第三题：将以下程序更改为友元函数重载的形式并上机运行：
#include<iostream.h>
class RMB{ //人民币类
public:
RMB(double d){ yuan=d; jf=(d-yuan)/100; }
RMB interest(double rate); //计算利息
RMB add(RMB d); //人民币加
void display(){ cout <<(yuan + jf / 100.0) << endl; }
RMB operator+(RMB d){ return RMB(yuan+d.yuan+(jf+d.jf)/100); }
//人民币加的运算符重载
RMB operator*(double rate){ return RMB((yuan+jf/100)*rate);}
private:
unsigned int yuan; //元
unsigned int jf; //角分
};
RMB RMB::interest(double rate)
{
return RMB((yuan + jf / 100.0) * rate);
}
RMB RMB::add(RMB d)
{
return RMB(yuan + d.yuan + jf / 100.0 + d.jf / 100.0);
} //以下是计算应付人民币的两个版本
RMB expense1(RMB principle, double rate)
{
RMB interest = principle.interest(rate);
return principle.add(interest);
}
RMB expense2(RMB principle, double rate)
{
RMB interest = principle * rate; //本金乘利息
return principle + interest; //连本带利
}
void main()
{
RMB x = 10000.0;
double yrate = 0.035;
expense1(x,yrate).display();
expense2(x,yrate).display();
}
修改后的友元函数程序（红色为关键代码）：
#include<iostream>
using namespace std;
class RMB{ //人民币类
public:
RMB(double d){ yuan=d; jf=(d-yuan)/100; }
RMB interest(double rate); //计算利息
RMB add(RMB d); //人民币加
void display(){ cout <<(yuan + jf / 100.0) << endl; }
friend RMB operator+(RMB a, RMB d) ;
//人民币加的运算符重载
friend RMB operator*(RMB a, double rate) ;
private:
unsigned int yuan; //元
unsigned int jf; //角分
};
RMB operator+(RMB a, RMB d) {
return RMB(a.yuan + d.yuan + (a.jf + d.jf) / 100);
}
RMB operator*(RMB a, double rate) {
return RMB((a.yuan + a.jf / 100) * rate);
}
RMB RMB::interest(double rate)
{
return RMB((yuan + jf / 100.0) * rate);
}
RMB RMB::add(RMB d)
{
return RMB(yuan + d.yuan + jf / 100.0 + d.jf / 100.0);
} //以下是计算应付人民币的两个版本
RMB expense1(RMB principle, double rate)
{
RMB interest = principle.interest(rate);
return principle.add(interest);
}
RMB expense2(RMB principle, double rate)
{
RMB interest = principle * rate; //本金乘利息
return principle + interest; //连本带利
}
int main()
{
RMB x = 10000.0;
double yrate = 0.035;
expense1(x,yrate).display();
expense2(x,yrate).display();
}
运行结果:
