第十/十一周训练1-7

#include <iostream>

using namespace std;

class A

{

protected:

int a,b;

public:

A(int aa, int bb):a(aa), b(bb) {}

void printA(){

cout<<"a: "<<a<<"\tb: "<<b<<endl;

}

};

class B: public A

{

int c;

public:

B(int aa, int bb, int cc):A(aa,bb),c(cc) {}

void printB()

{

cout<<"a: "<<a<<"\tb: "<<b<<"\tc: "<<c<<endl;

}

};

int main()

{

A a(1,1);

B b(2,3,4);

A &r1=a;

A &r2=b;

r1.printA();

r2.printA();

r2.printB();

return 0;

}

删除r2.printB(),因为r2的指针类型是A，不能调用B的函数

输出1，1 2，3