Operator Overloading: Need and Rules of Operator Overloading in C++

 Operator Overloading: 

Need and Rules 

 

·       Operator Overloading allows to redefine the meaning of an operator (like +, -, <<, ++, etc.) for user-defined types (classes/structs).

·       Helps make code natural

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Need of Operator Overloading

1. To Make User-Defined Types Behave Like Built-In Types

 

Example:

Complex c1(2,3), c2(4,5);

Complex c3 = c1 + c2;   // natural & readable

 

Without operator overloading, :-

c1.add(c2);

This is less intuitive.

 

2. To Improve Readability & Maintainability

Writing a + b, a * b, a == b is cleaner and feels mathematical.

 

3. To Support Operator Functionality for Custom Classes

E.g., vectors, matrices, strings, time classes, dates, and currency types.

 

4. To Integrate Objects with C++ Standard Library

<< overloading use:

cout << object;

 

5. Supports Abstraction & Encapsulation

Users can use operators without knowing internal implementation details.

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Rules of Operator Overloading

Rule 1: Only existing operators can be overloaded

Do not create a new operator like $$, **, <>.

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Rule 2: At least one operand must be a user-defined type

Do not overload operators for built-in types only.

Not allowed: int operator+(int, int);

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Rule 3: Precedence, associativity & arity( number of arguments) cannot be changed

Not change how the compiler groups operators.

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Rule 4: Do not change the number of operands

Unary and binary nature stays the same.

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Rule 5: Some operators cannot be overloaded

Not allowed to overload:

Operator	Reason
.	Member access
.*	Pointer to member
::	Scope resolution
?:	Ternary operator
sizeof	Compile time
typeid	RTTI

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Rule 6: Overloading cannot change operator behaviour drastically

Meaning should remain natural.

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Rule 7: Overloading does not give new syntax

Not do: obj =+ 5;   // wrong

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Rule 8: Friend functions can be used to overload operators

Used when the left operand is not the calling object.

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Rule 9: Some operators must be overloaded as member functions

Like:

• = (assignment)
• () (function call)
• [] (array subscript)
• -> (member access)

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Different Ways to Overload Operators

1. Member Function Overloading

The operator works on the current object (LHS).

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2. Friend Function Overloading

Used when the LHS operand is not an object of the class.

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