Introduction to Promises and Futures

Promise and future are a mighty pair. A promise can put a value, an exception, or simply a notification into the shared data channel. One promise can serve many std::shared_future futures. With C++20 we may get extended futures that are compose-able.

Here is an introductory example of the usage of std::promise and std::future. Both communication endpoints can be moved to separate threads, so the communication takes place between threads.