Operator Overloading

Operator Overloading is another instance of C++ polymorphism. It extends the overloading concept to operators will letting you assign multiple meanings to C++ operators. In fact, several C++ (and C) operators already are overloaded. For instance, the * operator, whenever applied to an address it yield the value stored at that address. It applying * to two numbers yield the product of the values. C++ uses the number and category of operands to decide that action to take.

C++ lets you extend operator overloading to user-defined types, allowing you, say, to use the + symbol to add two objects. Once more, the compiler will use the number and type of operands to determine that definition of further to use. Overloaded operators frequently can make code look more natural.  For instance, a general computing task is adding two arrays.  Commonly, these winds up looking such as the following for loop:

For (int i=0; i< 20; i++)

evening [i] = sam[i] + janet[i] // add element by element

Except in C++ , you can define a class which represents arrays and which overloads the + operator so that you can do this:

evening = sam + janet;        // add two array objects.

This easy addition notation conceals the mechanics and emphasizes what is essential and that is another object oriented programming goal.

For overload an operator, you use a special function form known as an operator function. Operator function has the form:

operatorop(argument-list)

Where op is the symbol for the operator being overloaded. That is, operator+ () overloads the + operator (op is +) and operator* () overloads the * operator (op is*). op has to be a valid C++ operator; you cannot only make up a new symbol. For instance, you cannot have an Operator @ ( ) function since C++ has no @ operator. But the operator [ ]() function   would   overload the [ ] operator since [ ] is the array-indexing operator. Assume, for example, which you have a Salesperson class for that you define an operator+ () member function to overload the + operator so that it adds sales figures of one salesperson object to another. So, if district2, sid and sara all are objects of the Salesperson class, you could write this equation.

district2 = sid. Operator+(sara) ;

The function will then use the sid object implicity (since it invoked the method) and the sara object explicitly (since it is passed as an argument) to calculate the sum, that it then returns. Of course, the pleasant part is which you can use the nifty + operator notation alternate of the clunky function notation.

C++ imposes a few restrictions on operator overloading, but they are simpler to understand after you have look how overloading works.