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|---|---|---|
| 4c2d6a70 AC |
1 | ------------------------------------------------------------------------------ |
| 2 | -- -- | |
| 3 | -- GNAT LIBRARY COMPONENTS -- | |
| 4 | -- -- | |
| 3084fecd | 5 | -- A D A . C O N T A I N E R S . P R I M E _ N U M B E R S -- |
| 4c2d6a70 AC |
6 | -- -- |
| 7 | -- B o d y -- | |
| 8 | -- -- | |
| 4b490c1e | 9 | -- Copyright (C) 2004-2020, Free Software Foundation, Inc. -- |
| 4c2d6a70 AC |
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- -- | |
| 748086b7 | 13 | -- ware Foundation; either version 3, or (at your option) any later ver- -- |
| 4c2d6a70 AC |
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 -- | |
| 748086b7 JJ |
16 | -- or FITNESS FOR A PARTICULAR PURPOSE. -- |
| 17 | -- -- | |
| 18 | -- As a special exception under Section 7 of GPL version 3, you are granted -- | |
| 19 | -- additional permissions described in the GCC Runtime Library Exception, -- | |
| 20 | -- version 3.1, as published by the Free Software Foundation. -- | |
| 21 | -- -- | |
| 22 | -- You should have received a copy of the GNU General Public License and -- | |
| 23 | -- a copy of the GCC Runtime Library Exception along with this program; -- | |
| 24 | -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- | |
| 25 | -- <http://www.gnu.org/licenses/>. -- | |
| 4c2d6a70 AC |
26 | -- -- |
| 27 | -- This unit was originally developed by Matthew J Heaney. -- | |
| 28 | ------------------------------------------------------------------------------ | |
| 29 | ||
| 30 | package body Ada.Containers.Prime_Numbers is | |
| 31 | ||
| 32 | -------------- | |
| 33 | -- To_Prime -- | |
| 34 | -------------- | |
| 35 | ||
| 36 | function To_Prime (Length : Count_Type) return Hash_Type is | |
| 37 | I, J, K : Integer'Base; | |
| 38 | Index : Integer'Base; | |
| 39 | ||
| 40 | begin | |
| 41 | I := Primes'Last - Primes'First; | |
| 42 | Index := Primes'First; | |
| 43 | while I > 0 loop | |
| 44 | J := I / 2; | |
| 45 | K := Index + J; | |
| 46 | ||
| 47 | if Primes (K) < Hash_Type (Length) then | |
| 48 | Index := K + 1; | |
| 49 | I := I - J - 1; | |
| 50 | else | |
| 51 | I := J; | |
| 52 | end if; | |
| 53 | end loop; | |
| 54 | ||
| 55 | return Primes (Index); | |
| 56 | end To_Prime; | |
| 57 | ||
| 58 | end Ada.Containers.Prime_Numbers; |