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

-- -- | |

-- GNAT RUN-TIME COMPONENTS -- | |

-- -- | |

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

-- -- | |

-- S p e c -- | |

-- -- | |

-- Copyright (C) 1995-2021, 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 3, 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. -- | |

-- -- | |

-- As a special exception under Section 7 of GPL version 3, you are granted -- | |

-- additional permissions described in the GCC Runtime Library Exception, -- | |

-- version 3.1, as published by the Free Software Foundation. -- | |

-- -- | |

-- You should have received a copy of the GNU General Public License and -- | |

-- a copy of the GCC Runtime Library Exception along with this program; -- | |

-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- | |

-- <http://www.gnu.org/licenses/>. -- | |

-- -- | |

-- 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. | |

-- Note: GNAT.Heap_Sort replaces and obsoletes GNAT.Heap_Sort_A, which is | |

-- retained in the GNAT library for backwards compatibility. | |

pragma Compiler_Unit_Warning; | |

package GNAT.Heap_Sort is | |

pragma Pure; | |

-- 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; |