module type S =sig..end
      module Foo : sig
        type t = ...
        include Comparable.S with type t := t
      end
    
    Then use Comparable.Make in the struct (see comparable.mli for an example).
include Comparable_intf.S_common
module Map:Core_map.Swith type Key.t = twith type Key.comparator = comparator
module Set:Core_set.Swith type Elt.t = twith type Elt.comparator = comparator