(* ========================================================================= *)
(* ORDERED TYPES *)
(* Copyright (c) 2004 Joe Hurd, distributed under the BSD License *)
(* ========================================================================= *)
signature Ordered =
sig
type t
val compare : t * t -> order
(*
PROVIDES
!x : t. compare (x,x) = EQUAL
!x y : t. compare (x,y) = LESS <=> compare (y,x) = GREATER
!x y : t. compare (x,y) = EQUAL ==> compare (y,x) = EQUAL
!x y z : t. compare (x,y) = EQUAL ==> compare (x,z) = compare (y,z)
!x y z : t.
compare (x,y) = LESS andalso compare (y,z) = LESS ==>
compare (x,z) = LESS
!x y z : t.
compare (x,y) = GREATER andalso compare (y,z) = GREATER ==>
compare (x,z) = GREATER
*)
end