Weak.Make

`functor (H : Hashtbl.HashedType) ->
sig
type data = H.t
type t
val create : int -> t
val clear : t -> unit
val merge : t -> data -> data
val add : t -> data -> unit
val remove : t -> data -> unit
val find : t -> data -> data
val find_all : t -> data -> data list
val mem : t -> data -> bool
val iter : (data -> unit) -> t -> unit
val fold : (data -> 'a -> 'a) -> t -> 'a -> 'a
val count : t -> int
val stats : t -> int * int * int * int * int * int
end`