Modern C++ Design: Generic Programming and Design Patterns Applied [Anglais] [Broché]

"Isn't it nifty just how much you can do with functions... that not only don't do anything but don't even really exist at all?" p.36

The title is a bit presumptuous; a more accurate title would be "Template Metaprogramming Stunts", since this book is primarily about tricks you can play with C++'s template mechanism.

The author does also make a go at proposing a new concept of "policy-based class design" -- by which he means using templates intead of multiple inheritance to create combinatorial mixtures of behavior. This is interesting, but seems hard to apply beyond the cliches he considers (ex: smart pointers), so his argument reads like a well-intended but parochial graduate thesis, with dutiful gestures of respect to his mentors (ex: Scot Myers) and limited range of real-world application.

The real meat of the book is his template techniques, which are ingenious -- if perverse, when seen from the standpoint of someone else trying to read and extend your code, or diagnose its arcane compiler errors. If you've ever had to work with other people on software, you may find his glib view of compiler errors disappointing. In many cases he relies on compiler errors to signal something more complex and semantic than the mere error would suggest. (If you're programmed much C++ you've surely experienced 10-line long STL template errors with a very simple underlying cause that is hard to discern from the error message. Learning to suss out what these mean is much of the sweat-work of learning C++.) I think this is simply that he's coming from the perspective that the interworkings of the language and the compiler are fascinating, and worth being a primary focus of study. But from the perspective of someone just tried to get your work done in the problem domain at hand, you may resent this attitude.

This book is best approached if you think C++ is really neat. Wheter you love C++ for its roccoco intricacy, or just see it as an evolutionary leaf node language full of botched misfeatures, you will find much here to confirm your opinion. I don't mean to belittle this book. There is real insight here: the idea of computing on types instead of values (to store the results of template-based computations) is a nifty idea. But it's worth keeping an eye on what problems you are really trying to solve, and which ones you may be creating.

Some telling quotes:

"Unfortunately, type_info's useful capabilities are packaged in a way that makes them unnecessarily hard to exploit." p.38

"For a variety of reasons, C++ is a language that leads its users sometimes to say, 'These are the smartest five lines of code I ever wrote.' Maybe it is its semantic richness or the ever-exciting (and surprising?) way its features interact." p.51

I really liked chapter 1 discussing policy-based class design, chapter 2 discussing various template techniques, chapter 6 discussing singleton implementation, anbd chapter 7 discussing smart pointers. Chapter 11 discussing multimethods, appears to be a good discussion of various alternatives but I'm not inclined to use multimethods anytime soon.

Chapter 3 about typelists is interesting, but after all the dazzling manipulations, all that typelists seem to be good for is generating class hierarchies, which I didn't find very compelling - it looks as if the typelists help to manage complexity that possibly wouldn't be there if the typelists hadn't been used in the first place.

Chapter 4 about small object allocation was of limited interest to me. The other chapters, 5 (Functors), 8 (Object Factories), 9 (Abstract Factory), and 10 (Visitor) offered fairly complex, template based solutions that to me did not look obviously superior to the straightforward manual implementations shown in _Design Patterns_.

Overall, a stimulating book, but one whose recipes will need careful evaluation before use.

Not wanting to risk anymore, I borrowed this book from a friend... to lose sleep for two nights reading it! It is the book I was looking for: no-nonsense, eye-opening, inspirational. The author's mastery of C++ and the creativity with which he solves real-world problems are phenomenal.

Alexandrescu discusses and implements the following design patterns: Command, Singleton, Proxy (in the form of smart pointers), Factory Method, Abstract Factory, and Visitor. In doing so, he creates highly configurable components that support most variations that accompany the patterns, and allow the component users to add their own variations. This is done through template parameters. The technique is not new but the author documents it thoroughly (coining the Policy-based design term) and uses it very creatively to achieve elegant designs.

The book also has foundation chapters: Techniques, Typelists, and a small object allocator. The latter is not really in sync with the rest of the book, being a low-level component written in straight C++, but in compensation, the chapter on typelists is as meta as you can imagine, and more :-).

In short: a great book if you use C++, especially so if you need to participate in the architectural stage of projects. But the best thing the book has done for me is, it made me extremely excited about programming - a feeling forgotten since my college days. Five stars plus.