calss A
{
public:
int x;
virtual void update()=0;
};
class B :public A
{
int y;
public:
B(){y=1;}
void update(){cout<<"hello"<<endl;}
void cgr(int y){cout<<y<<endl;}
};
void main()
{
A *p=new B;
}
这时候 B的cgr()函数怎样才能使用?