虚基类

【任务】	在【任务3】的基础上，由自行车（Bicycle）类、汽车（Motorcar）类派生出摩托车（MotorCycle）类。在继承过程中注意把Vehicle设置为虚基类。
实验要求	如果不把Vehicle设置为虚基类，会有什么问题？并分析原因。

#include <iostream>
using namespace std;
class Vehical
{
public:
	Vehical(){Weight=0;Maxspeed=0;}
	~Vehical(){}
protected:
	int Maxspeed;
	int Weight;
};
class Bike:virtual  public Vehical
{
public:
	Bike(){Height=1;}
	void Set(int s,int w){Maxspeed=s;Weight=w;}
	~Bike(){}
	void Display(){cout<<"The information of Bike:\n"<<"Maxspeed:"<<Maxspeed<<"m/s.\n"<<"Weight:"<<Weight<<"kg.\n"<<"Height:"<<Height<<"m."<<endl;}
protected:
	int Height;
};
class Motorcar:virtual public Vehical
{
public:
	Motorcar(){SeatNum=2;}
	~Motorcar(){}
	void Set(int s,int w){Maxspeed=s;Weight=w;}
	void Display(){cout<<"The information of Motorcar:\n"<<"Maxspeed:"<<Maxspeed<<"m/s.\n"<<"Weight:"<<Weight<<"kg\n"<<"SeatNum:"<<SeatNum<<"."<<endl;}
protected:
	int SeatNum;
};
class MotorCycle:public Bike,public Motorcar
{
	public:
		MotorCycle(){};
		~MotorCycle(){};
		void Set(int s,int w,int h,int t){Maxspeed=s;Weight=w;Height=h;SeatNum=t;}
		void Display(){cout<<"The information of Motorcar:\n"<<"Maxspeed:"<<Maxspeed<<"m/s.\n"<<"Weight:"<<Weight<<"kg\n"<<"Height:"<<Height<<"m.\n"<<"SeatNum:"<<SeatNum<<"."<<endl;}
};
int main()
{
	Bike b;
	Motorcar c;
	MotorCycle d;
	b.Set(10,50);
	c.Set(100,100);
	d.Set(120,100,1,3);
	b.Display();
	c.Display();
	d.Display();
	return 0;
} 

      如果不把Vehicle设置成虚基类的话，会出现[Error] reference to 'Maxspeed' is ambiguous等错误，因为编译器认为继承的Maxspeed是含糊不清的，继承的两个类Bike和Motorcar里面都有Maxspeed。