std::future - cppreference. com The class template std::future provides a mechanism to access the result of asynchronous operations: An asynchronous operation (created via std::async, std::packaged_task, or std::promise) can provide a std::future object to the creator of that asynchronous operation
std::future lt;T gt;:: future - en. cppreference. com Constructs a std::future with the shared state of other using move semantics After construction, other valid ( ) == false 3) std::future is not CopyConstructible