6.13

#include<iostream>
using namespace std;
class Base{
public:
	Base(double h1)
	{h=h1;}
	virtual void disp()
  {}  
protected:  
    double h;  
};  
  
class Cuboid :public Base{          
public:  
   Cuboid(double h1, double l1, double w1) :Base(h1)  
   {  
       l = l1;  
       w = w1;  
    }  
    virtual void disp()  
    {  
        cout << "正方体的体积为:" <<l*w*h<< endl;  
    }  
protected:  
    double l;               
   double w;               
}; 
 
class Cylinder :public Base {    
public:  
    Cylinder(double h1, double r1) :Base(h1)  
  {  
       r = r1;  
   }  
  virtual void disp()  
    {  
        cout << "圆柱体的体积为:" << 3.14*r*r*h << endl;  
   }  
protected:  
   double r;                 
};  
  
int main()  
{  
   Base *pc;                     
   Cuboid cu(2.0,2.0,4.0); Cylinder cy(3.0,2.0);  
   pc = &cu;  
   pc->disp();  
   pc = &cy;  
   pc->disp();  
   return 0;  
}  

【6.13】定义基类Base，其数据成员为高h，定义成员函数disp为虚函数。然后再由Base派生出长方体类Cuboid与圆柱类Cylinder。并在两个派生类中定义成员函数disp为虚函数。在主函数中，用基类Base定义指针变量pc，然后用指针pc动态调用基类与派生类中虚函数disp，显示长方体与圆柱体的体积。