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Department of I.T. Engineering
Presentation
On
Operator Overloading
Academic year 2018-19
Laxmi Institute of Technology, Sarigam
Approved by AICTE, New Delhi; Affiliated to Gujarat Technological University, Ahmedabad
Enrolment
number
Name
160860116018 Nishant P. Joshi
160860116029 Raj M. Patel
160860116032 Udit A. Patel

Content
 Introduction
 Operator overloading
 Defining operator overloading
 Overloading Input/output operator
 Overloading Unary Operator
 Overloading Binary Operator
 Rules for overloading operator
 Restrictions on Operator Overloading

Introduction
 Overloading an operator
◦ 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

Operator overloading
 Addition (+) operator can work on operands of type
char, int, float & double.
 However, if s1, s2, s3 are objects of the class string, the
we can write the statement,
s3 = s1 + s2;
 This means C++ has the ability to provide the operators
with a special meaning for a data type.
 Mechanism of giving special meaning to an operator is
known as operator overloading.

Operator overloading
 Operator – is a symbol that indicates an operation.
 Overloading – assigning different meanings to an
operation, depending upon the context.
 For example:
input(>>) / output(<<) operator
– The built-in definition of the operator << is for
shifting of bits.
– It is also used for displaying the values of various
data types

Defining operator overloading
 The general form of an operator function is:
return-type class-name :: operator op (argList)
{
function body // task defined.
}
– where return-type is the type of value returned by
the specified operation.
– op is the operator being overloaded.
– operator op is the function name, where operator is
a keyword.

Overloading Input/output operator
 C++ is able to input and output the built-in data types
using the stream extraction operator >> and the stream
insertion operator <<.
 Overloaded to perform input/output for user defined data
types.
 Left Operand will be of types ostream & and istream &.
 Function overloading this operator must be a Non-
Member function because left operand is not an Object
of the class.
 It must be a friend function to access private data
members.

#include<iostream>
using namespace std;
class time
{
int hr,min,sec;
public: time()
{
hr=0, min=0; sec=0;
}
time(int h,int m, int s)
{
hr=h, min=m; sec=s;
}
friend ostream& operator << (ostream &out, time &tm);
//overloading ‘<<' operator
};

ostream& operator << (ostream &out, time &tm) //operator function
{
out << "Time is " << tm.hr << "hour : " << tm.min<< "min : " <<
tm.sec
<< "sec";
return out;
}
int main()
{
time tm(3,15,45); cout << tm; return 0;
}
Output:
Time is 3 hour : 15 min : 45 sec

Overloading Unary Operator
#include <iostream>
using namespace std;
class temp
{
private:
int count;
public:
temp():count(5)
{ }
void operator ++()
{
count=count+1;
}
void Display()
{
cout<<“Count:”<<count;
}
};
int main()
{
temp t;
++t;
/* operator function void
operator ++() is called */
t.Display();
return 0;
Output
Count: 6

Overloading Binary Operator
#include<iostream.h>
#include<conio.h>
class complex
{
int a,b;
public:
void getvalue()
{
cout<<"Enter the
value of Complex Numbers
a,b:";
cin>>a>>b;
}
complex
operator+(complex ob)
{ complex t;
t.a=ob.a +a;
t.b=ob.b+b;
return(t);
complex operator-(complex ob)
{
complex t;
t.a=ob.a - a;
t.b=ob.b -b;
return(t);
}
void display()
{
cout<<a<<"+"<<b<<"i"
<<"n";
}
};

cout<<"Input Values:n";
obj1.display();
obj2.display();
cout<<"Result:";
result.display();
result1.display();
getch();
}
void main()
{
clrscr();
complex
obj1,obj2,result,result1;
obj1.getvalue();
obj2.getvalue();
result = obj1+obj2;
result1=obj1-obj2;
Overloading Binary Operator
In overloading of binary operators the left hand operand
is used to invoke the operator function and the right hand

Rules for overloading operator
 Only existing operators can be overloaded. We cannot
create a new operator.
 Overloaded operator should contain one operand of
user-defined data type. – Overloading operators are only
for classes. We cannot overload the operator for built-in
data types.
 Overloaded operators have the same syntax as the
original operator.
 Operator overloading is applicable within the scope
(extent) in which overloading occurs.

Restrictions on Operator Overloading
 Overloading restrictions
◦ Arity (number of operands) cannot be changed
◦ Unary operators remain unary, and binary operators remain
binary
 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

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

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operator overloading

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