h04: Class Design

Reading: Class Design, DS 2 In CMPSC 24, you likely already read parts of Chapter 2. I want to invite you to read it again, for two reasons: (1) to review parts you may have skipped or skimmed over the first time (2) to revisit things that you may have read many weeks or months ago, and that may not have fully made sense to you at the time.

I’ve included some questions here on a few of the important points from Chapter 2, but these are NOT the only things you need from Chapter 2. I don’t have enough room on the page to give you homework over everything from Chapter 2 you need to learn. Read few this material a few times between now and the first exam.

1. (10 pts) Fill in the information in the header. The following are required to get the 10 "participation" points.
   • Filling in your name and umail address.
     

   Also: For paper submission PLEASE submit on ONE SHEET OF PAPER, double-sided if at all possible. If you must submit on two printed sheets write name on BOTH sheets and no staples, paperclips, or folded corners.
   

2. According to Chapter 2 of DS:
   1. (4 pts) In C++ if you write a class, but do not specify any constructors, what happens?
   2. (4 pts) When you implement a so-called "default constructor" in C++, what specific capability does this give the user of your class? (By specific, I mean what capability does the default constructor give that is distinguished from other kinds of constructors?)
   3. (4 pts) Suppose you are writing a class called Student that has two private members, 'std::string name' and 'int perm'. Write the function prototype (function declaration) ONLY for a default constructor for Student. For full credit, include the semicolon that terminates the prototype, but DO NOT write the body of the constructor
3. Before enrolling in CMPSC 32, you should have learned about stacks in CMPSC 24 (or an equivalent course). I'm going to tell you a few things about an example stack implementation as a C++ class, then ask a few questions—these are designed to check your understanding of some important ideas about ADTs and C++ classes from Chapter 2 of DS.

   Suppose we implement a class for a stack of integers, called IntStack. Our implementation uses a variable int stack[MAX_SIZE]; and a variable int size;. The constant MAX_SIZE may be declared as const int MAX_SIZE=100;, for example. I will have methods push, pop, isEmpty and since my implementation has a max size, isFull.

   If I declare a method with the function prototype bool isEmpty() const;, I have the option of putting the function body either in a separate IntStack.cpp file, or directly inside the IntStack.h file like this:

   bool isEmpty() const { return size==0; }

   1. (2 pts) According to C++ recommended practice, in which section of the class should we find the declarations of int stack[MAX_SIZE]; and int size;?

      Circle one:   public     private

   2. (2 pts) When we put the method body (e.g. {return size==0;} for isEmpty inside the class declaration (i.e. in the IntStack.h file) that makes isEmpty a special type of member function (three word phrase with initials IMF). What does IMF stand for?
   3. (3 pts) What is one thing that is different about IMF from the perspective of how they are treated by the compiler?
   4. (4 pts) What is the significance of the keyword const that appears after isEmpty?
   5. (4 pts) Would const be appropriate for the pop operation?
      Circle one: yes     no
      Briefly explain your answer.
   6. (4 pts) Would const be appropriate for the isFull operation?
      Circle one: yes     no
      Briefly explain your answer.
4. DS Chapter 2 refers to something called a macro guard. This is a set of two pre-processor directives that appear at the start of a file, and one that appears at the end of a file. DS's macro guard for a file throttle.h uses a symbol MAIN_SAVITCH_THROTTLE, but it would be more traditional to use a symbol such as _THROTTLE_H_ (the name of the file, with underscores before, after, and replacing the dot.)
   1. (4 pts) Write a macro guard for a file called IntStack.h, using the symbol _INTSTACK_H_. Put an ellipsis (…) in the place between the first two lines and the last line.
   2. (5 pts) What is the purpose of a macro guard?