(* random.sig *)

(* Copyright (C) 2007 Alley Stoughton

   This file is part of crypto, a cryptogram encoder/decoder.  See the
   file COPYING.txt for copying and usage restrictions *)

(* signature of structure for generating random numbers *)

signature RANDOM =
sig

(* random number seed *)

type seed

(* make a seed that is a function of the current time *)

val makeFromTime : unit -> seed

exception BadRange

val getInRange : seed * int * int -> seed * int

(* if m <= n, then getInRange(seed, m, n) "randomly" turns seed
   into a new seed, uses modular arithmetic to turn this new seed into
   a number in the range m to n, and returns the new seed and this
   number; otherwise getInRange raises BadRange *)

end;