robot.clj

robot.clj

(def robot (atom {:x 0 :y 0 :direction :north}))

(def behaviour {:left {:north :west
                       :west :south
                       :south :east
                       :east :north}

                :right {:north :east
                        :east :south
                        :south :west
                        :west :north}})

(defn- error [msg] (println msg) :error)
(defn- set-val [k v] (swap! robot assoc k v) :ok)
(defn- face [dir] (set-val :direction dir))
(defn- valid? [x] (and (>= x 0) (< x 5)))

(defn- move-on-axis [axis f]
  (let [v (f (axis @robot))]
    (if (valid? v)
      (set-val axis v)
      (error "Out of bounds"))))

(defn- get-direction [] (@robot :direction))
(defn- new-direction [dir] (get-direction (behaviour dir)))
(defn- turn [dir] (face (new-direction dir)))

(defn left [] (turn :left))
(defn right [] (turn :right))

(defn move []
  (cond (facing? :north) (move-on-axis :y inc)
        (facing? :east)  (move-on-axis :x dec)
        (facing? :south) (move-on-axis :y dec)
        (facing? :west)  (move-on-axis :x inc)
        :else (error "No x/y position")))

(defn report [] (str (:x @robot) "," (:y @robot) "," (:direction @robot)))

(report) ;; "0,0,:north"
(left)   ;; :ok
(move)   ;; :ok
(right)  ;; :ok
(move)   ;; :ok
(move)   ;; :ok
(move)   ;; :ok
(move)   ;; :ok
(move)   ;; :error
(move)   ;; :error
(report) ;; "1,4,:north"
(right)  ;; :ok
(right)  ;; :ok
(move)   ;; :ok
(report) ;; "1,3,:south"
(right)  ;; :ok
(move)   ;; :ok
(move)   ;; :ok
(move)   ;; :ok
(move)   ;; :error
(report) ;; "4,3,:west"