Result

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type ('ok, 'err) t =

# \| Ok of 'ok
# \| Error of 'err

'a is a function's expected return type, and 'b is often an error message string.

let ric_of_ticker = function
    | "IBM" -> Ok "IBM.N"
    | "MSFT" -> Ok "MSFT.OQ"
    | "AA" -> Ok "AA.N"
    | "CSCO" -> Ok "CSCO.OQ"
    | _ as ticker -> Error (sprintf "can't find ric of %s" ticker)

The return type of ric_of_ticker could be string option, but (string, string) Result.t gives more control over the error message.

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val fail : 'err -> (_, 'err) t

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val failf : ('a, unit, string, (_, string) t) Pervasives.format4 -> 'a

e.g. failf "Couldn't find bloogle %s" (Bloogle.to_string b)

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val is_ok : (_, _) t -> bool

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val is_error : (_, _) t -> bool

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val ok : ('ok, _) t -> 'ok option

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val error : (_, 'err) t -> 'err option

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val of_option : 'ok option -> error:'err -> ('ok, 'err) t

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val iter : ('ok, _) t -> f:('ok -> unit) -> unit

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val iter_error : (_, 'err) t -> f:('err -> unit) -> unit

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val map : ('ok, 'err) t -> f:('ok -> 'c) -> ('c, 'err) t

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val map_error : ('ok, 'err) t -> f:('err -> 'c) -> ('ok, 'c) t

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val combine : ('ok1, 'err) t -> ('ok2, 'err) t -> ok:('ok1 -> 'ok2 -> 'ok3) -> err:('err -> 'err -> 'err) -> ('ok3, 'err) t

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val ok_fst : ('ok, 'err) t -> [

| `Fst of 'ok

| `Snd of 'err

]

ok_fst is useful with List.partition_map. Continuing the above example:

    let rics, errors = List.partition_map ~f:Result.ok_fst
      (List.map ~f:ric_of_ticker ["AA"; "F"; "CSCO"; "AAPL"])

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val ok_if_true : bool -> error:'err -> (unit, 'err) t

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val try_with : (unit -> 'a) -> ('a, exn) t

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val ok_exn : ('ok, exn) t -> 'ok

ok_exn t returns x if t = Ok x, and raises exn if t = Error exn

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val ok_or_failwith : ('ok, string) t -> 'ok

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val ok_unit : (unit, _) t

ok_unit = Ok (), used to avoid allocation as a performance hack

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module Export : sig

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type ('ok, 'err) _result = ('ok, 'err) t =

# \| Ok of 'ok
# \| Error of 'err

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val is_ok : (_, _) t -> bool

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val is_error : (_, _) t -> bool

end

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module Stable : sig

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module V1 : sig

include sig

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type ('ok, 'err) __pa_nonrec_0 = ('ok, 'err) t =

# \| Ok of 'ok
# \| Error of 'err

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type ('ok, 'err) t = ('ok, 'err) __pa_nonrec_0 =

# \| Ok of 'ok
# \| Error of 'err

end

with type ('a0, 'a1) __pa_nonrec_0 := ('a0, 'a1) t

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val compare : ('ok -> 'ok -> int) -> ('err -> 'err -> int) -> ('ok, 'err) t -> ('ok, 'err) t -> int

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val bin_t : 'ok Bin_prot.Type_class.t -> 'err Bin_prot.Type_class.t -> ('ok, 'err) t Bin_prot.Type_class.t

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val bin_read_t : 'ok Bin_prot.Read.reader -> 'err Bin_prot.Read.reader -> ('ok, 'err) t Bin_prot.Read.reader

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val __bin_read_t__ : 'ok Bin_prot.Read.reader -> 'err Bin_prot.Read.reader -> (int -> ('ok, 'err) t) Bin_prot.Read.reader

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val bin_reader_t : 'ok Bin_prot.Type_class.reader -> 'err Bin_prot.Type_class.reader -> ('ok, 'err) t Bin_prot.Type_class.reader

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val bin_size_t : 'ok Bin_prot.Size.sizer -> 'err Bin_prot.Size.sizer -> ('ok, 'err) t Bin_prot.Size.sizer

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val bin_write_t : 'ok Bin_prot.Write.writer -> 'err Bin_prot.Write.writer -> ('ok, 'err) t Bin_prot.Write.writer

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val bin_writer_t : 'ok Bin_prot.Type_class.writer -> 'err Bin_prot.Type_class.writer -> ('ok, 'err) t Bin_prot.Type_class.writer

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val t_of_sexp : (Sexplib.Sexp.t -> 'ok) -> (Sexplib.Sexp.t -> 'err) -> Sexplib.Sexp.t -> ('ok, 'err) t

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val sexp_of_t : ('ok -> Sexplib.Sexp.t) -> ('err -> Sexplib.Sexp.t) -> ('ok, 'err) t -> Sexplib.Sexp.t

end

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module V1_stable_unit_test : Stable_unit_test_intf.Arg

end

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