7.28组合

组合
class Student     
{public:
        Student(string num, string name, char sex, int age): num(num),
name(name), sex(sex), age(age){ }
private:
        string num;
        string name;
        char sex;
        int age;
};
class Date     
{public:
Date(int y, int m, int d) {  year = y; month = m; day = d;  }
private:
int year, month, day;
};
class Graduate: public Student  
{public:
Graduate(string num, string name, char sex, int age, int y, int m,
int d, string direct): Student(num, name, sex, age), 
birthday(y, m, d), direct(direct){ }


 private:
         Date birthday;   
string direct;   
};