306b.cpp

C++实训教程

/*
	306b.CPP
	P3D——派生类 应用的技术
	CopyRight by Feng.2003/10, 1997/10
*/
#include <iostream.h>
class P	//平面一个点 Point
{
   protected:
	long x,y;
   public:
	P(long a=0,long b=0) { x=a;y=b;}
	void Disp()
   { cout << "x=" <<x<<"  y="<<y;}
	void Multi(long m)
	{   x=x*m;  y=y*m;}
	void Move(long s,long t){x+=s;y+=t;}
};

class P3d : public P  //空间一点（三维）
{
	long z;
	void Multi(long m){}
  public:
	P3d():P() {z=0;}
  	P3d(long a,long b,long c=0):P(a,b)
  	{z=c;}
	long GetZ(){ return z;}
	void Move(long s,long t,long u)
	{
		P::Move(s,t);
		z+=u;
	}
	void Disp()
	{
		P::Disp();
	  	cout << "  z="<< z <<endl;
   }
};


main()
{
   P p1(1,1);
   p1.Multi(10);
   p1.Disp(); cout <<endl;
   P3d p2(3,-4);
   P3d *prt;
   prt=&p2;
   prt->Disp();
   p2.Disp();
   p2.Move(1,2,3);
   prt->Disp();
   //p2.Multi(10);  is not accessible
   return 0;
}
/*
x=10  y=10
x=3  y=-4  z=0
x=3  y=-4  z=0
x=4  y=-2  z=3

*/