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------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME COMPONENTS --
-- --
-- G N A T . H E A P _ S O R T --
-- --
-- S p e c --
-- --
-- Copyright (C) 1995-2005, AdaCore --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 2, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; see file COPYING. If not, write --
-- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
-- Boston, MA 02110-1301, USA. --
-- --
-- As a special exception, if other files instantiate generics from this --
-- unit, or you link this unit with other files to produce an executable, --
-- this unit does not by itself cause the resulting executable to be --
-- covered by the GNU General Public License. This exception does not --
-- however invalidate any other reasons why the executable file might be --
-- covered by the GNU Public License. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
-- Sort utility (Using Heapsort Algorithm)
-- This package provides a heapsort routine that works with access to
-- subprogram parameters, so that it can be used with different types with
-- shared sorting code.
-- See also GNAT.Heap_Sort_G and GNAT.Heap_Sort_A. These are older versions
-- of this routine. In some cases GNAT.Heap_Sort_G may be a little faster
-- than GNAT.Heap_Sort, at the expense of generic code duplication and a
-- less convenient interface. The generic version also has the advantage
-- of being Pure, while this unit can only be Preelaborate.
-- This heapsort algorithm uses approximately N*log(N) compares in the
-- worst case and is in place with no additional storage required. See
-- the body for exact details of the algorithm used.
package GNAT.Heap_Sort is
pragma Preelaborate;
-- The data to be sorted is assumed to be indexed by integer values
-- from 1 to N, where N is the number of items to be sorted.
type Xchg_Procedure is access procedure (Op1, Op2 : Natural);
-- A pointer to a procedure that exchanges the two data items whose
-- index values are Op1 and Op2.
type Lt_Function is access function (Op1, Op2 : Natural) return Boolean;
-- A pointer to a function that compares two items and returns True if
-- the item with index value Op1 is less than the item with Index value
-- Op2, and False if the Op1 item is greater than the Op2 item. If
-- the items are equal, then it does not matter if True or False is
-- returned (but it is slightly more efficient to return False).
procedure Sort (N : Natural; Xchg : Xchg_Procedure; Lt : Lt_Function);
-- This procedures sorts items in the range from 1 to N into ascending
-- order making calls to Lt to do required comparisons, and calls to
-- Xchg to exchange items. The sort is not stable, that is the order
-- of equal items in the input data set is not preserved.
end GNAT.Heap_Sort;
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