Question

3. Suppose the University has two types of academics: students and lecturers. Both of these have names and ids, but students attend lectures while lecturers give them. class Student private: string name; string id; public: Student (string name, string id); string getName ); string getIDO; void attendLecture(); class Lecturer private: string name; string id; public: Lecturer(string name, string id); string getName; string getIDO; void giveLecture ();

Answer 1

Answer 3:

(a) The updated classes are as follows:

class Academic {
    private:
        string name;
        string id;
    public:
        Academic(string name, string id);
};

class Lecturer : public Academic {
    public:
        Lecturer(string name, string id);
        void giveLecture();
};

class Student : public Academic {
    public:
        Student(string name, string id);
        void attendLecture();
};

(b): The constructors for the three classes are given below:

Academic::Academic(string _name, string _id)
    : name(_name), id(_id)
{
}

Student::Student(string name, string id)
    : Academic(name, id)
{
}

Lecturer::Lecturer(string name, string id)
    : Academic(name, id)
{
}

Answer 4:

(a) It is assumed that the Person will have a name but id is specific is academics only. The corresponding classes is as follows:

class Person {
    private:
        string name;
    public:
        Person(string name);
};

class Academic : public Person {
    private:
        string id;
    public:
        Academic(string name, string id);
};

(b): The constructors are as follows:

Person::Person(string _name)
    : name(_name)
{
}

Academic::Academic(string _name, string _id)
    : Person(_name), id(_id)
{
}

(c):

If all the methods are declared private, the code would not compile. This would be because the private constructors of the base class would not be accessible by the derived class. Thus, the constructor for Academic could not call the constructor for Person, and the constructors for Student and Lecturer would not be able to call the constructor for Academic. This would cause a compilation error.

When the constructor is private, it also implies that only member functions can create its objects.

If all the variables were declared public, the member variables of the base class would be accessible from the derived classes as well as functions that are not its members. Thus, the string name which is a member of Person, would be accessible by Academic and other classes as well as outside the derived classes as well. Similarly, string id in class Academic, if made public would be accessible anywhere.