Browse Books

Reviewer: Jeffrey B. Putnam

Both programming languages and program libraries need specifications and documentation, although it is probably safe to say that programming language specifications are far more carefully written than those that are written for libraries. This arises for any number of reasons, the most important of which may be that any language that will be implemented more than once needs to have its syntax and semantics sufficiently well defined to allow programs (and libraries in particular) to run in multiple implementations and produce the same answer. Furthermore, programming skills do not always translate to documentation skills. Specifications and documentation can run the gamut from terse, minimal, and exact to verbose and even chatty. Both sides have their problems-for example, short and precise documentation may not be easy to understand or interpret, and size often makes it harder to find answers. And, of course, there are often errors. This book-which is available in both print and for free online (http://r6rs.org)-is the sixth iteration of specifications for the programming language Scheme and its standard libraries. Scheme has been around (in varying forms) since 1975, and while there have been significant changes, it still retains many of the same design principles. The book consists of three parts. Part 1 includes language specifications and appendices, including one that provides a formal operational semantics for a significant subset of the language. Part 2 offers a description of the standard libraries. The final part consists of a few short, informative appendices. This book should be of interest to three main groups: those who are interested in programming language design and implementation (and who are probably quite aware of it already), those who write specifications or documentation for libraries, and those who read such documentation. This is an excellent example of how to do documentation well. Though it tends to be toward the terse end of the spectrum-the complete language specification is less than 150 pages-there are plenty of good examples. While it is clearly not a textbook, it could be used productively as a text for advanced students. From it, they can see how good specifications are written, explore programming language semantics, and learn how to read formal descriptions (this is not often touched upon, but it might be useful to know). Given this book and a working implementation of the standard, students can explore the different parts of the specification and how they should be interpreted. (Such a study would also benefit from using the implementation of the operational semantics available in executable form.) The only major problem with the book is that the index is a bit lacking. However, this probably only affects the print version since it is relatively easy to search electronic texts. Online Computing Reviews Service