Operator Overloading in C++ with example

The process of redefining the meaning of the operator for a specific purpose within a program is known as operator overloading.

For example, the function for the operator + can be written that defines concatenation of two string objects.

Polymorphism is a generic concept that involves operator and function overloading. It can be used across several classes where the same function name handle may be used for different types of object.

Overloadable /Non-overloadable Operators:

Following is the list of operators which can be overloaded:

+	-	*	/	%	^
&	|	~	!	,	=
<	>	<=	>=	++	--
<<	>>	==	!=	&&	||
+=	-=	/=	%=	^=	&=
|=	*=	<<=	>>=	[]	()
->	->*	new	new []	delete	delete []

Following is the list of operators, which cannot be overloaded:

::

.*

.

?:

In the C++ mostly all operator can be overloading but there are some operator cannot overload.

1.      :: Scope Resolution

2.      Size of operator

3.      Condition operator, ternary

4.      -> indirection operator

Two types of Overloading

1.      Unary Overloading and

2.      Binary Overloading

There are Unary and Binary function objects. A Unary function object requires one argument;

A binary function object requires two arguments.

Example of Unary Overloading

#include<iostream.h>

#include<conio.h>

class unary

               {

                              int a, b;

                              public:

                              void get ();

                              void put ();

                              void operator – ();

               };

void unary :: get ()

{

               cout<<”Enter the number a and b = ”;

               cin>>a>>b;

}

void unary :: put()

{

               cout<<”a = ”;

               cout<<a;

               cout<<”b = ”;

               cout<<b;

}

void unary :: operator – ()

{

               this -> a = this -> a – 1;

               this -> b = this -> b – 1;

}

void main ()

{

               clrscr ();

unary u, v;

               u.get ();

               u.put ();

               - u;

               u.put ();

               v.get ();

               v.put ();

               - v;

               v.put ();

               getch();

}

Input:

Enter the number a and b = 2 3

Output:

a =2 b = 3

a =1 b = 2

Input:

Enter the number a and b = 4 5

Output:

a =4 b = 5

a =3 b = 4

Example of Binary Overloading

#include<iostream.h>

#include<conio.h>

class complex

               {

                              int r, i;

                              public:

                              void get ();

                              void put ();

                              complex operator + (complex t)

               };

void complex :: get ()

{

               cout<<”Enter the number = ”;

               cin>>r>>i;

}

void complex :: put()

{

               cout<<”Real = ”<<r<<”+”<<”Imaginary =”<<i;

}

complex complex :: operator + (complex t)

{

               complex temp;

               temp.r = r + t.r;

               temp.i = I + t.i;

               return temp;

}

void main ()

{

clrscr ();

complex st, mt, kt;

st.get ();

mt.get ();

kt = st + mt;

st.put ();

mt.put ();

kt.put ();

getch ();

}

Input:

Enter the number = 3 4

Enter the number = 4 4

Output:

Real = 3 Imaginary = 4

Real = 4 Imaginary = 4

Real = 7 Imaginary = 8

Write C++ a program to overload the + operator for finding the sum of two Array.

#include<iostream.h>

#include<conio.h>

class array

               {

                              int a[4], i;

                              public:

                              void get ();

                              void put ();

                              array operator + (array t)

               };

void array :: get ()

{

               for (i=0; i<=3; i++)

               {

                              cin>>a[i];

               }

}

void array :: put ()

{

               for (i=0; i<=3; i++)

               {

                              Cout<<a[i]<<”\n”;

               }

}

array array :: operator + (array t)

{

               for (i=0; i<=3; i++)

               {

                              temp.a[i] = a + t.[i];

               }

               return temp;

}

void main ()

{

clrscr ();

array st, mt, kt;

st.get ();

mt.get ();

kt = st + mt;

               kt.put ();

               getch ();

}

Write C++ a program to overload the + operator for String Concatenation of two String.

#include<iostream.h>

#include<conio.h>

class String

               {

                              char *s;

                              public:

                              string ()

                              {

                              }

                              string (char *t)

                              {             

                                             len = strlen (t);

                                             S = new char [len + 1];

                                             strcpy (s, t);

                              }

                              void put ();

                              string operator + (string t);

}

void String :: put ()

{

               cout<<S;

}

String String :: operator + (string t)

{

               String temp;

               temp.len = strlen (S) + strlen (t.S);

               temp.S = new char [len + 1];

               strcpy (temp.S, S);

               strcpy (temp.S, t.S);

               return temp;

}

void main ()

{

               clrscr ();

char t[20], m[20];

               cout<<”Enter First string = ”;

               cin>>t;

               cout<<”Enter Second string = ”;

               cin>>m;

               String m1[t], m2[t], m3[t];

               m3 = m1 + m2;

               m1.put ();

               m2.put ();

               m3.put ();

               getch ();

}