cleanup: move game state from globals into game function

Author: stuarthalloway

examples/snake.clj

@@ -2,87 +2,104 @@
 ; Abhishek Reddy's snake: http://www.plt1.com/1070/even-smaller-snake/
 ; Mark Volkmann's snake: http://www.ociweb.com/mark/programming/ClojureSnake.html 
 
+; The START:/END: pairs are production artifacts for the book and not 
+; part of normal Clojure style
+
 (ns examples.snake
   (:import (java.awt Color) (javax.swing JPanel JFrame Timer JOptionPane)
            (java.awt.event ActionListener KeyListener))
   (:use clojure.contrib.import-static
 	[clojure.contrib.seq-utils :only (includes?)]))
 (import-static java.awt.event.KeyEvent VK_LEFT VK_RIGHT VK_UP VK_DOWN)
 
-; Game board and coordinates. points are [x,y] vectors 
+; ----------------------------------------------------------
+; functional model
+; ----------------------------------------------------------
+; START: constants
 (def width 75)
 (def height 50)
 (def point-size 10)
 (def turn-millis 75)
 (def win-length 5)
+(def dirs { VK_LEFT  [-1  0] 
+            VK_RIGHT [ 1  0]
+            VK_UP    [ 0 -1] 
+	    VK_DOWN  [ 0  1]})
+; END: constants
 
+; START: board math
 (defn add-points [& pts] 
   (vec (apply map + pts)))
 
 (defn point-to-screen-rect [pt] 
   (map #(* point-size %) 
        [(pt 0) (pt 1) 1 1]))
+; END: board math
 
-(def dirs { VK_LEFT  [-1  0] 
-            VK_RIGHT [ 1  0]
-            VK_UP    [ 0 -1] 
-	    VK_DOWN  [ 0  1]})
-
-; apple
-(def *apple* (ref nil))
-
+; START: apple
 (defn create-apple [] 
   {:location [(rand-int width) (rand-int height)]
    :color (Color. 210 50 90)
    :type :apple}) 
+; END: apple
 
-; snake
-(def *snake* (ref nil))
-
+; START: snake
 (defn create-snake []
   {:body (list [1 1]) 
    :dir [1 0]
    :type :snake
    :color (Color. 15 160 70)})
+; START: snake
 
-
+; START: move
 (defn move [{:keys [body dir] :as snake} & grow]
   (assoc snake :body (cons (add-points (first body) dir) 
 			   (if grow body (butlast body)))))
+; END: move
 
+; START: turn
 (defn turn [snake newdir] 
   (if newdir (assoc snake :dir newdir) snake))
+; END: turn
 
+; START: win
 (defn win? [{body :body}]
   (>= (count body) win-length))
+; END: win
 
+; START: lose
 (defn head-overlaps-body? [{[head & body] :body}]
   ; have proposed to SS that argument order be reversed:
   (includes? head body))
 
 (def lose? head-overlaps-body?)
+; END: lose
 
-(defn collision? [{[snake-head] :body} {apple :location}]
+; START: eats
+(defn eats? [{[snake-head] :body} {apple :location}]
    (= snake-head apple))
+; END: eats
 
-; state updates
+; ----------------------------------------------------------
+; mutable model
+; ----------------------------------------------------------
 (defn update-positions [snake apple]
   (dosync
-   (if (collision? @snake @apple)
+   (if (eats? @snake @apple)
      (do (ref-set apple (create-apple))
 	 (alter snake move :grow))
      (alter snake move))))
 
 (defn update-direction [snake newdir]
   (dosync (alter snake turn newdir)))
 
-(defn reset-game []
-  (dosync (ref-set *apple* (create-apple))
-	  (ref-set *snake* (create-snake))))
-
-(reset-game)
+(defn reset-game [snake apple]
+  (dosync (ref-set apple (create-apple))
+	  (ref-set snake (create-snake))))
 
-; drawing
+; ----------------------------------------------------------
+; gui
+; ----------------------------------------------------------
 (defn fill-point [g pt color] 
   (let [[x y width height] (point-to-screen-rect pt)]
     (.setColor g color) 
@@ -96,40 +113,38 @@
 
 (defmethod paint :apple [g {:keys [location color]}]
   (fill-point g location color))
- 
-; gui elements
-(def frame (JFrame. "Snake"))
-
-(def panel 
-  (proxy [JPanel ActionListener KeyListener] []
-    (paintComponent [g] 
-      (proxy-super paintComponent g)
-      (paint g @*snake*)
-      (paint g @*apple*))
-    (actionPerformed [e]
-      (update-positions *snake* *apple*)
-      (when (lose? @*snake*)
-	(reset-game)
-	(JOptionPane/showMessageDialog frame "You lose!"))
-      (when (win? @*snake*)
-	(reset-game)
-	(JOptionPane/showMessageDialog frame "You win!"))
-      (.repaint this))
-    (keyPressed [e] 
-      (update-direction *snake* (dirs (.getKeyCode e))))
-    (keyReleased [e])
-    (keyTyped [e])))
-
-(def timer (Timer. turn-millis panel))
- 
-(doto panel 
-  (.setFocusable true)
-  (.addKeyListener panel))
-
-(doto frame
-  (.add panel)
-  (.setSize (* width point-size) (* height point-size))
-  (.setVisible true))
-(.start timer)
+
+(defn game [] 
+  (let [snake (ref (create-snake))
+	apple (ref (create-apple))
+	frame (JFrame. "Snake")
+	panel (proxy [JPanel ActionListener KeyListener] []
+		(paintComponent [g] 
+		  (proxy-super paintComponent g)
+		  (paint g @snake)
+		  (paint g @apple))
+		(actionPerformed [e]
+                  (update-positions snake apple)
+		  (when (lose? @snake)
+		    (reset-game snake apple)
+		    (JOptionPane/showMessageDialog frame "You lose!"))
+		  (when (win? @snake)
+		    (reset-game snake apple)
+		    (JOptionPane/showMessageDialog frame "You win!"))
+		  (.repaint this))
+		(keyPressed [e] 
+		  (update-direction snake (dirs (.getKeyCode e))))
+		(keyReleased [e])
+		(keyTyped [e]))
+	timer (Timer. turn-millis panel)]
+    (doto panel 
+      (.setFocusable true)
+      (.addKeyListener panel))
+    (doto frame
+      (.add panel)
+      (.setSize (* width point-size) (* height point-size))
+      (.setVisible true))
+    (.start timer)
+    [snake, apple, timer]))
 
 

reader/snake.clj

@@ -0,0 +1,10 @@
+; START: namespace
+(ns reader.snake
+  (:import (java.awt Color) (javax.swing JPanel JFrame Timer JOptionPane)
+           (java.awt.event ActionListener KeyListener))
+  (:use clojure.contrib.import-static
+	[clojure.contrib.seq-utils :only (includes?)]))
+(import-static java.awt.event.KeyEvent VK_LEFT VK_RIGHT VK_UP VK_DOWN)
+; END: namespace
+
+; TODO: implement the Snake!