Project 6 Dynamic Arrays, More Operator Overloading Solution

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Part I The MyString class

Code the MyString class in indicated in the following UML diagram.  Note that the member variable is a DYNAMIC ARRAY, so this class will be implementing the Big 3 function (copy constructor, operator= and destructor).

 

A MyString object is similar to a string object which you have used in Project 5.  An object of type MyString will store a collection of characters – a string.  Internally, the MyString object will use a char array (c-string) to store the data.  This array will be a dynamic array, so that when a MyString object is created, the exact amount of storage needed can be allocated (don’t forget that a c-string stores a ‘\0’ following all chars).

 

MyString
–       char * str   // storage for characters in the string.  This array will contain a ‘\0’ at

//the end so that C-string functions can be used

–       int len       //number of characters in str (not counting the ‘\0’)

     + MyString()

+ MyString(char  newstr[])

+ MyString(const MyString& obj)       // copy constructor

+ ~MyString()                                 // destructor

 

+ int getLen() const

+ void setElement(int index, char item)

+ char getElement(int index) const

 

+ bool operator==(const MyString& obj)

+ bool operator!=(const MyString& obj)

+ char& operator[] (int);

+ MyString& operator=(const MyString& obj)  //assignment operator overload

friend ostream&  operator<<(ostream& out, const MyString& obj)

 

MyString()  Creates a string which contains “default”;

 

MyString(char newstr[])  Accepts one C-string argument, allocates

an array large enough for this CString (don’t forget room for the ‘\0’), stores it, and

initializes len

 

+ MyString(const MyString& obj)   This copy constructor initializes the new MyString object

to store the same characters as ‘obj’.  The new object is totally independent of the

object ‘obj’  (deep copy)

 

+ ~MyString()    Deletes any dynamic memory that was allocated for this object.

 

+ int getLen()   Returns the number of characters in this string (does not count \0)

 

//These functions have a precondition that 0 <= in < len

+ void setElement(int in, char item)  Sets the character at index ‘in’ to ‘item’

+ char getElement(int in)  Returns the character at index ‘in’

 

+ bool operator==(const MyString& obj) Returns true if this MyString object contains the same

characters (in the same order) as obj

 

+ bool operator!=(const MyString& obj) Returns true if this MyString object does not contain

the same characters (in the same order) as obj

 

+ char& operator[] (int in)  returns the character at index ‘in’

 

+ MyString& operator=(const MyString& obj)  assignment operator overload

ostream&  operator<<(ostream& out, const MyString& obj)  non-member function which outputs

all characters MyString object obj

 

Part II Application

Write an application which:

//tests simple constructors

Creates a MyString object, str1, using the no-arg constructor

Creates a MyString object, str2, using on-arg constructor (user provides string to be passed as argument)

Updates each of the characters of str1, allowing user to enter characters and position

Outputs str1 and str2

 

  // tests simple operator overloads

Outputs a message indicating if str1 and str2 are equal or not

Outputs the characters of str2, one per line (use the [] to access chars)

 

  //tests copy constructor, verifying object independence

Creates a MyString object, str3,  initializing it to str2

Output str2 and str3

Updates 2 characters of str2, allowing user to enter characters and position

Output str2 and str3

 

  //tests assignment operator, verifying object independence

Output str1 and str3

Assigns str3 to str1

Output str1 and str3

Updates 2 characters of str3, allowing user to enter characters and position

Output str1 and str3

 


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