构造函数

注意成员函数以及【operator()】的使用 std::ref 关键字 noexcept :告诉编译器函数不会出现异常

#include <iostream>
#include <utility>
#include <thread>
#include <chrono>
void f1(int n)
{
    for (int i = 0; i < 5; ++i) {
        std::cout << "Thread 1 executing\n";
        ++n;
        std::this_thread::sleep_for(std::chrono::milliseconds(10));
    }
}
void f2(int& n)
{
    for (int i = 0; i < 5; ++i) {
        std::cout << "Thread 2 executing\n";
        ++n;
        std::this_thread::sleep_for(std::chrono::milliseconds(10));
    }
}
class foo
{
public:
    void bar()
    {
        for (int i = 0; i < 5; ++i) {
            std::cout << "Thread 3 executing\n";
            ++n;
            std::this_thread::sleep_for(std::chrono::milliseconds(10));
        }
    }
    int n = 0;
};
class baz
{
public:
    void operator()()
    {
        for (int i = 0; i < 5; ++i) {
            std::cout << "Thread 4 executing\n";
            ++n;
            std::this_thread::sleep_for(std::chrono::milliseconds(10));
        }
    }
    int n = 0;
};
int main()
{
    int n = 0;
    foo f;
    baz b;
    std::thread t1; // t1 is not a thread
    std::thread t2(f1, n + 1); // pass by value
    std::thread t3(f2, std::ref(n)); // pass by reference
    std::thread t4(std::move(t3)); // t4 is now running f2(). t3 is no longer a thread
    std::thread t5(&foo::bar, &f); // t5 runs foo::bar() on object f
    std::thread t6(b); // t6 runs baz::operator() on a copy of object b
    t2.join();
    t4.join();
    t5.join();
    t6.join();
    std::cout << "Final value of n is " << n << '\n';
    std::cout << "Final value of f.n (foo::n) is " << f.n << '\n';
    std::cout << "Final value of b.n (baz::n) is " << b.n << '\n';
}

std::ref

std::ref 与 std::cref区别：
c代表const,即传 const 引用，只读！

#include <functional>
#include <iostream>
void f(int& n1, int& n2, const int& n3)
{
    std::cout << "In function: " << n1 << ' ' << n2 << ' ' << n3 << '\n';
    ++n1; // increments the copy of n1 stored in the function object
    ++n2; // increments the main()'s n2
    // ++n3; // compile error
}
int main()
{
    int n1 = 1, n2 = 2, n3 = 3;
    std::function<void()> bound_f = std::bind(f, n1, std::ref(n2), std::cref(n3));
    n1 = 10;
    n2 = 11;
    n3 = 12;
    std::cout << "Before function: " << n1 << ' ' << n2 << ' ' << n3 << '\n';
    bound_f();
    std::cout << "After function: " << n1 << ' ' << n2 << ' ' << n3 << '\n';
}
Before function: 10 11 12
In function: 1 11 12
After function: 10 12 12