lwt 5.7.0 · OCaml Package

Explicit error handling

since 2.6.0

This module provides helpers for values of type ('a, 'b) result Lwt.t. The module is experimental and may change in the future.

type (+'a, +'b) t = ('a, 'b) Stdlib.result Lwt.t

val return : 'a -> ('a, _) t

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

val lift : ('a, 'b) Stdlib.result -> ('a, 'b) t

val ok : 'a Lwt.t -> ('a, _) t

val error : 'b Lwt.t -> (_, 'b) t

since 5.6.0

val catch : (unit -> 'a Lwt.t) -> ('a, exn) t

catch x behaves like return y if x () evaluates to y, and like fail e if x () raises e

val get_exn : ('a, exn) t -> 'a Lwt.t

get_exn is the opposite of catch: it unwraps the result type, returning the value in case of success, calls Lwt.fail in case of error.

val map : ('a -> 'b) -> ('a, 'e) t -> ('b, 'e) t

val map_error : ('e1 -> 'e2) -> ('a, 'e1) t -> ('a, 'e2) t

since 5.6.0

val bind : ('a, 'e) t -> ('a -> ('b, 'e) t) -> ('b, 'e) t

val bind_error : ('a, 'e1) t -> ('e1 -> ('a, 'e2) t) -> ('a, 'e2) t

since 5.6.0

val bind_lwt : ('a, 'e) t -> ('a -> 'b Lwt.t) -> ('b, 'e) t

val bind_lwt_error : ('a, 'e1) t -> ('e1 -> 'e2 Lwt.t) -> ('a, 'e2) t

since 5.6.0

val bind_result : ('a, 'e) t -> ('a -> ('b, 'e) Stdlib.result) -> ('b, 'e) t

val both : ('a, 'e) t -> ('b, 'e) t -> ('a * 'b, 'e) t

Lwt.both p_1 p_2 returns a promise that is pending until both promises p_1 and p_2 become resolved. If only p_1 is Error e, the promise is resolved with Error e, If only p_2 is Error e, the promise is resolved with Error e, If both p_1 and p_2 resolve with Error _, the promise is resolved with the error that occurred first.

val iter : ('a -> unit Lwt.t) -> ('a, 'e) t -> unit Lwt.t

iter f r is f v if r is a promise resolved with Ok v, and Lwt.return_unit otherwise.

since Lwt 5.6.0

val iter_error : ('e -> unit Lwt.t) -> ('a, 'e) t -> unit Lwt.t

iter_error f r is f v if r is a promise resolved with Error v, and Lwt.return_unit otherwise.

since Lwt 5.6.0

module Infix : sig ... end

module Let_syntax : sig ... end

module Syntax : sig ... end

include module type of Infix

val (>|=) : ('a, 'e) t -> ('a -> 'b) -> ('b, 'e) t

val (>>=) : ('a, 'e) t -> ('a -> ('b, 'e) t) -> ('b, 'e) t

Deprecated

val map_err : ('e1 -> 'e2) -> ('a, 'e1) t -> ('a, 'e2) t

deprecated
Alias to map_error since 5.6.0.

val bind_lwt_err : ('a, 'e1) t -> ('e1 -> 'e2 Lwt.t) -> ('a, 'e2) t

deprecated
Alias to bind_lwt_error since 5.6.0.

package lwt

Deprecated