Operator overloading: need and definition

Operator overloading is a feature of C++ that gives an existing operator (such as +, -, ==, <<) an additional meaning for user-defined types (classes), while its original meaning for built-in types remains unchanged. It is done by writing a special function named operator followed by the operator symbol. It is a form of compile-time polymorphism.

Why it is needed:

• It lets objects of user-defined classes be used with the same natural notation as built-in types. For example, c3 = c1 + c2; for complex numbers or matrices is easier to read than c3 = c1.add(c2);.
• It makes programs shorter, more readable, and closer to mathematical notation.
• It makes user-defined types behave like built-in types (they can be added, compared, printed with cout <<).
• It increases extensibility, since a class can be used in expressions without changing the language.

Example: with Complex operator+(Complex b) defined, the statement c = a + b; adds the real and imaginary parts of two Complex objects.