File : g-heasor.ads
1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT RUN-TIME 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) 1995-2010, 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 -- --
19 -- --
20 -- --
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 -- Sort utility (Using Heapsort Algorithm)
33
34 -- This package provides a heapsort routine that works with access to
35 -- subprogram parameters, so that it can be used with different types with
36 -- shared sorting code.
37
38 -- This heapsort algorithm uses approximately N*log(N) compares in the
39 -- worst case and is in place with no additional storage required. See
40 -- the body for exact details of the algorithm used.
41
42 -- See also GNAT.Heap_Sort_G which is a generic version that will be faster
43 -- since the overhead of the indirect calls is avoided, at the expense of
44 -- generic code duplication and less convenient interface.
45
46 -- Note: GNAT.Heap_Sort replaces and obsoletes GNAT.Heap_Sort_A, which is
47 -- retained in the GNAT library for backwards compatibility.
48
49 package GNAT.Heap_Sort is
50 pragma Pure;
51
52 -- The data to be sorted is assumed to be indexed by integer values
53 -- from 1 to N, where N is the number of items to be sorted.
54
55 type Xchg_Procedure is access procedure (Op1, Op2 : Natural);
56 -- A pointer to a procedure that exchanges the two data items whose
57 -- index values are Op1 and Op2.
58
59 type Lt_Function is access function (Op1, Op2 : Natural) return Boolean;
60 -- A pointer to a function that compares two items and returns True if
61 -- the item with index value Op1 is less than the item with Index value
62 -- Op2, and False if the Op1 item is greater than the Op2 item. If
63 -- the items are equal, then it does not matter if True or False is
64 -- returned (but it is slightly more efficient to return False).
65
66 procedure Sort (N : Natural; Xchg : Xchg_Procedure; Lt : Lt_Function);
67 -- This procedures sorts items in the range from 1 to N into ascending
68 -- order making calls to Lt to do required comparisons, and calls to
69 -- Xchg to exchange items. The sort is not stable, that is the order
70 -- of equal items in the input data set is not preserved.
71
72 end GNAT.Heap_Sort;