main.cpp

this a good book.

#include <iostream>
#include <cmath>

using namespace std;

class Shape
{
public:
	//* * 1 * *
	
	//* * 2 * *
	
};

class Point
{
	double x,y;
public:
	Point(double x0=0.0,double y0=0.0): x(x0),y(y0)
	{
	}
	double getx()const {return x;	}
	double gety()const {return y;	}
};
class RECT: public Shape
{
	Point ul,dr;
public:
	RECT(double x1,double y1,double x2,double y2): ul(x1,y1),dr(x2,y2)
	{

	}
	virtual double area()const
	{
		return fabs( (dr.getx()-ul.getx())*(dr.gety()-ul.gety()) );
	}
	virtual void draw()
	{
		cout<<"矩形"<<endl;
	}
};
class Circle: public Shape
{
	Point cen;
	double rad;
public:
	//* * 3 * *
	
	{
	}
	virtual double area()const
	{
		return 3.14159*rad*rad;
	}
	virtual void draw()
	{
		cout<<"圆形"<<endl;
	}
};

//* * 4 * *
void Show()
{
	obj.draw();
	cout<<obj.area()<<endl;
}

void main()
{
	RECT rc(10,10,50,50);
	Show(rc);

	Circle obj2(100,100,20);
	Show(obj2);
}