Either(3)                        OCaml library                       Either(3)

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.



OCamldoc                          2024-02-29                         Either(3)