gcc/ada/g-rannum.ads

   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, 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 2,  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.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  19 -- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --
  20 -- Boston, MA 02110-1301, USA.                                              --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNAT was originally developed  by the GNAT team at  New York University. --
  30 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 --  Extended pseudo-random number generation
  35
  36 --  This package provides a type representing pseudo-random number
  37 --  generators, and subprograms to extract various distributions of numbers
  38 --  from them. It also provides types for representing initialization values
  39 --  and snapshots of internal generator state, which permit reproducible
  40 --  pseudo-random streams.
  41
  42 --  The generator currently provided by this package has an extremely long
  43 --  period (at least 2**19937-1), and passes the Big Crush test suite, with
  44 --  the exception of the two linear complexity tests. Therefore, it is
  45 --  suitable for simulations, but should not be used as a cryptographic
  46 --  pseudo-random source without additional processing.
  47
  48 --  The design of this package effects some simplification from that of
  49 --  the standard Ada.Numerics packages. There is no separate State type;
  50 --  the Generator type itself suffices for this purpose. The parameter
  51 --  modes on Reset procedures better reflect the effect of these routines.
  52
  53 with System.Random_Numbers;
  54 with Interfaces; use Interfaces;
  55
  56 package GNAT.Random_Numbers is
  57
  58    type Generator is limited private;
  59    subtype Initialization_Vector is
  60      System.Random_Numbers.Initialization_Vector;
  61
  62    function Random (Gen : Generator) return Float;
  63    function Random (Gen : Generator) return Long_Float;
  64    --  Return pseudo-random numbers uniformly distributed on [0 .. 1)
  65
  66    function Random (Gen : Generator) return Interfaces.Integer_32;
  67    function Random (Gen : Generator) return Interfaces.Unsigned_32;
  68    function Random (Gen : Generator) return Interfaces.Integer_64;
  69    function Random (Gen : Generator) return Interfaces.Unsigned_64;
  70    function Random (Gen : Generator) return Integer;
  71    function Random (Gen : Generator) return Long_Integer;
  72    --  Return pseudo-random numbers uniformly distributed on T'First .. T'Last
  73    --  for various builtin integer types.
  74
  75    generic
  76       type Result_Subtype is (<>);
  77       Default_Min : Result_Subtype := Result_Subtype'Val (0);
  78    function Random_Discrete
  79      (Gen   : Generator;
  80       Min   : Result_Subtype := Default_Min;
  81       Max   : Result_Subtype := Result_Subtype'Last) return Result_Subtype;
  82    --  Returns pseudo-random numbers uniformly distributed on Min .. Max
  83
  84    generic
  85       type Result_Subtype is digits <>;
  86    function Random_Float (Gen   : Generator) return Result_Subtype;
  87    --  Returns pseudo-random numbers uniformly distributed on [0 .. 1)
  88
  89    function Random_Gaussian (Gen : Generator) return Long_Float;
  90    function Random_Gaussian (Gen : Generator) return Float;
  91    --  Returns pseudo-random numbers normally distributed value with mean 0
  92    --  and standard deviation 1.0.
  93
  94    procedure Reset (Gen : out Generator);
  95    --  Re-initialize the state of Gen from the time of day
  96
  97    procedure Reset
  98      (Gen       : out Generator;
  99       Initiator : Initialization_Vector);
 100    procedure Reset
 101      (Gen       : out Generator;
 102       Initiator : Interfaces.Integer_32);
 103    procedure Reset
 104      (Gen       : out Generator;
 105       Initiator : Interfaces.Unsigned_32);
 106    procedure Reset
 107      (Gen       : out Generator;
 108       Initiator : Integer);
 109    --  Re-initialize Gen based on the Initiator in various ways. Identical
 110    --  values of Initiator cause identical sequences of values.
 111
 112    procedure Reset (Gen : out Generator; From_State : Generator);
 113    --  Causes the state of Gen to be identical to that of From_State; Gen
 114    --  and From_State will produce identical sequences of values subsequently.
 115
 116    procedure Reset (Gen : out Generator; From_Image : String);
 117    function Image (Gen : Generator) return String;
 118    --  The call
 119    --     Reset (Gen2, Image (Gen1))
 120    --  has the same effect as Reset (Gen2, Gen1);
 121
 122    Max_Image_Width : constant :=
 123      System.Random_Numbers.Max_Image_Width + 2 + 20 + 5;
 124    --  Maximum possible length of result of Image (...)
 125
 126 private
 127
 128    type Generator is limited record
 129       Rep : System.Random_Numbers.Generator;
 130
 131       Have_Gaussian : Boolean;
 132       --  The algorithm used for Random_Gaussian produces deviates in
 133       --  pairs. Have_Gaussian is true iff Random_Gaussian has returned one
 134       --  member of the pair and Next_Gaussian contains the other.
 135
 136       Next_Gaussian : Long_Float;
 137       --  Next random deviate to be produced by Random_Gaussian, if
 138       --  Have_Gaussian.
 139    end record;
 140
 141 end GNAT.Random_Numbers;