bf.clj

(defn do_bf_step [code stdin state]
  (let [c (first code)
        mem (get state :mem)
        ind (get state :ind)]
    (if (zero? (count code)) 
      state
      (cond
        (= c \+) (do_bf_step (rest code) stdin {:mem (assoc mem ind (mod (+ (mem ind) 1) 256)) :ind ind})
        (= c \-) (do_bf_step (rest code) stdin {:mem (assoc mem ind (mod (- (mem ind) 1) 256)) :ind ind})
        (= c \.) (do (print (char (mem ind)))
                       (do_bf_step (rest code) stdin state))
        (= c \,) (do_bf_step (rest code) (rest stdin) {:mem (assoc mem ind (int (first stdin))) :ind ind})
        (= c \>) (do_bf_step (rest code) stdin {:mem mem :ind (+ ind 1)})
        (= c \<) (do_bf_step (rest code) stdin {:mem mem :ind (- ind 1)})
        (= c \[) (loop [s state]
                   (if (zero? ((get s :mem) (get s :ind)))
                     (loop [c (rest code)
                            i 0]
                       (if (and (= (first c) \]) (zero? i))
                         (do_bf_step (rest c) stdin s)
                         (recur (rest c)
                                (cond
                                  (= (first c) \]) (- i 1)
                                  (= (first c) \[) (+ i 1)
                                  :else i
                                  ))))
                     (recur
                       (do_bf_step
                         (loop [c (rest code) 
                                nc '()
                                i 0]
                           (if (and (= (first c) \]) (zero? i))
                             (reverse nc)
                             (recur (rest c)
                                    (conj nc (first c))
                                    (cond
                                      (= (first c) \]) (- i 1)
                                      (= (first c) \[) (+ i 1)
                                      :else i
                                      ))))
                         stdin
                         s
                         ))))
        :else (do_bf_step (rest code) stdin state)
        ))))

(do_bf_step (seq "+[-[<<[+[--->]-[<<<]]]>>>-]>-.---.>..>.<<<<-.<+.>>>>>.>.<<.<-.") '() {:mem (vec (repeat 30000 0)) :ind 0})