学步园

//友元关系的双向都是不可继承的

#include<iostream>
class Base{
 friend class Frnd;
protected:
 int i;
};

class D1 : public Base{
protected:
 int j;
};

class Frnd{
public:
 int mem(Base b) { return b.i; }//ok
 int mem(D1 d) { return d.i; }//ok
 //int mem(D1 d) { return d.j; }//error
};

class D2 : public Frnd{//访问权限没继承来
public:
 //int mem(Base b) { return b.i; }//error,'int Base::i' is protected，
};


int main(){

 return 0;
 
}