Attack of the Killer Parentheses: ‘Clojure in Action, 2nd Edition’ – #bookreview

Clojure in Action, 2nd Edition

Amit Rathore and Francis Avila

Manning – paperback

Clojure seems to be afflicted with a measles-like outbreak of parentheses, and it generally just looks strange to many software developers. And there’s a good reason for that, as this book’s two author point out in their recently released second edition.

“Clojure’s syntax is derived from its Lisp roots: lots of parentheses. It’s alien to most developers with experience in languages with Algol-inspired syntax like C, C++, Java, Python, Ruby, Perl, and so on.”

But Clojure also is an intriguing and powerful choice for many software development projects, Amit Rathore and Francis Avila insist. Clojure is “a functional Lisp on the JVM” (the Java Virtual Machine), and: “It is impossible to separate the Lisp, functional programming, and JVM features of Clojure. At every step they play on each other and tell a compelling software development story….”

I have been tinkering with Clojure on the side, at random spare moments, for more than two years, using a disorganized approach of looking at web postings, building and modifying simple projects that others have posted, and sometimes looking at Clojure how-to books as time permits.

From my perspective, Clojure in Action, 2nd Edition fills a beginner’s need for a friendly, well-organized approach to learning the language and putting it to work effectively. Developers already working with Clojure can benefit from having this book, too, as a handy reference. It covers a lot of ground, using reasonably short paragraphs and offers many short code examples to illustrate its key points.

Clojure in Action, 2nd Edition “assumes no prior experience with Lisp or with any functional programming language,” the authors emphasize. “It starts out with the absolute basics and slowly layers on the different features of the language in  a way to make it all fit together in an intuitive way. It takes a first-principles approach to all the topics, first explaining why something needs to be done a certain way, and only then talking about the Clojure way.”

Clojure is not a language for absolute beginners. The authors assume “you’re familiar with an OO [object-oriented] language like Java, C++, Ruby, or Python, but no background in Java, Lisp, or Clojure is required.” They also assume you have downloaded Clojure and gotten it working on your PC. You can read more about Clojure and download it here.

This expanded 2nd edition states that it covers the “new” features of Clojure 1.6. Of course, Clojure already is up to 1.8, but I have tried many of the code examples at various points in the book and have not encountered problems while running 1.8.

Si Dunn


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