Merge from mainline (167278:168000).
[official-gcc/graphite-test-results.git] / gcc / ada / g-hesorg.ads
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1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT RUN-TIME COMPONENTS --
4 -- --
5 -- G N A T . H E A P _ S O R T _ G --
6 -- --
7 -- S p e c --
8 -- --
9 -- Copyright (C) 1995-2006, 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 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, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, 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 ------------------------------------------------------------------------------
34 -- Heapsort generic package using formal procedures
36 -- This package provides a generic heapsort routine that can be used with
37 -- different types of data.
39 -- See also GNAT.Heap_Sort, a version that works with subprogram access
40 -- parameters, allowing code sharing. The generic version is slightly more
41 -- efficient but does not allow code sharing and has an interface that is
42 -- more awkward to use.
44 -- There is also GNAT.Heap_Sort_A, which is now considered obsolete, but
45 -- was an older version working with subprogram parameters. This version
46 -- is retained for backwards compatibility with old versions of GNAT.
48 -- This heapsort algorithm uses approximately N*log(N) compares in the
49 -- worst case and is in place with no additional storage required. See
50 -- the body for exact details of the algorithm used.
52 generic
53 -- The data to be sorted is assumed to be indexed by integer values from
54 -- 1 to N, where N is the number of items to be sorted. In addition, the
55 -- index value zero is used for a temporary location used during the sort.
57 with procedure Move (From : Natural; To : Natural);
58 -- A procedure that moves the data item with index value From to the data
59 -- item with index value To (the old value in To being lost). An index
60 -- value of zero is used for moves from and to a single temporary location.
61 -- For best efficiency, this routine should be marked as inlined.
63 with function Lt (Op1, Op2 : Natural) return Boolean;
64 -- A function that compares two items and returns True if the item with
65 -- index Op1 is less than the item with Index Op2, and False if the Op1
66 -- item is greater than the Op2 item. If the two items are equal, then
67 -- it does not matter whether True or False is returned (it is slightly
68 -- more efficient to return False). For best efficiency, this routine
69 -- should be marked as inlined.
71 -- Note on use of temporary location
73 -- There are two ways of providing for the index value zero to represent
74 -- a temporary value. Either an extra location can be allocated at the
75 -- start of the array, or alternatively the Move and Lt subprograms can
76 -- test for the case of zero and treat it specially. In any case it is
77 -- desirable to specify the two subprograms as inlined and the tests for
78 -- zero will in this case be resolved at instantiation time.
80 package GNAT.Heap_Sort_G is
81 pragma Pure;
83 procedure Sort (N : Natural);
84 -- This procedures sorts items in the range from 1 to N into ascending
85 -- order making calls to Lt to do required comparisons, and Move to move
86 -- items around. Note that, as described above, both Move and Lt use a
87 -- single temporary location with index value zero. This sort is not
88 -- stable, i.e. the order of equal elements in the input is not preserved.
90 end GNAT.Heap_Sort_G;