    functor (H : HashedType) ->
      sig
        type key = H.t
        and 'a t
        val create : int -> 'a Hashtbl.S.t
        val clear : 'a Hashtbl.S.t -> unit
        val copy : 'a Hashtbl.S.t -> 'a Hashtbl.S.t
        val add : 'a Hashtbl.S.t -> Hashtbl.S.key -> 'a -> unit
        val remove : 'a Hashtbl.S.t -> Hashtbl.S.key -> unit
        val find : 'a Hashtbl.S.t -> Hashtbl.S.key -> 'a
        val find_all : 'a Hashtbl.S.t -> Hashtbl.S.key -> 'a list
        val replace : 'a Hashtbl.S.t -> Hashtbl.S.key -> 'a -> unit
        val mem : 'a Hashtbl.S.t -> Hashtbl.S.key -> bool
        val iter : (Hashtbl.S.key -> 'a -> unit) -> 'a Hashtbl.S.t -> unit
        val fold :
          (Hashtbl.S.key -> 'a -> 'b -> 'b) -> 'a Hashtbl.S.t -> 'b -> 'b
      end