What is a Future and how do I use it?
A future represents the result of an asynchronous operation, and can have two states: uncompleted or completed. Most likely, as you aren''t doing this just for fun, you actually
Standard library header <future> (C++11)
future (const future &) = delete; ~future (); future & operator =(const future &) = delete; future & operator =(future &&) noexcept; shared_future <R> share () noexcept; //
std::future
The class template std::future provides a mechanism to access the result of asynchronous operations: An asynchronous operation (created via std::async,
std::future<T>::valid
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::future<T>::get
The get member function waits (by calling wait ()) until the shared state is ready, then retrieves the value stored in the shared state (if any). Right after calling this function, valid
std::future<T>::wait_until
If the future is the result of a call to async that used lazy evaluation, this function returns immediately without waiting. The behavior is undefined if valid () is false before the call
std::promise
The promise is the "push" end of the promise-future communication channel: the operation that stores a value in the shared state synchronizes-with (as defined in
std::future_status
Specifies state of a future as returned by wait_for and wait_until functions of std::future and std::shared_future. Constants
std::future<T>::wait_for
If the future is the result of a call to std::async that used lazy evaluation, this function returns immediately without waiting. This function may block for longer than