What are futures and promises in C++?

Can you explain what futures and promises are in C++?

Sure! Futures and promises are used for asynchronous programming in C++. A promise is a way to set a value that will be available in the future, while a future is a way to retrieve that value once it's ready.

How do I create a promise in C++?

You can create a promise using the std::promise class. Here's a simple example:

#include <iostream>
#include <future>

std::promise<int> myPromise;
std::future<int> myFuture = myPromise.get_future();
myPromise.set_value(10);
std::cout << "Value from promise: " << myFuture.get() << std::endl;

What happens if I try to get a future value before it's set?

If you try to get a future value before it's set, the call will block until the value is available. If the promise is never fulfilled, it will result in an exception.

Can futures and promises be used with threads?

Yes, futures and promises are often used with threads to synchronize data between them. You can set a promise in one thread and retrieve the value in another using the associated future.