Module `Stdlib.Either`Source

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

Sourcetype ('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

Sourceval left : 'a -> ('a, 'b) Stdlib.Either.t

left v is Left v.

Sourceval right : 'b -> ('a, 'b) Stdlib.Either.t

right v is Right v.

Sourceval is_left : ('a, 'b) Stdlib.Either.t -> bool

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

Sourceval is_right : ('a, 'b) Stdlib.Either.t -> bool

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

Sourceval get_left : ('a, 'b) Stdlib.Either.t -> 'a

get_left e is v if e is Left v and raise otherwise.

raises Invalid_argument
if e is Right _.

since 5.4

Sourceval get_right : ('a, 'b) Stdlib.Either.t -> 'b

get_right e is v if e is Right v and raise otherwise.

raises Invalid_argument
if e is Left _.

since 5.4

Sourceval find_left : ('a, 'b) Stdlib.Either.t -> 'a option

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

Sourceval find_right : ('a, 'b) Stdlib.Either.t -> 'b option

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

Source

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

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

Source

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

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

Source

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

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

Source

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

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

Sourceval retract : ('a, 'a) Stdlib.Either.t -> 'a

retract (Left v) is v, and retract (Right v) is v.

since 5.4

Source

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

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

Source

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

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

Source

val equal : 
  left:('a -> 'a -> bool) ->
  right:('b -> 'b -> bool) ->
  ('a, 'b) Stdlib.Either.t ->
  ('a, 'b) Stdlib.Either.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 _.

Source

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

Module Stdlib.EitherSource

Module `Stdlib.Either`Source