class X
{
public:
	int foo(int a,std::string const& b){std::cout<<a<<std::endl<<b<<std::endl;return 3;}
	std::string bar(std::string const& a){std::cout<<a<<std::endl;return a;}
};

	X x;
	//在新執行緒中執行
	auto f1 = std::async(std::launch::async,&X::foo,x,1,"hi");
	//在wait（）/get（）中執行
	auto f2 = std::async(std::launch::deferred,&X::bar,std::ref(x),"hello");
	//執行f2
	f2.wait();
	//f2.get();