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

JavaScript as Compilation Target: ClojureScript and Dart – #programming #bookreview

Despite its widespread success, JavaScript has a reputation for being a computer language with many flaws. Still, it is now everywhere on the planet, so it is here to stay, very likely for a long, long time.

Not surprisingly, several new languages have emerged that jump over some of JavaScript’s hurdles, offer improved capabilities, and also compile to optimized JavaScript code.

Two of these languages are the focus of noteworthy new “Up and Running” books from O’Reilly: ClojureScript: Up and Running and Dart: Up and Running.

Here are short reviews of each book:

ClojureScript: Up and Running
Stuart Sierra and Luke VanderHart
(O’Reilly, paperback, Kindle)

ClojureScript, the authors contend, “provides developers with a language that is more powerful than JavaScript, which can reach all the same places JavaScript can, with fewer of JavaScript’s shortcomings.”

The primary targets of ClojureScript are “web browser applications, but it is also applicable to any environment where JavaScript is the only programmable technology available,” they add.

“ClojureScript is more than Clojure syntax layered on top of JavaScript: it supports the full semantics of the Clojure language, including immutable data structures, lazy sequences, first-class functions, and macros,” they emphasize.

Their 100-page book focuses on how to use ClojureScript’s features, starting at the “Hello world” level and gradually advancing to “Development Process and Workflow” and “Integrating with Clojure.” (ClojureScript is designed for building client-side applications, but it can be merged with Clojure on the JVM to create client-server applications.)

Early in the book, they also describe how to compile a ClojureScript file to JavaScript and emit code “that is fully compatible with the Advanced Optimizations mode of the Google Closure Compiler.”

The two writers are Clojure/ClojureScript developers with a previous book to their credit.

ClojureScript: Up and Running is written well and appropriately illustrated with code samples, flow charts, and other diagrams. The authors recommend using the Leiningen build system for Clojure, plus the lein-cljsbuild plug-in for ClojureScript.

Their book is a smooth introduction to ClojureScript that requires no prior knowledge of Clojure. But you do need a basic working knowledge of JavaScript, HTML, CSS, and the Document Object Model (DOM).


Dart: Up and Running
Kathy Walrath and Seth Ladd
(O’Reilly, paperback, Kindle)

Google created Dart to be “an open-source, batteries-included developer platform for building structured HTML5 web apps,” the two authors note.

Dart provides not only a new language, but libraries, an editor, a virtual machine (VM), a browser that can run Dart apps natively, and a compiler to JavaScript.”

Indeed, Dart looks very similar to JavaScript and is “easy to learn,” the two writers state. “A wide range of developers can learn Dart quickly. It’s an object-oriented language with classes, single inheritance, lexical scope, top-level functions, and a familiar syntax. Most developers are up and running with Dart in just a few hours.”

The authors work at Google and note that some of the software engineers who helped develop the V8 JavaScript engine that is “responsible for much of Chrome’s speed” are now “working on the Dart project.”

Dart has been designed to scale from simple scripts all the way up to complex apps, and it can run on both the client and the server.

Those who choose to code with Dart are urged to download the open-source Dart Editor tool, because it also comes with a “Dart-to-JavaScript compiler and a version of Chromium (nicknamed Dartium) that includes the Dart VM.”

Since Dart is new, the writers also urge readers to keep an eye periodically on the Dart website and on their book’s GitHub site, where code can be downloaded and errors and corrections noted.

Dart: Up and Running is a well-structured, well-written how-to book, nicely fortified with short code examples and other illustrations. While the book appears very approachable and simple, it is not for complete beginners. You should have a basic working knowledge of JavaScript, HTML, CSS, and the Document Object Model (DOM).

If you are looking for a web development language that matches JavaScript’s dynamic nature but also addresses JavaScript’s sometimes-aggravating shortcomings, consider trying Dart—with this book in hand.

Si Dunn