;;; cal-mayan.el --- calendar functions for the Mayan calendars. ;; Copyright (C) 1992 Free Software Foundation, Inc. ;; Author: Stewart M. Clamen ;; Edward M. Reingold ;; Keywords: calendar ;; Human-Keywords: Mayan calendar, Maya, calendar, diary ;; This file is part of GNU Emacs. ;; GNU Emacs is distributed in the hope that it will be useful, ;; but WITHOUT ANY WARRANTY. No author or distributor ;; accepts responsibility to anyone for the consequences of using it ;; or for whether it serves any particular purpose or works at all, ;; unless he says so in writing. Refer to the GNU Emacs General Public ;; License for full details. ;; Everyone is granted permission to copy, modify and redistribute ;; GNU Emacs, but only under the conditions described in the ;; GNU Emacs General Public License. A copy of this license is ;; supposed to have been given to you along with GNU Emacs so you ;; can know your rights and responsibilities. It should be in a ;; file named COPYING. Among other things, the copyright notice ;; and this notice must be preserved on all copies. ;;; Commentary: ;; This collection of functions implements the features of calendar.el and ;; diary.el that deal with the Mayan calendar. It was written jointly by ;; Stewart M. Clamen School of Computer Science ;; clamen@cs.cmu.edu Carnegie Mellon University ;; 5000 Forbes Avenue ;; Pittsburgh, PA 15213 ;; and ;; Edward M. Reingold Department of Computer Science ;; (217) 333-6733 University of Illinois at Urbana-Champaign ;; reingold@cs.uiuc.edu 1304 West Springfield Avenue ;; Urbana, Illinois 61801 ;; Comments, improvements, and bug reports should be sent to Reingold. ;; Technical details of the Mayan calendrical calculations can be found in ;; ``Calendrical Calculations, Part II: Three Historical Calendars'' ;; by E. M. Reingold, N. Dershowitz, and S. M. Clamen, ;; Software--Practice and Experience, Volume 23, Number 4 (April, 1993), ;; pages 383-404. ;;; Code: (require 'calendar) (defun mayan-adjusted-mod (m n) "Non-negative remainder of M/N with N instead of 0." (1+ (mod (1- m) n))) (defconst calendar-mayan-days-before-absolute-zero 1137140 "Number of days of the Mayan calendar epoch before absolute day 0. According to the Goodman-Martinez-Thompson correlation. This correlation is not universally accepted, as it still a subject of astro-archeological research. Using 1232041 will give you the correlation used by Spinden.") (defconst calendar-mayan-haab-at-epoch '(8 . 18) "Mayan haab date at the epoch.") (defconst calendar-mayan-haab-month-name-array ["Pop" "Uo" "Zip" "Zotz" "Tzec" "Xul" "Yaxkin" "Mol" "Chen" "Yax" "Zac" "Ceh" "Mac" "Kankin" "Muan" "Pax" "Kayab" "Cumku"]) (defconst calendar-mayan-tzolkin-at-epoch '(4 . 20) "Mayan tzolkin date at the epoch.") (defconst calendar-mayan-tzolkin-names-array ["Imix" "Ik" "Akbal" "Kan" "Chicchan" "Cimi" "Manik" "Lamat" "Muluc" "Oc" "Chuen" "Eb" "Ben" "Ix" "Men" "Cib" "Caban" "Etznab" "Cauac" "Ahau"]) (defun calendar-mayan-long-count-from-absolute (date) "Compute the Mayan long count corresponding to the absolute DATE." (let ((long-count (+ date calendar-mayan-days-before-absolute-zero))) (let* ((baktun (/ long-count 144000)) (remainder (% long-count 144000)) (katun (/ remainder 7200)) (remainder (% remainder 7200)) (tun (/ remainder 360)) (remainder (% remainder 360)) (uinal (/ remainder 20)) (kin (% remainder 20))) (list baktun katun tun uinal kin)))) (defun calendar-mayan-long-count-to-string (mayan-long-count) "Convert MAYAN-LONG-COUNT into traditional written form." (apply 'format (cons "%s.%s.%s.%s.%s" mayan-long-count))) (defun calendar-string-to-mayan-long-count (str) "Given STR, a string of format \"%d.%d.%d.%d.%d\", return list of nums." (let ((rlc nil) (c (length str)) (cc 0)) (condition-case condition (progn (while (< cc c) (let ((datum (read-from-string str cc))) (if (not (integerp (car datum))) (signal 'invalid-read-syntax (car datum)) (setq rlc (cons (car datum) rlc)) (setq cc (cdr datum))))) (if (not (= (length rlc) 5)) (signal 'invalid-read-syntax nil))) (invalid-read-syntax nil)) (reverse rlc))) (defun calendar-mayan-haab-from-absolute (date) "Convert absolute DATE into a Mayan haab date (a pair)." (let* ((long-count (+ date calendar-mayan-days-before-absolute-zero)) (day-of-haab (% (+ long-count (car calendar-mayan-haab-at-epoch) (* 20 (1- (cdr calendar-mayan-haab-at-epoch)))) 365)) (day (% day-of-haab 20)) (month (1+ (/ day-of-haab 20)))) (cons day month))) (defun calendar-mayan-haab-difference (date1 date2) "Number of days from Mayan haab DATE1 to next occurrence of haab date DATE2." (mod (+ (* 20 (- (cdr date2) (cdr date1))) (- (car date2) (car date1))) 365)) (defun calendar-mayan-haab-on-or-before (haab-date date) "Absolute date of latest HAAB-DATE on or before absolute DATE." (- date (% (- date (calendar-mayan-haab-difference (calendar-mayan-haab-from-absolute 0) haab-date)) 365))) (defun calendar-next-haab-date (haab-date &optional noecho) "Move cursor to next instance of Mayan HAAB-DATE. Echo Mayan date if NOECHO is t." (interactive (list (calendar-read-mayan-haab-date))) (calendar-goto-date (calendar-gregorian-from-absolute (calendar-mayan-haab-on-or-before haab-date (+ 365 (calendar-absolute-from-gregorian (calendar-cursor-to-date)))))) (or noecho (calendar-print-mayan-date))) (defun calendar-previous-haab-date (haab-date &optional noecho) "Move cursor to previous instance of Mayan HAAB-DATE. Echo Mayan date if NOECHO is t." (interactive (list (calendar-read-mayan-haab-date))) (calendar-goto-date (calendar-gregorian-from-absolute (calendar-mayan-haab-on-or-before haab-date (1- (calendar-absolute-from-gregorian (calendar-cursor-to-date)))))) (or noecho (calendar-print-mayan-date))) (defun calendar-mayan-haab-to-string (haab) "Convert Mayan haab date (a pair) into its traditional written form." (let ((month (cdr haab)) (day (car haab))) ;; 19th month consists of 5 special days (if (= month 19) (format "%d Uayeb" day) (format "%d %s" day (aref calendar-mayan-haab-month-name-array (1- month)))))) (defun calendar-mayan-tzolkin-from-absolute (date) "Convert absolute DATE into a Mayan tzolkin date (a pair)." (let* ((long-count (+ date calendar-mayan-days-before-absolute-zero)) (day (mayan-adjusted-mod (+ long-count (car calendar-mayan-tzolkin-at-epoch)) 13)) (name (mayan-adjusted-mod (+ long-count (cdr calendar-mayan-tzolkin-at-epoch)) 20))) (cons day name))) (defun calendar-mayan-tzolkin-difference (date1 date2) "Number of days from Mayan tzolkin DATE1 to next occurrence of tzolkin DATE2." (let ((number-difference (- (car date2) (car date1))) (name-difference (- (cdr date2) (cdr date1)))) (mod (+ number-difference (* 13 (mod (* 3 (- number-difference name-difference)) 20))) 260))) (defun calendar-mayan-tzolkin-on-or-before (tzolkin-date date) "Absolute date of latest TZOLKIN-DATE on or before absolute DATE." (- date (% (- date (calendar-mayan-tzolkin-difference (calendar-mayan-tzolkin-from-absolute 0) tzolkin-date)) 260))) (defun calendar-next-tzolkin-date (tzolkin-date &optional noecho) "Move cursor to next instance of Mayan TZOLKIN-DATE. Echo Mayan date if NOECHO is t." (interactive (list (calendar-read-mayan-tzolkin-date))) (calendar-goto-date (calendar-gregorian-from-absolute (calendar-mayan-tzolkin-on-or-before tzolkin-date (+ 260 (calendar-absolute-from-gregorian (calendar-cursor-to-date)))))) (or noecho (calendar-print-mayan-date))) (defun calendar-previous-tzolkin-date (tzolkin-date &optional noecho) "Move cursor to previous instance of Mayan TZOLKIN-DATE. Echo Mayan date if NOECHO is t." (interactive (list (calendar-read-mayan-tzolkin-date))) (calendar-goto-date (calendar-gregorian-from-absolute (calendar-mayan-tzolkin-on-or-before tzolkin-date (1- (calendar-absolute-from-gregorian (calendar-cursor-to-date)))))) (or noecho (calendar-print-mayan-date))) (defun calendar-mayan-tzolkin-to-string (tzolkin) "Convert Mayan tzolkin date (a pair) into its traditional written form." (format "%d %s" (car tzolkin) (aref calendar-mayan-tzolkin-names-array (1- (cdr tzolkin))))) (defun calendar-mayan-tzolkin-haab-on-or-before (tzolkin-date haab-date date) "Absolute date that is Mayan TZOLKIN-DATE and HAAB-DATE. Latest such date on or before DATE. Returns nil if such a tzolkin-haab combination is impossible." (let* ((haab-difference (calendar-mayan-haab-difference (calendar-mayan-haab-from-absolute 0) haab-date)) (tzolkin-difference (calendar-mayan-tzolkin-difference (calendar-mayan-tzolkin-from-absolute 0) tzolkin-date)) (difference (- tzolkin-difference haab-difference))) (if (= (% difference 5) 0) (- date (mod (- date (+ haab-difference (* 365 difference))) 18980)) nil))) (defun calendar-read-mayan-haab-date () "Prompt for a Mayan haab date" (let* ((completion-ignore-case t) (haab-day (calendar-read "Haab kin (0-19): " '(lambda (x) (and (>= x 0) (< x 20))))) (haab-month-list (append calendar-mayan-haab-month-name-array (and (< haab-day 5) '("Uayeb")))) (haab-month (cdr (assoc (capitalize (completing-read "Haab uinal: " (mapcar 'list haab-month-list) nil t)) (calendar-make-alist haab-month-list 1 'capitalize))))) (cons haab-day haab-month))) (defun calendar-read-mayan-tzolkin-date () "Prompt for a Mayan tzolkin date" (let* ((completion-ignore-case t) (tzolkin-count (calendar-read "Tzolkin kin (1-13): " '(lambda (x) (and (> x 0) (< x 14))))) (tzolkin-name-list (append calendar-mayan-tzolkin-names-array nil)) (tzolkin-name (cdr (assoc (capitalize (completing-read "Tzolkin uinal: " (mapcar 'list tzolkin-name-list) nil t)) (calendar-make-alist tzolkin-name-list 1 'capitalize))))) (cons tzolkin-count tzolkin-name))) (defun calendar-next-calendar-round-date (tzolkin-date haab-date &optional noecho) "Move cursor to next instance of Mayan HAAB-DATE TZOKLIN-DATE combination. Echo Mayan date if NOECHO is t." (interactive (list (calendar-read-mayan-tzolkin-date) (calendar-read-mayan-haab-date))) (let ((date (calendar-mayan-tzolkin-haab-on-or-before tzolkin-date haab-date (+ 18980 (calendar-absolute-from-gregorian (calendar-cursor-to-date)))))) (if (not date) (error "%s, %s does not exist in the Mayan calendar round" (calendar-mayan-tzolkin-to-string tzolkin-date) (calendar-mayan-haab-to-string haab-date)) (calendar-goto-date (calendar-gregorian-from-absolute date)) (or noecho (calendar-print-mayan-date))))) (defun calendar-previous-calendar-round-date (tzolkin-date haab-date &optional noecho) "Move to previous instance of Mayan TZOKLIN-DATE HAAB-DATE combination. Echo Mayan date if NOECHO is t." (interactive (list (calendar-read-mayan-tzolkin-date) (calendar-read-mayan-haab-date))) (let ((date (calendar-mayan-tzolkin-haab-on-or-before tzolkin-date haab-date (1- (calendar-absolute-from-gregorian (calendar-cursor-to-date)))))) (if (not date) (error "%s, %s does not exist in the Mayan calendar round" (calendar-mayan-tzolkin-to-string tzolkin-date) (calendar-mayan-haab-to-string haab-date)) (calendar-goto-date (calendar-gregorian-from-absolute date)) (or noecho (calendar-print-mayan-date))))) (defun calendar-absolute-from-mayan-long-count (c) "Compute the absolute date corresponding to the Mayan Long Count C. Long count is a list (baktun katun tun uinal kin)" (+ (* (nth 0 c) 144000) ; baktun (* (nth 1 c) 7200) ; katun (* (nth 2 c) 360) ; tun (* (nth 3 c) 20) ; uinal (nth 4 c) ; kin (days) (- ; days before absolute date 0 calendar-mayan-days-before-absolute-zero))) (defun calendar-print-mayan-date () "Show the Mayan long count, tzolkin, and haab equivalents of date." (interactive) (let* ((d (calendar-absolute-from-gregorian (or (calendar-cursor-to-date) (error "Cursor is not on a date!")))) (tzolkin (calendar-mayan-tzolkin-from-absolute d)) (haab (calendar-mayan-haab-from-absolute d)) (long-count (calendar-mayan-long-count-from-absolute d))) (message "Mayan date: Long count = %s; tzolkin = %s; haab = %s" (calendar-mayan-long-count-to-string long-count) (calendar-mayan-tzolkin-to-string tzolkin) (calendar-mayan-haab-to-string haab)))) (defun calendar-goto-mayan-long-count-date (date &optional noecho) "Move cursor to Mayan long count DATE. Echo Mayan date unless NOECHO is t." (interactive (let (lc) (while (not lc) (let ((datum (calendar-string-to-mayan-long-count (read-string "Mayan long count (baktun.katun.tun.uinal.kin): " (calendar-mayan-long-count-to-string (calendar-mayan-long-count-from-absolute (calendar-absolute-from-gregorian (calendar-current-date)))))))) (if (calendar-mayan-long-count-common-era datum) (setq lc datum)))) (list lc))) (calendar-goto-date (calendar-gregorian-from-absolute (calendar-absolute-from-mayan-long-count date))) (or noecho (calendar-print-mayan-date))) (defun calendar-mayan-long-count-common-era (lc) "T if long count represents date in the Common Era." (let ((base (calendar-mayan-long-count-from-absolute 1))) (while (and (not (null base)) (= (car lc) (car base))) (setq lc (cdr lc) base (cdr base))) (or (null lc) (> (car lc) (car base))))) (defun diary-mayan-date () "Show the Mayan long count, haab, and tzolkin dates as a diary entry." (let* ((d (calendar-absolute-from-gregorian date)) (tzolkin (calendar-mayan-tzolkin-from-absolute d)) (haab (calendar-mayan-haab-from-absolute d)) (long-count (calendar-mayan-long-count-from-absolute d))) (format "Mayan date: Long count = %s; tzolkin = %s; haab = %s" (calendar-mayan-long-count-to-string long-count) (calendar-mayan-tzolkin-to-string haab) (calendar-mayan-haab-to-string tzolkin)))) (provide 'cal-mayan) ;;; cal-mayan.el ends here