:expand`: Syntactic Closures
- `synclo:load`: Syntactic Closures
- `syntax-rules`: Macro by Example
- `system`: System Interface
- `system->line`: Line I/O
- `table->linked-html`: HTML Tables
- `table->linked-page`: HTML Tables
- `table-exists? on relational-database`: Database Operations
- `table-name->filename`: HTML Tables
- `take`: SRFI-1
- `take!`: SRFI-1
- `take-right`: SRFI-1
- `temperature->chromaticity`: Spectra
- `temperature->XYZ`: Spectra
- `tenth`: SRFI-1
- `third`: SRFI-1
- `time-zone`: Time Zone
- `time:gmtime`: Time Infrastructure
- `time:invert`: Time Infrastructure
- `time:split`: Time Infrastructure
- `title-bottom`: Legending
- `title-top`: Legending
- `tmpnam`: Input/Output
- `tok:bump-column`: Token definition
- `tok:char-group`: Token definition
- `top-refs`: Top-level Variable References
- `top-refs<-file`: Top-level Variable References
- `topological-sort`: Topological Sort
- `trace`: Trace
- `trace-all`: Debug
- `tracef`: Trace
- `track`: Trace
- `track-all`: Debug
- `trackf`: Trace
- `transact-file-replacement`: Transactions
- `transcript-off`: Transcripts
- `transcript-on`: Transcripts
- `transformer`: Syntactic Closures
- `transpose`: Matrix Algebra
- `truncate-up-to`: Batch
- `tsort`: Topological Sort
- `type-of`: Type Coercion
- `tz:params`: Time Zone
- `tz:std-offset`: Time Zone
- `tzfile:read`: Time Infrastructure
- `tzset`: Time Zone
- `unbreak`: Breakpoints
- `unbreakf`: Breakpoints
- `union`: Lists as sets
- `unmake-method!`: Object
- `unstack`: Trace
- `untrace`: Trace
- `untracef`: Trace
- `untrack`: Trace
- `unzip1`: SRFI-1
- `unzip2`: SRFI-1
- `unzip3`: SRFI-1
- `unzip4`: SRFI-1
- `unzip5`: SRFI-1
- `uri->tree`: URI
- `uri:decode-query`: URI
- `uri:make-path`: URI
- `uri:path->keys`: URI
- `uri:split-fields`: URI
- `uric:decode`: URI
- `uric:encode`: URI
- `url->color-dictionary`: Color Names
- `user-email-address`: Transactions
- `user-vicinity`: Vicinity
- `values`: Values
- `vector->array`: Arrays
- `vector-fill!`: Rev4 Optional Procedures
- `vet-slib`: Module Analysis
- `vicinity:suffix?`: Vicinity
- `vrml`: Solid Modeling
- `vrml-append`: Solid Modeling
- `vrml-to-file`: Solid Modeling
- `wavelength->chromaticity`: Spectra
- `wavelength->XYZ`: Spectra
- `whole-page`: Rectangles
- `whole-page`: PostScript Graphing
- `with-input-from-file`: With-File
- `with-load-pathname`: Vicinity
- `with-output-to-file`: With-File
- `within-database`: Within-database
- `world:info`: Solid Modeling
- `wrap-command-interface`: Database Extension
- `write-base on base-table`: The Base
- `write-byte`: Byte
- `write-bytes`: Byte
- `write-database`: Using Databases
- `write-database on relational-database`: Database Operations
- `write-line`: Line I/O
- `wt-tree/add`: Basic Operations on Weight-Balanced Trees
- `wt-tree/add!`: Basic Operations on Weight-Balanced Trees
- `wt-tree/delete`: Basic Operations on Weight-Balanced Trees
- `wt-tree/delete!`: Basic Operations on Weight-Balanced Trees
- `wt-tree/delete-min`: Indexing Operations on Weight-Balanced Trees
- `wt-tree/delete-min!`: Indexing Operations on Weight-Balanced Trees
- `wt-tree/difference`: Advanced Operations on Weight-Balanced Trees
- `wt-tree/empty?`: Basic Operations on Weight-Balanced Trees
- `wt-tree/fold`: Advanced Operations on Weight-Balanced Trees
- `wt-tree/for-each`: Advanced Operations on Weight-Balanced Trees
- `wt-tree/index`: Indexing Operations on Weight-Balanced Trees
- `wt-tree/index-datum`: Indexing Operations on Weight-Balanced Trees
- `wt-tree/index-pair`: Indexing Operations on Weight-Balanced Trees
- `wt-tree/intersection`: Advanced Operations on Weight-Balanced Trees
- `wt-tree/lookup`: Basic Operations on Weight-Balanced Trees
- `wt-tree/member?`: Basic Operations on Weight-Balanced Trees
- `wt-tree/min`: Indexing Operations on Weight-Balanced Trees
- `wt-tree/min-datum`: Indexing Operations on Weight-Balanced Trees
- `wt-tree/min-pair`: Indexing Operations on Weight-Balanced Trees
- `wt-tree/rank`: Indexing Operations on Weight-Balanced Trees
- `wt-tree/set-equal?`: Advanced Operations on Weight-Balanced Trees
- `wt-tree/size`: Basic Operations on Weight-Balanced Trees
- `wt-tree/split<`: Advanced Operations on Weight-Balanced Trees
- `wt-tree/split>`: Advanced Operations on Weight-Balanced Trees
- `wt-tree/subset?`: Advanced Operations on Weight-Balanced Trees
- `wt-tree/union`: Advanced Operations on Weight-Balanced Trees
- `x-axis`: Legending
- `x1`: Legacy Plotting
- `xcons`: SRFI-1
- `xRGB->CIEXYZ`: Color Conversions
- `xrgb->color`: Color Spaces
- `xRGB->sRGB`: Color Conversions
- `xyY->XYZ`: Spectra
- `xyY:normalize-colors`: Spectra
- `XYZ->chromaticity`: Spectra
- `XYZ->xyY`: Spectra
- `y-axis`: Legending
- `zenith-xyy`: Daylight
- `zip`: SRFI-1

Next: Concept and Feature Index, Previous: Procedure and Macro Index, Up: Index

## Variable Index

- `*argv*`: Getopt
- `*base-table-implementations*`: Base Table
- `*catalog*`: Require
- `*http:byline*`: HTTP and CGI
- `*operating-system*`: Batch
- `*optarg*`: Getopt
- `*optind*`: Getopt
- `*qp-width*`: Quick Print
- `*random-state*`: Exact Random Numbers
- `*ruleset*`: Commutative Rings
- `*syn-defs*`: Ruleset Definition and Use
- `*syn-ignore-whitespace*`: Ruleset Definition and Use
- `*timezone*`: Time Zone
- `atm-hec-polynomial`: Cyclic Checksum
- `bottomedge`: Legending
- `char-code-limit`: Configuration
- `charplot:dimensions`: Character Plotting
- `CIEXYZ:A`: Color Conversions
- `CIEXYZ:B`: Color Conversions
- `CIEXYZ:C`: Color Conversions
- `CIEXYZ:D50`: Color Conversions
- `CIEXYZ:D65`: Color Conversions
- `CIEXYZ:E`: Color Conversions
- `crc-08-polynomial`: Cyclic Checksum
- `crc-10-polynomial`: Cyclic Checksum
- `crc-12-polynomial`: Cyclic Checksum
- `crc-16-polynomial`: Cyclic Checksum
- `crc-32-polynomial`: Cyclic Checksum
- `crc-ccitt-polynomial`: Cyclic Checksum
- `D50`: Color Data-Type
- `D65`: Color Data-Type
- `daylight?`: Time Zone
- `debug:max-count`: Trace
- `distribute*`: Commutative Rings
- `distribute/`: Commutative Rings
- `dowcrc-polynomial`: Cyclic Checksum
- `graph:dimensions`: Legacy Plotting
- `graphrect`: Rectangles
- `leftedge`: Legending
- `modulo`: Irrational Integer Functions
- `most-positive-fixnum`: Configuration
- `nil`: Miscellany
- `number-wt-type`: Construction of Weight-Balanced Trees
- `plotrect`: Rectangles
- `prime:prngs`: Prime Numbers
- `prime:trials`: Prime Numbers
- `quotient`: Irrational Integer Functions
- `remainder`: Irrational Integer Functions
- `rightedge`: Legending
- `slib:form-feed`: Configuration
- `slib:tab`: Configuration
- `stderr`: Standard Formatted I/O
- `stdin`: Standard Formatted I/O
- `stdout`: Standard Formatted I/O
- `string-wt-type`: Construction of Weight-Balanced Trees
- `t`: Miscellany
- `tok:decimal-digits`: Token definition
- `tok:lower-case`: Token definition
- `tok:upper-case`: Token definition
- `tok:whitespaces`: Token definition
- `topedge`: Legending
- `tzname`: Time Zone
- `usb-token-polynomial`: Cyclic Checksum

Previous: Variable Index, Up: Index

## Concept and Feature Index

- =>: Guarded COND Clause
- aggregate: Module Semantics
- aggregate: Library Catalogs
- alarm: Multi-Processing
- alarm-interrupt: Multi-Processing
- `alist`: Association Lists
- `alist-table`: Relational Database Objects
- `alist-table`: The Base
- `alist-table`: Base Table
- `and-let*`: Guarded LET* special form
- ange-ftp: URI
- appearance: Solid Modeling
- `array`: Arrays
- `array-for-each`: Array Mapping
- association function: Association Lists
- Attribute: Parsing XML
- attribute-value: HTML
- AttValue: Parsing XML
- Auto-sharing: Using Databases
- balanced binary trees: Weight-Balanced Trees
- base: URI
- base-table: Base Table
- `batch`: Batch
- `bignum`: Feature
- binary: Byte
- binary trees: Weight-Balanced Trees
- binary trees, as discrete maps: Weight-Balanced Trees
- binary trees, as sets: Weight-Balanced Trees
- binding power: Precedence Parsing Overview
- `break`: Breakpoints
- `byte`: Byte
- `byte-number`: Byte/Number Conversions
- calendar time: Posix Time
- calendar time: Time and Date
- `Calendar-Time`: Posix Time
- caltime: Posix Time
- canonical: Color Names
- careful: Commutative Rings
- catalog: Require
- Catalog File: Library Catalogs
- certificate: Transactions
- `cgi`: HTTP and CGI
- `chapter-order`: Chapter Ordering
- `charplot`: Character Plotting
- Chroma: Color Spaces
- `cie1931`: Spectra
- `cie1964`: Spectra
- `ciexyz`: Spectra
- `CIEXYZ`: Color Spaces
- cksum-string: Cyclic Checksum
- `coerce`: Type Coercion
- `collect`: Collections
- `color-database`: Color Names
- `color-names`: Color Names
- command line: Command Line
- `commentfix`: Rule Types
- `common-list-functions`: Common List Functions
- `common-list-functions`: Collections
- `commutative-ring`: Commutative Rings
- compiled: Library Catalogs
- compiling: Module Conventions
- `complex`: Feature
- `Coordinated Universal Time`: Posix Time
- copyright: Copyrights
- `crc`: Cyclic Checksum
- `cvs`: CVS
- `database-commands`: Command Example
- `databases`: Command Example
- `databases`: Define-tables Example
- `databases`: Using Databases
- `databases`: Batch
- `daylight`: Daylight
- `db->html`: HTML Tables
- `debug`: Breakpoints
- `debug`: Debug
- `define-record-type`: Define-Record-Type
- defmacro: Library Catalogs
- `defmacroexpand`: Pretty-Print
- `defmacroexpand`: Defmacro
- `delim`: Rule Types
- dequeues: Queues
- `determinant`: Matrix Algebra
- `dft, Fourier-transform`: Discrete Fourier Transform
- `diff`: Sequence Comparison
- `directory`: Directories
- Discrete Fourier Transform: Discrete Fourier Transform
- discrete maps, using binary trees: Weight-Balanced Trees
- `DrScheme`: Installation
- `dynamic`: Dynamic Data Type
- `dynamic-wind`: Dynamic-Wind
- `e-sRGB`: Color Spaces
- `ELK`: Installation
- emacs: Transactions
- Encapsulated-PostScript: PostScript Graphing
- escaped: URI
- EUC: Extra-SLIB Packages
- Euclidean Domain: Commutative Rings
- `eval`: Eval
- exchanger: Miscellany
- `factor`: Prime Numbers
- `feature`: About this manual
- `feature`: Require
- feature: Feature
- File Transfer Protocol: URI
- file-lock: Transactions
- `filename`: Batch
- `filename`: Filenames
- `fluid-let`: Fluid-Let
- fold: Parsing XML
- form: HTML
- `format`: Format
- `Gambit-C 3.0`: Installation
- gamut: Color Spaces
- `generic-write`: Generic-Write
- `getenv`: System Interface
- getit: URI
- `getopt`: Command Example
- `getopt`: Getopt
- `getopt-parameters`: Command Example
- `getopt-parameters`: Getopt Parameter lists
- `glob`: Filenames
- Gray code: Hilbert Space-Filling Curve
- `guarded-cond-clause`: Guarded COND Clause
- `Guile`: Installation
- `hash`: Hashing
- `hash-table`: Hash Tables
- Hilbert: Hilbert Space-Filling Curve
- Hilbert Space-Filling Curve: Hilbert Space-Filling Curve
- `hilbert-fill`: Hilbert Space-Filling Curve
- HOME: Vicinity
- HOME: Catalog Creation
- homecat: Catalog Vicinities
- `html-for-each`: Parsing HTML
- `html-form`: HTML
- `http`: HTTP and CGI
- Hue: Color Spaces
- `ICC Profile`: Color Spaces
- implcat: Catalog Vicinities
- indexed-sequential-access-method: Byte/Number Conversions
- `inexact`: Feature
- `infix`: Rule Types
- Info: Top-level Variable References
- `inmatchfix`: Rule Types
- install: Installation
- installation: Installation
- intrinsic feature: Feature
- ISAM: Indexed Sequential Access Methods
- Japanese: Extra-SLIB Packages
- JFILTER: Extra-SLIB Packages
- JIS: Extra-SLIB Packages
- `Kawa`: Installation
- `L*a*b*`: Color Spaces
- `L*C*h`: Color Spaces
- `L*u*v*`: Color Spaces
- lamination: Hilbert Space-Filling Curve
- `Larceny`: Installation
- Left Denotation, led: Nud and Led Definition
- `let-values`: Binding to multiple values
- Lightness: Color Spaces
- `line-i`: Line I/O
- list-processing library: SRFI-1
- `load-option`: Weight-Balanced Trees
- `logical`: Bit-Twiddling
- `macro`: Repl
- `macro`: R4RS Macros
- macro: Library Catalogs
- `macro-by-example`: Macro by Example
- macro-by-example: Library Catalogs
- `macros-that-work`: Macros That Work
- macros-that-work: Library Catalogs
- `manifest`: Module Manifests
- match: Match Keys
- match-keys: Match Keys
- match-keys: Match-Keys
- `matchfix`: Rule Types
- `matfile`: MAT-File Format
- `math-integer`: Irrational Integer Functions
- `math-real`: Irrational Real Functions
- `matlab`: MAT-File Format
- `metric-units`: Metric Units
- `minimize`: Minimizing
- minimum field width (`printf`): Standard Formatted Output
- `MIT Scheme`: Installation
- mkimpcat.scm: Catalog Vicinities
- mklibcat.scm: Catalog Vicinities
- `modular`: Modular Arithmetic
- `multiarg`: Multi-argument / and -
- `multiarg-apply`: Multi-argument Apply
- `MzScheme`: Installation
- `nary`: Rule Types
- `ncbi-dma`: NCBI-DNA
- new-catalog: Catalog Creation
- `nofix`: Rule Types
- null: HTML Tables
- Null Denotation, nud: Nud and Led Definition
- `object`: Object
- `object->string`: Object-To-String
- `oop`: Yasos
- option, run-time-loadable: Weight-Balanced Trees
- options file: Command Line
- `parameters`: Command Example
- `parameters`: Batch
- `parameters`: Parameter lists
- `parse`: Precedence Parsing
- pbm: Portable Image Files
- pbm-raw: Portable Image Files
- `peano-fill`: Peano Space-Filling Curve
- pgm: Portable Image Files
- pgm-raw: Portable Image Files
- plain-text: HTML
- `PLT Scheme`: Installation
- `pnm`: Portable Image Files
- portable bitmap graphics: Portable Image Files
- `posix-time`: Posix Time
- `postfix`: Rule Types
- ppm: Portable Image Files
- ppm-raw: Portable Image Files
- `pprint-file`: Pretty-Print
- PRE: HTML
- `precedence`: Precedence Parsing
- precision (`printf`): Standard Formatted Output
- `prefix`: Rule Types
- `prestfix`: Rule Types
- `pretty-print`: Pretty-Print
- `primes`: Prime Numbers
- `printf`: Standard Formatted Output
- `priority-queue`: Priority Queues
- PRNG: Random Numbers
- `process`: Multi-Processing
- `program-arguments`: System Interface
- `program-arguments`: Getopt
- Prolog: Extra-SLIB Packages
- `promise`: Promises
- PSD: Extra-SLIB Packages
- `qp`: Quick Print
- `qp`: Getopt
- query-string: HTTP and CGI
- `queue`: Queues
- `r2rs`: RnRS
- `r3rs`: Coding Guidelines
- `r3rs`: RnRS
- `r4rs`: RnRS
- `r5rs`: RnRS
- `random`: Exact Random Numbers
- `random-inexact`: Inexact Random Numbers
- range: Column Ranges
- `rational`: Feature
- `rationalize`: Rationalize
- `read-command`: Command Line
- `real`: Feature
- `receive`: Binding to multiple values
- `record`: Records
- rectangle: Rectangles
- `relational-database`: Relational Database
- relational-system: Using Databases
- `repl`: Repl
- `repl`: Syntax-Case Macros
- `resene`: Color Names
- Resene: Color Names
- reset: HTML
- `rev2-procedures`: Rev2 Procedures
- `rev4-optional-procedures`: Rev4 Optional Procedures
- `RGB709`: Color Spaces
- ring, commutative: Commutative Rings
- RNG: Random Numbers
- `root`: Root Finding
- run-time-loadable option: Weight-Balanced Trees
- `rwb-isam`: Base Table
- saturate: Color Names
- `scanf`: Standard Formatted Input
- SCHELOG: Extra-SLIB Packages
- scheme: URI
- Scheme Request For Implementation: SRFI
- `Scheme48`: Installation
- schmooz: Schmooz
- `SCM`: Installation
- script: Installation
- self-set: Commutative Rings
- Sequence Comparison: Sequence Comparison
- Server-based Naming Authority: URI
- session: Feature
- sets, using binary trees: Weight-Balanced Trees
- shell: Command Line
- `sierpinski`: Sierpinski Curve
- `SISC`: Installation
- sitecat: Catalog Vicinities
- `sky`: Daylight
- slib: Installation
- slibcat: Catalog Vicinities
- `solid`: Solid Modeling
- `solid-modeling`: Solid Modeling
- `solids`: Solid Modeling
- `sort`: Sorting
- `soundex`: Soundex
- source: Library Catalogs
- Space-Filling: Hilbert Space-Filling Curve
- sparse: MAT-File Format
- Spectral Tristimulus Values: Spectra
- spiff: Sequence Comparison
- `srfi`: SRFI
- SRFI-1: SRFI-1
- `srfi-1`: SRFI-1
- `srfi-11`: SRFI
- `srfi-11`: Binding to multiple values
- `srfi-2`: SRFI
- `srfi-2`: Guarded LET* special form
- `srfi-23`: SRFI
- `srfi-28`: SRFI
- `srfi-47`: SRFI
- `srfi-59`: SRFI
- `srfi-60`: SRFI
- `srfi-60`: Bit-Twiddling
- `srfi-61`: SRFI
- `srfi-61`: Guarded COND Clause
- `srfi-63`: SRFI
- `srfi-8`: SRFI
- `srfi-8`: Binding to multiple values
- `srfi-9`: SRFI
- `srfi-9`: Define-Record-Type
- `srfi-94`: SRFI
- `srfi-95`: SRFI
- `srfi-95`: Sorting
- `srfi-96`: SRFI
- `sRGB`: Color Spaces
- `stdio`: Standard Formatted I/O
- `string-case`: String-Case
- `string-port`: String Ports
- `string-search`: String Search
- `subarray`: Subarrays
- `sun`: Daylight
- `sunlight`: Daylight
- symmetric: Modular Arithmetic
- `syntactic-closures`: Syntactic Closures
- syntactic-closures: Library Catalogs
- syntax tree: Precedence Parsing Overview
- `syntax-case`: Syntax-Case Macros
- syntax-case: Library Catalogs
- `system`: System Interface
- time: Time and Date
- `time-zone`: Time Zone
- top-level variable references: Top-level Variable References
- `top-refs`: Top-level Variable References
- `topological-sort`: Topological Sort
- `trace`: Trace
- `transact`: Transactions
- `transcript`: Transcripts
- `tree`: Tree Operations
- trees, balanced binary: Weight-Balanced Trees
- tristimulus: Color Spaces
- `tsort`: Topological Sort
- turbidity: Daylight
- `TZ-string`: Time Zone
- Uniform Resource Identifiers: URI
- Uniform Resource Locator: URI
- Unique Factorization: Commutative Rings
- unsafe: URI
- URI: URI
- `uri`: URI
- URI: HTTP and CGI
- usercat: Catalog Vicinities
- UTC: Posix Time
- `values`: Values
- variable references: Top-level Variable References
- `vet`: Module Analysis
- `VSCM`: Installation
- WB: Base Table
- `wb-table`: Base Table
- weight-balanced binary trees: Weight-Balanced Trees
- wget: Color Names
- white point: Color Data-Type
- wild-card: Match Keys
- `with-file`: With-File
- Word: Transactions
- `wt-tree`: Weight-Balanced Trees
- `xRGB`: Color Spaces
- xyY: Spectra
- `yasos`: Yasos

#### Footnotes

[1] scheme-implementation-type is the name symbol of the running Scheme implementation (RScheme, |STk|, Bigloo, chez, Elk, gambit, guile, JScheme, kawa, MacScheme, MITScheme, Pocket-Scheme, Scheme48, Scheme->C, Scheme48, Scsh, SISC, T, umb-scheme, or Vscm). Dependence on scheme-implementation-type is almost always the wrong way to do things.

[2] There are some functions with internal `require` calls to delay loading modules until they are needed. While this reduces startup latency for interpreters, it can produce headaches for compilers.

[3] Although it will work on large info files, feeding it an excerpt is much faster; and has less chance of being confused by unusual text in the info file. This command excerpts the SLIB index into `slib-index.info`:

         info -f slib2d6.info -n "Index" -o slib-index.info

[4] How do I know this? I parsed 250kbyte of random input (an e-mail file) with a non-trivial grammar utilizing all constructs.

[5] Readers may recognize these color string formats from Xlib. X11's color management system was doomed by its fiction that CRT monitors' (and X11 default) color-spaces were linear RGBi. Unable to shed this legacy, the only practical way to view pictures on X is to ignore its color management system and use an sRGB monitor. In this implementation the device-independent RGB709 and sRGB spaces replace the device-dependent RGBi and RGB spaces of Xlib.

[6] A comprehensive encoding of transforms between CIEXYZ and device color spaces is the International Color Consortium profile format, ICC.1:1998-09:

> The intent of this format is to provide a cross-platform device profile format. Such device profiles can be used to translate color data created on one device into another device's native color space.

[7] David Kahaner, Cleve Moler, and Stephen Nash Numerical Methods and Software Prentice-Hall, 1989, ISBN 0-13-627258-4

[8] If you are porting a Revised^3 Report on the Algorithmic Language Scheme implementation, then you will need to finish writing `sc4sc3.scm` and `load` it from your initialization file.