C++ Neural Networks and Fuzzy Logic by Valluru B. Rao M&T Books, IDG Books Worldwide, Inc. ISBN: 1558515526   Pub Date: 06/01/95

Inheritance

The primary distinction for C++ from C is that C++ has classes. Objects are defined in classes. Classes themselves can be data items in other classes, in which case one class would be an element of another class. Of course, then one class is a member, which brings with it its own data and functions, in the second class. This type of relationship is referred to as a “has-a” relationship: Object A has an Object B inside it.

A relationship between classes can be established not only by making one class a member of another but also by the process of deriving one class from another. One class can be derived from another class, which becomes its base class. Then a hierarchy of classes is established, and a sort of parent–child relationship between classes is established. The derived class inherits, from the base class, some of the data members and functions. This type of relationship is referred to as an “is-a” relationship. You could have class Rectangle be derived from class Shape, since Rectangle is a Shape. Naturally, if a class A is derived from a class B, and if B itself is derived from a class C, then A inherits from both B and C. A class can be derived from more than one class. This is how multiple inheritance occurs. Inheritance is a powerful mechanism for creating base functionality that is passed onto next generations for further enhancement or modification.

Derived Classes

When one class has some members declared in it as protected, then such members would be hidden from other classes, but not from the derived classes. In other words, deriving one class from another is a way of accessing the protected members of the parent class by the derived class. We then say that the derived class is inheriting from the parent class those members in the parent class that are declared as protected or public.

In declaring a derived class from another class, access or visibility specification can be made, meaning that such derivation can be public or the default case, private. Table 2.1 shows the consequences of such specification when deriving one class from another.

Reuse of Code

C++ is also attractive for the extendibility of the programs written in it and for the reuse opportunity, thanks to the features in C++ such as inheritance and polymorphism mentioned earlier. A new programming project cannot only reuse classes that are created for some other program, if they are appropriate, but can extend another program with additional classes and functions as deemed necessary. You could inherit from an existing class hierarchy and only change functionality where you need to.

C++ Compilers

All of the programs in this book have been compiled and tested with Turbo C++, Borland C++, Microsoft C/C++, and Microsoft Visual C++. These are a few of the popular commercial C++ compilers available. You should be able to use most other commercial C++ compilers also. All of the programs should also port easily to other operating systems like Unix and the Mac, because they are all character-based programs.