第十周作业 3

#include <iostream>  using namespace std;  class Point   {  protected:      double x,y;//分别代表横坐标和纵坐标  public:      Point(double m=0,double n=0);      void setpoint(double d,double e){x=d;y=e;}      friend ostream& operator << (ostream& output,Point&c);      double getx(){return x;}      double gety(){return y;}  };  Point::Point(double m,double n)  {      x=m;      y=n;  }  ostream& operator << (ostream& output,Point&c)  {      output<<"点为："<<"("<<c.x<<","<<c.y<<")"<<endl;      return output;  }      class Circle:public Point  {  public:      Circle(double c1,double c2,double c3):Point(c1,c2){r=c3;}      friend ostream& operator << (ostream& output,Circle&c);      void setR(double);      double area( );      double getR(){return r;}   protected:      double r;//圆的半径   };  void Circle::setR(double m)  {      r=m;  }  double Circle::area()  {      return 3.1415926*r*r;  }  ostream& operator << (ostream& output,Circle&c)  {      output<<"圆心："<<"("<<c.x<<","<<c.y<<")"<<"面积为："<<c.area()<<endl;      return output;  }    class Cylinder:public Circle  {  private:      double h;//圆柱的高  public:      Cylinder(double t1,double t2,double t3,double t4):Circle(t1,t2,t3){h=t4;}      friend ostream& operator << (ostream& output,Cylinder&c);      double area( ) ;       double volume();      void setHeight(double m){h=m;}      double getHeight(){return h;}  };  double Cylinder::area( )  {       return 2*Circle::area( )+2*3.14159*r*h;   }    double Cylinder::volume()  {      return area()*h;  }    ostream& operator << (ostream& output,Cylinder&c)  {      output<<"Center=["<<c.x<<","<<c.y<<"], r="<<c.r<<", h="<<c.h            <<"\narea="<<c.area( )<<", volume="<<c.volume( )<<endl;        return output;  }  int main( )    {        Point t(5,6);      cout<<t;      Circle t1(7,3,1);      cout<<t1;      Cylinder cy1(3.5,2.4,5.2,10);        cout<<"\noriginal cylinder:\nx="<<cy1.getx( )<<", y="<<cy1.gety( )<<", r="            <<cy1.getR( )<<", h="<<cy1.getHeight( )<<"\narea="<<cy1.area()            <<",volume="<<cy1.volume()<<endl;        cy1.setHeight(5);             cy1.setR(7.5);              cy1.setpoint(5,4);               cout<<"\nnew cylinder:\n"<<cy1;                system("pause");        return 0;    }    

感言：有点小难度 感觉派生不是很了解！！