gcc/ada/libgnat/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) 1995-2019, 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 --  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;