val mem : elt -> t -> boolval remove : elt -> t -> tval equal : t -> t -> boolval subset : t -> t -> boolval fold : (elt -> 'a1 -> 'a1) -> t -> 'a1 -> 'a1val 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 choose : t -> elt optionval eq_dec : t -> t -> bool