C++常量引用

#include<iostream>

using namespace std;

void showValue(const int& val){
//    val = 1000;
    //error: Cannot assign to variable 'val' with const-qualified type 'const int &'
    //不能把给常量引用类型的val变量赋值
    cout << "val = " << val << endl;
}

/**
 * 测试常量引用
 * 常量引用:使用const关键字修饰引用类型, 被修饰后将不能再使用该引用修改被引用的变量的值
 * 常量引用的作用:常用于函数的形参, 防止误操作
 */
int main() {
    //try define a reference type of constant
    //int& ref = 10;
    //error: invalid initialization of non-const reference of type 'int&' from an rvalue of type 'int'
    const int& ref = 10;
    //when the complier encounters statement "const int& ref = 10;",
    //the complier will convert it to statement "int temp = 10;const int& ref = temp;
    int a = 10;
    int& ref2 = a;
    showValue(a);
    cout << "ref2 = " << ref2 << endl;
    system("pause");

    return 0;
}

常量引用常用于函数的形参, 防止误操作!