第一章9.txt

本书在复习C++基础知识后

#include <iostream.h>
class CShape
	{
public:
		float area()	
		{ 	return 0.0;	}							
};
class CTriangle : public CShape
{
public:
		CTriangle(float h = 0, float w = 0)	
		{ 	H = h;	 W = w;	}
		float area()
		{	return (float)(H * W * 0.5); }	
private:
		float H, W;
};
class CCircle : public CShape
{
public:
		CCircle(float r = 0)	
		{	R = r;	}
		float area()
		{	return (float)(3.14159265 * R * R);	}
private:
		float R;
};
int main()
{
		CTriangle tri( 3, 4 );
		cout<<"tri.area() = "<<tri.area()<<endl;			// A
		CCircle cir(5);
		cout<<"cir.area() = "<<cir.area()<<endl;			// B
		CShape *s1 = &tri;
		cout<<"s1->area() = "<<s1->area()<<endl;		// C
		CShape &s2 = cir;
		cout<<"s2.area() = "<<s2.area()<<endl;			// D
		return 0;
}