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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) 2007-2015, 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 --  Note: this package is marked SPARK_Mode Off, because functions Random work
  51 --  by side-effect to change the value of the generator, hence they should not
  52 --  be called from SPARK code.
  53
  54 with System.Random_Numbers;
  55 with Interfaces; use Interfaces;
  56
  57 package GNAT.Random_Numbers with
  58   SPARK_Mode => Off
  59 is
  60    type Generator is limited private;
  61    subtype Initialization_Vector is
  62      System.Random_Numbers.Initialization_Vector;
  63
  64    function Random (Gen : Generator) return Float;
  65    function Random (Gen : Generator) return Long_Float;
  66    --  Return pseudo-random numbers uniformly distributed on [0 .. 1)
  67
  68    function Random (Gen : Generator) return Interfaces.Integer_32;
  69    function Random (Gen : Generator) return Interfaces.Unsigned_32;
  70    function Random (Gen : Generator) return Interfaces.Integer_64;
  71    function Random (Gen : Generator) return Interfaces.Unsigned_64;
  72    function Random (Gen : Generator) return Integer;
  73    function Random (Gen : Generator) return Long_Integer;
  74    --  Return pseudo-random numbers uniformly distributed on T'First .. T'Last
  75    --  for various builtin integer types.
  76
  77    generic
  78       type Result_Subtype is (<>);
  79       Default_Min : Result_Subtype := Result_Subtype'Val (0);
  80    function Random_Discrete
  81      (Gen   : Generator;
  82       Min   : Result_Subtype := Default_Min;
  83       Max   : Result_Subtype := Result_Subtype'Last) return Result_Subtype;
  84    --  Returns pseudo-random numbers uniformly distributed on Min .. Max
  85
  86    generic
  87       type Result_Subtype is delta <>;
  88       Default_Min : Result_Subtype := 0.0;
  89    function Random_Ordinary_Fixed
  90      (Gen   : Generator;
  91       Min   : Result_Subtype := Default_Min;
  92       Max   : Result_Subtype := Result_Subtype'Last) return Result_Subtype;
  93    --  Returns pseudo-random numbers uniformly distributed on Min .. Max
  94
  95    generic
  96       type Result_Subtype is delta <> digits <>;
  97       Default_Min : Result_Subtype := 0.0;
  98    function Random_Decimal_Fixed
  99      (Gen   : Generator;
 100       Min   : Result_Subtype := Default_Min;
 101       Max   : Result_Subtype := Result_Subtype'Last) return Result_Subtype;
 102    --  Returns pseudo-random numbers uniformly distributed on Min .. Max
 103
 104    generic
 105       type Result_Subtype is digits <>;
 106    function Random_Float (Gen   : Generator) return Result_Subtype;
 107    --  Returns pseudo-random numbers uniformly distributed on [0.0 .. 1.0)
 108
 109    function Random_Gaussian (Gen : Generator) return Long_Float;
 110    function Random_Gaussian (Gen : Generator) return Float;
 111    --  Returns pseudo-random numbers normally distributed value with mean 0
 112    --  and standard deviation 1.0.
 113
 114    procedure Reset (Gen : out Generator);
 115    --  Re-initialize the state of Gen from the time of day
 116
 117    procedure Reset
 118      (Gen       : out Generator;
 119       Initiator : Initialization_Vector);
 120    procedure Reset
 121      (Gen       : out Generator;
 122       Initiator : Interfaces.Integer_32);
 123    procedure Reset
 124      (Gen       : out Generator;
 125       Initiator : Interfaces.Unsigned_32);
 126    procedure Reset
 127      (Gen       : out Generator;
 128       Initiator : Integer);
 129    --  Re-initialize Gen based on the Initiator in various ways. Identical
 130    --  values of Initiator cause identical sequences of values.
 131
 132    procedure Reset (Gen : out Generator; From_State : Generator);
 133    --  Causes the state of Gen to be identical to that of From_State; Gen
 134    --  and From_State will produce identical sequences of values subsequently.
 135
 136    procedure Reset (Gen : out Generator; From_Image : String);
 137    function Image (Gen : Generator) return String;
 138    --  The call
 139    --     Reset (Gen2, Image (Gen1))
 140    --  has the same effect as Reset (Gen2, Gen1);
 141
 142    Max_Image_Width : constant :=
 143      System.Random_Numbers.Max_Image_Width + 2 + 20 + 5;
 144    --  Maximum possible length of result of Image (...)
 145
 146 private
 147
 148    type Generator is limited record
 149       Rep : System.Random_Numbers.Generator;
 150
 151       Have_Gaussian : Boolean;
 152       --  The algorithm used for Random_Gaussian produces deviates in
 153       --  pairs. Have_Gaussian is true iff Random_Gaussian has returned one
 154       --  member of the pair and Next_Gaussian contains the other.
 155
 156       Next_Gaussian : Long_Float;
 157       --  Next random deviate to be produced by Random_Gaussian, if
 158       --  Have_Gaussian.
 159    end record;
 160
 161 end GNAT.Random_Numbers;