HP aC++/HP C Programmer's Guide (B3901-90036; A.06.26; September 2011)

library to create reusable classes when low-level constructs are needed. Use traditional
OOP techniques to combine classes to solve a larger problem.
In future, most libraries will use the Standard C++ Library as their foundation. Using the
Standard C++ Library, either directly or through an encapsulation such as Tools.h++
Library, ensures interoperability. This is important in large projects that may rely on
communication among several libraries. A good thumb rule is to use the highest
encapsulation level available to you, but make sure that the Standard C++ Library is
available as the base for inter-library communication and operation.
The C++ language supports a wide range of programming approaches. The language,
and the Standard C++ Library that supports it, are designed to give you the flexibility to
approach each unique problem from the best possible angle.
The Standard C++ Library, when combined with traditional OOP techniques, is a flexible
tool to build a collection of C++ classes. These classes can stand alone as a library or
are tailored to a specific task.
Differences between Standard C++ Library and Other Libraries
A major portion of the Standard C++ Library is comprises a collection of class definitions
for standard data structures, and a collection of algorithms commonly used to manipulate
such structures. This part of the library is derived from the Standard Template Library
(STL). The organization and design of this part of the library differs in almost all respects
from the design of most other C++ class libraries, because it avoids encapsulation and
uses almost no inheritance.
An emphasis on encapsulation is a key hallmark of object-oriented programming. The
emphasis on combining data and functionality into an object is a powerful organization
principle in software development; indeed it is the primary organizational technique.
Inheritance is a powerful technique to share code and reuse software. It is applicable
when two or more classes share a common set of basic features. For example, in a
graphical user interface, two types of windows may inherit from a common base window
class, and the individual subclasses provide any required unique features. In another
use of inheritance, object-oriented container classes may ensure common behavior and
support code reuse by inheriting from a more general class, and factoring out common
member functions.
The designers of the STL decided against using an entirely object-oriented approach,
and separated the tasks to be performed using common data structures from the
representation of the structures themselves. The STL is designed as a collection of
algorithms and a separate collection of data structures that are manipulated using the
algorithms.
The Non-Object-Oriented Design of the Standard C++ Library
The portion of the Standard C++ Library derived from the STL was purposely designed
with an architecture that is not object-oriented. This design has both advantages and
disadvantages. Some of them are mentioned below.
Creating and Using Libraries 221