Types of Operator Overloading in C++

Operator Overloading in C++ is one of the exciting features that has enhanced the power of the extensibility of C++. C++ permits us to add two variables of user-defined types with the same syntax that is applied to the basic types. It means that C++ can provide the operators with a special meaning for a data type. The mechanism of giving such special meanings to an operator is known as Operator Overloading.

Operator Overloading provides a flexible option for creating of new definitions for most of the C++ operators. We can overload all the C++ operators except the following:
1. Class member access operators (.*)
2. Scope Resolution operator (::)
3. Size Operator (sizeof)
4. Conditional operator (?:)

Overload Unary minus Operator:

Example:

#include<iostream.h>
#include<conio.h>
using namespace std;
class test 
{
  int x, y, z;
 public:
 void getdata(int a, int b, int c);
 void display(void);
 void operator-();
 };
 void test::getdata(int a, int b, int c)
{
 x=a;
 y=b;
 z=c;
}
 void test::display(void)
{
 cout<<"x="<<x<<" ";
 cout<<"y="<<y<<" ";
 cout<<"z="<<z<<" ";
}
void space::operator-()
{
 x=-x;
 y=-y;
 z=-z;
}
int main()
{
 test t1;
 t1.getdata(15,-25,30);
 cout<<"T:";
 t1.display();
 -t1;
 cout<<"-T:";
 t1.display();
 return 0;
}

Output:

 T: x=15 y=-25 z=30
-T: x=-15 y=25 z=-30

Overload Binary Operator:

Example:

#include<iostream.h>
#include<conio.h>
using namespace std;
class test
{
 float p;
 float q;
 public:
 test(){}
 test( float r, float i){ p=r; q=i;}
 test operator+(test);
 void display(void);
};
test test::operator+(test t)
{
 test t1;
 t1.p=p+c.p;
 t1.q=q+c.q;
 return (t1);
}
 void test::display(void)
{
 cout<<p<<"+J"<<q<<"\n";
}
int main()
{
 test C1, C2, C3;
 C1=test(4.5, 5.5);
 C2=test(2.5, 3.7);
 C3=C1+C2;
 cout<<"C1 =";C1.display();
 cout<<"C2 =";C2.display();
 cout<<"C3 =";C3.display();
return 0;
}

Output:

C1 = 4.5 + j5.5
C2 = 2.5 + j3.7
C3 = 7.0 + j9.2

Overload Operator using Friend Function:

Example:

#include<iostream.h>
const size=3;
class vector
{
 int v[size];
 public:
 vector();
 vector(int *x);
 friend vector operator *(int a, vector b);
 friend vector operator *(vector b, int a);
 friend istream & operator >> (istream &, vector &);
 friend ostream & operator >> (ostream &, vector &);
}
vector :: vector()
{
 for(int i=0; i<size; i++)
v[i]=0;
}
vector :: vector(int *x)
{
 for(int i=0; i<size; i++)
v[i]=x[i];
}
vector operator *(int a, vector b)
{
 vector c;
 for(int i=0; i<size; i++)
c.v[i]=a*b.v[i];
return c;
}
vector operator *(vector b, int a)
{
 vector c;
 for(int i=0; i<size; i++)
c.v[i]=b.v[i] *a;
return c;
}
istream & operator >> (istream &din, vector &b)
{
 for(int i=0; i<size; i++)
 din>>b.v[i];
return(din);
}
ostream & operator >> (ostream &din, vector &b)
{
 dout<<"("<<b.v[0];
for(int i=1; i<size; i++)
dout<<"," <<b.v[i];
dout<<")";
return (dout);
}
int x[size]=[2,4,6];
int main()
{
 vector m;
vector n=x;
cout<<"Enter the elements of vector m:"<<;
cin>>m;
cout<<"\n";
cout<<"m="<<m<<;
vector p,q;
p=2*m;
q=n*2;
cout<<"\n";
cout<<"p="<<p<<;
cout<<"q="<<q<<;
return 0;
}

Overloading Pointer to Member Operator:

Pointer to Member Operator in C++ (->) is normally used in conjunction with an object pointer to access any of the object’s members.

Example:

#include<iostream.h>
#include<conio.h>
using namespace std;
class temp
{
 public:
 int n;
 temp(int j)
{
 n=j;
}
temp*operator ->(void)
{
 return this;
}
};
int main()
{
 temp T(4);
 temp *ptr=&T;
 cout<<"T.n="<<T.n;
cout<<"ptr->n="<<ptr->n;
cout<<T->n="<<T->n;
getch();
return 0;
}

Output:

T.n= 4
ptr->n= 4
T->n= 4

Subscript Operator Overloading:

Subscript Operator Overloading in C++ is normally used to access and modify a specific element in an array.
Example:

#include<iostream.h>
#include<conio.h>
using namespace std;
class test
{
 int x[5];
public:
test(int *p)
{
 int i;
for(i=0;i<5;i++)
x[i]=p[i];
}
int operator [] (int k)
{
 return (x[k]);
}
};
int main()
{
 int k[5]={1, 2, 3, 4, 5};
 test T(k);
int i;
for(i=0;i<5;i++)
{
 cout<<k[i]<<;
}
getch();
return 0;
}

Output:

1 2 3 4 5