val mem : elt -> t -> boolval remove : elt -> t -> tval compare : t -> t -> intval equal : t -> t -> boolval subset : t -> t -> boolval iter : (elt -> unit) -> t -> unitval fold : (elt -> 'a -> 'a) -> t -> 'a -> 'aval for_all : (elt -> bool) -> t -> boolval exists : (elt -> bool) -> t -> boolval filter : (elt -> bool) -> t -> tval partition : (elt -> bool) -> t -> t * tval elements : t -> elt listval split : elt -> t -> t * bool * t