How do I make a function asynchronous in C++?

Question

I want to call a function which will be asynchronous (I will give a callback when this task is done).

I want to do this in single thread.

Answer 1

As of C++11, plain c++ does have a concept of threads, but the most concise way to call a function asynchronously is to use the C++11 async command along with futures. This ends up looking a lot like the way you'd do the same thing in pthreads, but it's 100% portable to all OSes and platforms:

Say your function has a return value... int = MyFunc(int x, int y)

#include <future>

Just do:

// This function is called asynchronously
std::future<int> EventualValue = std::async(std::launch::async, MyFunc, x, y); 

Catch? How do you know when it's done? (The barrier.)

Eventually, do:

int MyReturnValue = EventualValue.get(); // block until MyFunc is done

Note it's easy to do a parallel for loop this way - just create an array of futures.