Assignment 2, C++ Intro - Word Class

This page last updated on: Jan. 14, 2002

Due Date

Feb. 4, 2002 by end of day

Description

Implement a Word class. This will be one of the fundamental low-level building blocks of the dictionary spell checker project and will store data and provide operations (including Soundex functionality) for a single word. A Word class will have the following operations associated with it:

Constructors - initialize a Word object, either with a given initial string or without parameters
Destructor - deconstruct a Word object
IsEqual - compare two Word objects for equality (contents are the same)
Compare - compare two Word objects for sorting purposes (returns int, either less than 0, equal to 0, or greater than 0)
IsSoundexSame - compare two Word objects for similar sounding pronunciation (Soundex values)
GetLength - return the length of the internal word string
GetSoundex - return a pointer to the internal soundex value
DebugPrint - print the internal data of the word for debugging (non-user-interface) purposes

Other operations (including operator overloading of assignment, equality, and stream output), will be added in the next assignment.

Requirements

There will two parts to this assignment - the source code which implements the Word class, and a test program which tests the Word member functions. The Word source will be separated into word.h, which contains the class declaration, and word.cpp, which contains the member function implementations. The test program will be called tstword.cpp.

The test data will come from one or more command line arguments. The test program will display each of the Word objects created from the command line arguments. The test program will exercise all of the class public member functions (the public interface), and test boundary conditions as well as functionality. Create Word objects on both the stack and from the heap (using the new operator). Destroying the objects will be performed either automatically by the compiler (if on the stack), or explicitly using the delete operator (if on the heap). Create at least one empty Word object and compare it with a non-empty Word object.

Const will be used appropriately in all cases - const parameters (both pointer and reference parameters), const member functions, and const return types. bool return types will be used for true / false return types.

Internals

A Word object will be represented by a class containing the following member data:

Internal word length (integer)
Pointer to dynamic sized word string (character pointer)
Soundex value (fixed size character array - note that #define MAXSDX is in soundex.h)

Internally the character pointer points to the actual word string, which should be null character terminated (although it's not necessary to be null character terminated, if the appropriate logic is implemented). During object construction, non-alphabetic characters should be ignored. Case insensitive logic should be performed for comparisons. NOTE - the easiest and most efficient way to implement the case insensitive comparisons is to shift all of the characters to upper or lower case during object construction, and then do regular comparisons in the comparison functions.

The soundex value is computed by calling the soundex function (contained inside the soundex.c file, and declared in the soundex.h header file). (There are alternative implementations of phonetic processing - discuss with the instructor if interested.) (In addition to the hypertext links in this paragraph to the source code, there are links in the teaching index Web page.) Be sure to handle null character termination appropriately as well as soundex function call error returns. The soundex value should be computed in the constructor.

To allocate space for the internal word character array, the newoperator can be used as follows in the constructor (note the square brackets in both the new and delete operators):

mWordPtr = new char[length+1];

The delete operator will need to be used in the destructor:

delete [] mWordPtr;

The getSoundex function will return a const char pointer to the mSoundexValue array, which could be used as an external hash value in a Word object collection, or as a key in some other associative array container. More usage of this soundex value in Wordobject collections will be performed in future assignments.

The length will be computed in the constructor, which speeds up the rest of the functions. isEqual should first compare lengths before doing a strcmp on the internal word strings. The design tradeoff is extra space for each Wordobject, but faster comparison checking.

Since the soundex function is a C function, 'name-mangling' needs to be turned off. This is performed by wrapping the #include (or function declaration) with the keyword extern "C", as follows:

extern "C" {
#include "soundex.h"
}

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