WITH Spider;
WITH Ada.Numerics.Discrete_Random;
PROCEDURE Drunken_Spider IS
------------------------------------------------------------------------
--| Spider tries to tour its room but has drunk too much, so
--| takes a random number of steps and may hit the wall. If the
--| spider hits the wall, it turns around and keeps going.
--| Author: Michael B. Feldman, The George Washington University
--| Last Modified: July 1995
------------------------------------------------------------------------

  SUBTYPE RandomSteps IS Positive RANGE 1..20;

  PACKAGE Random_20 IS NEW Ada.Numerics.Discrete_Random
    (Result_Subtype => RandomSteps);

  G: Random_20.Generator;  -- funny variable; we must keep passing it
                           -- to Random, but can't use it.

  HowMany: RandomSteps;

BEGIN -- Drunken_Spider

  Spider.Start;

  LOOP                     -- keep going forever

    HowMany := Random_20.Random(Gen => G);

    -- Spider will count steps correctly but might change direction
    FOR Count IN 1..HowMany LOOP

      BEGIN   -- to handle exception 
        Spider.Step;
      EXCEPTION
        WHEN Spider.Hit_the_Wall =>  -- turn around 180 degrees
          Spider.Right;
          Spider.Right;
      END;

    END LOOP;

    Spider.Right;

  END LOOP;

END Drunken_Spider;