gcc/ada/a-nudira.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   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          --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --                                                                          --
  10 --          Copyright (C) 1992-2001 Free Software Foundation, Inc.          --
  11 --                                                                          --
  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. --
  15 --                                                                          --
  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.                                                      --
  26 --                                                                          --
  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.                                      --
  33 --                                                                          --
  34 -- GNAT was originally developed  by the GNAT team at  New York University. --
  35 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  36 --                                                                          --
  37 ------------------------------------------------------------------------------
  38
  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.
  48
  49 with Interfaces;
  50
  51 generic
  52    type Result_Subtype is (<>);
  53
  54 package Ada.Numerics.Discrete_Random is
  55
  56    --  Basic facilities.
  57
  58    type Generator is limited private;
  59
  60    function Random (Gen : Generator) return Result_Subtype;
  61
  62    procedure Reset (Gen : Generator);
  63    procedure Reset (Gen : Generator; Initiator : Integer);
  64
  65    --  Advanced facilities.
  66
  67    type State is private;
  68
  69    procedure Save  (Gen : Generator; To_State   : out State);
  70    procedure Reset (Gen : Generator; From_State : State);
  71
  72    Max_Image_Width : constant := 80;
  73
  74    function Image (Of_State    : State)  return String;
  75    function Value (Coded_State : String) return State;
  76
  77 private
  78    subtype Int is Interfaces.Integer_32;
  79    subtype Rst is Result_Subtype;
  80
  81    type Flt is digits 14;
  82
  83    RstF : constant Flt := Flt (Rst'Pos (Rst'First));
  84    RstL : constant Flt := Flt (Rst'Pos (Rst'Last));
  85
  86    Offs : constant Flt := RstF - 0.5;
  87
  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);
  93
  94    type State is record
  95       X1  : Int := Int (2999 ** 2);
  96       X2  : Int := Int (1439 ** 2);
  97       P   : Int := K1;
  98       Q   : Int := K2;
  99       FP  : Flt := K1F;
 100       Scl : Flt := Scal;
 101    end record;
 102
 103    type Generator is limited record
 104       Gen_State : State;
 105    end record;
 106
 107 end Ada.Numerics.Discrete_Random;