This document discusses operator overloading in C++. It provides the following key points: 1. Operator overloading allows defining new meanings for most C++ operators when used with user-defined types. Operators that cannot be overloaded include ., ->, ::, sizeof, and ?:. 2. To overload an operator, a member function is written with the name operator followed by the operator symbol. This function performs the new task defined for the operator on class objects. 3. Common operators that can be overloaded include +, -, *, /, %, <<, >>, ==, !=, etc. Examples are provided for overloading unary, binary, and subscript operators to manipulate class objects.

1. OBJECT ORIENTED
PROGRAMMING WITH C++
PRESENTED BY –
Darpen Patel (130110107032)
Jay Patel (130110107036)
Gujarat Technological University
G.H Patel College of Engineering and Technology
Department of Computer Engineering

2. Operator Overloading

3. Introduction
• Operator Overloading provides a flexible option for the creation of new
definitions for most of the c++ operators.
• We can overload all the c++ operators except the following:
 Class member access operators (., .*).
 Scope resolution operator (::).
 Size operator (sizeof).
 Conditional operator (?:).

4. • Overloading an operator
• Write function definition as normal
• Function name is keyword operator followed by the symbol for the
operator being overloaded
Ex. Operator+ used to overload the addition operator (+)
• Using operators
• To use an operator on a class object it must be overloaded unless the
assignment operator(=)or the address operator(&)
• Assignment operator by default performs memberwise assignment
• Address operator (&) by default returns the address of an object
Introduction

5. return type classname :: operator op(arglist)
{
function body //task defined
}
SYNTAX FOR OPERATOR OVERLOADING

6. • Operator functions are declared in the class using prototypes as follows:
 vector operator + (vector);
 vector operator – ();
 friend vector operator + (vector, vector);
 friend vector operator – (vector);
 vector operator – (vector &a);
 int operator == (vector);
 friend int operator == (vector, vector);
• Arguments may be passed either by value or by reference.

7. RULES FOR OVERLOADING OPERATOR
• Only existing operator can be overloaded .New operator cannot be
created.
• The overloaded operator must have at least one operand that is of user
defined type.
• Overloaded operator follow the syntax rules of original operators.
They cannot be changed.
• When using binary operator overloaded through member function the
left hand operand must be an object of the relevant class .

8. Restrictions on Operator Overloading
• C++ operators that can be overloaded
• C++ Operators that cannot be overloaded
Operators that cannot be overloaded
. .* :: ?: sizeof
Operators that can be overloaded
+ - * / % ^ & |
~ ! = < > += -= *=
/= %= ^= &= |= << >> >>=
<<= == != <= >= && || ++
-- ->* , -> [] () new delete
new[] delete[]

9. Overloading Unary Operators
• Overloading unary operators
• Can be overloaded with no arguments or one argument
• Should usually be implemented as member functions
• Example declaration as a member function:
class String {
public:
void operator+() const;
...
};
– Example declaration as a non-member function
class String {
friend void operator+( const String & )
...
}

10. #include<iostream.h>
#include<conio.h>
class un
{
int x;
public:
un(int a)
{
x=a;
}
operator -()
{
x=-x;
}
void display()
{
cout<<x<<"n";
}
};
Example
void main()
{
un a(10);
a.display();
-a;
a.display();
getch();
}
o/p:-
10
-10

11. Overloading Binary Operators
• Overloaded Binary operators
• Non-static member function, one argument
• Example:
class String {
public:
String operator+(String );
...
};
• Non-member function, two arguments
– Example:
class String {
friend String operator+(String , String );
...
};

12. #include<iostream.h>
#include<conio.h>
class bin
{
int a;
public:
bin(int x)
{
a=x;
}
void display()
{
cout<<a;
}
friend int operator +(bin ,bin);
};
Example int operator +(bin x,bin y)
{
int z;
z=x.a+y.a;
return(z);
}
void main()
{
bin x(10),y(20);
int z;
clrscr();
cout<<"x=";
x.display();
cout<<"ny=";
y.display();
z=x+y;
cout<<"nz="<<z;
getch();
}
o/p:-
x=10
y=20
z=30

13. Manipulation of Strings Using Operator
• In c++ we can add two string by using operator overloading
• We shall be able to use statement like this:
string3=string1+string2;

14. Example
#include<iostream.h>
#include<conio.h>
#include<string.h>
class str
{
char a[10];
public:
void get()
{
cin>>a;
}
str operator +(str b)
{
str c;
int l,i=0;
l=strlen(a);
for(i=0;i<l;i++)
{
c.a[i]=a[i];
}
l=strlen(b.a);
for(int j=0;j<l;j++)
{
c.a[i]=b.a[j];
i++;
}
c.a[i]=NULL;
return(c);
}
void display()
{
int l,i;
l=strlen(a);
for(i=0;i<l;i++)
cout<<a[i];
}
};
void main()
{
str x,y,z;
clrscr();
x.get();
y.get();
z=x+y;
cout<<"x=";
x.display();
cout<<"ny=";
y.display();
cout<<"nz=";
z.display();
getch();
}
o/p:-
x=hi
y=hello
z=hihello

15. Overloading of the Subscript[] Operator
#include<iostream.h>
#include<conio.h>
class extra
{
int a[5];
public:
void get()
{
for(int i=0;i<5;i++)
cin>>a[i];
}
int operator [](int x)
{
if(x<=5)
return(a[x-1]);
else
{
x=x%5;
return(a[x-1]);
}
}
};
void main()
{
extra y;
int x,z;
clrscr();
y.get();
cout<<"enter element:";
cin>>x;
z=y[x];
cout<<"element is "<<z;
getch();
}
o/p:-
1
2
3
4
5
enter element:3
3

16. THANK YOU