Functor Core_map.Make_using_comparator

module Make_using_comparator: 
functor (Key : sig
type t 

include Comparator.S
val t_of_sexp : Sexplib.Sexp.t -> t
val sexp_of_t : t -> Sexplib.Sexp.t
end) -> S 
    with type Key.t                  = Key.t 
    with type Key.comparator_witness = Key.comparator_witness