1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT RUN-TIME COMPONENTS                         --
4--                                                                          --
5--                     G N A T . H E A P _ S O R T _ A                      --
6--                                                                          --
7--                                 S p e c                                  --
8--                                                                          --
9--                     Copyright (C) 1995-2013, AdaCore                     --
10--                                                                          --
11-- GNAT is free software;  you can  redistribute it  and/or modify it under --
12-- terms of the  GNU General Public License as published  by the Free Soft- --
13-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
14-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
15-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
16-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
17--                                                                          --
18-- As a special exception under Section 7 of GPL version 3, you are granted --
19-- additional permissions described in the GCC Runtime Library Exception,   --
20-- version 3.1, as published by the Free Software Foundation.               --
21--                                                                          --
22-- You should have received a copy of the GNU General Public License and    --
23-- a copy of the GCC Runtime Library Exception along with this program;     --
24-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
25-- <http://www.gnu.org/licenses/>.                                          --
26--                                                                          --
27-- GNAT was originally developed  by the GNAT team at  New York University. --
28-- Extensive contributions were provided by Ada Core Technologies Inc.      --
29--                                                                          --
30------------------------------------------------------------------------------
31
32--  Heapsort using access to procedure parameters
33
34--  This package provides a heap sort routine that works with access to
35--  subprogram parameters, so that it can be used with different types with
36--  shared sorting code. It is considered obsoleted by GNAT.Heap_Sort which
37--  offers a similar routine with a more convenient interface.
38
39--  This heapsort algorithm uses approximately N*log(N) compares in the
40--  worst case and is in place with no additional storage required. See
41--  the body for exact details of the algorithm used.
42
43pragma Compiler_Unit_Warning;
44
45package GNAT.Heap_Sort_A is
46   pragma Preelaborate;
47
48   --  The data to be sorted is assumed to be indexed by integer values from
49   --  1 to N, where N is the number of items to be sorted. In addition, the
50   --  index value zero is used for a temporary location used during the sort.
51
52   type Move_Procedure is access procedure (From : Natural; To : Natural);
53   --  A pointer to a procedure that moves the data item with index From to
54   --  the data item with index To. An index value of zero is used for moves
55   --  from and to the single temporary location used by the sort.
56
57   type Lt_Function is access function (Op1, Op2 : Natural) return Boolean;
58   --  A pointer to a function that compares two items and returns True if
59   --  the item with index Op1 is less than the item with index Op2, and False
60   --  if the Op1 item is greater than or equal to the Op2 item.
61
62   procedure Sort (N : Natural; Move : Move_Procedure; Lt : Lt_Function);
63   --  This procedures sorts items in the range from 1 to N into ascending
64   --  order making calls to Lt to do required comparisons, and Move to move
65   --  items around. Note that, as described above, both Move and Lt use a
66   --  single temporary location with index value zero. This sort is not
67   --  stable, i.e. the order of equal elements in the input is not preserved.
68
69end GNAT.Heap_Sort_A;
70