c++关于函数的问题

Question

#include<iostream>
using namespace std;
int sum(int x, int y) { return x + y; }
int product(int x, int y) { return x*y; }
void main()
{
 ______________________;
 int a, b, result;
 cout << "a="; cin >> a;
 cout << "b="; cin >> b;
 pf= sum; result = pf(a, b);
 cout << a << "+" << b << "=" << result << endl;
 pf = product; result = pf(a, b);
 cout << a << "*" << b << "=" << result << endl;
}

横线处填什么 使之成立

Answer 1

不用了  我知道了