functor MKRANDOM() =
struct
  (* Given a seed, mkRandom returns a psuedo-random number generator
     which takes an integer argument of one more than the maximum
     return value required. ( Linear Congruential, after Sedgewick,
     "Algorithms", Addison-Wesley, 1983, Chapter 3 pp 37-38.) *)

  fun mkRandom seed = 
        let val r = ref seed
	    val a = 31415821
	    val m = 100000011

	    fun f n =
	      let val rand = (r := ((a * !r + 1) mod m);
			      (!r * n) div m)
	      in if n < 0 then rand + 1 else rand
	      end
         in f
        end;
end;