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------------------------------------------------------------------------------

--                                                                          --

--                         GNAT RUN-TIME COMPONENTS                         --

--                                                                          --

--            A D A . N U M E R I C S . F L O A T _ R A N D O M             --

--                                                                          --

--                                 S p e c                                  --

--                                                                          --

--          Copyright (C) 1992-2002 Free Software Foundation, Inc.          --

--                                                                          --

-- This specification is derived from the Ada Reference Manual for use with --

-- GNAT. The copyright notice above, and the license provisions that follow --

-- apply solely to the  contents of the part following the private keyword. --

--                                                                          --

-- GNAT is free software;  you can  redistribute it  and/or modify it under --

-- terms of the  GNU General Public License as published  by the Free Soft- --

-- ware  Foundation;  either version 2,  or (at your option) any later ver- --

-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --

-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --

-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --

-- for  more details.  You should have  received  a copy of the GNU General --

-- Public License  distributed with GNAT;  see file COPYING.  If not, write --

-- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --

-- Boston, MA 02110-1301, USA.                                              --

--                                                                          --

-- As a special exception,  if other files  instantiate  generics from this --

-- unit, or you link  this unit with other files  to produce an executable, --

-- this  unit  does not  by itself cause  the resulting  executable  to  be --

-- covered  by the  GNU  General  Public  License.  This exception does not --

-- however invalidate  any other reasons why  the executable file  might be --

-- covered by the  GNU Public License.                                      --

--                                                                          --

-- GNAT was originally developed  by the GNAT team at  New York University. --

-- Extensive contributions were provided by Ada Core Technologies Inc.      --

--                                                                          --

------------------------------------------------------------------------------

--  Note: the implementation used in this package was contributed by

--  Robert Eachus. It is based on the work of L. Blum, M. Blum, and

--  M. Shub, SIAM Journal of Computing, Vol 15. No 2, May 1986. The

--  particular choices for P and Q chosen here guarantee a period of

--  562,085,314,430,582 (about 2**49), and the generated sequence has

--  excellent randomness properties. For further details, see the

--  paper "Fast Generation of Trustworthy Random Numbers", by Robert

--  Eachus, which describes both the algorithm and the efficient

--  implementation approach used here.

with Interfaces;

package Ada.Numerics.Float_Random is

   --  Basic facilities

   type Generator is limited private;

   subtype Uniformly_Distributed is Float range 0.0 .. 1.0;

   function Random (Gen : Generator) return Uniformly_Distributed;

   procedure Reset (Gen : Generator);

   procedure Reset (Gen : Generator; Initiator : Integer);

   --  Advanced facilities

   type State is private;

   procedure Save  (Gen : Generator; To_State   : out State);

   procedure Reset (Gen : Generator; From_State : State);

   Max_Image_Width : constant := 80;

   function Image (Of_State :    State)  return String;

   function Value (Coded_State : String) return State;

private

   type Int is new Interfaces.Integer_32;

   --  We prefer to use 14 digits for Flt, but some targets are more limited

   type Flt is digits Positive'Min (14, Long_Long_Float'Digits);

   K1   : constant := 94_833_359;

   K1F  : constant := 94_833_359.0;

   K2   : constant := 47_416_679;

   K2F  : constant := 47_416_679.0;

   Scal : constant := 1.0 / (K1F * K2F);

   type State is record

      X1  : Int := 2999 ** 2;      --  Square mod p

      X2  : Int := 1439 ** 2;      --  Square mod q

      P   : Int := K1;

      Q   : Int := K2;

      X   : Int := 1;

      Scl : Flt := Scal;

   end record;

   type Generator is limited record

      Gen_State : State;

   end record;

end Ada.Numerics.Float_Random;