Module
Result
:
sig end
Result values.
Result values handle computation results and errors in an explicit and declarative manner without resorting to exceptions.
Since 4.08
type
('a, 'e)
t
=
('a, 'e) result
=
| Ok
of
'a
| Error
of
'e
The type for result values. Either a value Ok v or an error Error e .
val ok : 'a -> ('a, 'e) result
ok v is Ok v .
val error : 'e -> ('a, 'e) result
error e is Error e .
val value : ('a, 'e) result -> default:'a -> 'a
value r ~default is v if r is Ok v and default otherwise.
val get_ok : ('a, 'e) result -> 'a
get_ok r is v if r is Ok v and
Raises Invalid_argument otherwise.
val get_error : ('a, 'e) result -> 'e
get_error r is e if r is Error e and
Raises Invalid_argument otherwise.
val bind : ('a, 'e) result -> ('a -> ('b, 'e) result) -> ('b, 'e) result
bind r f is f v if r is Ok v and r if r is Error _ .
val join : (('a, 'e) result, 'e) result -> ('a, 'e) result
join rr is r if rr is Ok r and rr if rr is Error _ .
val map : ('a -> 'b) -> ('a, 'e) result -> ('b, 'e) result
map f r is Ok (f v) if r is Ok v and r if r is Error _ .
val map_error : ('e -> 'f) -> ('a, 'e) result -> ('a, 'f) result
map_error f r is Error (f e) if r is Error e and r if r is Ok _ .
val fold : ok:('a -> 'c) -> error:('e -> 'c) -> ('a, 'e) result -> 'c
fold ~ok ~error r is ok v if r is Ok v and error e if r is Error e .
val iter : ('a -> unit) -> ('a, 'e) result -> unit
iter f r is f v if r is Ok v and () otherwise.
val iter_error : ('e -> unit) -> ('a, 'e) result -> unit
iter_error f r is f e if r is Error e and () otherwise.
val is_ok : ('a, 'e) result -> bool
is_ok r is true iff r is Ok _ .
val is_error : ('a, 'e) result -> bool
is_error r is true iff r is Error _ .
val equal : ok:('a -> 'a -> bool) -> error:('e -> 'e -> bool) -> ('a, 'e) result -> ('a, 'e) result -> bool
equal ~ok ~error r0 r1 tests equality of r0 and r1 using ok and error to respectively compare values wrapped by Ok _ and Error _ .
val compare : ok:('a -> 'a -> int) -> error:('e -> 'e -> int) -> ('a, 'e) result -> ('a, 'e) result -> int
compare ~ok ~error r0 r1 totally orders r0 and r1 using ok and error to respectively compare values wrapped by Ok _ and Error _ . Ok _ values are smaller than Error _ values.
val to_option : ('a, 'e) result -> 'a option
to_option r is r as an option, mapping Ok v to Some v and Error _ to None .
val to_list : ('a, 'e) result -> 'a list
to_list r is [v] if r is Ok v and [] otherwise.
val to_seq : ('a, 'e) result -> 'a Seq.t
to_seq r is r as a sequence. Ok v is the singleton sequence containing v and Error _ is the empty sequence.