Improving my first Clojure program
- by StackedCrooked
After a few weekends exploring Clojure I came up with this program. It allows you to move a little rectangle in a window. Here's the code:
(import java.awt.Color)
(import java.awt.Dimension)
(import java.awt.event.KeyListener)
(import javax.swing.JFrame)
(import javax.swing.JPanel)
(def x (ref 0))
(def y (ref 0))
(def panel
(proxy [JPanel KeyListener] []
(getPreferredSize [] (Dimension. 100 100))
(keyPressed [e]
(let [keyCode (.getKeyCode e)]
(if (== 37 keyCode) (dosync (alter x dec))
(if (== 38 keyCode) (dosync (alter y dec))
(if (== 39 keyCode) (dosync (alter x inc))
(if (== 40 keyCode) (dosync (alter y inc))
(println keyCode)))))))
(keyReleased [e])
(keyTyped [e])))
(doto panel
(.setFocusable true)
(.addKeyListener panel))
(def frame (JFrame. "Test"))
(doto frame
(.add panel)
(.pack)
(.setDefaultCloseOperation JFrame/EXIT_ON_CLOSE)
(.setVisible true))
(defn drawRectangle [p]
(doto (.getGraphics p)
(.setColor (java.awt.Color/WHITE))
(.fillRect 0 0 100 100)
(.setColor (java.awt.Color/BLUE))
(.fillRect (* 10 (deref x)) (* 10 (deref y)) 10 10)))
(loop []
(drawRectangle panel)
(Thread/sleep 10)
(recur))
Despite being an experienced C++ programmer I found it very challenging to write even a simple application in a language that uses a radically different style than what I'm used to.
On top of that, this code probably sucks. I suspect the globalness of the various values is a bad thing. It's also not clear to me if it's appropriate to use references here for the x and y values.
Any hints for improving this code are welcome.
