21.引用指针

#include <iostream>
using namespace std;
//改变指针,需要二级指针,也可以用引用

//左值引用与右值引用
void main1()
{
    int a(4);
    int *p(new int(5));
    cout << a << endl;
    cout << *p << endl;
    //右值引用
    int &&rra(move(a));//右值引用,有内存实体就直接引用,没有就开辟内存
    rra = 1;
    cout << a << endl;

    //左值引用
    int &la(a);
    int *&lp(p);
    la = 3;
    *lp = 12;
    cout << a << endl;
    cout << *p << endl;


    cin.get();
}

//引用一级指针
int num1 = 10;
int num2 = 20;
//C++能用引用就别用指针
//引用可以改变指针的地址也可以改变指针指向的地址或值
void change(int *&rp)
{
    rp = &num2;
}


void main2()
{
    int *p = &num1;
    change(p);
}

//引用二级指针
int data1 = 10;
int data2 = 20;
int *p = &data1;
int *p2 = &data2;

//引用传递的是变量的地址
void changeit(int **&rpp)
{
    //变量的地址指向的地址改变
    //*rpp = &data2;
    //变量的地址改变
    rpp = &p2;
}

void main()
{
    int **pp = &p;//二级指针
    changeit(pp);
    cout << **pp << endl;
    cin.get();
}