gcc/ada/a-nuflra.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   5 --            A D A . N U M E R I C S . F L O A T _ R A N D O M             --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2010, 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 -- GNAT was originally developed  by the GNAT team at  New York University. --
  28 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 with Interfaces; use Interfaces;
  33
  34 with System.Random_Numbers; use System.Random_Numbers;
  35
  36 package body Ada.Numerics.Float_Random is
  37
  38    -------------------------
  39    -- Implementation Note --
  40    -------------------------
  41
  42    --  The design of this spec is a bit awkward, as a result of Ada 95 not
  43    --  permitting in-out parameters for function formals (most naturally
  44    --  Generator values would be passed this way). In pure Ada 95, the only
  45    --  solution would be to add a self-referential component to the generator
  46    --  allowing access to the generator object from inside the function. This
  47    --  would work because the generator is limited, which prevents any copy.
  48
  49    --  This is a bit heavy, so what we do is to use Unrestricted_Access to
  50    --  get a pointer to the state in the passed Generator. This works because
  51    --  Generator is a limited type and will thus always be passed by reference.
  52
  53    subtype Rep_Generator is System.Random_Numbers.Generator;
  54    subtype Rep_State is System.Random_Numbers.State;
  55
  56    ------------
  57    -- Random --
  58    ------------
  59
  60    function Random (Gen : Generator) return Uniformly_Distributed is
  61    begin
  62       return Random (Gen.Rep);
  63    end Random;
  64
  65    -----------
  66    -- Reset --
  67    -----------
  68
  69    --  Version that works from given initiator value
  70
  71    procedure Reset (Gen : Generator; Initiator : Integer) is
  72       G : Rep_Generator renames Gen.Rep'Unrestricted_Access.all;
  73    begin
  74       Reset (G, Integer_32 (Initiator));
  75    end Reset;
  76
  77    --  Version that works from calendar
  78
  79    procedure Reset (Gen : Generator) is
  80       G : Rep_Generator renames Gen.Rep'Unrestricted_Access.all;
  81    begin
  82       Reset (G);
  83    end Reset;
  84
  85    --  Version that works from specific saved state
  86
  87    procedure Reset (Gen : Generator; From_State : State) is
  88       G : Rep_Generator renames Gen.Rep'Unrestricted_Access.all;
  89    begin
  90       Reset (G, From_State);
  91    end Reset;
  92
  93    ----------
  94    -- Save --
  95    ----------
  96
  97    procedure Save  (Gen : Generator; To_State : out State) is
  98    begin
  99       Save (Gen.Rep, State (To_State));
 100    end Save;
 101
 102    -----------
 103    -- Image --
 104    -----------
 105
 106    function Image (Of_State : State) return String is
 107    begin
 108       return Image (Rep_State (Of_State));
 109    end Image;
 110
 111    -----------
 112    -- Value --
 113    -----------
 114
 115    function Value (Coded_State : String) return State is
 116       G : Generator;
 117       S : Rep_State;
 118    begin
 119       Reset (G.Rep, Coded_State);
 120       System.Random_Numbers.Save (G.Rep, S);
 121       return State (S);
 122    end Value;
 123
 124 end Ada.Numerics.Float_Random;