DEFINITION MODULE Rand;
FROM NumTypes IMPORT Real8;

  (* Random numbers generator.
     Algorithm : Based on the additive congruential method
                 (Knuth, The art of computer programming, Vol.2, pp 26-27)
  *)

  PROCEDURE Randomize;
    (* Initializes the random number generator. The random number sequence
       following a call to Randomize cannot be reproduced.
       A call to Randomize is done automatically at the initialization
       of this module.
    *)

  PROCEDURE RandomInit (seed : CARDINAL);
    (* Initializes the random number generator.
       The 'seed' parameter is used to generate the first number of the
         sequence. Thus, following a call to RandomInit with a given seed,
         the random number sequence will always be the same, regardless of
         any previous call to Randomize, RandomCard, etc...
       Note: RandomCard, RandomInt, RandomReal are based on the same
         generator, so in order to get the same sequence, these functions
         must be called in the same order.
    *)

  PROCEDURE RandomCard (bound : CARDINAL) : CARDINAL;
    (* Returns a random cardinal in the range (0 <= r < bound) if bound is
       greater than 0, or in the range (0 <= r <= MaxCard) if bound = 0.
    *)

  PROCEDURE RandomInt (bound : INTEGER): INTEGER;
    (* Returns a random integer in the range (0 <= r < bound) if bound is
       greater than 0, or in the range (0 <= r <= MaxInt) if bound = 0.
    *)
(*
  PROCEDURE RandomReal (): Real8;
*)    (* Returns a random real uniformly distributed  the range (0.0 <= r < 1.0)
       with 15-16 decimal digits (IEEE double precision floating point numbers
       standard)
    *)

END Rand.