Robot Sim in Clojure (https://github.com/SanDiegoKats/katas/tree/master/2016-06-29)

robot_sim.clj

(ns robot-sim.core)

;; robot = { :direction [0 1], :position [4, 5] }

(defn rotate-right [[x y]]
  [y (- x)])

(defn rotate-left [[x y]]
  [(- y) x])

(defn dir->displacement-vector [dir]
  (case dir
    :N [0 1]
    :S [0 -1]
    :W [-1 0]
    :E [1 0]))

(defn move-robot [robot instruction]
  (case instruction
    \R (update robot :direction rotate-right)
    \L (update robot :direction rotate-left)
    \A (update robot :position (partial mapv + (:direction robot)))))

(defn main [initial-position initial-direction instructions]
  (let [robot { :direction (dir->displacement-vector initial-direction)
                :position initial-position }]
    (reduce move-robot robot instructions)))