Tasks and async calls

Calling an async function starts a Task and returns a one-use handle. await obtains its result; T! errors still require ? or try/catch.

async fn Double(value: int): int! {
    return ok(value * 2)
}

async fn main(): null! {
    first = Double(20)
    second = Double(21)
    println((await first)?)
    println((await second)?)
    return ok(null)
}

Save as tasks.ku and run ku run tasks.ku. It prints 40 and 42; the example is also within the restricted native Task subset.

Ownership and completion

A Task moves; it cannot be cloned or awaited twice. When its owning scope exits, unfinished child tasks receive cancellation. Cancellation attempts finally cleanup within a shared one-second deadline. Cancellation and timeout are not ordinary Results caught as business errors.

& borrowing is synchronous; async functions cannot declare borrowed parameters. An async task must own its input data.

Waiting and backends

time.sleep and supported file operations use their respective execution paths. Complete M:N, general network suspension and arbitrary dynamic heap combinations are not implemented. This arithmetic example does not imply async support for every library, database or net call.

ku supervise manages whole-program workers, a different unit from a Task handle. See support and process limits.