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
50with System.Random_Numbers;
51with Interfaces; use Interfaces;
52
53package 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
123private
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
138end GNAT.Random_Numbers;
139