What you need for this book
To be able to follow along, you need a running Clojure REPL. Getting to a working Clojure environment is generally done through Leiningen (https://leiningen.org), which will need a JVM installation in order to be able to work. Clojure 1.6 will be fine for all the recipes except for the second recipe in Chapter 7, Transformations as First-class Citizens, which will need Clojure 1.7. Though not absolutely necessary, you can consider using a full-fledged Clojure development environment, such as Emacs/CIDER, IntelliJ/Cursive, Light Table, or Nightcode.
