89 lines
5.1 KiB
Ada
89 lines
5.1 KiB
Ada
------------------------------------------------------------------------------
|
|
-- --
|
|
-- GNAT RUN-TIME COMPONENTS --
|
|
-- --
|
|
-- G N A T . H E A P _ S O R T _ G --
|
|
-- --
|
|
-- S p e c --
|
|
-- --
|
|
-- Copyright (C) 1995-2010, 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 3, 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. --
|
|
-- --
|
|
-- As a special exception under Section 7 of GPL version 3, you are granted --
|
|
-- additional permissions described in the GCC Runtime Library Exception, --
|
|
-- version 3.1, as published by the Free Software Foundation. --
|
|
-- --
|
|
-- You should have received a copy of the GNU General Public License and --
|
|
-- a copy of the GCC Runtime Library Exception along with this program; --
|
|
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
|
|
-- <http://www.gnu.org/licenses/>. --
|
|
-- --
|
|
-- GNAT was originally developed by the GNAT team at New York University. --
|
|
-- Extensive contributions were provided by Ada Core Technologies Inc. --
|
|
-- --
|
|
------------------------------------------------------------------------------
|
|
|
|
-- Heapsort generic package using formal procedures
|
|
|
|
-- This package provides a generic heapsort routine that can be used with
|
|
-- different types of data.
|
|
|
|
-- See also GNAT.Heap_Sort, a version that works with subprogram access
|
|
-- parameters, allowing code sharing. The generic version is slightly more
|
|
-- efficient but does not allow code sharing and has an interface that is
|
|
-- more awkward to use.
|
|
|
|
-- There is also GNAT.Heap_Sort_A, which is now considered obsolete, but
|
|
-- was an older version working with subprogram parameters. This version
|
|
-- is retained for backwards compatibility with old versions of GNAT.
|
|
|
|
-- 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.
|
|
|
|
generic
|
|
-- 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. In addition, the
|
|
-- index value zero is used for a temporary location used during the sort.
|
|
|
|
with procedure Move (From : Natural; To : Natural);
|
|
-- A procedure that moves the data item with index value From to the data
|
|
-- item with index value To (the old value in To being lost). An index
|
|
-- value of zero is used for moves from and to a single temporary location.
|
|
-- For best efficiency, this routine should be marked as inlined.
|
|
|
|
with function Lt (Op1, Op2 : Natural) return Boolean;
|
|
-- A function that compares two items and returns True if the item with
|
|
-- index Op1 is less than the item with Index Op2, and False if the Op1
|
|
-- item is greater than the Op2 item. If the two items are equal, then
|
|
-- it does not matter whether True or False is returned (it is slightly
|
|
-- more efficient to return False). For best efficiency, this routine
|
|
-- should be marked as inlined.
|
|
|
|
-- Note on use of temporary location
|
|
|
|
-- There are two ways of providing for the index value zero to represent
|
|
-- a temporary value. Either an extra location can be allocated at the
|
|
-- start of the array, or alternatively the Move and Lt subprograms can
|
|
-- test for the case of zero and treat it specially. In any case it is
|
|
-- desirable to specify the two subprograms as inlined and the tests for
|
|
-- zero will in this case be resolved at instantiation time.
|
|
|
|
package GNAT.Heap_Sort_G is
|
|
pragma Pure;
|
|
|
|
procedure Sort (N : Natural);
|
|
-- This procedures sorts items in the range from 1 to N into ascending
|
|
-- order making calls to Lt to do required comparisons, and Move to move
|
|
-- items around. Note that, as described above, both Move and Lt use a
|
|
-- single temporary location with index value zero. This sort is not
|
|
-- stable, i.e. the order of equal elements in the input is not preserved.
|
|
|
|
end GNAT.Heap_Sort_G;
|