![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[]](https://image.slidesharecdn.com/operatoroverloading-191030180239/85/Operator-overloading-4-320.jpg)
![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, it could be done with 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 friend if needs to access private or protected
members
Enable the operator to be commutative](https://image.slidesharecdn.com/operatoroverloading-191030180239/85/Operator-overloading-8-320.jpg)
Operator overloading
- 1. Aruna Devi P. Assistant Professor, Department of CS
- 2. Operator Overloading It Facilitates the use of Compile time Polymorphism When overloading the meaning of the operator should not be changed. Allowing C++’s operators to work with user defined data type such as objects Use all operators with user-defined objects Requires great care while overloading operators. Program will be difficult to understand Examples of already overloaded operators Operator << is both the stream-insertion operator and the bitwise left-shift operator + and -, perform arithmetic on multiple types Compiler generates the appropriate code based on the manner in which the operator is used
- 3. Overloading … Operator Overloading Function definition is written as usual Operator keyword is used in declaration followed by the symbol for the operator being overloaded operator+ is used to overload the addition operator (+) Using operators To use an operator on a class object it must be overloaded first Assignment operator by default performs member wise assignment Address operator (&) by default returns the address of an object
- 4. 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[]
- 5. 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
- 6. Operator Function Uses the Operator Keyword for function declaration Overloading the operator is done by statements in the operator function definition. Operator function can be Member function Non member function as Friend The way of defining the function differs for both the method.
- 7. Syntax for Binary operator overloading Member function Return-type Class-name :: operator +(arglist) { //Definition of operator overloading } Argument list will have only one argument and other argument is implicitly used when the function is called. Friend Function Return-type operator +(arglist) { } Argument list will have 2 argument for binary operator overloading
- 8. 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, it could be done with 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 friend if needs to access private or protected members Enable the operator to be commutative
- 9. Overloading Stream-Insertion and Stream-Extraction Operators Overloaded << and >> operators Overloaded to perform input/output for user-defined types Left operand of types ostream & and istream & Must be a non-member function because left operand is not an object of the class Must be a friend function to access private data members
- 10. Overloading Unary Operators Operators that accept only one operand is unary Can be overloaded with no arguments or one argument No argument when it is a member function One argument when it is friend function or non member function Should usually be implemented as member functions Avoid friend functions and classes because they violate the encapsulation of a class
- 11. Syntax for Unary operator overloading Member function Return-type Class-name :: operator +() { //Definition of operator overloading } Argument list will be empty since the argument is implicit in its call Friend Function Return-type operator +(arglist) { } Argument list will have 1 argument for unary operator overloading
- 12. Conclusion Operator overloading is one of the feature of C++ that’s implements Compile time polymorphism. Overloading code should be written with greater care. Meaning of the operator should be preserved Use any of the two method for declaring the operator function