Module Std.Result

include module type of struct include Result end

Results

type (('a : value_or_null), ('e : value_or_null)) t = ('a, 'e) result =
  1. | Ok of 'a
  2. | Error of 'e

The type for result values. Either a value Ok v or an error Error e.

val ok : 'a 'e. 'a -> ('a, 'e) result @@ portable

ok v is Ok v.

val error : 'a 'e. 'e -> ('a, 'e) result @@ portable

error e is Error e.

val value : 'a 'e. ('a, 'e) result -> default:'a -> 'a @@ portable

value r ~default is v if r is Ok v and default otherwise.

val get_ok : 'a 'e. ('a, 'e) result -> 'a @@ portable

get_ok r is v if r is Ok v and raise otherwise.

val get_error : 'a 'e. ('a, 'e) result -> 'e @@ portable

get_error r is e if r is Error e and raise otherwise.

val join : 'a 'e. (('a, 'e) result, 'e) result -> ('a, 'e) result @@ portable

join rr is r if rr is Ok r and rr if rr is Error _.

val map_error : 'a 'e 'f. ('e -> 'f) -> ('a, 'e) result -> ('a, 'f) result @@ portable

map_error f r is Error (f e) if r is Error e and r if r is Ok _.

val fold : 'a 'c 'e. ok:('a -> 'c) -> error:('e -> 'c) -> ('a, 'e) result -> 'c @@ portable

fold ~ok ~error r is ok v if r is Ok v and error e if r is Error e.

val iter : 'a 'e. ('a -> unit) -> ('a, 'e) result -> unit @@ portable

iter f r is f v if r is Ok v and () otherwise.

val iter_error : 'a 'e. ('e -> unit) -> ('a, 'e) result -> unit @@ portable

iter_error f r is f e if r is Error e and () otherwise.

Predicates and comparisons

val is_ok : 'a 'e. ('a, 'e) result -> bool @@ portable

is_ok r is true if and only if r is Ok _.

val is_error : 'a 'e. ('a, 'e) result -> bool @@ portable

is_error r is true if and only if r is Error _.

val equal : 'a 'e. ok:('a -> 'a -> bool) -> error:('e -> 'e -> bool) -> ('a, 'e) result -> ('a, 'e) result -> bool @@ portable

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 : 'a 'e. ok:('a -> 'a -> int) -> error:('e -> 'e -> int) -> ('a, 'e) result -> ('a, 'e) result -> int @@ portable

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.

Converting

val to_option : 'a 'e. ('a, 'e) result -> 'a option @@ portable

to_option r is r as an option, mapping Ok v to Some v and Error _ to None.

val to_list : 'a 'e. ('a, 'e) result -> 'a list @@ portable

to_list r is [v] if r is Ok v and [] otherwise.

val to_seq : 'a 'e. ('a, 'e) result -> 'a Seq.t @@ portable

to_seq r is r as a sequence. Ok v is the singleton sequence containing v and Error _ is the empty sequence.

val map : f:('a -> 'b) -> ('a, 'c) result -> ('b, 'c) result
val bind : f:('a -> ('b, 'c) result) -> ('a, 'c) result -> ('b, 'c) result