Re: Random Number Generation

[James_Rogers <jrogers@velveeta.apdev.cs.mci.com>]

Nigel J. Tracey wrote:
> 
> Can anyone point me in the direction of a routines to do
> random number generation. The requirements are as follows.
> 
>         A routine which will generate a integer between a given
>                 minimum and maximum value. Up to Integer'First and Integer'Last
> 
>         A routine which will do the same for floats i.e. a random
>                 value from Float'First to Float'Last but between two
>                 given values.
> 
> The values of the min and max value for the above routines
> are not known at compile time, hence why I don't thing
> I can use Ada.Numerics.Discrete_Random
> 
> Any help would be very much appreciated (please also e-mail
> a copy of relies as the news feed is a little unreliable here)
> 
> Thanks a lot,
> 

The solution is really quite simple.  Wrap your random number
generator calls inside a function in the following manner:

-------------------------------------------------------------
-- Flexible generic example
-------------------------------------------------------------
with Ada.Numerics.Discrete_Random;
with Ada.Text_IO; use Ada.Text_IO;

procedure example is

   package int_io is new integer_io(integer);

   function flex_rand (Low, High : Integer) return Integer is
      subtype rand_type is Integer range Low..High;
      package myrand is new Ada.Numerics.Discrete_Random(rand_type);
      seed : myrand.generator;
      Result : rand_type;
   begin
      myrand.reset(seed);
      Result := myrand.random(seed);
      return Result;
   end flex_rand;

   Low, High : Integer;

begin

   put("Enter the low bounds: ");
   int_io.get(Low);
   put("Enter the high bounds: ");
   int_io.get(High);
   put("Random number in the range of ");
   int_io.put(Low, Width => 1);
   put(" to ");
   int_io.put(High, Width => 1);
   put(" = ");
   int_io.put(flex_rand(Low, High), Width => 1);
end example;

-----------------------------------------------------------------
The wrapper function "flex_rand" provides all the flexibility you
reqest.  Of course, the same approach can be used for float types.

-- 
Jim Rogers
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