Delay

A dead simple data-structure for delaying side effects. Written in the excellent gleam ✨ language. Supporting both Erlang & Javascript targets

Basic Usage

import gleam/io

let d = delay_effect(fn() {
 io.println("Hello")
 Ok(1)
}) |> delay.map(fn(x) {
 io.println("World")
 Ok(x + 1)
})

let res = delay.run(d)
// Hello
// World
// res = Ok(2)

More info

The result of delay_effect is really just a first class function with a nice API wrapper. It isn’t executed until put through one of run/1, drain/1 or fallthrough/1. And can be called as many times as you want.

let d = delay_effect(fn() {
 io.println("Hello")
 Error("bummer")
}) |> delay.map(fn(x) {
 io.println("World")
 Ok(x + 1)
})

let res = delay.run(d)
// Hello
// res = Error("bummer")

If one of the functions in the chain fails, the rest will short circuit and the error will be returned.

Effects can be retried as well via retry/3

// using the same effect `d` from above

let res = delay.retry(d, 3, 200) |> delay.run()
// Hello
// Hello
// Hello
// Hello
// res = Error("bummer")

FAQ

Doesn’t the concept of a delayed side effect kind of lose value in the world of actor model concurrency and zero shared memory?!

A little

Then why did you write this?

For fun

Is gleam ✨ actually excellent?

So far