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std:: future. future. 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. The creator of the asynchronous operation can then use a variety of methods to query, wait for, or extract a value from the std::future.
The future statement is intended to ease migration to future versions of Python that introduce incompatible changes to the language. It allows use of the new features on a per-module basis before the release in which the feature becomes standard. If you actually want to import the __future__ module, just do.
std::future<T>:: get. 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 () is false. If valid () is false before the call to this function, the behavior is undefined.
std::future<T>:: wait_for. Waits for the result to become available. Blocks until specified timeout_duration has elapsed or the result becomes available, whichever comes first. The return value identifies the state of the result. If the future is the result of a call to std::async that used lazy evaluation, this function returns immediately ...
The use of FutureOr, as introduced with Dart 2, is to allow you to provide either a value or a future at a point where the existing Dart 1 API allowed the same thing for convenience, only in a way that can be statically typed. The canonical example is Future.then. The signature on Future<T> is Future<R> then<R>(FutureOr<R> action(T value), {Function onError}). The idea is that you can have an ...
shared_future. The class template std::shared_future provides a mechanism to access the result of asynchronous operations, similar to std::future, except that multiple threads are allowed to wait for the same shared state. Unlike std::future, which is only moveable (so only one instance can refer to any particular asynchronous result), std ...
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::packaged_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 destructor, the move-assignment operator, or valid is ...
std::future<T>:: wait. wait. Blocks until the result becomes available. valid() == true after the call. The behavior is undefined if valid() == false before the call to this function.
A Future<T> is something that in the future will give you a T. Lets try a different explanation: 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 need the results of that Future<T> to progress in your application.
2) Move constructor. Constructs a std::future with the shared state of other using move semantics. After construction, other.valid() == false.