1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME COMPONENTS --
5 -- A D A . N U M E R I C S . D I S C R E T E _ R A N D O M --
11 -- Copyright (C) 1992-2001 Free Software Foundation, Inc. --
13 -- This specification is derived from the Ada Reference Manual for use with --
14 -- GNAT. The copyright notice above, and the license provisions that follow --
15 -- apply solely to the contents of the part following the private keyword. --
17 -- GNAT is free software; you can redistribute it and/or modify it under --
18 -- terms of the GNU General Public License as published by the Free Soft- --
19 -- ware Foundation; either version 2, or (at your option) any later ver- --
20 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
21 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
22 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
23 -- for more details. You should have received a copy of the GNU General --
24 -- Public License distributed with GNAT; see file COPYING. If not, write --
25 -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
26 -- MA 02111-1307, USA. --
28 -- As a special exception, if other files instantiate generics from this --
29 -- unit, or you link this unit with other files to produce an executable, --
30 -- this unit does not by itself cause the resulting executable to be --
31 -- covered by the GNU General Public License. This exception does not --
32 -- however invalidate any other reasons why the executable file might be --
33 -- covered by the GNU Public License. --
35 -- GNAT was originally developed by the GNAT team at New York University. --
36 -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
38 ------------------------------------------------------------------------------
40 -- Note: the implementation used in this package was contributed by
41 -- Robert Eachus. It is based on the work of L. Blum, M. Blum, and
42 -- M. Shub, SIAM Journal of Computing, Vol 15. No 2, May 1986. The
43 -- particular choices for P and Q chosen here guarantee a period of
44 -- 562,085,314,430,582 (about 2**49), and the generated sequence has
45 -- excellent randomness properties. For further details, see the
46 -- paper "Fast Generation of Trustworthy Random Numbers", by Robert
47 -- Eachus, which describes both the algorithm and the efficient
48 -- implementation approach used here.
53 type Result_Subtype is (<>);
55 package Ada.Numerics.Discrete_Random is
59 type Generator is limited private;
61 function Random (Gen : Generator) return Result_Subtype;
63 procedure Reset (Gen : Generator);
64 procedure Reset (Gen : Generator; Initiator : Integer);
66 -- Advanced facilities.
68 type State is private;
70 procedure Save (Gen : Generator; To_State : out State);
71 procedure Reset (Gen : Generator; From_State : State);
73 Max_Image_Width : constant := 80;
75 function Image (Of_State : State) return String;
76 function Value (Coded_State : String) return State;
79 subtype Int is Interfaces.Integer_32;
80 subtype Rst is Result_Subtype;
82 type Flt is digits 14;
84 RstF : constant Flt := Flt (Rst'Pos (Rst'First));
85 RstL : constant Flt := Flt (Rst'Pos (Rst'Last));
87 Offs : constant Flt := RstF - 0.5;
89 K1 : constant := 94_833_359;
90 K1F : constant := 94_833_359.0;
91 K2 : constant := 47_416_679;
92 K2F : constant := 47_416_679.0;
93 Scal : constant Flt := (RstL - RstF + 1.0) / (K1F * K2F);
96 X1 : Int := Int (2999 ** 2);
97 X2 : Int := Int (1439 ** 2);
104 type Generator is limited record
108 end Ada.Numerics.Discrete_Random;