Basic motion functions implemented

project.clj

@@ -1,6 +1,6 @@
 (defproject coloured-balls "0.0.1-SNAPSHOT"
   :description "A visual game challenge for the Clojure dojo"
   :main coloured-balls.core
-  :dependencies [[org.clojure/clojure "1.2.0"]
+  :dependencies [[org.clojure/clojure "1.2.0"] [org.clojure/clojure-contrib "1.2.0"]
 		[midje "1.1-alpha-3"]
 		[org.clojars.automata/rosado.processing "1.1.0"]])

src/coloured_balls/motion.clj

@@ -1,4 +1,14 @@
-(ns coloured-balls.motion)
+(ns coloured-balls.motion
+	(:use [clojure.contrib.generic.math-functions :only (floor, cos, sin)]))
+
+(defn degrees-to-radians [degrees]
+	(* (/ Math/PI 180) degrees))
 
 (defn move [item]
-	{:x 3})
+	(let [heading (degrees-to-radians (:heading item))
+		velocity (:velocity item)
+		old-x (:x item)
+		old-y (:y item)
+		new-x (floor (* velocity (cos heading)))
+		new-y (floor (* velocity (sin heading)))]
+		(conj {:x (+ old-x new-x) :y (+ old-y new-y)} (dissoc item :x :y))))

test/coloured_balls/core_test.clj

@@ -2,4 +2,10 @@
 	(:use coloured-balls.motion coloured-balls.collision
 		midje.sweet))
 
-(fact (:x (move {:x 0 :y 0 :heading 45 :velocity 5})) => 3)
+(fact (:x (move {:x 0 :y 0 :heading 45 :velocity 5})) => 3)
+
+(fact (:y (move {:x 0 :y 0 :heading 45 :velocity 5})) => 3)
+
+(fact (:x (move {:x 4 :y 4 :heading 225 :velocity 5})) => 0)
+
+(fact (:y (move {:x 4 :y 4 :heading 225 :velocity 5})) => 0)

test/coloured_balls/motion_test.clj

@@ -0,0 +1,7 @@
+(ns coloured-balls.core-test
+	(:use coloured-balls.motion
+		midje.sweet))
+
+(fact (direction {:heading 45}) => [1 1])
+
+(fact (direction {:heading 225}) => [-1 -1])