引用

#include <iostream>

using namespace std;

int main()
{
    int num = 0;
    int &num_ref = num;
    cout << "num = " << num << endl;

    num_ref = 10;
    cout << "num = " << num << endl;

    return 0;
}

函数引用

#include <iostream>
#include <cmath>

using namespace std;

float norm_l1(float x, float y);               // declaration
float norm_l2(float x, float y);               // declaration
float (&norm_ref)(float x, float y) = norm_l1; // norm_ref is a function reference

int main()
{
    cout << "L1 norm of (-3, 4) = " << norm_ref(-3, 4) << endl;
    return 0;
}

float norm_l1(float x, float y)
{
    return fabs(x) + fabs(y);
}

float norm_l2(float x, float y)
{
    return sqrt(x * x + y * y);
}