Modern C++ Programming Cookbook

How it works...

The promise-future pair is basically a communication channel that enables a thread to communicate a value or exception with another thread through a shared state. The promise is an asynchronous provider of the result and has an associated future that represents an asynchronous return object. To establish this channel, you must first create a promise. This, in turn, creates the shared state that can be later read through the future associated with the promise.

To set a result to a promise, you can use any of the following methods:

• The set_value() or set_value_at_thread_exit() method is used to set a return value; the later function stores the value in the shared state but only makes it available through the associated future ...