1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT RUNTIME COMPONENTS                          --
4--                                                                          --
5--                       G N A T . H E A P _ S O R T                        --
6--                                                                          --
7--                                 S p e c                                  --
8--                                                                          --
9--           Copyright (C) 1995-2002 Ada Core Technologies, Inc.            --
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 2,  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.  See the GNU General Public License --
17-- for  more details.  You should have  received  a copy of the GNU General --
18-- Public License  distributed with GNAT;  see file COPYING.  If not, write --
19-- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
20-- MA 02111-1307, USA.                                                      --
21--                                                                          --
22-- As a special exception,  if other files  instantiate  generics from this --
23-- unit, or you link  this unit with other files  to produce an executable, --
24-- this  unit  does not  by itself cause  the resulting  executable  to  be --
25-- covered  by the  GNU  General  Public  License.  This exception does not --
26-- however invalidate  any other reasons why  the executable file  might be --
27-- covered by the  GNU Public License.                                      --
28--                                                                          --
29-- GNAT was originally developed  by the GNAT team at  New York University. --
30-- Extensive contributions were provided by Ada Core Technologies Inc.      --
31--                                                                          --
32------------------------------------------------------------------------------
33
34--  Sort utility (Using Heapsort Algorithm)
35
36--  This package provides a heapsort routine that works with access to
37--  subprogram parameters, so that it can be used with different types with
38--  shared sorting code.
39
40--  See also GNAT.Heap_Sort_G and GNAT.Heap_Sort_A. These are older versions
41--  of this routine. In some cases GNAT.Heap_Sort_G may be a little faster
42--  than GNAT.Heap_Sort, at the expense of generic code duplication and a
43--  less convenient interface. The generic version also has the advantage
44--  of being Pure, while this unit can only be Preelaborate.
45
46--  This heapsort algorithm uses approximately N*log(N) compares in the
47--  worst case and is in place with no additional storage required. See
48--  the body for exact details of the algorithm used.
49
50package GNAT.Heap_Sort is
51pragma Preelaborate (Heap_Sort);
52
53   --  The data to be sorted is assumed to be indexed by integer values
54   --  from 1 to N, where N is the number of items to be sorted.
55
56   type Xchg_Procedure is access procedure (Op1, Op2 : Natural);
57   --  A pointer to a procedure that exchanges the two data items whose
58   --  index values are Op1 and Op2.
59
60   type Lt_Function is access function (Op1, Op2 : Natural) return Boolean;
61   --  A pointer to a function that compares two items and returns True if
62   --  the item with index value Op1 is less than the item with Index value
63   --  Op2, and False if the Op1 item is greater than the Op2 item. If
64   --  the items are equal, then it does not matter if True or False is
65   --  returned (but it is slightly more efficient to return False).
66
67   procedure Sort (N : Natural; Xchg : Xchg_Procedure; Lt : Lt_Function);
68   --  This procedures sorts items in the range from 1 to N into ascending
69   --  order making calls to Lt to do required comparisons, and calls to
70   --  Xchg to exchange items. The sort is not stable, that is the order
71   --  of equal items in the input data set is not preserved.
72
73end GNAT.Heap_Sort;
74