12 Separate Compilation and Namespaces

1. 12.1 Separate Compilation 706

   1. ADTs Reviewed 707

   2. Case Study: DigitalTime—A Class Compiled Separately 708

   3. Using #ifndef 717

   4. Programming Tip: Defining Other Libraries 720

2. 12.2 Namespaces 721

   1. Namespaces and using Directives 722

   2. Creating a Namespace 723

   3. Qualifying Names 726

   4. A Subtle Point About Namespaces (Optional) 727

   5. Unnamed Namespaces 728

   6. Programming Tip: Choosing a Name for a Namespace 733

   7. Pitfall: Confusing the Global Namespace and the Unnamed Namespace 734

1. Chapter Summary 735

2. Answers to Self-Test Exercises 736

3. Practice Programs 738

4. Programming Projects 740

From mine own library with volumes that I prize above my dukedom.

WILLIAM SHAKESPEARE, The Tempest

Introduction

This chapter covers two topics that have to do with how you organize a C++ program into separate parts. Section 12.1 on separate compilation discusses how a C++ program can be distributed across a number of files so that when some parts of the program change, only those parts need to be recompiled. The separate parts can also be more easily reused in other applications.

Section 12.2 discusses namespaces, which we introduced briefly in Chapter 2. Namespaces are a way of allowing you to reuse the names of classes, functions, and other items by qualifying the names to indicate different uses. Namespaces divide your code into sections so that the different sections may reuse the same names with differing meanings. Namespaces allow a kind of local meaning for names that is more general than local variables.

Prerequisites

This chapter uses material from Chapters 2 through 6 and 10 through 11.