| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNAT RUNTIME COMPONENTS -- |
| -- -- |
| -- G N A T . H E A P _ S O R T _ G -- |
| -- -- |
| -- S p e c -- |
| -- -- |
| -- Copyright (C) 1995-2002 Ada Core Technologies, Inc. -- |
| -- -- |
| -- 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, 59 Temple Place - Suite 330, Boston, -- |
| -- MA 02111-1307, 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. -- |
| -- -- |
| ------------------------------------------------------------------------------ |
| |
| -- Heapsort generic package using formal procedures |
| |
| -- This package provides a generic heapsort routine that can be used with |
| -- different types of data. |
| |
| -- See also GNAT.Heap_Sort, a version that works with subprogram access |
| -- parameters, allowing code sharing. The generic version is slightly more |
| -- efficient but does not allow code sharing and has an interface that is |
| -- more awkward to use. The generic version is also Pure, while the access |
| -- subprogram version can only be Preelaborate. |
| |
| -- There is also GNAT.Heap_Sort_A, which is now considered obsolete, but |
| -- was an older version working with subprogram parameters. This version |
| -- is retained for bacwards compatibility with old versions of GNAT. |
| |
| -- 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. |
| |
| generic |
| -- 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. |
| |
| with procedure Move (From : Natural; To : Natural); |
| -- A procedure that moves the data item with index value From to the data |
| -- item with index value To (the old value in To being lost). An index |
| -- value of zero is used for moves from and to a single temporary location |
| |
| with function Lt (Op1, Op2 : Natural) return Boolean; |
| -- 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 the Op2 item. If the two items are equal, then |
| -- it does not matter whether True or False is returned (it is slightly |
| -- more efficient to return False). |
| |
| -- Note on use of temporary location |
| |
| -- There are two ways of providing for the index value zero to represent |
| -- a temporary value. Either an extra location can be allocated at the |
| -- start of the array, or alternatively the Move and Lt subprograms can |
| -- test for the case of zero and treat it specially. In any case it is |
| -- desirable to specify the two subprograms as inlined and the tests for |
| -- zero will in this case be resolved at instantiation time. |
| |
| package GNAT.Heap_Sort_G is |
| pragma Pure (Heap_Sort_G); |
| |
| procedure Sort (N : Natural); |
| -- 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_G; |
