将引用作为函数参数 （三）

page 227

#include <iostream>

void swapr(int &a, int &b);
void swapp(int *p, int *q);
void swapv(int a, int b);

int main()
{
    using namespace std;

    int wallet1 = 300;
    int wallet2 = 350;

    cout << "wallet1 =$" << wallet1;
    cout << "wallet2 =$" << wallet2 << endl << endl;

    //引用
    cout << "using references to swap contents:\n";
    swapr(wallet1, wallet2); //引用
    cout << "wallet1 =$ " << wallet1;
        cout << "wallet2 =$ " << wallet2 << endl << endl;

    //指针
    cout << "using pointers to swap contents:\n";
        swapp(&wallet1, &wallet2); //指针
        cout << "wallet1 =$ " << wallet1;
        cout << "wallet2 =$ " << wallet2 << endl << endl;

    //传值
    cout << "using references to swap contents:\n";
        swapv(wallet1, wallet2); //
        cout << "wallet1 =$" << wallet1;
        cout << "wallet2 =$" << wallet2 <<endl;

    return 0;
}


void swapr(int &a, int &b)
{
    int tmp;
    tmp = a;
    a = b;
    b = tmp;
}

void swapp(int *p, int *q)
{
    int tmp;
    tmp = *p;
    *p = *q;
    *q = tmp;
}

void swapv(int a, int b)
{
    int tmp;
    tmp = a;
    b = a;
    a = tmp;
}

ywx@yuweixian:~/yu/c++$ ./swaps
wallet1 =$300wallet2 =$350

using references to swap contents:
wallet1 =$ 350wallet2 =$ 300        引用 改变

using pointers to swap contents:
wallet1 =$ 300wallet2 =$ 350         指针 改变

using references to swap contents:
wallet1 =$300wallet2 =$350           值传递 没有改变