// future example

#include <iostream>       // std::cout

#include <future>         // std::async, std::future

#include <chrono>         // std::chrono::milliseconds

​

// a non-optimized way of checking for prime numbers:

bool is_prime (int x) {

  for (int i=2; i<x; ++i) if (x%i==0) return false;

  return true;

}

​

int main ()

{

  // call function asynchronously:

  std::future<bool> fut = std::async (is_prime,444444443); 

​

  // do something while waiting for function to set future:

  std::cout << "checking, please wait";

  std::chrono::milliseconds span (100);

  while (fut.wait_for(span)==std::future_status::timeout)

    std::cout << '.' << std::flush;

​

  bool x = fut.get();     // retrieve return value

​

  std::cout << "\n444444443 " << (x?"is":"is not") << " prime.\n";

​

  return 0;

}