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From: "Papastefanos Serafeim" <serafeim@otenet.gr>
Newsgroups: comp.lang.ada
Subject: Re: Random numbers in tasks
Date: Tue, 3 Jun 2003 22:37:18 +0300
Organization: National Technical University of Athens, Greece
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Date: 2003-06-03T22:37:18+03:00
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Thank you

"Robert I. Eachus" <rieachus@attbi.com> wrote in message
news:3EDBB85D.3050505@attbi.com...
> Papastefanos Serafeim wrote:
> > Thank you for the big answer... I tried your program and
> > it works just fine, but when I try to convert it to my
> > requirements it is not working:
>
> > I want to use it with discrete rundom numbers with a
> > variable range... I have made changes to your program
> > and now looks like this ->
> > with Ada.Numerics.Discrete_Random;
> > with Ada.Task_Attributes;
> > package body Rnds is
> >    function Give_Rnd (
> >          L : Integer;
> >          U : Integer;
> > )      return Integer is
> >       subtype Rng is Integer range L..U;
> >       package Rnd_Num is new Ada.Numerics.Discrete_Random (Rng);
>
> Never instantiate a random number package inside a function.  As you
> have noticed, the results are not what you want.  Here is a version of
> what I gave you before, but with the init generator settings based on
> one clock call.
>
> with Ada.Numerics.Discrete_Random;
> package body My_Float_Random is
>     type Generator_Pointer is access Ada.Numerics.Float_Random.Generator;
>
>     package Int_Rand is new Ada.Numerics.Discrete_Random(Positive);
>
>     protected Gen_Source is
>       procedure Initialize_Generator(Pointer: in out Generator_Pointer);
>     private
>       Int_Gen: Int_Rand.Generator;
>       Initial: Boolean := True;
>     end Gen_Source;
>
>     protected body Gen_Source is
>       procedure Initialize_Generator
>                   (Pointer: in out Generator_Pointer) is
>        begin
>          if Initial then
>            Int_Rand.Reset(Int_Gen);
>            Initial := False; -- use time of day once
>          end if;
>          Pointer := new Ada.Numerics.Float_Random.Generator;
>          Ada.Numerics.Float_Random.Reset
>                 (Pointer.all, Int_Rand.Random(Int_Gen));
>        end  Initialize_Generator;
>     end Gen_Source;
>
>     function Initialize return Generator_Pointer is
>       GP : Generator_Pointer;
>     begin
>       Gen_Source.Initialize_Generator(GP);
>       return GP;
>     end Initialize;
>
>     package Per_Task is new
>       Ada.Task_Attributes(Generator_Pointer, Initialize);
>
>     function Random return
>        Ada.Numerics.Float_Random.Uniformly_Distributed is
>     begin
>       return Ada.Numerics.Float_Random.Random(Per_Task.Value.all);
>     end Random;
>
> end My_Float_Random;
>