module type VALUE_DOMAIN = sig
	type t

	(* constructors *)
	val top		: t
	val bottom	: t
	val const	: Z.t -> t
	val rand	: Z.t -> Z.t -> t

	(* order *)
	val subset	: t -> t -> bool

	(* set-theoretic operations *)
	val join	: t -> t -> t   (* union *)
	val meet	: t -> t -> t	(* intersection *)
	val widen	: t -> t -> t

	(* arithmetic operations *)
	val neg		: t -> t
	val add		: t -> t -> t
	val sub		: t -> t -> t
	val mul		: t -> t -> t
	val div		: t -> t -> t
	val rem		: t -> t -> t

	(* boolean test *)
	val leq		: t -> t -> t * t	(* For intervals : [a, b] -> [c, d] -> ([a, min b d], [max a c, d]) *)

	(* pretty-printing *)
	val to_string : t -> string
end