val map : ('a -> 'c) -> ('b -> 'd) -> ('a, 'b) union -> ('c, 'd) unionval equal : ('a -> 'a -> bool) -> ('b -> 'b -> bool) -> ('a, 'b) union -> ('a, 'b) union -> boolval fold_left : ('c -> 'a -> 'c) -> ('c -> 'b -> 'c) -> 'c -> ('a, 'b) union -> 'c