The class template std::future provides a mechanism to access the result of asynchronous operations: The get member function waits (by calling wait ()) until the shared state is ready, then retrieves the value stored in the shared state (if. Unlike std::future, which is only moveable (so only one instance can refer to any particular asynchronous result), std::shared_future.
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Checks if the future refers to a shared state. } above, somelongcomputation will immediately return a.
