第六周 课后实践：项目四——成员函数，友元函数和一般函数的区别

#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 &);
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(1,6),p2(-2,3);
cout<<"第一种："<<p1.distance1(p2)<<endl;
cout<<"第二种："<<distance2(p1,p2)<<endl;
cout<<"第三种："<<distance3(p1,p2)<<endl;
return 0;
}