gcc/ada/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) 1995-2006, 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 ------------------------------------------------------------------------------
  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 --  This heapsort algorithm uses approximately N*log(N) compares in the
  41 --  worst case and is in place with no additional storage required. See
  42 --  the body for exact details of the algorithm used.
  43
  44 --  See also GNAT.Heap_Sort_G which is a generic version that will be faster
  45 --  since the overhead of the indirect calls is avoided, at the expense of
  46 --  generic code duplication and less convenient interface. The generic version
  47 --  also has the advantage of being Pure, while this unit can only be
  48 --  Preelaborate, because of the access types.
  49
  50 --  Note: GNAT.Heap_Sort replaces and obsoletes GNAT.Heap_Sort_A, which is
  51 --  retained in the GNAT library for backwards compatibility.
  52
  53 package GNAT.Heap_Sort is
  54    pragma Pure;
  55
  56    --  The data to be sorted is assumed to be indexed by integer values
  57    --  from 1 to N, where N is the number of items to be sorted.
  58
  59    type Xchg_Procedure is access procedure (Op1, Op2 : Natural);
  60    --  A pointer to a procedure that exchanges the two data items whose
  61    --  index values are Op1 and Op2.
  62
  63    type Lt_Function is access function (Op1, Op2 : Natural) return Boolean;
  64    --  A pointer to a function that compares two items and returns True if
  65    --  the item with index value Op1 is less than the item with Index value
  66    --  Op2, and False if the Op1 item is greater than the Op2 item. If
  67    --  the items are equal, then it does not matter if True or False is
  68    --  returned (but it is slightly more efficient to return False).
  69
  70    procedure Sort (N : Natural; Xchg : Xchg_Procedure; Lt : Lt_Function);
  71    --  This procedures sorts items in the range from 1 to N into ascending
  72    --  order making calls to Lt to do required comparisons, and calls to
  73    --  Xchg to exchange items. The sort is not stable, that is the order
  74    --  of equal items in the input data set is not preserved.
  75
  76 end GNAT.Heap_Sort;