Either(3o) OCaml library Either(3o)
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 2023-02-12 Either(3o)
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