项目二

#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 &); //成员函数的声明、
    friend double distance2(CPoint &,CPoint &);
	double getx(){return x;}
	double gety(){return y;}
};
double distance3(CPoint &,CPoint &);  //一般函数声明



double CPoint::distance1(CPoint &p)
{
	return (sqrt((x-p.x)*(x-p.x)+(y-p.y)*(y-p.y)));
}
double distance2(CPoint &p1,CPoint &p2)
{
	double x=p1.x-p2.x;
	double y=p1.y-p2.y;
	return (sqrt((x*x)+(y*y)));
}
double distance3(CPoint &p1,CPoint &p2)
{
  double x=p1.getx()-p2.getx();
  double y=p1.gety()-p2.gety();
  return (sqrt((x*x)+(y*y)));
}

int main()
{
	CPoint p1(1,1), p2(0,0);
    cout<<p1.distance1(p2)<<endl;
    cout<<distance2(p1,p2)<<endl;
    cout<<distance3(p1,p2)<<endl;
    return 0;
}