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 --
10 -- Copyright (C) 1992-2001 Free Software Foundation, Inc. --
12 -- This specification is derived from the Ada Reference Manual for use with --
13 -- GNAT. The copyright notice above, and the license provisions that follow --
14 -- apply solely to the contents of the part following the private keyword. --
16 -- GNAT is free software; you can redistribute it and/or modify it under --
17 -- terms of the GNU General Public License as published by the Free Soft- --
18 -- ware Foundation; either version 2, or (at your option) any later ver- --
19 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
20 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
21 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
22 -- for more details. You should have received a copy of the GNU General --
23 -- Public License distributed with GNAT; see file COPYING. If not, write --
24 -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
25 -- MA 02111-1307, USA. --
27 -- As a special exception, if other files instantiate generics from this --
28 -- unit, or you link this unit with other files to produce an executable, --
29 -- this unit does not by itself cause the resulting executable to be --
30 -- covered by the GNU General Public License. This exception does not --
31 -- however invalidate any other reasons why the executable file might be --
32 -- covered by the GNU Public License. --
34 -- GNAT was originally developed by the GNAT team at New York University. --
35 -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
37 ------------------------------------------------------------------------------
39 -- Note: the implementation used in this package was contributed by
40 -- Robert Eachus. It is based on the work of L. Blum, M. Blum, and
41 -- M. Shub, SIAM Journal of Computing, Vol 15. No 2, May 1986. The
42 -- particular choices for P and Q chosen here guarantee a period of
43 -- 562,085,314,430,582 (about 2**49), and the generated sequence has
44 -- excellent randomness properties. For further details, see the
45 -- paper "Fast Generation of Trustworthy Random Numbers", by Robert
46 -- Eachus, which describes both the algorithm and the efficient
47 -- implementation approach used here.
52 type Result_Subtype
is (<>);
54 package Ada
.Numerics
.Discrete_Random
is
58 type Generator
is limited private;
60 function Random
(Gen
: Generator
) return Result_Subtype
;
62 procedure Reset
(Gen
: Generator
);
63 procedure Reset
(Gen
: Generator
; Initiator
: Integer);
65 -- Advanced facilities.
67 type State
is private;
69 procedure Save
(Gen
: Generator
; To_State
: out State
);
70 procedure Reset
(Gen
: Generator
; From_State
: State
);
72 Max_Image_Width
: constant := 80;
74 function Image
(Of_State
: State
) return String;
75 function Value
(Coded_State
: String) return State
;
78 subtype Int
is Interfaces
.Integer_32
;
79 subtype Rst
is Result_Subtype
;
81 type Flt
is digits 14;
83 RstF
: constant Flt
:= Flt
(Rst
'Pos (Rst
'First));
84 RstL
: constant Flt
:= Flt
(Rst
'Pos (Rst
'Last));
86 Offs
: constant Flt
:= RstF
- 0.5;
88 K1
: constant := 94_833_359
;
89 K1F
: constant := 94_833_359
.0
;
90 K2
: constant := 47_416_679
;
91 K2F
: constant := 47_416_679
.0
;
92 Scal
: constant Flt
:= (RstL
- RstF
+ 1.0) / (K1F
* K2F
);
95 X1
: Int
:= Int
(2999 ** 2);
96 X2
: Int
:= Int
(1439 ** 2);
103 type Generator
is limited record
107 end Ada
.Numerics
.Discrete_Random
;