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C++多态性程序例子

#include <iostream.h>

class Point
{
public:
	Point(double i, double j) { x=i; y=j; }
	virtual double Area() const { return 0.0; }
private:
	double x, y;
};
class Rectangle:public Point
{
public:
	Rectangle(double i, double j, double k, double l);
	//double Area() const { return w*h; }
	virtual double Area() const { return w*h; }
private:
	double w, h;
};
Rectangle::Rectangle(double i, double j, double k, double l):Point(i, j)
{
	w=k; h=l;
}
void fun(Point &s)
{
	cout<<s.Area()<<endl;
}

void main()
{
	Rectangle rec(3.0, 5.2, 15.0, 25.0);
	fun(rec);
}