type !'a t = 'a option = | None| Some of 'a
val some : 'a -> 'a optionval value : 'a option -> default:'a -> 'aval get : 'a option -> 'aval bind : 'a option -> ('a -> 'b option) -> 'b optionval join : 'a option option -> 'a optionval map : ('a -> 'b) -> 'a option -> 'b optionval fold : none:'a -> some:('b -> 'a) -> 'b option -> 'aval iter : ('a -> unit) -> 'a option -> unitval is_none : 'a option -> boolval is_some : 'a option -> boolval equal : ('a -> 'a -> bool) -> 'a option -> 'a option -> boolval compare : ('a -> 'a -> int) -> 'a option -> 'a option -> intval to_result : none:'e -> 'a option -> ('a, 'e) resultval to_list : 'a option -> 'a listval to_seq : 'a option -> 'a Seq.t