type 'x set

val empty : 'a1 set

val is_empty: 'a1 set -> bool

val mem : 'a1 -> 'a1 set -> bool

val add : 'a1 -> 'a1 set -> 'a1 set

val remove: 'a1 -> 'a1 set -> 'a1 set

val cardinal: 'a1 set -> int

val fold: ('a1 -> 'a -> 'a) -> 'a1 set -> 'a -> 'a

val iter: ('a1 -> unit) -> 'a1 set -> unit

val equal : 'a1 set -> 'a1 set -> bool

val diff : 'a1 set -> 'a1 set -> 'a1 set

val singleton : 'a1 -> 'a1 set

val subset : 'a1 set -> 'a1 set -> bool

val union : 'a1 set -> 'a1 set -> 'a1 set