future Futures and promises. This implementation follows the model of shared futures. Thus multiple waiters on the same future are allowed. Functions new() → promise, future Constructor. Creates a promise and its associated future and returns them. future functions get(self) → value If result is available, returns result. Otherwise, blocks current fiber until result is ready and returns it. promise functions set_value(self, v) Atomically stores the value into the shared state and makes the state ready. set_error(self, e) Atomically stores the exception e into the shared state and makes the state ready. condition_variable open_flag