gcc/ada/libgnat/g-hesora.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   5 --                     G N A T . H E A P _ S O R T _ A                      --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --                     Copyright (C) 1995-2017, 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 --  Heapsort using access to procedure parameters
  33
  34 --  This package provides a heap sort routine that works with access to
  35 --  subprogram parameters, so that it can be used with different types with
  36 --  shared sorting code. It is considered obsoleted by GNAT.Heap_Sort which
  37 --  offers a similar routine with a more convenient interface.
  38
  39 --  This heapsort algorithm uses approximately N*log(N) compares in the
  40 --  worst case and is in place with no additional storage required. See
  41 --  the body for exact details of the algorithm used.
  42
  43 pragma Compiler_Unit_Warning;
  44
  45 package GNAT.Heap_Sort_A is
  46    pragma Preelaborate;
  47
  48    --  The data to be sorted is assumed to be indexed by integer values from
  49    --  1 to N, where N is the number of items to be sorted. In addition, the
  50    --  index value zero is used for a temporary location used during the sort.
  51
  52    type Move_Procedure is access procedure (From : Natural; To : Natural);
  53    --  A pointer to a procedure that moves the data item with index From to
  54    --  the data item with index To. An index value of zero is used for moves
  55    --  from and to the single temporary location used by the sort.
  56
  57    type Lt_Function is access function (Op1, Op2 : Natural) return Boolean;
  58    --  A pointer to a function that compares two items and returns True if
  59    --  the item with index Op1 is less than the item with index Op2, and False
  60    --  if the Op1 item is greater than or equal to the Op2 item.
  61
  62    procedure Sort (N : Natural; Move : Move_Procedure; Lt : Lt_Function);
  63    --  This procedures sorts items in the range from 1 to N into ascending
  64    --  order making calls to Lt to do required comparisons, and Move to move
  65    --  items around. Note that, as described above, both Move and Lt use a
  66    --  single temporary location with index value zero. This sort is not
  67    --  stable, i.e. the order of equal elements in the input is not preserved.
  68
  69 end GNAT.Heap_Sort_A;