Homework 4 - Classes with Dynamic Arrays

Coding Conventions

Assignment

You will be making your own implementation of a string class called myString. Use seperate compilation for this class. Name the header file mystring.h and name the implementation file mystring.cpp.

Your string class will have the following features:

• It will contain a character pointer for the string and an integer for the capacity of the currently allocated dynamic array as its member variables. You do not need a member variable to track how much of the array is in use currently since strings use the null character ('\0') to mark the end of the array. But, you can add such a member variable if you so choose.
• The character array pointer should reallocate when needed to hold the number of characters it is requested to hold.
• The class will be an abstract data type, so all member variables and helper functions need to be private. Additionally, you should describe each member function in the header file.
• The class will have the following constructors and destructor:
  • Default constructor - Allocate a character array that can hold a string with 20 characters (don't forget space for the null character too). Make this new array the empty string by setting the first character to the null character.
  • Copy constructor - Allocate a character array based on the source's capacity and copy the source string over into that array.
  • Destructor - Deallocate the array if it is allocated.
  • Constructor that takes a single character - Allocate a character array that can hold a string with 20 characters (plus the null character) like the default constructor. Then assign the passed character to the first slot in the array and also set the null character.
  • Constructor that takes a C-style string (character array) - Allocate a character array large enough to hold the passed C-style string (plus the null character). Then copy the characters from the passed array into the class's array.
• The class will support the following operators:
  • = Assignment - Copy the string of the source into the current string, deleting anything the current string may contain. Only reallocate if your current character array does not have the capacity to hold the source string.
  • >> The input operator - It will replace the current string with the first word (up to the first whitespace) on the input stream. You may need to reallocate the character array if there are more characters on the input stream before the first whitespace than the array can hold.
  • << The output operator - If the string exists, output the string to the output stream. Otherwise, output the empty string ("").
  • + Concatenation - Return a new string that is the left operand followed by the right operand. ie "Hello "+"world" would return "Hello world". Your temporary string object within the operator needs to have a capacity large enough to hold left's characters, right's characters and the null character.
  • += Append - Append the contents of the right hand operand to the current string. You may need to expand the character array in the current object so that it has enough capacity to hold the new string.
  • [] Index operator - Return the character at the specified index if the string exists.
  • < Less than - Return true if the left string is lexiographically less than the right string. Hint: wrap around strncmp()
  • > Greater than - Return true if the left string is lexiographically greater than the right string. Hint: wrap around strncmp()
  • == Equality - Return true if the two strings have the same characters. Hint: wrap around strncmp()
  • != Inequality - Return true if the two strings differ for any character. Hint: wrap around strncmp()
• The class will also have the following member functions:
  • int length() - Returns the current length of the string. If the string exists, just wrap around the strlen() function. Otherwise, return 0.
  • void erase() - Deletes the string. You may either delete the memory allocated or set the first character to the null character.
  • myString reverse() - Returns the string in reverse. Do NOT alter the string as stored in the class. Create a new string and make the changes in it. Return the new string.
  • void getline(istream &i, int count) - Get count - 1 characters from the input stream i and store it in the current string object, replacing the current string. If count is greater than the current capacity, reallocate the array to be able to hold count characters.

Additional Notes and Requirements

For += (append), if the current string is does not have enough memory allocated to store itself plus the appended string, you must allocate a new string that is long enough. In this process, you have to save the contents of the current string so that you can copy it over to the new string. Do not forget to save the current string before reallocating, if you need to reallocate.

For = (assignment), >> (input) and getline(), if the current string is not long enough to store the source string, delete the current string and allocate enough space. Unlike +=, you do not need to store the current string as it will be completely replaced by the new string. Also, do NOT point the character pointer of the current object to the character pointer of the source. Copy the data over to the current object's own array using a for() loop or strncpy().

The copy constructor and the constructor that takes a C-style string will allocate an array large enough for the source string and copy the string over to its array. Do NOT point the character pointer of the current object to the character pointer of the source. Copy the data over to the current object's own array using a for() loop or strncpy().

Main function

To submit the assignment, email me your header file and your implementation file.