第七周任务

#include<iostream>   
#include<cmath>   
using namespace std;  
class Cpoint  
{  
private:  
    double x;  
    double y;  
public:  
    Cpoint(double xx=0,double yy=0):x(xx),y(yy){}  
    double distance1(Cpoint &);  
    friend double distance2(Cpoint &,Cpoint &);  
    double getX(){return x;}  
    double getY(){return y;}  
};  
double distance3(Cpoint &,Cpoint &);  
double Cpoint::distance1(Cpoint &p)  
{  
    double dx=(x-p.x),dy=(y-p.y);  
    return sqrt(dx*dx+dy*dy);  
}  
double distance2(Cpoint &p1,Cpoint &p2)  
{  
    double dx=(p1.x-p2.x),dy=(p1.y-p2.y);  
    return sqrt(dx*dx+dy*dy);  
}  
double distance3(Cpoint &p1,Cpoint &p2)  
{  
    double dx=(p1.getX()-p2.getX()),dy=(p1.getY()-p2.getY());  
    return sqrt(dx*dx+dy*dy);  
}  
int main()  
{  
    Cpoint p1(10,13),p2(-2,6);  
    cout<<"1.成员函数："<<p1.distance1(p2)<<endl;  
   cout<<"2.友元函数："<<distance2(p1,p2)<<endl;  
    cout<<"3.一般函数："<<distance3(p1,p2)<<endl;  
    return 0;  
}