C++爱好者 - 网友留言

#include
const double PI=3.14;

class C0
{public:
  virtual void area();//虚函数接口(功能是计算面积)//
};

class yuan:public C0//继承  做了个圆//
{public:
    yuan(float a);//构造函数//
    void area();
private:
float r;//半径//
};

yuan::yuan(float a){r=a;}
void yuan::area()
{
cout<<" PI*r*r:"<}


class square:public C0//继承  做个长方形//
{public:
    square(float b);//构造函数//
    void area();
private:
float s;//边长//
};

square::square(float b){s=b;}
void square::area()
{
cout<<" s*s:"<}

void fun(C0 *ptr)//通过函数用虚函数//
{ ptr->area();
}

void main()
{
C0 *p;
square c1(3.0);
yuan c2(3.0);
p=&c1;//指针调用长方形//
           fun(p);//计算长方形面积//
p=&c2;//..圆//
fun(p);//圆面积//

}





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