Learning to program is more than learning the syntactic and semantic rules of a programming language. It also requires learning how to design programs. Any good book on programming must therefore teach program design.

Like any other form of design, program design has competing schools. These schools are often associated with a particular set of languages. Since Java is an object-oriented programming language, people teaching Java should emphasize object-oriented design.

Felleisen and Friedman show that the functional (input-output driven) method of program design naturally leads to the use of well-known object-oriented design patterns. In fact, they integrate the two styles seamlessly and show how well they work together. Their book proves that the functional design method does not clash with, but supports object-oriented programming.

Their success doesn't surprise me, because I've seen it in Smalltalk for many years, though unfortunately, it seems to have remained one of the secrets of object-oriented design. I am happy to see that Felleisen and Friedman have finally exposed it. This book will be especially useful if you are a C++ programmer learning Java, since you probably haven't seen functional program design before. If you know functional design, the book will gently introduce you to pattern-based programming in Java. If you don't know it, Felleisen and Friedman will teach you a powerful new way of thinking that you should add to your design toolbox.

Enjoy the pizzas!

Ralph E. Johnson
Champaign, Illinois