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--                                                                          --

--                         GNAT RUN-TIME COMPONENTS                         --

--                                                                          --

--                     G N A T . H E A P _ S O R T _ A                      --

--                                                                          --

--                                 S p e c                                  --

--                                                                          --

--                     Copyright (C) 1995-2008, AdaCore                     --

--                                                                          --

-- GNAT is free software;  you can  redistribute it  and/or modify it under --

-- terms of the  GNU General Public License as published  by the Free Soft- --

-- ware  Foundation;  either version 2,  or (at your option) any later ver- --

-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --

-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --

-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --

-- for  more details.  You should have  received  a copy of the GNU General --

-- Public License  distributed with GNAT;  see file COPYING.  If not, write --

-- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --

-- Boston, MA 02110-1301, USA.                                              --

--                                                                          --

-- As a special exception,  if other files  instantiate  generics from this --

-- unit, or you link  this unit with other files  to produce an executable, --

-- this  unit  does not  by itself cause  the resulting  executable  to  be --

-- covered  by the  GNU  General  Public  License.  This exception does not --

-- however invalidate  any other reasons why  the executable file  might be --

-- covered by the  GNU Public License.                                      --

--                                                                          --

-- GNAT was originally developed  by the GNAT team at  New York University. --

-- Extensive contributions were provided by Ada Core Technologies Inc.      --

--                                                                          --

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--  Heapsort using access to procedure parameters

--  This package provides a heap sort routine that works with access to

--  subprogram parameters, so that it can be used with different types with

--  shared sorting code. It is considered obsoleted by GNAT.Heap_Sort which

--  offers a similar routine with a more convenient interface.

--  This heapsort algorithm uses approximately N*log(N) compares in the

--  worst case and is in place with no additional storage required. See

--  the body for exact details of the algorithm used.

pragma Compiler_Unit;

package GNAT.Heap_Sort_A is

   pragma Preelaborate;

   --  The data to be sorted is assumed to be indexed by integer values from

   --  1 to N, where N is the number of items to be sorted. In addition, the

   --  index value zero is used for a temporary location used during the sort.

   type Move_Procedure is access procedure (From : Natural; To : Natural);

   --  A pointer to a procedure that moves the data item with index From to

   --  the data item with index To. An index value of zero is used for moves

   --  from and to the single temporary location used by the sort.

   type Lt_Function is access function (Op1, Op2 : Natural) return Boolean;

   --  A pointer to a function that compares two items and returns True if

   --  the item with index Op1 is less than the item with index Op2, and False

   --  if the Op1 item is greater than or equal to the Op2 item.

   procedure Sort (N : Natural; Move : Move_Procedure; Lt : Lt_Function);

   --  This procedures sorts items in the range from 1 to N into ascending

   --  order making calls to Lt to do required comparisons, and Move to move

   --  items around. Note that, as described above, both Move and Lt use a

   --  single temporary location with index value zero. This sort is not

   --  stable, i.e. the order of equal elements in the input is not preserved.

end GNAT.Heap_Sort_A;