17 Language support library [support]

17.12 Coroutines [support.coroutine]

17.12.4 No-op coroutines [coroutine.noop]

17.12.4.1 Class noop_­coroutine_­promise [coroutine.promise.noop]

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struct noop_coroutine_promise {};
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The class noop_­coroutine_­promise defines the promise type for the coroutine referred to by noop_­coroutine_­handle ([coroutine.syn]).

17.12.4.2 Class coroutine_­handle<noop_­coroutine_­promise> [coroutine.handle.noop]

namespace std {
  template<>
  struct coroutine_handle<noop_coroutine_promise> : coroutine_handle<>
  {
    // [coroutine.handle.noop.observers], observers
    constexpr explicit operator bool() const noexcept;
    constexpr bool done() const noexcept;

    // [coroutine.handle.noop.resumption], resumption
    constexpr void operator()() const noexcept;
    constexpr void resume() const noexcept;
    constexpr void destroy() const noexcept;

    // [coroutine.handle.noop.promise], promise access
    noop_coroutine_promise& promise() const noexcept;

    // [coroutine.handle.noop.address], address
    constexpr void* address() const noexcept;
  private:
    coroutine_handle(unspecified);
  };
}

17.12.4.2.1 Observers [coroutine.handle.noop.observers]

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constexpr explicit operator bool() const noexcept;
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Returns: true.
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constexpr bool done() const noexcept;
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Returns: false.

17.12.4.2.2 Resumption [coroutine.handle.noop.resumption]

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constexpr void operator()() const noexcept; constexpr void resume() const noexcept; constexpr void destroy() const noexcept;
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Effects: None.
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Remarks: If noop_­coroutine_­handle is converted to coroutine_­handle<>, calls to operator(), resume and destroy on that handle will also have no observable effects.

17.12.4.2.3 Promise access [coroutine.handle.noop.promise]

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noop_coroutine_promise& promise() const noexcept;
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Returns: A reference to the promise object associated with this coroutine handle.

17.12.4.2.4 Address [coroutine.handle.noop.address]

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constexpr void* address() const noexcept;
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Returns: ptr.
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Remarks: A noop_­coroutine_­handle's ptr is always a non-null pointer value.

17.12.4.3 Function noop_­coroutine [coroutine.noop.coroutine]

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noop_coroutine_handle noop_coroutine() noexcept;
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Returns: A handle to a coroutine that has no observable effects when resumed or destroyed.
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Remarks: A handle returned from noop_­coroutine may or may not compare equal to a handle returned from another invocation of noop_­coroutine.