What are C++11 futures and promises?

Can you explain what futures and promises are in C++11?

Sure! Futures and promises in C++11 are used for asynchronous programming, allowing you to retrieve values from operations that may not have completed yet.

How do I create a promise and get its future?

You can create a promise using std::promise<T>, and then call get_future() on it to obtain a std::future<T>.

What happens if the promise is not fulfilled?

If a promise is not fulfilled, the associated future will be in a state of 'unfulfilled', and trying to access its value will throw an exception.

Can you give me a simple code example?

Certainly! Here's a basic example:

#include <iostream>
#include <future>
#include <thread>

void asyncTask(std::promise<int> &&p) {
    std::this_thread::sleep_for(std::chrono::seconds(1));
    p.set_value(42);
}

int main() {
    std::promise<int> promise;
    std::future<int> future = promise.get_future();
    std::thread t(asyncTask, std::move(promise));
    std::cout << "Result: " << future.get() << std::endl;
    t.join();
    return 0;
}

This code demonstrates creating a promise, launching a thread, and retrieving the result.