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std::future::valid(3) C++ Standard Libary std::future::valid(3) NAME std::future::valid - std::future::valid Synopsis 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::pack- aged_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 de- structor, 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. Example // Run this code #include <future> #include <iostream> int main() { std::promise<void> p; std::future<void> f = p.get_future(); std::cout << std::boolalpha; std::cout << f.valid() << '\n'; p.set_value(); std::cout << f.valid() << '\n'; f.get(); std::cout << f.valid() << '\n'; } Output: true true false See also wait waits for the result to become available (public member function) http://cppreference.com 2022.07.31 std::future::valid(3)
NAME | Synopsis | Parameters | Return value | Example | Output: | See also
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