ex_purevirtual.cpp

虽然是一个小小的例子,却是基本上包括了C++多态的含义!是很好的学习材料

#include<iostream.h>
class CShape
{
public:
	virtual float area()=0;
};
class CTriangle:public CShape
{
public:
	CTriangle(float h,float w)
	{  High=h; Width=w; }
	float area()
	{  return (float)(High*Width*0.5);}
private:
	float High,Width;
};
class CCircle:public CShape
{
public:
	CCircle(float r)
	{  R=r; }
	float area()
	{  return (float)(3.14159*R*R);}
private:
	float R;
};

void main()
{
//	CShape a;//错误，抽象类不能定义对象，只能用指针
	CShape *s[2],*p1;
	CTriangle  tri(8,6);

	s[0]= new CTriangle(3,4);
	cout<<"s[0] area is: "<<s[0]->area()<<endl;
	s[1]= new CCircle(1);
	cout<<"s[1] area is: "<<s[1]->area()<<endl;

	p1=&tri;
	cout<<"tri area is: "<<tri.area()<<endl;
	cout<<"p1 area is: "<<p1->area()<<endl;
}