Module Sugar__Promise_builder.Make

A parametric module that implements the monadic interface for values. The complete documentation can be found in Sugar.S.Promise.

Parameters

UserMonad : Sugar.S.Params.Monad
UserError : Sugar.S.Params.Error

Signature

type error

Error definition imported from your project

type 'a value = ('a, UserError.t) Result.result

An alias for Pervasives.result that can only work with errors of your project.

type 'a monad

This type is an alias to the underlining monad used to create your Promise module. In other words, it points to the main type of your threading library (Lwt.t for Lwt, or Async.Std.Deferred.t for Async).

type 'a result = ('a, UserError.t) Result.result UserMonad.t

This type describes a result monad inside a project.

For example, if the concrete module is built on top of Lwt, a value of type unit result will be translated as (unit, error) Pervasives.result Lwt.t.

val (>>=) : 'a result ‑> ('a ‑> 'b result) ‑> 'b result

This combinator is also called bind.

It can be used to chain sequential operations with the current monad. If the computation in the left failed, the operator will propagate the error, skipping the function completely.

val bind : 'a result ‑> ('a ‑> 'b result) ‑> 'b result

Similar to S.Result.bind

val bind_unless : 'a result ‑> (error ‑> 'a result) ‑> 'a result

Similar to S.Result.bind_unless

val map : 'a result ‑> ('a ‑> 'b) ‑> 'b result

Similar to S.Result.map

val return : 'a ‑> 'a result

Similar to S.Result.return

val throw : error ‑> 'a result

Similar to S.Result.throw

module Infix : sig ... end
val unwrap : 'a value monad ‑> 'a monad

Unwraps the successful value as a normal value in the threading monad. If the value is not successful, it will raise an Invalid_arg exception.

val unwrap_or : (error ‑> 'a monad) ‑> 'a value monad ‑> 'a monad

Unwraps the successful value as a value in the threading monad. Different from unwrap, you can assign an error handler to be executed if the computation failed.

val expect : 'a value monad ‑> string ‑> 'a monad

Extracts a successful value from an computation, or raises and Invalid_arg exception with a customized error message.