1 class base
 2 {
 3 public:
 4    base(string szNm) : basename(szNm) {}
 5    string name() {return basename;}
 6    virtual void print(ostream &os) {os << basename;}
 7 private:
 8    string basename;
 9 }
10 
11 
12 class derived : base
13 {
14 public:
15    derived(string szNm, int ival):
16       base(szNm), 
17       mem(ival) {}
18    void print()
19    {
20       print(base::ostream &os);    // 答案是这个
21       base::rint(ostream &os);      // 我觉得是这个
22       os < "--" << mem;
23    }
24 private:
25    int mem;
26 }