Computer Programming with C++

Overview

All the operators in C++ are designed to operate with the basic data types only. For example, an arithmetic operator + can be used to perform addition of integers, floats, doubles etc. but cannot be used to perform addition of user-defined objects. Let's say if we create a class Point to represent points in Cartesian coordinate system, we are not able to perform addition of two Point objects using operator + like we do it for primitive types. Recall from Chapter 11 section 11.10 that addition of Point objects P1 and P2 is performed using a function add() defined inside the class. We performed the addition of two points P1 and P2 by making a call to add() as follows:

P3=P1.add(P2);

The function is invoked by P1 passing P2 is passed as an argument, the result of addition is stored in object P3, which gives the x and y coordinate values of the resultant point. The addition of Point objects is performed using a member function add(), merely because the arithmetic operator + cannot be used to perform addition of user-defined objects. The basic principle of operator overloading is to extend the capability of C++ operators in order to use them with user-defined types in the same way and with the same syntax as with basic types. When we say that classes are used to create user-defined data types, it is a fair expectation that the operation with user-defined objects should be performed in the same way as they are performed with primitive types.

If we overload operator + in class Point, we will be able to perform addition of Point objects as follows:

P3=P1+P2;

Making use of operator + to add Point objects makes the statement very easy to read and understand when compared to the former statement. Operator overloading is essentially used by the programmers to create programs with a friendly syntax. Clearly it is not a necessity, but it provides great luxury to the programmers to read and maintain the program.