------------------------------------------------------------------------------
-- --
--- GNAT RUNTIME COMPONENTS --
+-- GNAT RUN-TIME COMPONENTS --
-- --
-- G N A T . H E A P _ S O R T _ G --
-- --
-- S p e c --
-- --
--- $Revision: 1.6 $
--- --
--- Copyright (C) 1995-2000 Ada Core Technologies, Inc. --
+-- Copyright (C) 1995-2006, 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- --
-- 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, 59 Temple Place - Suite 330, Boston, --
--- MA 02111-1307, USA. --
+-- 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, --
-- however invalidate any other reasons why the executable file might be --
-- covered by the GNU Public License. --
-- --
--- GNAT is maintained by Ada Core Technologies Inc (http://www.gnat.com). --
+-- 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, a version that works
--- with subprogram parameters, allowing code sharing. The generic version
--- is slightly more efficient but does not allow code sharing. The generic
--- version is also Pure, while the access version can only be Preelaborate.
+-- 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
-- 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 From to the data item
- -- with Index To. An index value of zero is used for moves from and to a
- -- single temporary location used by the sort.
+ -- 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 or equal to the Op2 item.
+ -- 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 (Heap_Sort_G);
+ pragma Pure;
procedure Sort (N : Natural);
-- This procedures sorts items in the range from 1 to N into ascending
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