1. An object of a class can be treated as an object of its corresponding class.

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1 Instructions: This homework assignment covers the basics of inheritance and polymorphism in C++. The answers may be determined from the lecture notes and assigned reading in Weiss. 1. An object of a class can be treated as an object of its corresponding class. 1) base, derived 2) derived, base 3) Both 1 and 2 2. Suppose that X is a class and that F() is a function that is not a member, or a friend, of X or of any class derived from X. Then, as far as F() is concerned, there is no difference between which of the following access specifiers for members of X? 1) public and private 2) public and protected 3) private and protected 4) public, private and protected For questions 3 through 7, assume that Foo and Bar are C++ classes, and that the class Bar is derived, using public inheritance, from the class Foo. 3. If X is an object of type Bar, then the member functions of X: 1) cannot directly access any of the members of class Foo. 2) can directly access only the public members of class Foo. 3) can directly access only the public and protected members of class Foo. 4) can directly access the public, protected, and private members of class Foo. 4. A programmer who wishes to use inheritance to produce a specialized derived class from the class Foo, does not need access to the source code for the implementation of Foo. 1) True 2) False 5. Suppose that an object X of type Bar is declared. Then: 1) no constructor for the base class, Foo, will be executed at all. 2) a constructor for the base class, Foo, will be executed before any constructor for the derived class, Bar. 3) a constructor for the base class, Foo, will be executed after any constructor for the derived class, Bar. 4) a constructor for the base class, Foo, may (or may not) be executed, and that may take place either before or after the execution of a constructor for the derived class, Bar. 5) constructors for both classes will be executed at the same time. 6. Suppose that an object X of type Bar is declared. Then when the lifetime of that object ends: 1) the destructor for the base class, Foo, will not be executed at all. 2) the destructor for the base class, Foo, will be executed before the destructor for the derived class, Bar. 3) the destructor for the base class, Foo, will be executed after the destructor for the derived class, Bar. 4) the destructor for the base class, Foo, may (or may not) be executed, and that may take place either before or after the execution of the destructor for the derived class, Bar. 5) destructors for both classes will be executed at the same time. Due: in class TBA Page 1 of 5

2 7. Which of the following is true? 1) Public members of Foo become public members of Bar. 2) Public members of Foo become private members of Bar. 3) Public members of Bar become public members of Foo. 4) Public members of Bar become private members of Foo. 5) 2 and 3 only For questions 8 and 9, consider the following C++ class declarations: class X { private: int M; void Func2(); X(int im = 0); void Func1(); ~X(); class Y : public X { private: float F; Y(); Y(float if, int im); void Func3(); ~Y(); 8. Which of the following function(s) may legally be invoked by a user of class Y? 1) Func1() 2) Func2() 3) Func3() 4) All of the above 5) 1 and 3 only 9. Consider the following constructor implementation for the class Y: Y::Y(float if, int im) : X(iM){ F = if; What is the purpose of the sequence of characters : X(iM)? 1) To invoke a member function of the class Y. 2) To declare a new member function for the class Y. 3) To invoke a constructor for a data member an object of the class Y. 4) To invoke a constructor for the base level of an object of the class Y. 5) Either 3 or 4. 6) The syntax is invalid. 7) None of these 10. In the object-oriented design of an airline passenger reservation program, suppose that airplane seat, aisle seat, and window seat have been identified as classes. Focusing specifically on the aisle seat class, how does it relate to the airplane seat class? 1) aisle seat exhibits a has-a relationship with airplane seat. 2) aisle seat exhibits a knows-a relationship with airplane seat. 3) aisle seat exhibits an is-a-kind-of relationship with airplane seat. 4) aisle seat and airplane seat are independent and unrelated. 2

3 For questions 11 and 12, suppose that a C++ class D is derived from a base class B, that class B has a public member function F(), and class D overrides B::F() with its own version. At execution time, suppose that the address of a D object is passed to the following function: void Foo(B* x) { x->f(); 11. If F()is declared to be virtual in class B, whose version of F() does Foo() call? 4) It is illegal to pass the address of a D here. 12. If F()is not declared to be virtual in class B, whose version of F() does Foo() call? 4) It is illegal to pass the address of a D here. For questions 13 and 14, suppose that a C++ class D is derived from a base class B, that class B has a public member function F(), and class D overrides B::F() with its own version. At execution time, suppose that a D object is passed to the following function: void Bar(B x) { x.f(); 13. If F()is declared to be virtual in class B, whose version of F()does Bar() call? 4) It is illegal to pass a D here. 14. If F()is not declared to be virtual in class B, whose version of F()does Bar() call? 4) It is illegal to pass a D here. 3

4 For questions 15 through 25, assume the following class declarations and main(). Assume that corresponding implementations are supplied for each class. class Base { void F(); virtual void G() = 0; virtual void H(); virtual void I(); class D : public Base { virtual void F(); void G(); void H(); virtual void J(); class E : public D { void F(); void G(); int main() { D* pd = new D; Base* pb = pd; E* pe = new E; pb->f(); // line 1 pb->g(); // line 2 pb->h(); // line 3 pb->i(); // line 4 pd->f(); // line 5 pd->g(); // line 6 pd->i(); // line 7 pd->j(); // line 8 pb = pe; pd = pe; pb->f(); // line 9 pb->g(); // line 10 pb->h(); // line 11 pb->i(); // line 12 pd->f(); // line 13 pd->j(); // line 14 pe->f(); // line 15 pe->h(); // line 16 It is possible to answer the following questions by simply testing code. Don t do that. Try to determine the answers logically first, then check your analysis by testing if you wish. For each question, determine which function (or functions) are called when the statement in the indicated line is executed: 15. line line 2 1) Base::G() 2) D::G() 3) E::G() 4) Base::H() 5) D::H() 6) 1 and then 4 7) 2 and then 4 8) 2 and then 5 9) None of these. 17. line 3 4

5 18. line 4 1) Base::I() 2) D::I() 3) E::I() 19. line line 10 1) Base::G() 2) D::G() 3) E::G() 4) Base::H() 5) D::H() 6) 2 and then 4 7) 2 and then 5 8) 3 and then 5 9) None of these. 21. line line 12 1) Base::I() 2) D::I() 3) E::I() 23. line line line 16 5