The Greek philosopher Socrates taught by asking his students questions--questions designed to guide them and help them draw conclusions from what they already knew, and to show them how the things they were learning related to each other and to their existing knowledge. This method has become so famous that we now call it the "Socratic method." From our point of view as students, Socrates' approach involves us, makes us think, and helps us relate and apply what we already know to new information.
This book takes a page from Socrates, as did its predecessor, Exceptional C++ Sutter00. It assumes you're involved in some aspect of writing production C++ software today, and uses a question-answer format to teach you how to make effective use of standard C++ and its standard library with a particular focus on sound software engineering in modern C++. Many of the problems are drawn directly from experiences I and others have encountered while working with production C++ code. The goal of the questions is to help you draw conclusions from things you already know as well as things you've just learned, and to show how they interrelate. The puzzles will show how to reason about C++ design and programming issues--some of them common issues, some not so common; some of them plain issues, some more esoteric; and a couple because, well, just because they're fun.
This book is about all aspects of C++. I don't mean to say that it touches on every detail of C++--that would require many more pages--but rather that it draws from the wide palette of the C++ language and library features to show how apparently unrelated items can be used together to synthesize novel solutions to common problems. It also shows how apparently unrelated parts of the palette interrelate on their own, even when you don't want them to, and what to do about it. You will find material here about templates and namespaces, exceptions and inheritance, solid class design and design patterns, generic programming and macro magic--and not just as randomized tidbits, but as cohesive Items showing the interrelationships among all of these parts of modern C++.
What's "More?"
More Exceptional C++ continues where Exceptional C++ left off. This book follows in the tradition of the first: It delivers new material, organized in bite-sized Items and grouped into themed sections. Readers of the first book will find some familiar section themes, now including new material, such as exception safety, generic programming, and memory management techniques. The two books overlap in structure and theme, not in content.
Where else does More Exceptional C++ differ? This book has a much stronger emphasis on generic programming and on using the C++ standard library effectively, including coverage of important techniques such as traits and predicates. Several Items provide in-depth looks at considerations to keep in mind when using the standard containers and algorithms; many of these considerations I've not seen covered elsewhere. There's a new section and two appendixes that focus on optimization in single- and multithreaded environments--issues that are now more than ever of practical consequence for development shops writing production code.
Versions of most Items originally appeared in Internet and magazine columns, particularly as Guru of the Week GotW issues #31 to 62, and as print columns and articles I've written for C/C++ Users Journal, Dr. Dobb's Journal, the former C++ Report, and other publications. The material in this book has been significantly revised, expanded, corrected, and updated since those initial versions, and this book (along with its de rigueur errata list available at www.gotw.ca) should be treated as the current and authoritative version of that original material.What I Assume You Know
I expect that you already know the basics of C++. If you don't, start with a good C++ introduction and overview. Good choices are a classic tome like Bjarne Stroustrup's The C++ Programming Language Stroustrup00, or Stan Lippman and Josee Lajoie's C++ Primer, Third Edition Lippman98. Next, be sure to pick up a style guide such as Scott Meyers' classic Effective C++ books Meyers96 Meyers97. I find the browser-based CD version Meyers99 convenient and useful.
How to Read This Book
Each Item in this book is presented as a puzzle or problem, with an introductory header that resembles the following:
Item #: The Topic of This Puzzle
Difficulty: X
The topic tag and difficulty rating gives you a hint of what you're in for. Note that the difficulty rating is my subjective guess at how difficult I expect most people will find each problem, so you may well find that a "7" problem is easier for you than some "5" problem. Since writing Exceptional C++, I've regularly received e-mail saying that "Item #N is easier (or harder) than that!" It's common for different people to vote "easier!" and "harder!" for the same Item. Ratings are personal; any Item's actual difficulty for you really depends on your knowledge and experience and could be easier or harder for someone else. In most cases, though, you should find the rating to be a good rule-of-thumb guide to what to expect.
You might choose to read the whole book front to back; that's great, but you don't have to. You might decide to read all the Items in a section together because you're particularly interested in that section's topic; that's cool, too. Except where there are what I call a "miniseries" of related problems which you'll see designated as "Part 1," "Part 2," and so on, the Items are pretty independent, and you should feel free to jump around, following the many cross-references among the Items in the book, as well as some references to Exceptional C++. The only guidance I'll offer is that the miniseries are designed to be read consecutively as a group; other than that, the choice is yours.
Namespaces, Typename, References, and Other Conventions
I make quite a few recommendations in this book, and I won't give you guidelines that tell you to do something I don't already do myself. That includes what I do in my own example code throughout this book. I'll also bow to existing practice and modern style, even when it really makes no material difference.
On that note, a word about namespaces: In the code examples, if you see a using-directive at file scope in one example and at function scope in another example a few pages or Items later, there's no deeper reason than that's what felt right and aesthetically pleasing to me for that particular case; for the rationale, turn to Item 40. In the narrative text itself, I've chosen to qualify standard library names with std:: when I want to emphasize that it's the standard facility I'm talking about. Once that's established, I'll generally switch back to using the unqualified name.
When it comes to declaring template parameters, I sometimes come across people who think that writing class instead of typename is old-fashioned, even though there's no functional difference between the two and the standard itself uses class most everywhere. Purely for style, and to emphasize that this book is about today's modern C++, I've switched to using typename instead of class to declare template parameters. The only exception is one place in Item 33, where I quote directly from the standard; the standard says class, so I left it in there.
Unless I call something a "complete program," it's probably not. Remember that the code examples are usually just snippets or partial programs and aren't expected to compile in isolation. You'll usually have to provide some obvious scaffolding to make a complete program out of the snippet shown.
Finally, a word about URLs: On the Web, stuff moves. In particular, stuff I have no control over moves. That makes it a real pain to publish random Web URLs in a print book lest they become out of date before the book makes it to the printer's, never mind after it's been sitting on your desk for five years. When I reference other people's articles or Web sites in this book, I do it via a URL on my own Web site, www.gotw.ca, which I can control and which contains just a straight redirect to the real Web page. If you find that a link printed in this book no longer works, send me e-mail and tell me; I'll update that redirector to point to the new page's location (if I can find the page again) or to say that the page no longer exists (if I can't). Either way, this book's URLs will stay up-to-date despite the rigors of print media in an Internet world. Whew.
Herb Sutter
Toronto, June 2001
020170434XP11292001 
