------------------------------------------------------------------------------ -- -- -- GNAT RUN-TIME COMPONENTS -- -- -- -- G N A T . H E A P _ S O R T _ G -- -- -- -- S p e c -- -- -- -- Copyright (C) 1995-2005, 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. -- -- -- ------------------------------------------------------------------------------ -- 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 backwards 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. -- For best efficiency, this routine should be marked as inlined. 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). For best efficiency, this routine -- should be marked as inlined. -- 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; 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;