The Asynchronous Layer

Keikaku’s async support builds on the generator/coroutine machinery. Functions become non-blocking with async protocol (or async sequence), and await pauses execution until a promise resolves or a generator yields, a uniform suspension point across both. Promises are represented as objects, and resolve(value) constructs an already-resolved promise that await can consume. The documented pattern is idiomatic async/await: an async protocol main() does user := await fetch_user(1) then posts := await fetch_posts(user) and declares both, driven by await main().

Two scheduling primitives complete the layer. defer(delay, fn, args...) schedules a function call for later execution (defer(500, declare, "Executed after 500ms")), and sleep(ms) pauses for a duration in milliseconds. The async layer deliberately mirrors mainstream async/await semantics so it is immediately usable, while keeping Keikaku’s themed protocol/sequence vocabulary. Because await suspends on both promises and generator yields through the same mechanism, the async and generator systems are two faces of one underlying coroutine runtime.