NAME

       Result - Result values.

Module

       Module   Result

Documentation

       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

   Results
       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 raise otherwise.

       Raises Invalid_argument if r is Error _ .

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

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

       Raises Invalid_argument if r is Ok _ .

       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.

   Predicates and comparisons
       val is_ok : ('a, 'e) result -> bool

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

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

       is_error r is true if and only if 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.

   Converting
       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.