Tommy Chheng

I decided it’s about time to learn a functional programming language. Clojure is an excellent choice to get started. I looked at Scala and Erlang as other possible functional programming languages to learn but I settled on Clojure because:

a) It’s a LISP dialect
b) Runs on JVM
c) Community support.

I was amazed at the amount of talk going on in the clojure community. The creator of clojure, Rick Hickey regularly answers questions on the clojure google groups.

To get started on the mac, Citizen428 has created an easy to use package. It has all the necessary jars and support for TextMate and Emacs. Download it from the github project

Take some time to read more from the Clojure website and google groups. They have plenty of answers.

Here’s a sample app:

(import '(javax.swing JFrame JLabel JTextField JButton)
        '(java.awt.event ActionListener)
        '(java.awt GridLayout))
(defn celsius []
  (let [frame (JFrame. "Celsius Converter")
        temp-text (JTextField.)
        celsius-label (JLabel. "Celsius")
        convert-button (JButton. "Convert")
        fahrenheit-label (JLabel. "Fahrenheit")]
    (.addActionListener convert-button
      (proxy [ActionListener] []
        (actionPerformed [evt]
          (let [c (Double/parseDouble (.getText temp-text))]
            (.setText fahrenheit-label
               (str (+ 32 (* 1.8 c)) " Fahrenheit"))))))
    (doto frame
      (.setLayout (GridLayout. 2 2 3 3))
      (.add temp-text)
      (.add celsius-label)
      (.add convert-button)
      (.add fahrenheit-label)
      (.setSize 300 80)
      (.setVisible true))))
(celsius)