std::bind使用

#include <iostream>
#include <functional>
 
void fn(int n1, int n2, int n3) {
    std::cout << n1 << " " << n2 << " " << n3 << std::endl;
}
 
int fn2() {
    std::cout << "fn2 has called.\n";
    return -1;
}
 
int main()
{
    using namespace std::placeholders;
    auto bind_test1 = std::bind(fn, 1, 2, 3);
    auto bind_test2 = std::bind(fn, _1, _2, _3);
    auto bind_test3 = std::bind(fn, 0, _1, _2);
    auto bind_test4 = std::bind(fn, _2, 0, _1);
 
    bind_test1();//输出1 2 3
    bind_test2(3, 8, 24);//输出3 8 24
    bind_test2(1, 2, 3, 4, 5);//输出1 2 3，4和5会被丢弃
    bind_test3(10, 24);//输出0 10 24
    bind_test3(10, fn2());//输出0 10 -1
    bind_test3(10, 24, fn2());//输出0 10 24，fn2会被调用，但其返回值会被丢弃
    bind_test4(10, 24);//输出24 0 10
    return 0;
}

输出：

1 2 3
3 8 24
1 2 3
0 10 24
fn2 has called.
0 10 -1
fn2 has called.
0 10 24
24 0 10