ANY NONE
deferred class interface ABSTRACT_SORTER[X]
   --
   -- Some algorithms to sort any COLLECTION, using a given order relation
   -- in deferred methods lt, gt, lte and gte.
   --
   -- Elements are sorted using increasing order: small elements
   -- at the beginning of the collection, large at the end (decreasing
   -- order is implemented by class REVERSE_COLLECTION_SORTER). Note that
   -- "small" means "a is smaller than b" when "lt (a, b)", no matter what
   -- lt is.
   --
   --
   -- Some algorithms to sort any COLLECTION[COMPARABLE].
   --
   -- Elements are sorted using the order defined by lt.
   --

feature(s) from ABSTRACT_SORTER
   is_sorted (c: COLLECTION[X]): BOOLEAN
      -- Is c already sorted ?
      -- Uses lte for comparison.
      require
         c /= Void
      ensure
         c.is_equal(old c.twin)

   has (c: COLLECTION[X]; element: X): BOOLEAN
      require
         c /= Void;
         is_sorted(c)
      ensure
         Result = c.has(element)

   index_of (c: COLLECTION[X]; element: X): INTEGER
      require
         c /= Void;
         is_sorted(c)
      ensure
         not c.is_empty implies c.valid_index(Result);
         c.has(element) implies c.item(Result).is_equal(element)

   add (c: COLLECTION[X]; element: X)
      -- Add element in collection c keeping the sorted property.
      require
         c /= Void;
         is_sorted(c)
      ensure
         c.count = old c.count + 1;
         is_sorted(c)

   insert_index (c: COLLECTION[X]; element: X): INTEGER
      -- retrieve the upper index for wich gt
      require
         c /= Void;
         is_sorted(c)
      ensure
         c.valid_index(Result) implies gt(c.item(Result),element);
         c.valid_index(Result - 1) implies lte(c.item(Result - 1),element);
         Result.in_range(c.lower,c.upper + 1)

   sort (c: COLLECTION[X])
      -- Sort c using the default most efficient sorting algorithm
      -- already implemented.
      require
         c /= Void
      ensure
         c.count = old c.count;
         is_sorted(c)

   quick_sort (c: COLLECTION[X])
      -- Sort c using the quick sort algorithm.
      require
         c /= Void
      ensure
         c.count = old c.count;
         is_sorted(c)

   von_neuman_sort (c: COLLECTION[X])
      -- Sort c using the Von Neuman algorithm.
      -- This algorithm needs to create a second collection.
      -- Uses infix "<=" for comparison.
      require
         c /= Void
      ensure
         c.count = old c.count;
         is_sorted(c)

   heap_sort (c: COLLECTION[X])
      -- Sort c using the heap sort algorithm.
      require
         c /= Void
      ensure
         c.count = old c.count;
         is_sorted(c)

   bubble_sort (c: COLLECTION[X])
      -- Sort c using the bubble sort algorithm.
      -- Uses infix "<" for comparison.
      require
         c /= Void
      ensure
         c.count = old c.count;
         is_sorted(c)



end of deferred ABSTRACT_SORTER[X]