std::future<T>::valid

 

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std::future

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future::valid

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bool valid() const noexcept;		(since C++11)

Checks if the future refers to a shared state.

This is the case only for futures that were not default-constructed or moved from (i.e. returned by std::promise::get_future(), std::packaged_task::get_future() or std::async()) until the first time get() or share() is called.

The behavior is undefined if any member function other than the destructor, the move-assignment operator, or valid is called on a future that does not refer to shared state (although implementations are encouraged to throw std::future_error indicating no_state in this case). It is valid to move from a future object for which valid() is false

Parameters

(none)

Return value

true if *this refers to a shared state, otherwise false.

See also

wait	waits for the result to become available (public member function)