Module Base__.Result

Result is often used to handle error messages.

type ('ok, 'err) t = ('ok'err) Pervasives.result =
| Ok of 'ok
| Error of 'err

'ok is a function's expected return type, and 'err 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.

include sig ... end
val compare : ('ok ‑> 'ok ‑> int) ‑> ('err ‑> 'err ‑> int) ‑> ('ok'errt ‑> ('ok'errt ‑> int
val t_of_sexp : (Base__.Sexplib.Sexp.t ‑> 'ok) ‑> (Base__.Sexplib.Sexp.t ‑> 'err) ‑> Base__.Sexplib.Sexp.t ‑> ('ok'errt
val sexp_of_t : ('ok ‑> Base__.Sexplib.Sexp.t) ‑> ('err ‑> Base__.Sexplib.Sexp.t) ‑> ('ok'errt ‑> Base__.Sexplib.Sexp.t
include Base.Monad.S2 with type (a, err) t := (a, err) t
type ('a, 'e) t
include Base__.Monad_intf.Infix2 with type (a, e) t := (a, e) t
type ('a, 'e) t
val (>>=) : ('a'et ‑> ('a ‑> ('b'et) ‑> ('b'et
val (>>|) : ('a'et ‑> ('a ‑> 'b) ‑> ('b'et
include Base__.Monad_intf.Syntax2 with type (a, e) t := (a, e) t
type ('a, 'e) t
module Let_syntax : sig ... end
module Monad_infix : Base__.Monad_intf.Infix2 with type (a, e) t := (a, e) t
val bind : ('a'et ‑> f:('a ‑> ('b'et) ‑> ('b'et
val return : 'a ‑> ('a_t
val map : ('a'et ‑> f:('a ‑> 'b) ‑> ('b'et
val join : (('a'et'et ‑> ('a'et
val ignore_m : (_'et ‑> (unit, 'et
val all : ('a'et list ‑> ('a list, 'et
val all_ignore : (unit, 'et list ‑> (unit, 'et
val ignore : (_'errt ‑> (unit, 'errt
val fail : 'err ‑> (_'errt
val failf : ('a, unit, string, (_, string) t) Pervasives.format4 ‑> 'a

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

val is_ok : (__t ‑> bool
val is_error : (__t ‑> bool
val ok : ('ok_t ‑> 'ok option
val ok_exn : ('ok, exn) t ‑> 'ok
val ok_or_failwith : ('ok, string) t ‑> 'ok
val error : (_'errt ‑> 'err option
val of_option : 'ok option ‑> error:'err ‑> ('ok'errt
val iter : ('ok_t ‑> f:('ok ‑> unit) ‑> unit
val iter_error : (_'errt ‑> f:('err ‑> unit) ‑> unit
val map : ('ok'errt ‑> f:('ok ‑> 'c) ‑> ('c'errt
val map_error : ('ok'errt ‑> f:('err ‑> 'c) ‑> ('ok'ct
val combine : ('ok1'errt ‑> ('ok2'errt ‑> ok:('ok1 ‑> 'ok2 ‑> 'ok3) ‑> err:('err ‑> 'err ‑> 'err) ‑> ('ok3'errt

Returns Ok if both are Ok and Error otherwise.

val ok_fst : ('ok'errt ‑> [ `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"]) 
val ok_if_true : bool ‑> error:'err ‑> (unit, 'errt

ok_if_true returns Ok () if bool is true, and Error error if it is false

val try_with : (unit ‑> 'a) ‑> ('a, exn) t
val ok_unit : (unit, _t

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

module Export : sig ... end