gistfile1.clj

(defn subleq
  ([in out mem regs] ; in this case data and program memory are the same
   (apply subleq in out mem regs (subvec mem (:ip regs) (+ 3 (:ip regs)))))
  ([in out mem regs a b c]
   (let [a-ind (if (neg? a) (nth mem (- a)) a)
         b-ind (if (neg? b) (nth mem (- b)) b)
         c-ind (if (neg? c) (nth mem (- c)) c)

         mem (assoc mem b-ind
                    (- (mem b-ind) (mem a-ind)))]
     [mem (assoc regs
                 :ip (if (pos? (mem b-ind))
                       (+ 3 (:ip regs))
                       c-ind)
                 :in (= b-ind in)
                 :out (= b-ind out))])))