packaged_task和future, 还有function和bind

int sum(int a) {
	return a * 3;
}
int main(){
	std::packaged_task<int()> tsk(std::bind(sum, 33)); // package task

	std::future<int> fut = tsk.get_future();
	tsk();
	cout << 111 << endl;
	std::cout << "The triple of 33 is " << fut.get() << ".\n";

	// re-use same task object:
	tsk.reset();
	fut = tsk.get_future();

}