------------------------------------------------------------------------------ | |

-- -- | |

-- GNAT RUNTIME COMPONENTS -- | |

-- -- | |

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

-- -- | |

-- 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. -- | |

-- -- | |

------------------------------------------------------------------------------ | |

-- 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. | |

-- See also GNAT.Heap_Sort_G and GNAT.Heap_Sort_A. These are older versions | |

-- of this routine. In some cases GNAT.Heap_Sort_G may be a little faster | |

-- than GNAT.Heap_Sort, at the expense of generic code duplication and a | |

-- less convenient interface. The generic version also has the advantage | |

-- of being Pure, while this unit can only be Preelaborate. | |

-- 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. | |

package GNAT.Heap_Sort is | |

pragma Preelaborate (Heap_Sort); | |

-- 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; |