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std::future::wait(3) C++ Standard Libary std::future::wait(3) NAME std::future::wait - std::future::wait Synopsis void wait() const; (since C++11) Blocks until the result becomes available. valid() == true after the call. The behavior is undefined if valid() == false before the call to this function. Parameters (none) Return value (none) Exceptions May throw implementation-defined exceptions. Notes The implementations are encouraged to detect the case when valid() == false before the call and throw a std::future_error with an error condition of std::future_errc::no_state. Example // Run this code #include <chrono> #include <iostream> #include <future> #include <thread> int fib(int n) { if (n < 3) return 1; else return fib(n-1) + fib(n-2); } int main() { std::future<int> f1 = std::async(std::launch::async, [](){ return fib(40); }); std::future<int> f2 = std::async(std::launch::async, [](){ return fib(43); }); std::cout << "waiting... " << std::flush; const auto start = std::chrono::system_clock::now(); f1.wait(); f2.wait(); const auto diff = std::chrono::system_clock::now() - start; std::cout << std::chrono::duration<double>(diff).count() << " sec- onds\n"; std::cout << "f1: " << f1.get() << '\n'; std::cout << "f2: " << f2.get() << '\n'; } Possible output: waiting... 1.61803 seconds f1: 102334155 f2: 433494437 See also waits for the result, returns if it is not available for the specified wait_for timeout duration (public member function) waits for the result, returns if it is not available un- til specified time wait_until point has been reached (public member function) http://cppreference.com 2022.07.31 std::future::wait(3)
NAME | Synopsis | Parameters | Return value | Exceptions | Notes | Example | Possible output: | See also
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