{

ThreadPool pool;

std::vector< std::future<int> > results;

for(int i = 0; i < 8; ++i) {

results.emplace_back(

pool.enqueue([i] {

std::cout << "hello " << i << std::endl;

std::this_thread::sleep_for(std::chrono::seconds(1));

std::cout << "world " << i << std::endl;

return i*i;

})

);

}

pool.wait_until_empty();

pool.wait_until_nothing_in_flight ();

for(auto && result: results)

std::cout << result.get() << ' ';

std::cout << std::endl;

return 0;