Reason · Reason lets you write simple, fast and quality type safe code while leveraging both the JavaScript & OCaml ecosystems.

sig
 type ('a, 'b) t = Left of 'a | Right of 'b
 val left : 'a -> ('a, 'b) Either.t
 val right : 'b -> ('a, 'b) Either.t
 val is_left : ('a, 'b) Either.t -> bool
 val is_right : ('a, 'b) Either.t -> bool
 val find_left : ('a, 'b) Either.t -> 'a option
 val find_right : ('a, 'b) Either.t -> 'b option
 val map_left : ('a1 -> 'a2) -> ('a1, 'b) Either.t -> ('a2, 'b) Either.t
 val map_right : ('b1 -> 'b2) -> ('a, 'b1) Either.t -> ('a, 'b2) Either.t
 val map :
  left:('a1 -> 'a2) ->
  right:('b1 -> 'b2) -> ('a1, 'b1) Either.t -> ('a2, 'b2) Either.t
 val fold : left:('a -> 'c) -> right:('b -> 'c) -> ('a, 'b) Either.t -> 'c
 val iter :
  left:('a -> unit) -> right:('b -> unit) -> ('a, 'b) Either.t -> unit
 val for_all :
  left:('a -> bool) -> right:('b -> bool) -> ('a, 'b) Either.t -> bool
 val equal :
  left:('a -> 'a -> bool) ->
  right:('b -> 'b -> bool) ->
  ('a, 'b) Either.t -> ('a, 'b) Either.t -> bool
 val compare :
  left:('a -> 'a -> int) ->
  right:('b -> 'b -> int) -> ('a, 'b) Either.t -> ('a, 'b) Either.t -> int
end