基于C++11异步编程std::async和std::future

#include 
#include 
#include 
#include 

using namespace std;



int test_fun(int x)
{
    std::this_thread::sleep_for(std::chrono::seconds(2));
    return x+100;
}

void print_int (std::future& fut) 
{
    int x = fut.get();
    std::cout << "value: " << x << 'n';
}

int main()
{
    //std::future只能用于单线程中调用 ，多线程调用使用std::share_future();
    //async会创建线程执行test_fun，任务创建之后，std::async立即返回一个std::future对象
    
    std::future fut = std::async(test_fun, 1011);
    std::cout << "please wait"< prom;                      // create promise

    std::future fut2 = prom.get_future();    // engagement with future

    std::thread th1 (print_int, std::ref(fut2));  // send future to new thread
    
    prom.set_value(10);                         // fulfill promise
                                                // (synchronizes with getting the future)
    th1.join();

    return 0;
}