example1-21.cpp

来自「关于书籍《Borland c++Builder工程实践》的源代码」· C++ 代码 · 共 46 行

#include <iostream.h>
const double pi=3.1415;
class  shape  //声明基类
{
public:
virtual double Area() const=0;  //声明纯虚函数
};
class rectangle:public shape  //声明派生类rectangle
{
public :
rectangle(double m,double n)
{
w=m;
h=n;
}
double Area() const        //纯虚函数在派生类的实现
{
return w*h;
}
private:
double w,h;
};
class circle:public shape  //声明派生类circle
{
public :
circle(double m)
{
r=m;
}
double Area() const        //纯虚函数在派生类的实现
{
return pi*r*r;
}
private:
double r;
};
void main()
{
rectangle rec(20,15);
cout<<"The rectangle Area is :"<<rec.Area();
cout<<endl;
circle cle(5);
cout<<"The circle Area is :"<<cle.Area();
cout<<endl;
}