启动线程有detach()和join()两个函数，前者是异步启动，后者是同步启动并等待结束。

#include <iostream>
#include <thread>

struct task
{
    int& i;
    task(int& i_) :i(i_)
    {};

    void operator()()
    {
        for (int j = 0; j < 200; j++)
         std::cout << "param is " << i << std::endl;
    }
};

struct job
{
    void operator()()
    {
        std::cout << "that is ok\n";
    }
};

int main()
{
    int a = 12;
    task tk(a);

    std::thread t(tk);

    job j;
    std::thread t2(j);
    t2.detach();
    t.join();

    return 0;
}