Foreword

by John Vlissides

What's left to say about C++ that hasn't already been said? Plenty, it turns out. This book documents a convergence of programming techniques—generic programming, template meta programming, object-oriented programming, and design patterns—that are well understood in isolation but whose synergies are only beginning to be appreciated. These synergies have opened up whole new vistas for C++, not just for programming but for software design itself, with profound implications for software analysis and architecture as well.

Andrei's generic components raise the level of abstraction high enough to make C++ begin to look and feel like a design specification language. Unlike dedicated design languages, however, you retain the full expressiveness and familiarity of C++. Andrei shows you how to program in terms of design concepts: singletons, visitors, proxies, abstract factories, and more. You can even vary implementation trade-offs through template parameters, with positively no runtime overhead. And you don't have to blow big bucks on new development tools or learn reams of methodological mumbo jumbo. All you need is a trusty, late-model C++ compiler—and this book.

Code generators have held comparable promise for years, but my own research and practical experience have convinced me that, in the end, code generation doesn't compare. You have the round-trip problem, the not-enough-code-worth-generating problem, the inflexible-generator problem, the inscrutable-generated-code problem, and of course the I-can't-integrate-the-bloody-generated-code-with-my-own-code problem. Any one of these problems may be a showstopper; together, they make code generation an unlikely solution for most programming challenges.

Wouldn't it be great if we could realize the theoretical benefits of code generation—quicker, easier development, reduced redundancy, fewer bugs—without the drawbacks? That's what Andrei's approach promises. Generic components implement good designs in easy-to-use, mixable-and-matchable templates. They do pretty much what code generators do: produce boilerplate code for compiler consumption. The difference is that they do it within C++, not apart from it. The result is seamless integration with application code. You can also use the full power of the language to extend, override, and otherwise tweak the designs to suit your needs.

Some of the techniques herein are admittedly tricky to grasp, especially the template metaprogramming in Chapter 3. Once you've mastered that, however, you'll have a solid foundation for the edifice of generic componentry, which almost builds itself in the ensuing chapters. In fact, I would argue that the metaprogramming material of Chapter 3 alone is worth the book's price—and there are ten other chapters full of insights to profit from. "Ten" represents an order of magnitude. Even so, the return on your investment will be far greater.

John Vlissides
IBM T.J. Watson Research
September 2000