| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNAT RUN-TIME COMPONENTS -- |
| -- -- |
| -- G N A T . H E A P _ S O R T -- |
| -- -- |
| -- 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. -- |
| -- -- |
| ------------------------------------------------------------------------------ |
| |
| -- Sort utility (Using Heapsort Algorithm) |
| |
| -- This package provides a heapsort routine that works with access to |
| -- subprogram parameters, so that it can be used with different types with |
| -- shared sorting code. |
| |
| -- 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. |
| |
| -- See also GNAT.Heap_Sort_G which is a generic version that will be faster |
| -- since the overhead of the indirect calls is avoided, at the expense of |
| -- generic code duplication and less convenient interface. The generic version |
| -- also has the advantage of being Pure, while this unit can only be |
| -- Preelaborate, because of the access types. |
| |
| -- Note: GNAT.Heap_Sort replaces and obsoletes GNAT.Heap_Sort_A, which is |
| -- retained in the GNAT library for backwards compatibility. |
| |
| package GNAT.Heap_Sort 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. |
| |
| type Xchg_Procedure is access procedure (Op1, Op2 : Natural); |
| -- A pointer to a procedure that exchanges the two data items whose |
| -- index values are Op1 and Op2. |
| |
| 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 value Op1 is less than the item with Index value |
| -- Op2, and False if the Op1 item is greater than the Op2 item. If |
| -- the items are equal, then it does not matter if True or False is |
| -- returned (but it is slightly more efficient to return False). |
| |
| procedure Sort (N : Natural; Xchg : Xchg_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 calls to |
| -- Xchg to exchange items. The sort is not stable, that is the order |
| -- of equal items in the input data set is not preserved. |
| |
| end GNAT.Heap_Sort; |
