C++作业3

项目二、友元函数

#include<iostream>  
using namespace std;  
#include<math.h>  
class Distance
{    
 private:      
    double x;    
    double y;     
 public:     
    Distance(double xx=0,double yy=0):x(xx),y(yy){}  
    double distance1();  
    friend double distance2(Distance &);  
    double get_x();  
    double get_y();  
};   
double Distance::distance1()  
{  
    double distance;  
    distance=sqrt(x*x+y*y);  
    return distance;  
}  
double distance2(Distance &c)  
{  
    double distance;  
    distance=sqrt(c.x*c.x+c.y*c.y);  
    return distance;  
}  
double Distance::get_x()  
{  
    return x;  
}  
double Distance::get_y()  
{  
    return y;  
}  
double distance3(Distance &c)  
{  
    double distance,a,b;  
    a=c.get_x();  
    b=c.get_y();  
    distance=sqrt(a*a+b*b);  
    return distance;  
}  
int main()  
{  
   Distance c1(3.0,4.0);  
    cout<<"distance is :"<<c1.distance1()<<endl;  
    cout<<"distance is :"<<distance2(c1)<<endl;  
    cout<<"distance is :"<<distance3(c1)<<endl;  
    return 0;  
}