NAME

       Either - Either type.

Module

       Module   Either

Documentation

       Module Either
        : sig end

       Either type.

       Either  is the simplest and most generic sum/variant type: a value of ('a, 'b) Either.t is
       either a Left (v : 'a) or a Right (v : 'b) .

       It is a natural choice in the API of generic functions where  values  could  fall  in  two
       different cases, possibly at different types, without assigning a specific meaning to what
       each case should be.

       For example:

       List.partition_map:
           ('a -> ('b, 'c) Either.t) -> 'a list -> 'b list * 'c list

       If you are looking for a parametrized type where one alternative  means  success  and  the
       other means failure, you should use the more specific type Result.t .

       Since 4.12

       type ('a, 'b) t =
        | Left of 'a
        | Right of 'b

       A value of ('a, 'b) Either.t contains either a value of 'a or a value of 'b

       val left : 'a -> ('a, 'b) t

       left v is Left v .

       val right : 'b -> ('a, 'b) t

       right v is Right v .

       val is_left : ('a, 'b) t -> bool

       is_left (Left v) is true , is_left (Right v) is false .

       val is_right : ('a, 'b) t -> bool

       is_right (Left v) is false , is_right (Right v) is true .

       val find_left : ('a, 'b) t -> 'a option

       find_left (Left v) is Some v , find_left (Right _) is None

       val find_right : ('a, 'b) t -> 'b option

       find_right (Right v) is Some v , find_right (Left _) is None

       val map_left : ('a1 -> 'a2) -> ('a1, 'b) t -> ('a2, 'b) t

       map_left f e is Left (f v) if e is Left v and e if e is Right _ .

       val map_right : ('b1 -> 'b2) -> ('a, 'b1) t -> ('a, 'b2) t

       map_right f e is Right (f v) if e is Right v and e if e is Left _ .

       val map : left:('a1 -> 'a2) -> right:('b1 -> 'b2) -> ('a1, 'b1) t -> ('a2, 'b2) t

       map ~left ~right (Left v) is Left (left v) , map ~left ~right (Right v) is Right (right v)
       .

       val fold : left:('a -> 'c) -> right:('b -> 'c) -> ('a, 'b) t -> 'c

       fold ~left ~right (Left v) is left v , and fold ~left ~right (Right v) is right v .

       val iter : left:('a -> unit) -> right:('b -> unit) -> ('a, 'b) t -> unit

       iter ~left ~right (Left v) is left v , and iter ~left ~right (Right v) is right v .

       val for_all : left:('a -> bool) -> right:('b -> bool) -> ('a, 'b) t -> bool

       for_all ~left ~right (Left v) is left v , and for_all ~left ~right (Right v) is right v .

       val equal : left:('a -> 'a -> bool) -> right:('b -> 'b -> bool) -> ('a, 'b) t -> ('a,  'b)
       t -> bool

       equal  ~left ~right e0 e1 tests equality of e0 and e1 using left and right to respectively
       compare values wrapped by Left _ and Right _ .

       val compare : left:('a -> 'a -> int) -> right:('b -> 'b -> int) -> ('a, 'b) t -> ('a,  'b)
       t -> int

       compare  ~left  ~right e0 e1 totally orders e0 and e1 using left and right to respectively
       compare values wrapped by Left _ and Right _ .  Left _ values are  smaller  than  Right  _
       values.