signature String =
sig
(*
 * Types
 *)
   eqtype string;

(*
 * String constants
 *)

(*
 * Binary Operations
 *)
   val ^ : string * string -> string;

(*
 * Unary Operations
 *)
   val ord : string -> int
   and chr : int -> string

(*
 * Predicates
 *)
   and <  : string * string -> bool
   and <= : string * string -> bool
   and >  : string * string -> bool
   and >= : string * string -> bool

end;
 
structure String : String = 
struct 
   type string = string

   val op ^  = op ^
   and ord   = ord
   and chr   = chr

(*
 * Predicates
 *)
   and op <  = op <  : string * string -> bool
   and op <= = op <= : string * string -> bool
   and op >  = op >  : string * string -> bool
   and op >= = op >= : string * string -> bool

end;