12438_12 Operator Overloading

7/29/2019 12438_12 Operator Overloading

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Operator Overloading


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Introduction It is one of the important features of C++

language Compile time polymorphism.

Using overloading feature, we can add two user

defined data types such as, objects, with thesame syntax, just as basic data types.

We can overload almost all the C++ operators

except the following:

Class member access operators( ., .*)

Scope resolution operator (::)

Size operator (sizeof)

Conditional operator (?:)


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Defining Operator Overloading

It is done with the help of a special function,called operator function, which describes the

special task to an operator.

General form:return typeclassname :: operator op (argulist)

{

function body //task defined}

where return typetype of value returned by the specified

operation & op operator being overloaded.

operator op function name


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Steps :

Create a class that defines the data type i.e.

to be used in the overloading operation.

Declare the operator function operator op() inthe public part of the class.

Note: It may be either a member function or a

friend function.

Define the operator function to implement the

required operations.


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Rules for overloadingoperators Only existing operators can be overloaded. New

operators cannot be created.

At least one operand (user defined type).

Cannot change the basic meaning of the operator.

Follow the syntax rules of the original operators.

Some operators cannot be overloaded.

Cannot use friend function to overload certain operators.

When using binary operators overloaded through amember function, the left hand operand must be an

object of the relevant class.

Binary arithmetic operators must explicitly return a value.


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Not used / overloaded

Operators that cannot Where a friend

be overloaded function cant be used

Sizeof = (assignment)

. (membership operator) ( ) (function call)

.* (pointer to member operator) [ ] (subscripting)

:: (class member access)

?:


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Overloading of Unary Operators

++ & -- Operator

Unary Operator

>> &


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Overloading of Binary Operators

Arithmetic operators (+, - , *, /)

Relational Operators (, ==, =, !=)


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Program: - Arithmetic Operatorclass complex

{ float x,y;

public:complex() { } int main()

complex(float real, float img) {

{ x = real; y = img;} complex c1, c2, c3;

complex operator + (complex); c1 = complex(2.5, 3.5);

void display(void); } ; c2 = complex(1.5, 2.5);

complex complex :: operator + (complex c) c3 = c1 + c2;

{ complex temp; cout


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Explain coding

complex complex :: operator + (complex c)

{ complex temp;

temp.x = x + c.x;

temp.y = y + c.y;

return (temp);}

Features: -1. it receives only one complex type argumentexplicitly

2. It returns a complex type value.

3. It is a member function ofcomplex.


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Overloading Binary OperatorsUsing Friends

Friend functions may be used in the place of

member functions for overloading a binary

operator.

Difference : - a friend function requires two

arguments to be explicitly passed to it, while

a member function requires only one.


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Using Friend Function

Replace the member function declaration by the friend

function declaration.

friend complex operator + (complex, complex);

Redefine the operator function as follows: complex operator + (complex a, complex b)

{

return complex ((a.x + b.x), (a.y + b.y));

}

In this case, the statement c3 = c1 + c2; is equivalent to

c3 = operator + (c1, c2);


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Thank You!!!

12438_12 Operator Overloading

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