第六周项目：成员函数、友元函数和一般函数有区别（2）

#include <iostream>
#include<cmath>
using namespace std;

class CPoint
{
private:
double x;  // 横坐标
double y;  // 纵坐标
public:
CPoint(double xx=0,double yy=0):x(xx),y(yy){}
double distance1(CPoint &p1) const;
friend void distance2(CPoint &p2,CPoint &p3);
double getx()
{
return x;
}
double gety()
{
return y;
}
};
double CPoint::distance1(CPoint &p)const
{
double dis;
return dis=sqrt((x-p.x)*(x-p.x)+(y-p.y)*(y-p.y));
}
void distance2(CPoint &p2,CPoint &p3)
{

cout<<sqrt((p3.x-p2.x)*(p3.x-p2.x)+(p3.y-p2.y)*(p3.y-p2.y));
}
double distance3(CPoint &p4,CPoint &p5)
{
double dis;
return dis=sqrt((p4.getx()-p5.getx())*(p4.getx()-p5.getx())+(p4.gety()-p5.gety())*(p4.gety()-p5.gety()));
}
int main()
{
CPoint c1(1,3),c2(6,4);
cout<<c1.distance1(c2)<<endl;
distance2(c2,c1);
cout<<endl;
cout<<distance3(c2,c1);
return 0;
}