cppdraft_translate/cppdraft/exec/with/awaitable/senders.md

[exec.with.awaitable.senders]

33 Execution control library [exec]

33.13 Coroutine utilities [exec.coro.util]

33.13.2 execution​::​with_awaitable_senders [exec.with.awaitable.senders]

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with_awaitable_senders, when used as the base class of a coroutine promise type, makes senders awaitable in that coroutine type.

In addition, it provides a default implementation of unhandled_stopped such that if a sender completes by calling set_stopped, it is treated as if an uncatchable "stopped" exception were thrown from the await-expression.

[Note 1:

The coroutine is never resumed, and the unhandled_stopped of the coroutine caller's promise type is called.

— end note]

namespace std::execution {template<class-type Promise>struct with_awaitable_senders {templaterequires (<OtherPromise, void>)void set_continuation(coroutine_handle h) noexcept;

coroutine_handle<> continuation() const noexcept { return continuation; } coroutine_handle<> unhandled_stopped() noexcept {return stopped-handler(continuation.address()); }templatesee below await_transform(Value&& value); private:noreturn static coroutine_handle<>default-unhandled-stopped(void*) noexcept { // exposition only terminate(); } coroutine_handle<> continuation{}; // exposition only coroutine_handle<> (stopped-handler)(void) noexcept = // exposition only&default-unhandled-stopped; };}

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template<class OtherPromise> requires (![same_as](concept.same#concept:same_as "18.4.2 Concept same_­as [concept.same]")<OtherPromise, void>) void set_continuation(coroutine_handle<OtherPromise> h) noexcept;

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Effects: Equivalent to:continuation = h;if constexpr ( requires(OtherPromise& other) { other.unhandled_stopped(); } ) {stopped-handler = [](void* p) noexcept -> coroutine_handle<> {return coroutine_handle::from_address(p).promise().unhandled_stopped(); };} else {stopped-handler = &default-unhandled-stopped;}

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template<class Value> call-result-t<as_awaitable_t, Value, Promise&> await_transform(Value&& value);

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Effects: Equivalent to:return as_awaitable(std::forward(value), static_cast<Promise&>(*this));