问题描述

C++的mem_fun_ref如何支持多参数的类函数

今天想探究一下mem_fun_ref的用法。发现，对于无参数或者一个参数的类函数它可以建立引用，但两个或多个参数的函数呢，应该怎么建立引用呢？求高人指点。像下面代码那样，怎么给add函数建立引用呢？

#include <functional>#include <iostream>using namespace std;class Base {public:    void say() {        cout << ""hello"" << endl;    }    double pi() {        return 3.1415926;    }    int twice(int x) {        return (2 * x);    }    int add(int x int y) {        return (x + y);    }};int main() {    mem_fun_ref_t<void Base> handle1 = mem_fun_ref(&Base::say);    mem_fun_ref_t<double Base> handle2 = mem_fun_ref(&Base::pi);    mem_fun1_ref_t<int Base int> handle3 = mem_fun_ref(&Base::twice);    // mem_fun1_ref_t<int Base int int> handle4 = mem_fun_ref(&Base::add);    Base b;    handle1(b);    cout << handle2(b) << endl;    cout << handle3(b 4) << endl;    // cout << handle4(b 4 3) << endl;    return 0;}