#include <iostream>
#include<Cmath>
using namespace std;
class Point{
public:
    Point():x(0),y(0){};
    Point(double x0,double y0):x(x0),y(y0){};
    void PrintPoint();
    double x,y;
};
void Point::PrintPoint(){
 cout<<"Point:("<<x<<","<<y<<")";
}
class Line:public Point
{
public:
  Line(Point pts,Point pte):pts(pts),pte(pte){};
  double Length();
  void PrintLine();
private:
 class Point pts,pte;
};
double Line::Length(){
  return sqrt((pts.x-pte.x)*(pts.x-pte.x)+(pts.y-pte.y)*(pts.y-pte.y));

}
void Line::PrintLine(){
cout<<"point message:"<<(pts.x+pte.x)/2<<"  "<<(pts.y+pte.y)/2<<endl;
}
int main(){
  Point ps(-2,5),pe(7,9);
  Line l(ps,pe);
  cout<<"\n The Length of line  ";
  cout<<l.Length()<<endl;
  cout<<"\n The minddle point of Line";
  l.PrintLine();
}
 

運算結果：