std::future

// 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;
}