{

std::shared_ptr<ThreadPool> pool = std::make_shared<ThreadPool>(4);

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;

})

);

}

int cnt = 0;

for(auto && result: results) {

std::cout << "cnt: " << ++cnt << ", result: " << result.get() << ' ';

}

std::cout << std::endl;

return 0;