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Module Stdlib.ResultSource

Result values.

Result values handle computation results and errors in an explicit and declarative manner without resorting to exceptions.

Results

Sourcetype ('a, 'e) t = ('a, 'e) Stdlib.result =
  1. | Ok of 'a
  2. | Error of 'e

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

Sourceval ok : 'a -> ('a, 'e) Stdlib.result

ok v is Ok v.

Sourceval error : 'e -> ('a, 'e) Stdlib.result

error e is Error e.

Sourceval value : ('a, 'e) Stdlib.result -> default:'a -> 'a

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

Sourceval get_ok : ('a, 'e) Stdlib.result -> 'a

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

Sourceval get_ok' : ('a, string) Stdlib.result -> 'a

get_ok' is like get_ok but in case of error uses the error message for raising Invalid_argument.

  • since 5.4
Sourceval get_error : ('a, 'e) Stdlib.result -> 'e

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

Sourceval error_to_failure : ('a, string) Stdlib.result -> 'a

error_to_failure r is v if r is Ok v and raises Failure e if r is Error e.

  • since 5.4
Sourceval bind : ('a, 'e) Stdlib.result -> ('a -> ('b, 'e) Stdlib.result) -> ('b, 'e) Stdlib.result

bind r f is f v if r is Ok v and r if r is Error _.

Sourceval join : (('a, 'e) Stdlib.result, 'e) Stdlib.result -> ('a, 'e) Stdlib.result

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

Sourceval map : ('a -> 'b) -> ('a, 'e) Stdlib.result -> ('b, 'e) Stdlib.result

map f r is Ok (f v) if r is Ok v and r if r is Error _.

Sourceval product : ('a, 'e) Stdlib.result -> ('b, 'e) Stdlib.result -> ('a * 'b, 'e) Stdlib.result

product r0 r1 is Ok (v0, v1) if r0 is Ok v0 and r1 is Ok v2 and otherwise returns the error of r0, if any, or the error of r1.

  • since 5.4
Sourceval map_error : ('e -> 'f) -> ('a, 'e) Stdlib.result -> ('a, 'f) Stdlib.result

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

Sourceval fold : ok:('a -> 'c) -> error:('e -> 'c) -> ('a, 'e) Stdlib.result -> 'c

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

Sourceval retract : ('a, 'a) Stdlib.result -> 'a

retract r is v if r is Ok v or Error v.

  • since 5.4
Sourceval iter : ('a -> unit) -> ('a, 'e) Stdlib.result -> unit

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

Sourceval iter_error : ('e -> unit) -> ('a, 'e) Stdlib.result -> unit

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

Predicates and comparisons

Sourceval is_ok : ('a, 'e) Stdlib.result -> bool

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

Sourceval is_error : ('a, 'e) Stdlib.result -> bool

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

Sourceval equal : ok:('a -> 'a -> bool) -> error:('e -> 'e -> bool) -> ('a, 'e) Stdlib.result -> ('a, 'e) Stdlib.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 _.

Sourceval compare : ok:('a -> 'a -> int) -> error:('e -> 'e -> int) -> ('a, 'e) Stdlib.result -> ('a, 'e) Stdlib.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.

Converting

Sourceval to_option : ('a, 'e) Stdlib.result -> 'a option

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

Sourceval to_list : ('a, 'e) Stdlib.result -> 'a list

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

Sourceval to_seq : ('a, 'e) Stdlib.result -> 'a Stdlib.Seq.t

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

Syntax

Sourcemodule Syntax : sig ... end

Binding operators.