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   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   5 --                   G N A T . R A N D O M _ N U M B E R S                  --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --      Copyright (C) 2007-2009  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 -- 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 --  Extended pseudo-random number generation
  33
  34 --  This package provides a type representing pseudo-random number generators,
  35 --  and subprograms to extract various distributions of numbers from them. It
  36 --  also provides types for representing initialization values and snapshots of
  37 --  internal generator state, which permit reproducible pseudo-random streams.
  38
  39 --  The generator currently provided by this package has an extremely long
  40 --  period (at least 2**19937-1), and passes the Big Crush test suite, with the
  41 --  exception of the two linear complexity tests. Therefore, it is suitable for
  42 --  simulations, but should not be used as a cryptographic pseudo-random source
  43 --  without additional processing.
  44
  45 --  The design of this package effects is simplified compared to the design
  46 --  of standard Ada.Numerics packages. There is no separate State type; the
  47 --  Generator type itself suffices for this purpose. The parameter modes on
  48 --  Reset procedures better reflect the effect of these routines.
  49
  50 with System.Random_Numbers;
  51 with Interfaces; use Interfaces;
  52
  53 package GNAT.Random_Numbers is
  54
  55    type Generator is limited private;
  56    subtype Initialization_Vector is
  57      System.Random_Numbers.Initialization_Vector;
  58
  59    function Random (Gen : Generator) return Float;
  60    function Random (Gen : Generator) return Long_Float;
  61    --  Return pseudo-random numbers uniformly distributed on [0 .. 1)
  62
  63    function Random (Gen : Generator) return Interfaces.Integer_32;
  64    function Random (Gen : Generator) return Interfaces.Unsigned_32;
  65    function Random (Gen : Generator) return Interfaces.Integer_64;
  66    function Random (Gen : Generator) return Interfaces.Unsigned_64;
  67    function Random (Gen : Generator) return Integer;
  68    function Random (Gen : Generator) return Long_Integer;
  69    --  Return pseudo-random numbers uniformly distributed on T'First .. T'Last
  70    --  for various builtin integer types.
  71
  72    generic
  73       type Result_Subtype is (<>);
  74       Default_Min : Result_Subtype := Result_Subtype'Val (0);
  75    function Random_Discrete
  76      (Gen   : Generator;
  77       Min   : Result_Subtype := Default_Min;
  78       Max   : Result_Subtype := Result_Subtype'Last) return Result_Subtype;
  79    --  Returns pseudo-random numbers uniformly distributed on Min .. Max
  80
  81    generic
  82       type Result_Subtype is digits <>;
  83    function Random_Float (Gen   : Generator) return Result_Subtype;
  84    --  Returns pseudo-random numbers uniformly distributed on [0 .. 1)
  85
  86    function Random_Gaussian (Gen : Generator) return Long_Float;
  87    function Random_Gaussian (Gen : Generator) return Float;
  88    --  Returns pseudo-random numbers normally distributed value with mean 0
  89    --  and standard deviation 1.0.
  90
  91    procedure Reset (Gen : out Generator);
  92    --  Re-initialize the state of Gen from the time of day
  93
  94    procedure Reset
  95      (Gen       : out Generator;
  96       Initiator : Initialization_Vector);
  97    procedure Reset
  98      (Gen       : out Generator;
  99       Initiator : Interfaces.Integer_32);
 100    procedure Reset
 101      (Gen       : out Generator;
 102       Initiator : Interfaces.Unsigned_32);
 103    procedure Reset
 104      (Gen       : out Generator;
 105       Initiator : Integer);
 106    --  Re-initialize Gen based on the Initiator in various ways. Identical
 107    --  values of Initiator cause identical sequences of values.
 108
 109    procedure Reset (Gen : out Generator; From_State : Generator);
 110    --  Causes the state of Gen to be identical to that of From_State; Gen
 111    --  and From_State will produce identical sequences of values subsequently.
 112
 113    procedure Reset (Gen : out Generator; From_Image : String);
 114    function Image (Gen : Generator) return String;
 115    --  The call
 116    --     Reset (Gen2, Image (Gen1))
 117    --  has the same effect as Reset (Gen2, Gen1);
 118
 119    Max_Image_Width : constant :=
 120      System.Random_Numbers.Max_Image_Width + 2 + 20 + 5;
 121    --  Maximum possible length of result of Image (...)
 122
 123 private
 124
 125    type Generator is limited record
 126       Rep : System.Random_Numbers.Generator;
 127
 128       Have_Gaussian : Boolean;
 129       --  The algorithm used for Random_Gaussian produces deviates in
 130       --  pairs. Have_Gaussian is true iff Random_Gaussian has returned one
 131       --  member of the pair and Next_Gaussian contains the other.
 132
 133       Next_Gaussian : Long_Float;
 134       --  Next random deviate to be produced by Random_Gaussian, if
 135       --  Have_Gaussian.
 136    end record;
 137
 138 end GNAT.Random_Numbers;