Signal

A Signal<T> lets threads block until another thread sends a value. Declare one as a shared variable so all threads can access it.

shared Signal<Int> sig

def worker:
    print("waiting...")
    let val = sig.wait()
    print("got", val)
end

spawn worker()
sleep_ms(10) // if notify triggers before wait, thread will never see it
sig.notify(42)

.wait() blocks the calling thread until .notify() is called and returns the value passed to notify. All threads currently waiting on the signal are unblocked at once.

.notify(value) sets the signal's value and wakes every waiting thread. If no value is given it uses the zero value of T.