OPERATOR OVERLOADING IN C++

OPERATOR OVERLOADING

Operator overloading is an important concept in C++. It is a type of polymorphism in which an operator is overloaded to give user defined meaning to it. Overloaded operator is used to perform operation on user-defined data type. For example '+' operator can be overloaded to perform addition on various data types, like for Integer, String(concatenation) etc.

Almost any operator can be overloaded in C++. However there are few operator which can not be overloaded.Operator that are not overloaded are follows

• scope operator - ::
• sizeof
• member selector - .
• member pointer selector - *
• ternary operator - ?:

Operator Overloading Syntax

Implementing Operator Overloading

Operator overloading can be done by implementing a function which can be :

1. Member Function
2. Non-Member Function
3. Friend Function

Operator overloading function can be a member function if the Left operand is an Object of that class, but if the Left operand is different, then Operator overloading function must be a non-member function.

Operator overloading function can be made friend function if it needs access to the private and protected members of class.

Overloading Unary Operators

The unary operators operate on a single operand and following are the examples of Unary operators:

• The increment (++) and decrement (--) operators.
• The unary minus (-) operator.
• The logical not (!) operator.

The unary operators operate on the object for which they were called and normally, this operator appears on the left side of the object, as in !obj, -obj, and ++obj but sometime they can be used as postfix as well like obj++ or obj--.

Following example explain how minus (-) operator can be overloaded for prefix as well as postfix usage.

Example:

#include <iostream>
using namespace std;
 
class Distance
{
   private:
      int feet;             // 0 to infinite
      int inches;           // 0 to 12
   public:
      // required constructors
      Distance(){
         feet = 0;
         inches = 0;
      }
      Distance(int f, int i){
         feet = f;
         inches = i;
      }
      // method to display distance
      void displayDistance()
      {
         cout << "F: " << feet << " I:" << inches <<endl;
      }
      // overloaded minus (-) operator
      void operator- ()  
      {
         feet = -feet;
         inches = -inches;
         
      }
};
int main()
{
   Distance D1(11, 10), D2(-5, 11);
 
   -D1;                     // apply negation
   D1.displayDistance();    // display D1

   -D2;                     // apply negation
   D2.displayDistance();    // display D2

   return 0;
}

Output:

F: -11 I: -10

F: 5 I:-11

Binary Operator Overloading

The binary operators take two arguments and following are the examples of Binary operators. You use binary operators very frequently like addition (+) operator, subtraction (-) operator and division (/) operator.

Following example explains how addition (+) operator can be overloaded. Similar way, you can overload subtraction (-) and division (/) operators.

#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=a+ob.a;

                            t.b=b+ob.b;

                            return(t);

              }

              complex operator-(complex ob)

              {

                            complex t;

                            t.a=a-ob.a;

                            t.b=b-ob.b;

                            return(t);

              }

              void display()

              {

                            cout<<a<<"+"<<b<<"i"<<"\n";

              }

};

void main()

{

   clrscr();

   complex obj1,obj2,result,result1;

   obj1.getvalue();

   obj2.getvalue();

   result = obj1+obj2;

   result1=obj1-obj2;

   cout<<"Input Values:\n";

   obj1.display();

   obj2.display();

   cout<<"Result:";

   result.display();

  result1.display();

   getch();

}

Output: