8-14(

C++多态性程序例子

#include <iostream.h>

class point
{
public:
	point(int i=0, int j=0) { x0=i; y0=j; }
	virtual void set() = 0;
	virtual void draw() = 0;
protected:
	int x0, y0;
};

class line : public point
{
public:
	line(int i=0, int j=0, int m=0, int n=0):point(i, j)
	{
		x1=m; y1=n;
	}
	void set() { cout<<"line::set() called.\n"; }
	void draw() { cout<<"line::draw() called.\n"; }
protected:
	int x1, y1;
};

class ellipse : public point
{
public:
	ellipse(int i=0, int j=0, int p=0, int q=0):point(i, j)
	{
		x2=p; y2=q;
	}
	void set() { cout<<"ellipse::set() called.\n"; }
	void draw() { cout<<"ellipse::draw() called.\n"; }
protected:
	int x2, y2;
};

void drawobj(point *p)
{
	p->draw();
}

void setobj(point *p)
{
	p->set();
}

void main()
{
	line *lineobj = new line;
	ellipse *elliobj = new ellipse;
	drawobj(lineobj);
	drawobj(elliobj);
	cout<<endl;
	setobj(lineobj);
	setobj(elliobj);
	cout<<"\nRedraw the object...\n";
	drawobj(lineobj);
	drawobj(elliobj);
}