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------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME COMPONENTS --
-- --
-- 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 --
-- --
-- B o d y --
-- --
-- Copyright (C) 1992-2010, Free Software Foundation, Inc. --
-- --
-- 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 3, 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. --
-- --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception, --
-- version 3.1, as published by the Free Software Foundation. --
-- --
-- You should have received a copy of the GNU General Public License and --
-- a copy of the GCC Runtime Library Exception along with this program; --
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
-- <http://www.gnu.org/licenses/>. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
with System.Random_Numbers; use System.Random_Numbers;
package body Ada.Numerics.Discrete_Random is
-------------------------
-- Implementation Note --
-------------------------
-- The design of this spec is a bit awkward, as a result of Ada 95 not
-- permitting in-out parameters for function formals (most naturally
-- Generator values would be passed this way). In pure Ada 95, the only
-- solution would be to add a self-referential component to the generator
-- allowing access to the generator object from inside the function. This
-- would work because the generator is limited, which prevents any copy.
-- This is a bit heavy, so what we do is to use Unrestricted_Access to
-- get a pointer to the state in the passed Generator. This works because
-- Generator is a limited type and will thus always be passed by reference.
subtype Rep_Generator is System.Random_Numbers.Generator;
subtype Rep_State is System.Random_Numbers.State;
function Rep_Random is
new Random_Discrete (Result_Subtype, Result_Subtype'First);
function Random (Gen : Generator) return Result_Subtype is
begin
return Rep_Random (Gen.Rep);
end Random;
procedure Reset
(Gen : Generator;
Initiator : Integer)
is
G : Rep_Generator renames Gen.Rep'Unrestricted_Access.all;
begin
Reset (G, Initiator);
end Reset;
procedure Reset (Gen : Generator) is
G : Rep_Generator renames Gen.Rep'Unrestricted_Access.all;
begin
Reset (G);
end Reset;
procedure Save
(Gen : Generator;
To_State : out State)
is
begin
Save (Gen.Rep, State (To_State));
end Save;
procedure Reset
(Gen : Generator;
From_State : State)
is
G : Rep_Generator renames Gen.Rep'Unrestricted_Access.all;
begin
Reset (G, From_State);
end Reset;
function Image (Of_State : State) return String is
begin
return Image (Rep_State (Of_State));
end Image;
function Value (Coded_State : String) return State is
G : Generator;
S : Rep_State;
begin
Reset (G.Rep, Coded_State);
System.Random_Numbers.Save (G.Rep, S);
return State (S);
end Value;
end Ada.Numerics.Discrete_Random;
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