Description
Description
As you know, the string class in C++ maintains a list of characters. Up to this point, you might have
thought that a string is a primitive data type since it was introduced at a surface level in your previous CS
course.
In fact it is a custom type but it does seem to almost be a primitive type since strings are popular
in programming.
You will create a custom string class which we will call myString, the class can be seen
below:
class myString
{
public :
myString ();
myString ( const char str []);
myString ( const myString &);
myString ( char );
char & operator []( int );
int length () const ;
const myString & operator =( const myString &);
const myString & operator =( const char []);
const myString & operator =( char );
myString operator +( const myString &) const ;
myString operator +( const char []) const ;
myString operator +( char ) const ;
const myString & operator +=( const myString &);
const myString & operator +=( const char []);
const myString & operator +=( char );
bool operator ==( const myString &) const ;
~ myString ();
friend myString operator +( const char [] , const myString &);
friend myString operator +( char , const myString &);
friend ostream & operator < <( ostream & out , const myString &);
friend istream & operator > >( istream & in , myString &);
private :
int sLength ;
char * s ;
};
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Description of class
Each member of the class will perform/contain the following:
• myString::myString() – will be the default constructor that sets s = NULL and sLength = 0
• myString::myString(const char str[]) – will be the constructor that takes a string literal str and
assigns it to the s array, and the sLength field will be set to the length of the string literal, you will
have to iterate through the str array to determine the size, details are explained on page 3, for example
myString s1(“Hello”); invokes this constructor and it sets the s field to hold Hello and sLength
will be set to 5
• myString::myString(const myString& str) – will be the default copy constructor that creates a
deep copy of the str object, so sLength = str.sLength and we need to allocate s to size str.sLength
and copy one character at a time from str.s to s, str could hold an empty string
• myString::myString(char c) – will be a constructor that sets the sLength to 1 and the only character
in the array s will be c, the parameter passed
• char& myString::operator[](int i) – overloads the [] operator which will return s[i]
• int myString::length() const – returns the sLength field
• myString& myString::operator=(const myString& str) – will be the default assignment operator
that assigns the myString object on the left side of the operator with the str object which is the object
on the right side, you must perform a deep copy, so first you need to deallocate the s array if it is not
pointing to nullptr, assign the sLength = str.sLength and set s to str.sLength by copying each
character one at a time from str.s to s, str could be an empty string so in that case sLength = 0
and s = nullptr
• myString& myString::operator=(const char str[]) – will be an assignment operator that assigns
the object that called the function (the left side object) with a string literal str, a deep copy must be
performed, for example myString s1 = “Hello World” will trigger this function, so s1’s s field will
contain “Hello World” and sLength will be set to 11, so once again first you will deallocate s if it is
not pointing to nullptrL, and the count the number of characters in str and allocate s to that size
and then perform the copying which will copy each character from str array into s array one character
at a time, str could be an empty string so make sure your code sets everything correctly in that case
• myString& myString::operator=(char rhs) – will be an assignment operator that that assigns the
object that called the function (the left side object) with a character rhs, a deep copy must be
performed, for example myString s1 = ’A’ will trigger this function, once again you will have to
deallocate s if it is not pointing to nullptr and set s[0] = rhs; and sLength = 1, you will perform
similar stuff as you did for the other assignment operators
• bool myString::operator==(const myString& str) const – will be the comparison operator that
returns true if the myString object on the left side of the == sign is equal to the myString on the right
side of the operator (the right side object will be denoted by str), if both strings are empty strings
then return false
• myString myString::operator+(const myString& str) – will overload the + operator which will
concatenate the myString object on the left side of the operator with the str object which will be
on the right side, a new concatenated myString object will be returned, so you will need to create
a temporary myString tmp; object and set tmp.sLength = sLength + str.sLength; and allocate
tmp.s array to that length, and then s will be copied into tmp.s from 0 to sLength – 1 and then you
will copy str.s into tmp.s from sLength to tmp.sLength – 1, remember either s or str.s could be
nullptr
• myString myString::operator+(const char rhs[]) – will overload the + operator which will concatenate the myString object on the left side with a string literal rhs on the right side, a new concatenated myString object will be returned, for example s1 + “Hello” will trigger this function, hint:
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you could use functions and constructors that you implemented already inside this function to avoid
writing new code, make use of the this pointer which points to itself (the object that called this
function), *this dereferences itself, once again s could be nullptr and rhs could be an empty string
• myString myString::operator+(char rhs) – will overload the + operator which will concatenate the
myString object on the left side with a character rhs on the right side, a new concatenated myString
object will be returned, for example s1 + ’A’ will trigger this function, hint: you can once again
reuse other functions, once again s could be nullptr
• myString& myString::operator+=(const myString& rhs) – will overload the += operator which
will concatenate the myString object on the left side with the rhs object on the right side and will
assign the new concatenated myString to the left side object, basically s1 += s2 will be equivalent to
s1 = s1 + s2, hint: make use of this pointer and the operator+(const myString& str) function,
once again s or rhs.s could be nullptr
• myString& myString::operator+=(const char rhs[]) – will overload the += operator which will
concatenate the myString object on the left side with the string literal rhs on the right side and
will assign the new concatenated myString to the left side object, basically s1 += “Hello” will be
equivalent to s1 = s1 + “Hello”, hint: you can reuse again, but once again s could be nullptr and
rhs could be an empty string
• myString myString::operator+=(char rhs) – will overload the += operator which will concatenate
the myString object on the left side with a character rhs on the right side and will assign the new
concatenated myString to the left side object, so s1 += ’a’ will be equivalent to s1 = s1 + ’a’,
hint: you can reuse again and once again s could be nullptr
• myString::~myString() – will be the destructor for the class that will deallocate the character array
when the object goes out of scope
• myString operator+(const char lhs[], const myString& rhs) – will be a friend function that
allows us to concatenate a string literal with a myString object, for example “Hello”+ s1 will trigger
this function, hint: create a temporary myString object from lhs, now you have two myString objects
and the you could reuse some of the operators but once again be able to handle nullptr pointers
• myString operator+(char lhs, const myString& rhs) – will be a friend function that allows us to
concatenate a character with a myString object, for example ’A’ + s1 will trigger this function, hint:
you can reuse other functions again but be able to handle nullptr pointers
• ostream& operator<<(ostream& out, const myString& str) – friend function that overload the
<< operator that will output the string using the ostream variable out, you will need to output one
character at a time until the end of str.s array is reached, if str.s == nullptr, then nothing will
be printed
• istream& operator>>(istream& in, myString& str) – friend function that overloads the >> operator that will read in a string and assign it to str.s array, so basically you will need to use in.get(ch);
to read a character from the input where ch will be a character declared inside the function, you will
keep reading in a character and appending it to the str.s array until a ’\n’ character is read (hint:
you could use operator+=(char) function to append the character read into a myString object assuming you implemented the += function)
• int sLength – holds the length of the myString object
• char * s – holds the character array that will represent the string inside the myString object
Every string literal in C++ is terminated by a null character, ’\0’ character. Suppose you declare the
following object in main
myString object (” Sunday Funday “);
Then the constructor myString::myString(const char[] str) would be invoked when object is being
instantiated. You can traverse the string literal in the following way.
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int i = 0;
while ( str [ i ] != ’\0 ’)
i ++;
// the value of i contains the length of str
And then you can allocate the char array to this->s array, and then just deep copy str array into this->s
array.
Sample Run
% make
g ++ – Wall – Wextra – pedantic -std= c ++11 -g -c main01 . cpp myString . h
g ++ – Wall – Wextra – pedantic -std= c ++11 -g -c myString . cpp
g ++ – Wall – Wextra – pedantic -std= c ++11 -g -o m01 main01 . o myString . o
g ++ – Wall – Wextra – pedantic -std= c ++11 -g -c main02 . cpp myString . h
g ++ – Wall – Wextra – pedantic -std= c ++11 -g -o m02 main02 . o myString . o
g ++ – Wall – Wextra – pedantic -std= c ++11 -g -c main03 . cpp myString . h
g ++ – Wall – Wextra – pedantic -std= c ++11 -g -o m03 main03 . o myString . o
g ++ – Wall – Wextra – pedantic -std= c ++11 -g -c main04 . cpp myString . h
g ++ – Wall – Wextra – pedantic -std= c ++11 -g -o m04 main04 . o myString . o
g ++ – Wall – Wextra – pedantic -std= c ++11 -g -c main05 . cpp myString . h
g ++ – Wall – Wextra – pedantic -std= c ++11 -g -o m05 main05 . o myString . o
g ++ – Wall – Wextra – pedantic -std= c ++11 -g -c main06 . cpp myString . h
g ++ – Wall – Wextra – pedantic -std= c ++11 -g -o m06 main06 . o myString . o
g ++ – Wall – Wextra – pedantic -std= c ++11 -g -c main07 . cpp myString . h
g ++ – Wall – Wextra – pedantic -std= c ++11 -g -o m07 main07 . o myString . o
% ./ m01
HelloWorld
Hello # World
HelloRockview
World !
% ./ m02
ByeByeBye
ByeEveryone
ByeEveryone !
% ./ m03
GreenDay
ADay
% ./ m04
Same string
Not the same string
Not the same string
% ./ m05
Enter a string : Zip
Zip
Enter another string : ZipZap
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ZipZap
% ./ m06
B r a c k e t o p e r a t o r t e s t
BRACKET OPERATOR TEST
Specifications
• Document your functions
• Make sure your code is memory leak free
• Do not use string or cstring functions
Submission
Submit the source file to code grade by the deadline
References
• Supplemental Video https://youtu.be/LD-962yQOsk
• Link to the top image can be found at https://www.deviantart.com/lazoofficial/art/Patrick-SpongeBobWhere-s-the-Leak-Ma-am-Full-903350786
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