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