async

overview

void supports async/await for non-blocking IO operations.

import std.io.net.HttpClient as Http;
import std.io.stdout;

async fn main(args: Array[str]) uint8 {
    let http = Http.new();
    let res = http.get("api.example.com/data").await?;
    stdout.println("status: {}", res.status);
    return 0;
}

async functions

any function can be marked async. it returns an Async[T, E] implicitly.

async fn fetch(url: str) Result[Response, str] {
    // ...
}

await

.await suspends the current function until the async operation completes. it unwraps the Async[T, E] into Result[T, E].

combined with ? for concise error propagation:

let res = http.get("example.com").await?;

async type

Async[T, E] = {
    status: AsyncStatus,
    result: Option[Result[T, E]],
}

AsyncStatus = Pending | Resolved | Failed

model

void async is promise-based, similar to JavaScript. the runtime model (event loop vs thread-per-task) is not yet finalized.