UMBC CMSC 202, Computer Science II, Fall 1999

Project 4: Inheritance and Polymorphism

Due: December 9, 1999

See Also Project Notes, Questions and Answers

Objectives

The objectives of this project are to:

Write a derived class based on an existing class.
Use virtual functions, including virtual destructors.
Write a copy constructor and an overloaded assignment operator for a derived class.
Overload the insertion (output) operator.
Demonstrate the use of dynamic binding.
Use pointers and dynamic memory allocation/deallocation in C++.

Background

In this project you will write a C++ class to implement a set of key/value pairs, often referred to as a map or associative array. In particular, you will "map" integers (the keys) to strings (the values). Since you've already built a class that maintains a set of integers, we will derive the new class (Map) from the existing class Set. We will demonstrate dynamic binding (polymorphism) by including virtual functions and by processing an array of base class pointers.

Tasks

Begin with Set.H and Set.C from Project 3. In Set.H:
- Change the declaration of the Display() function so that it takes an argument of type ostream& with default value of cout:
```
void Display (ostream& os = cout) const;
      
```
- Add a declaration for the overloaded insertion (output) operator.
In Set.C:
- Revise the function definition for Display().
- Implement the overloaded insertion operator by calling the Display() function:
```
ostream& operator << (ostream& os, const Set& s) {
    s.Display (os);
    return os;
} 
      
```
Test these changes.
Write the derived class Map. Begin with this Map.H. Add a header comment and a comment for each member function. You may add additional data or function members in the private section, but do not change the public section. Implement the member functions in a file called Map.C. Test the new class. Here is a sample test program and output.
In Set.H, revise the declarations for Display() and the destructor so that these functions are virtual. Test these changes with a test program that creates and displays some sets and maps, using an array of Set pointers. You may want to insert some temporary print statements into the destructors in Set.C and Map.C to prove that they are getting called. Here is a sample test program and output.
After you are confident that your classes are working properly, test them with a more robust test program. Here is a sample test program.
For this project, you should submit a makefile and four source files named as follows:
- Set.H
- Set.C
- Map.H
- Map.C
Your makefile should be set up to make an executable named Proj4 using source file Proj4.C. Do not submit your own Proj4.C. Your project will be tested using an undisclosed test program similar (but not identical) to the sample shown in the previous step.

Extra Credit

Extra credit points will be added to the total points for the four projects.

Use Quicksort or Merge Sort to sort the integer keys. (15 points)
Use a binary search when you write the GetValue() function in the Map class. (15 points)