虚基类简单应用

/****************************************************
* 文件名：
* 功能：虚基类简单应用
* 说明：声明虚基类之后，虚基类的成员在进一步派生过程中
        和派生类一起维护同一个内存数据拷贝。
        只对紧跟其后的基类起作用
* 时间：2011-3-30 --Lzy
****************************************************/
#include <iostream.h>

class A
{
protected:
    int a;

public:
    A(){a = 50;}
    void f(){cout<<"A "<<a<<endl;}
};

class B:virtual public A
{
protected:
    int b;

public:
    B(){b = 60;}
    void f(){cout<<"B "<<b<<","<<a<<endl;}
};

class C:virtual public A
{
protected:
    int c;

public:
    C(){c = 70;}
    void f(){cout<<"C "<<c<<","<<a<<endl;}
};

class D:public B, public C
{
private:
    int d;
public:
    D(){d = 80;}
    void f()
    {
        a = 30;b = 40; c = 50;
        cout<<"D "<<d<<","<<a<<","<<b<<","<<c<<","<<d<<endl;
    }
};

void main()
{
    D d1;
    d1.f();
    d1.B::f();
    d1.C::f();
    d1.f();

}