tmp/tmpmhpyf0jk/{from.md → to.md}
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| 1 |
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### `execution::with_awaitable_senders` <a id="exec.with.awaitable.senders">[[exec.with.awaitable.senders]]</a>
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`with_awaitable_senders`, when used as the base class of a coroutine
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promise type, makes senders awaitable in that coroutine type.
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In addition, it provides a default implementation of `unhandled_stopped`
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such that if a sender completes by calling `set_stopped`, it is treated
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as if an uncatchable "stopped" exception were thrown from the
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*await-expression*.
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[*Note 1*: The coroutine is never resumed, and the `unhandled_stopped`
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of the coroutine caller’s promise type is called. — *end note*]
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``` cpp
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namespace std::execution {
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template<class-type Promise>
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struct with_awaitable_senders {
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template<class OtherPromise>
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requires (!same_as<OtherPromise, void>)
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void set_continuation(coroutine_handle<OtherPromise> h) noexcept;
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coroutine_handle<> continuation() const noexcept { return continuation; }
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coroutine_handle<> unhandled_stopped() noexcept {
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return stopped-handler(continuation.address());
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}
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template<class Value>
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see below await_transform(Value&& value);
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private:
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[[noreturn]] static coroutine_handle<>
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default-unhandled-stopped(void*) noexcept { // exposition only
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terminate();
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}
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coroutine_handle<> continuation{}; // exposition only
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coroutine_handle<> (*stopped-handler)(void*) noexcept = // exposition only
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&default-unhandled-stopped;
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};
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}
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```
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``` cpp
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template<class OtherPromise>
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requires (!same_as<OtherPromise, void>)
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void set_continuation(coroutine_handle<OtherPromise> h) noexcept;
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```
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*Effects:* Equivalent to:
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``` cpp
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continuation = h;
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if constexpr ( requires(OtherPromise& other) { other.unhandled_stopped(); } ) {
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stopped-handler = [](void* p) noexcept -> coroutine_handle<> {
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return coroutine_handle<OtherPromise>::from_address(p)
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.promise().unhandled_stopped();
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};
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} else {
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stopped-handler = &default-unhandled-stopped;
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}
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```
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``` cpp
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template<class Value>
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call-result-t<as_awaitable_t, Value, Promise&> await_transform(Value&& value);
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```
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*Effects:* Equivalent to:
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``` cpp
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return as_awaitable(std::forward<Value>(value), static_cast<Promise&>(*this));
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```
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