33 Execution control library [exec]

run-loop-scheduler is an unspecified type that models scheduler.

Instances of run-loop-scheduler remain valid until the end of the lifetime of the run_loop instance from which they were obtained.

Two instances of run-loop-scheduler compare equal if and only if they were obtained from the same run_loop instance.

Let sch be an expression of type run-loop-scheduler.

The expression schedule(sch) has type run-loop-
sender and is not potentially-throwing if sch is not potentially-throwing.

run-loop-sender is an exposition-only type that satisfies sender.

completion_signatures_of_t<run-
loop-sender> is completion_signatures<set_value_t(), set_error_t(exception_ptr), set_stopped_t()>

An instance of run-loop-sender remains valid until the end of the lifetime of its associated run_loop instance.

Let sndr be an expression of type run-loop-sender, let rcvr be an expression such that receiver_of<decltype((rcvr)), CS> is true where CS is the completion_signatures specialization above.

Let C be either set_value_t or set_stopped_t.

Then:

• (7.1)
  The expression connect(sndr, rcvr) has type run-loop-opstate<decay_t<decltype((rcvr))>> and is potentially-throwing if and only if (void(sndr), auto(rcvr)) is potentially-throwing.
• (7.2)
  The expression get_completion_scheduler<C>(get_env(sndr)) is potentially-throwing if and only if sndr is potentially-throwing, has type run-loop-scheduler, and compares equal to the run-loop-
  scheduler instance from which sndr was obtained.

run-loop-opstate<Rcvr> inherits privately and unambiguously from run-loop-opstate-base.

Let o be a non-const lvalue of type run-loop-opstate<Rcvr>, and let REC(o) be a non-const lvalue reference to an instance of type Rcvr that was initialized with the expression rcvr passed to the invocation of connect that returned o.

Then:

• (9.1)
  The object to which REC(o) refers remains valid for the lifetime of the object to which o refers.
• (9.2)
  The type run-loop-opstate<Rcvr> overrides run-loop-opstate-base​::​execute() such that o.execute() is equivalent to: if (get_stop_token(REC(o)).stop_requested()) { set_stopped(std::move(REC(o))); } else { set_value(std::move(REC(o))); }
• (9.3)
  The expression start(o) is equivalent to: try { o.loop->push-back(addressof(o)); } catch(...) { set_error(std::move(REC(o)), current_exception()); }