sig
type elt = hashable
type 'a elt_ = elt
type 'a set
val create : int -> 'a set
val add : 'a set -> 'a elt_ -> unit
val strict_add : 'a set -> 'a elt_ -> unit
val remove : 'a set -> 'a elt_ -> unit
val strict_remove : 'a set -> 'a elt_ -> unit
val clear : 'a set -> unit
val fold : f:('a -> 'b elt_ -> 'a) -> init:'a -> 'b set -> 'a
val iter : f:('a elt_ -> unit) -> 'a set -> unit
val length : 'a set -> int
val mem : 'a set -> 'a elt_ -> bool
val of_list : 'a elt_ list -> 'a set
val to_list : 'a set -> 'a elt_ list
type t = unit set
val sexp_of_t : t -> Sexplib.Sexp.t
val t_of_sexp : Sexplib.Sexp.t -> t
end