Dr. Mujtaba Asad has a PhD from Shanghai Jiao Tong University and has 10 years of teaching and research experience, with 6 impact factor journal publications in the last 3 years. His research areas include deep learning, computer vision, and anomaly detection. Operator overloading in C++ allows operators like + and << to be applied to user-defined classes by defining corresponding operator functions. For example, the + operator can be overloaded as a member function to add two complex number objects. The << operator can be overloaded as a non-member function to output complex number objects. Some operators like . and :: cannot be overloaded.

1. My Introduction
Dr. Mujtaba Asad
Education:
PhD: Shanghai Jiao Tong University
Subject QS Rank: 23, Overall QS Rank: 47
MS(CS), BS(TE): FAST-NUCES Lahore
Intermediate (I.C.S): Govt. College University (G.C.U) Lahore
Experience:
10 Years of Teaching & Research Experience
Publications:
6 Impact Factor Journal Publications in Last 3 Years
Research Area:
Deep Learning, Computer Vision (Video Analysis), Anomaly Detection

2. Operator Overloading in C++

3. Why Operator Overloading Is
Needed ?
• As we know that the only applicable operators on the class
objects are the assignment operator ( = ) , member
selection operator ( . ).
• Therefore, other operators cannot be directly applied to
class objects.
• However, C++ allows the programmer to extend the
definitions of most of the operators so that operators—such
as relational operators, arithmetic operators, the insertion
operator for data output, and the extraction operator for
data input—can be applied to classes.
• In C++ terminology, this is called operator overloading.

4. Class Example (Complex Numbers)

5. How to Redefine (Overload) Operators)
• Overloading an operator (Syntax)
– Write function definition as normal
– Function name is keyword operator followed by the
symbol for the operator being overloaded
– 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

6. Operator Functions as Class Members
vs. as friend Functions
• Member vs non-member
– Operator functions can be member or non-member functions
– When overloading ( ), [ ], -> or any of the assignment
operators, must use a member function
• Operator functions as member functions
– Leftmost operand must be an object (or reference to an object)
of the class
• If left operand of a different type, operator function must be a non-
member function
• Operator functions as non-member functions
– Must be friends if needs to access private or protected
members
– Enable the operator to be commutative

7. Overloading “+” operator as
Member function for Complex
Class

8. Overloading “<<” operator as
Non-Member function for
Complex Class

9. 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[]

10. Restrictions on Operator Overloading
• Overloading restrictions
– Precedence of an operator cannot be changed
– Associativity of an operator cannot be changed
– Arity (number of operands) cannot be changed
• Unary operators remain unary, and binary operators remain binary
• Operators &, *, + and - each have unary and binary versions
• Unary and binary versions can be overloaded separately
• No new operators can be created
– Use only existing operators
• No overloading operators for built-in types
– Cannot change how two integers are added
– Produces a syntax error