CSE2050 Exam #3.  Open book, open notes.  Name _________________________

1.  Write the destructor and the two other methods required by the
"rule of 3" for class D.  Assume that B is abstract with no constructor
or data members. (40 pts).

  template <class T> class D: public B {
    T* p;
  public:
    D(const T& t): p(new T(t)) {}
    void print() const {cout << *p;}

    // Answer
    ~D() {delete p;}

    D(const D& d): p(new T(*d.p)) {}

    D& operator=(const D& d) {
      *p = *d.p;
      return *this;
    }

    /* or
    D& operator=(const D& d) {
      if (&d != this) {
        delete p;
        p = new T(*d.p);
      }
      return *this;
    }
    */
  };


2.  Write the abstract base class B that specifies the interface for
both D and E. (15 pts).

  class E: public B {
  public:
    void print() const {}
  };

  // Answer
  class B {
  public:
    virtual void print() const = 0;
    virtual ~B() {} // -5 if you forgot this
  };



3.  Given the classes above, are each of these statements legal?
If no, explain why not. (3 pts each).

  // -1 if you got the right answer but the wrong reason

  B b;                // no, B is abstract
  const D<int> d(5);  // yes
  E e;                // yes
  B* p;               // yes
  p = new B;          // no, B is abstract
  p = new D;          // no, D requires a template and constructor argument
  p = new E;          // yes
  p.print();          // no, p is a pointer
  p->print();         // yes
  E::print();         // no, print() is not static
  B &r = *p;          // yes
  e = r;              // no, conversion from base to derived
  e = *p;             // no, conversion from base to derived
  e = new E;          // no, e is not a pointer
  d = 0;              // no, d is const