Operator overloading allows user-defined types to have special meanings applied to operators like + and *. It is a form of polymorphism that allows operators to work on custom data types like user-defined objects in the same way they work on built-in types. To overload an operator, a programmer defines operator functions that specify the behavior for that operator when used on a class. These functions can be member functions or non-member functions. Certain operators cannot be overloaded and rules govern the number of arguments for operator functions.

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Operator Overloading
CE 142: Object Oriented
Programming with C++
Kamlesh Makvana

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C++ Operator Overloading
 One to type of polymorphism
 Gives user defined meaning of operators
 i.e. perform operations on user defined data
types.
 Meaning of operator is already defined
by the compiler for built-in data types.
 Redefine same for user defined data
types like objects.

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Why Operator Overloading
 Make program more readable
 c= add(c1,c2);
 c= c1+c2;
 z=add(mul(a,b),sub(x,y));
 z=(a*b)+(x-y);

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How to overload Operator in C++
 Create a operator functions
 Operator functions could be a member
functions.
 Operator functions could be a normal user
defined functions.

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Operator functions could be a
member functions

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Operator functions could be a
member functions

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Operator functions could be a
normal UDF.

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Department of Information TechnologyOperator functions could be
a normal UDF.

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Rules for operator overloading
 Only existing operators is overloaded. Can
not create new operators.
 Overloaded operator must have at least one
operands.
 Basic meaning of operator could not be
changed.
 Some operators can not be overloaded like
dot(.), ::, ?:, sizeof, etc.
 We can not use friend function to overload
some operators like =, (), [], ->.

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Rules for operator overloading
 If operator function is friend function
 Unary operator: one arguments.
 Binary operator: two arguments.
 If operator is non-static member function.
 Unary operator: no arguments.
 Binary operator: one arguments.
 Left-hand operand must be a type of relevant type.
 Binary arithmetic should explicitly return a value.

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Overloading Binary Addition
operator