1------------------------------------------------------------------------------ 2-- -- 3-- GNAT RUNTIME COMPONENTS -- 4-- -- 5-- G N A T . H E A P _ S O R T -- 6-- -- 7-- S p e c -- 8-- -- 9-- Copyright (C) 1995-2002 Ada Core Technologies, Inc. -- 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 2, 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. See the GNU General Public License -- 17-- for more details. You should have received a copy of the GNU General -- 18-- Public License distributed with GNAT; see file COPYING. If not, write -- 19-- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, -- 20-- MA 02111-1307, USA. -- 21-- -- 22-- As a special exception, if other files instantiate generics from this -- 23-- unit, or you link this unit with other files to produce an executable, -- 24-- this unit does not by itself cause the resulting executable to be -- 25-- covered by the GNU General Public License. This exception does not -- 26-- however invalidate any other reasons why the executable file might be -- 27-- covered by the GNU Public License. -- 28-- -- 29-- GNAT was originally developed by the GNAT team at New York University. -- 30-- Extensive contributions were provided by Ada Core Technologies Inc. -- 31-- -- 32------------------------------------------------------------------------------ 33 34-- Sort utility (Using Heapsort Algorithm) 35 36-- This package provides a heapsort routine that works with access to 37-- subprogram parameters, so that it can be used with different types with 38-- shared sorting code. 39 40-- See also GNAT.Heap_Sort_G and GNAT.Heap_Sort_A. These are older versions 41-- of this routine. In some cases GNAT.Heap_Sort_G may be a little faster 42-- than GNAT.Heap_Sort, at the expense of generic code duplication and a 43-- less convenient interface. The generic version also has the advantage 44-- of being Pure, while this unit can only be Preelaborate. 45 46-- This heapsort algorithm uses approximately N*log(N) compares in the 47-- worst case and is in place with no additional storage required. See 48-- the body for exact details of the algorithm used. 49 50package GNAT.Heap_Sort is 51pragma Preelaborate (Heap_Sort); 52 53 -- The data to be sorted is assumed to be indexed by integer values 54 -- from 1 to N, where N is the number of items to be sorted. 55 56 type Xchg_Procedure is access procedure (Op1, Op2 : Natural); 57 -- A pointer to a procedure that exchanges the two data items whose 58 -- index values are Op1 and Op2. 59 60 type Lt_Function is access function (Op1, Op2 : Natural) return Boolean; 61 -- A pointer to a function that compares two items and returns True if 62 -- the item with index value Op1 is less than the item with Index value 63 -- Op2, and False if the Op1 item is greater than the Op2 item. If 64 -- the items are equal, then it does not matter if True or False is 65 -- returned (but it is slightly more efficient to return False). 66 67 procedure Sort (N : Natural; Xchg : Xchg_Procedure; Lt : Lt_Function); 68 -- This procedures sorts items in the range from 1 to N into ascending 69 -- order making calls to Lt to do required comparisons, and calls to 70 -- Xchg to exchange items. The sort is not stable, that is the order 71 -- of equal items in the input data set is not preserved. 72 73end GNAT.Heap_Sort; 74