C++ Primer Third Edition

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C++ Primer 3rd Edition – ｅ类出版物 [http://www.epubcn.com] 制作出品
C++ Primer Third Edition
Many of the designations used by manufacturers and sellers to distinguish their
products are claimed as trademarks. Where those designations appear in this
book, and Addison-Wesley was aware of a trademark claim, the designations
have been printed in initial capital letters or all capital letters.
The authors and publisher have taken care in preparation of this book, but make
no expressed or implied warranty of any kind and assume no responsibility for
errors or omissions. No liability is assumed for incidental or consequential
damages in connection with or arising out of the use of the information or
programs contained herein.
The programs and applications presented in this book have been included for
their instructional value. They have been tested with care, but are not
guaranteed for any particular purpose. The authors and publisher do not offer
any warranties or representations, nor do they accept any liabilities with respect
to the programs or applications.
The publisher offers discounts on this book when ordered in quantity for special
sales. For more information please contact:
Corporate, Government, and Special Sales Addison Wesley Longman, Inc. One
Jacob Way Reading, Massachusetts 01867
Copyright Information
Copyright © 1998 by AT&T, Objectwrite, Inc., and Josée Lajoie
Library of Congress Cataloging-in-Publication Data
Lippman, Stanley B.
C++ Primer / Stanley B. Lippman, Josée Lajoie.— 3rd ed.
p. cm.
Includes bibliographical references and index.
ISBN 0-201-82470-1
1. C++ (Computer program language) I. Lajoie, Josée. II. Title .
QA76.73.C15L57 1998
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005. 13'3—dc21
98-9464
CIP
All rights reserved. No part of this publication may be reproduced, stored in a
retrieval system, or transmitted, in any form, or by any means, electronic,
mechanical, photocopying, recording, or otherwise, without the prior consent of
the publisher. Printed in the United States of America. Published simultaneously
in Canada.
Cover photograph © 1997 Barbara Hricko Wait
3 4 5 6 7 8 9--CRS--0302010099
Third printing, June 1999
To Beth, who makes this, and all things, possible
To Daniel and Anna, who contain virtually all possibilities
- SBL
To Mark and Mom, for their unconditional love and support.
- JL
Preface
Quite a few changes have occurred between the second and third editions of C++
Primer. Most notably, C++ has undergone international standardization, which
has not only added new features to the language, such as exception handling,
run-time type identification, namespaces, a built-in Boolean data type, and a new
cast notation, but has also extensively modified and extended existing features,
such as templates, the class mechanism in support of both object-oriented and
object-based programming, nested types, and overload function resolution.
Perhaps of even more significance, an extensive library is now part of Standard
C++, including what was previously referred to as the Standard Template
Library, or STL. A new string type, a set of sequence and associative container
types — such as vector, list, map, and set — and an extensible collection of
generic algorithms to operate on those types are all features of this new standard
library. There's not only quite a lot of new material to cover but also new ways to
think about how we program in C++. In short, not only has C++ been, in effect,
newly invented, but so has the C++ Primer for this, its third edition.
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Not only has the treatment of the language changed fundamentally in this third
edition, but so has the authorship: in the first place, we've doubled ourselves!
Moreover, we've internationalized in the process, although we're firmly rooted in
the North American continent: Stan is American; Josée is Canadian. Finally, the
twin authorship reflects the twin primary activities of the C++ community: Stan
is currently involved in the efficient workplace application of C++ at Walt Disney
Feature Animation for 3D computer graphics and animation, while Josée is
involved in the definition and implementation of C++, both as chair of the Core
Language subcommittee of the standards effort and as a member of the C++
compiler team at the IBM Canada Laboratory.
Stan was one of the original members of the Bell Laboratories team working
with Bjarne Stroustrup, the inventor of C++, and has been involved with C++
since 1984. Stan worked on the various implementations of cfront, the original
C++ implementation, from Release 1.1 in 1986 through Release 3.0, leading the
development team for the 2.1 and 3.0 releases. After that, he worked under
Stroustrup on what was known as the Foundation Research Project on the
Object Model component of a programming development environment.
Josée has been a member of the C++ compiler team at the IBM Canada
Laboratory for eight years. She has been a member of the Standards committee
since 1990. She was vice-chair of the committee for three years and has been the
chair of the Core Language subcommittee for four years.
C++ Primer, Third Edition, represents an extensive revision of the text to reflect
not only the changes and extensions to the language but also changes to the
authors' insights and experience.
Structure of This Book
C++ Primer provides a comprehensive introduction to the International
Standard on C++. It is a primer in the sense that it provides a consciously
tutorial approach to describing the C++ language. (It is not a primer in the sense
of providing a simplistic or "gentle" description of the language.) Programming
aspects of the language, such as exception handling, the container types,
object-oriented programming, and so on, are presented in the context of solving
a particular problem or programming task. Language rules, such as the
resolution of an overloaded function call or the type conversions supported
under object-oriented programming, are given extensive treatment that may
initially seem out of place in a primer. We believe that the coverage is necessary
to a practical understanding of the language, and we view the material as
something one goes back to rather than digests at one sitting. If you find it
initially overwhelming or simply too dry, put this material aside until later — we
identify such sections with the following convention:
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Knowledge of the C language is not assumed, although familiarity with some
modern, block structured language will make the going easier. The book is
intended as a first book on C++; it is not intended as a first book on
programming! To be sure, we all start with a common vocabulary; however, the
initial chapters cover some basic concepts, such as looping statements and
variables, that some readers might find too introductory. Not to worry: the depth
of coverage picks up quickly.
Much of the power of C++ comes from its support for new ways of programming
and thinking about programming problems. Learning to use C++ effectively,
therefore, requires more than simply learning a new set of syntax and semantics.
To facilitate this larger learning, the book is organized around a series of
extended examples. These examples are used both to introduce the details of
various language features and to motivate them. When we learn language
features in the context of a full example, it becomes clear why such features are
useful, providing a sense of when and how we would use them for real-world
problem solving. Additionally, this focus on examples allows early use of
concepts that will be explained more fully as the reader's knowledge base is built
up. Early examples contain simple uses of fundamental C++ concepts, giving a
flavor for the kinds of programming one can do in C++ without requiring
complete understanding of the details of design and implementation.
Chapters 1 and 2 form a self-contained introduction and overview to the entire
C++ language. Part I is intended to get us up to speed on the concepts and
language facilities supported by C++ — and the fundamentals on writing and
executing a program. Upon finishing this part of the text, you should have a feel
for the language support C++ provides and a sense of not really understanding it
at all. That's ok: that's what the rest of the text is for!
Chapter 1 introduces us to the basic elements of the language: the built-in data
types, variables, expressions, statements, and functions. It looks at a minimum
legal C++ program, briefly discusses the process of compiling our programs,
walks through what is spoken of as the preprocessor, and takes a first look at
support for input and output. It presents a number of simple but complete C++
programs that the reader is encouraged to compile and execute. Chapter 2
introduces the support C++ provides for object-based and object-oriented
programming through the class mechanism, illustrating both through the
evolution of an array abstraction. In addition, it briefly introduces templates,
namespaces, exception handling, and the standard library support for general
container types and generic programming. This chapter is rather fast-paced, and
some readers may find it somewhat overwhelming. If that is the case, we suggest
you skim through it and return to it later.
Fundamental to C++ are the various facilities that allow the user to extend the
language itself by defining new data types that then can be used with the
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flexibility and simplicity of the built-in data types. The first step to mastery is to
understand the base language itself. Chapters 3, 4, 5, 6 (Part II) introduce the
language at this level.
Chapter 3 introduces the built-in and compound data types predefined by the
language together with the string, complex, and vector class data types provided
by the C++ standard library. These types form the basic building blocks of all
our programs. Chapter 4 provides a detailed discussion of the expressions
supported by the language, such as the arithmetic, relational, and assignment
expressions. Statements, which form the smallest independent unit within a C++
program, are the topic of Chapter 5. The container types provided by the
standard C++ library are the focus of Chapter 6. Rather than provide a simple
listing of the available operations, we have walked through the implementation
of a text query system to illustrate their design and use.
Chapters 7, 8, 9, 10, 11, 12 (Part III) focus on the procedural-based
programming support provided by C++. Chapter 7 introduces the C++ function
mechanism. Functions encapsulate a set of operations that generally form a
single task, such as print(). (The empty parentheses following a name indicate
that it represents a function.) The notions of program scope and lifetime of
variables, together with a discussion of the namespace facility, are the topics of
Chapter 8. Chapter 9 extends the discussion of functions introduced in Chapter 7
to introduce function overloading. Function overloading allows multiple function
instances that provide a common operation (but require differing
implementations) to share a common name. For example, we can define a
collection of print() functions to output different types of data. Chapter 10
introduces and illustrates the use of function templates. A function template
provides a prescription for the automatic generation of a potentially infinite set
of function instances varying by type but whose implementations remain
invariant.
C++ supports an exception handling facility. An exception represents unexpected
program behavior, such as the exhaustion of all available program memory. The
portion of the program within which the exception occurs throws an exception —
that is, makes it available to the rest of the program. Some function within the
program must then catch the exception and do whatever is necessary. The
treatment of exception handling is split across two chapters. In Chapter 11, the
basic syntax and use of exception handling are introduced using a simple
example of catching and throwing an exception of class type. Because the actual
exceptions handled in our programs are usually class objects of an
object-oriented class hierarchy, the discussion of how to throw and handle
exceptions continues in Chapter 19, after the introduction of object-oriented
programming.
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Chapter 12 introduces the extensive collection of generic algorithms provided by
the standard library and examines how they interact with the container types of
Chapter 6 as well as with the built-in array type. The chapter begins by walking
through a program design using the generic algorithms. Iterators, introduced in
Chapter 6, are discussed further in Chapter 12 because they provide the glue
that binds the generic algorithms to the actual containers. The concept of a
function object is also introduced and illustrated. Function objects allow us to
provide alternative semantics for operators used with the generic algorithms,
such as the equality or the less-than operator. The algorithms themselves are
detailed, with an illustration of their use, in the Appendix.
Chapters 13, 14, 15, 16 (Part IV) focus on object-based programming — that is,
the definition and use of the class facility to create independent abstract data
types. By creating new types to describe the problem domain, C++ allows the
programmer to write applications with much less concern for the various
bookkeeping aspects that make programming tedious. The types fundamental to
the application can be implemented once and reused, allowing the programmer
to concentrate on the problem rather than the details of the implementation.
Facilities for encapsulating the data can dramatically simplify subsequent
maintenance and evolution of our applications.
Chapter 13 focuses on the general class mechanism: how to define a class, the
concept of information hiding — that is, of separating the public class interface
from the private implementation — and how to define and manipulate object
instances of a class, as well as a discussion of class scope, nested classes, and
classes as namespace members.
Chapter 14 details the special support C++ provides for the initialization,
destruction, and assignment of class objects using special member functions
spoken of, respectively, as a constructor, destructor, and copy assignment
operator. We also look at the issue of memberwise initialization and copy, in
which one class object is initialized or assigned with another object of its class,
and the special named return value optimization for the efficient support of
memberwise initialization and copy.
Chapter 15 looks at class-specific operator overloading, first presenting general
concepts and design considerations and then looking at specific operators, such
as the assignment, subscript, call, and class-specific new and delete operators.
The notion of a friend to a class with special access permission and why friends
are sometimes needed is also presented. User-defined conversions are then
discussed, including the underlying concepts and an extensive example of their
use. The rules for function overload resolution are also discussed in this chapter
in some detail, with extensive illustration by code examples.
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Class templates are the topic of Chapter 16. A class template is a prescription for
creating a class in which one or more types or values are parameterized. A vector
class, for example, may parameterize the type of element it contains. A buffer
class may parameterize not only the type of element it holds but also the size of
its buffer. In a more sophisticated usage, such as in distributed computing, the
IPC interface, addressing interface, and synchronization interface might all be
parameterized. This chapter includes discussions on how to define a class
template, how to create specific type instances of a class template, how to define
the members of a class template (member functions, static members, and nested
types), and how to organize our programs using class templates. It concludes
with an extended class template example.
Object-oriented programming and the facilities in C++ that support it are the
topic of Chapters 17, 18, 19, and 20 (Part IV). Chapter 17 introduces the C++
facilities that support the primary elements of object-oriented programming:
inheritance and dynamic binding. In object-oriented programming, parent/child
relationships (spoken of as type/subtype relationships) are defined between
classes that share common behavior. Rather than reimplement shared
characteristics, a class inherits the data and operations of its parent class. The
child class, or subtype, programs only its differences with its parent class. For
example, we may define a parent Employee class type and two children:
TemporaryEmpl and Manager. These subtypes inherit all the behavior of an
Employee. They implement the behavior that is unique to each of their respective
types.
A second aspect of inheritance, spoken of as polymorphism, is the ability of a
parent type to refer to any of the subtypes that are inherited from it. An
Employee, for example, can address its own type or that of TemporaryEmpl or
Manager. Dynamic binding is the ability to resolve at run-time which operation
to execute based on the actual type of the polymorphic object. In C++, this is
handled through the virtual function mechanism.
Chapter 17 introduces the basic features of object-oriented programming. It
walks through the design and implementation of a Query class hierarchy in
support of the text query system we began implementing in Chapter 6.
Chapter 18 introduces the more-complicated inheritance hierarchies that are
made possible through multiple and virtual inheritance. It extends the template
class example of Chapter 16 into a three-level class template hierarchy using
multiple and virtual inheritance.
Chapter 19 introduces the run-time type identification (RTTI) facility. RTTI
allows our programs to query a polymorphic class object as to its type during
execution of the program. For example, we can ask an Employee object whether
it actually addresses a Manager type. In addition, Chapter 19 revisits exception
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handling to discuss the standard library exception class hierarchy and illustrate
defining and handling our own exception class hierarchies. It also provides an
in-depth look at the support of overload function resolution in the presence of
inheritance.
Chapter 20 illustrates in detail how to use the C++ iostream input/output library.
It provides explanation and examples of the general input and output of data, of
defining class-specific instances of the input and output operators, of how to
recognize and set condition states, and of how to format data. The iostream
library is a class hierarchy implemented using both virtual and multiple
inheritance.
The C++ Primer concludes with an Appendix that provides a discussion and
program example of each generic algorithm in alphabetical order for easy
reference.
Finally, whenever one writes a book, what one chooses to leave out is often as
important as what one covers. Certain aspects of the language — such as a
detailed discussion of how constructors work, under what conditions internal
temporary objects are created by the compiler, or general concerns about
efficiency — do not fit well into a tutorial introduction to the language, although
they are of general importance to programming real-world applications. Prior to
embarking on a third edition of C++ Primer, Stan wrote Inside the C++ Object
Model (see [LIPPMAN96a] in the Bibliography at the end of this Preface) to
cover much of this companion material. Often, the text refers to a discussion
within the Object Model when readers may wish to have the more detailed
explanation, particularly for the treatment of object-based and object-oriented
programming.
Certain portions of the C++ standard library have been intentionally left out,
such as the support for locales and the numerical library. The C++ standard
library is very extensive, and presenting all its aspects is beyond the scope of this
primer. Some of the books in the Bibliography discuss the library in more detail
(see [MUSSER96] and [STROUSTRUP97]). We believe that many books on
various aspects of the C++ standard library will follow the publication of this
book.
Changes to the Third Edition
The changes to the third edition fall into four general categories:
1. Coverage of new features added to the language: exception handling,
run-time type identification, namespaces, the built-in bool type, and
new-style cast notation.
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