1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT LIBRARY COMPONENTS                          --
4--                                                                          --
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          --
6--                                                                          --
7--                                 B o d y                                  --
8--                                                                          --
9--          Copyright (C) 2004-2009, Free Software Foundation, 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 3,  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.                                     --
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/>.                                          --
26--                                                                          --
27-- This unit was originally developed by Matthew J Heaney.                  --
28------------------------------------------------------------------------------
29
30package 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
58end Ada.Containers.Prime_Numbers;
59