作业6.12

#include<iostream>  
using namespace std;  
class area_cl  
{  
protected:  
    double height;  
    double width;  
public:  
    area_cl(double a,double b)  
    {  
        height=a;  
        width=b;  
    }  
    virtual double area()=0;  
};  
class rectangle:public area_cl  
{  
public:  
    rectangle(double a,double b):area_cl(a,b)  
    {}  
    double area()  
    {  
        return height*width;  
    }  
};  
class ioscseles:public area_cl  
{  
public:  
    ioscseles(double a,double b):area_cl(a,b)  
    { }  
    double area()  
    {return 0.5*height*width;}  
};  
int main()  
{  
    area_cl* p;  
    rectangle A(10.0,5.0); 
	p=&A;  
    cout<<"矩形面积为："<<p->area()<<endl;  
    ioscseles B(4.0,6.0);  
    p=&B;  
    cout<<"三角形面积为:"<<p->area()<<endl;
}