第五次实验代码（其他班）——继承多态

 /**********************************************************/
   //Function                                :   main,Geometric及其派生类
   //parm                                    :
   //comment                                 :
   //return                                  :   void
   //Author                                  :
   //date                                    :   2013.1.4
 /**********************************************************/
 #include
 #include

 const double PI=3.14159;

 class Geometric{
 public:
     Geometric()
     {}
     virtual double Get_Girth()=0;  //周长
     virtual double Get_Area()=0;   //面积
     virtual double Get_Volume()=0; //体积
     virtual void print()=0;        //输出
 };

 class Rectangle:public Geometric{
 protected:
     double length,width;
 public:
     Rectangle(double l,double w):Geometric(),length(l),width(w){}
     double Get_Girth()
     {
         return 2 * (width+length);
     }
     double Get_Area()
     {
         return width * length;
     }
     double Get_Volume()
     {
         return 0.0;
     }
     void print()
     {
         cout<<"The Rectangle's Girth is:"<
         cout<<"The Rectangle's Area is:"<
     }
 };

 class Circle:public Geometric{
 protected:
     double radius;
 public:
     Circle(double r):Geometric()
     {
         radius = r;
     }
     double Get_Girth()
     {
         return 2 * PI * radius;
     }
     double Get_Area()
     {
         return PI * radius * radius;
     }
     double Get_Volume()
     {
         return 0.0;
     }
     void print()
     {
         cout<<"The Circle's Girth is:"<
         cout<<"The Circle's Area is:"<
     }
 };

 class Ball:public Circle{
 public:
     Ball(double r):Circle(r)
     {}
     double Get_Girth()
     {
         return 0;
     }
     double Get_Area()
     {
         return 4 * Circle::Get_Area();
     }
     virtual double Get_Volume()
     {
         return 4.0 / 3 * Get_Area() * radius;
     }
     void print()
     {
         cout<<"The Ball's Area is:"<
         cout<<"The Ball's volume is:"<
     }
 };

 class Column:public Circle{
 protected:
     double height;
 public:
     Column(double r,double h):Circle(r),height(h){}
     double Get_Area()
     {
         return Circle::Get_Girth() * height + 2 * Circle::Get_Area();
     }
     double Get_Volume()
     {
         return Circle::Get_Area() * height;
     }
     void print()
     {
         cout<<"The Column's Area is:"<
         cout<<"The Column's volume is:"<
     }
 };

 void fun(Geometric &p)
 {
     p.print();
 }

 void main()
 {
     double r,h,w,l;
     cout<<"Please input the radius and height:"<
     cin>>r>>h;
     Circle obj_Cir(r);
     fun(obj_Cir);
     Ball obj_Bal(r);
     fun(obj_Bal);
     Column obj_Col(r,h);
     fun(obj_Col);
     cout<<"Please input the length and width:"<
     cin>>l>>w;
     Rectangle obj_Rec(l,w);
     fun(obj_Rec);
 }