;; -- Common Lisp version of Wolfram's experiment --
;;
;; Simply run the experiment with this line of code:
;; (run-it '(0 1 1 0 1 0 0 0) 40)
;;
;; Change the set of rules: try different rules
;; to see how it affects the result.
;; (0 1 1 1 1 0 0 0) is one of the seemingly random
;; outputs.
;;
;; You can also change the # of iterations, also
;; the ouptut is raw ASCII, so you have to extend
;; the width of your terminal to see something...

(defun print-line (line)
  (loop for i from 0 to (- (length line) 1)
     do (if (eq (nth i line) 0) (format t ".")
	    (format t "H")))
  (format t "~%"))

(defun next-line (line rule)
  (let ((n-line (copy-list line))
	(state 0))
    (loop for i from 1 to (- (length line) 2)
       do (progn
	    (setf state (+ (* 4 (nth (- i 1) line))
			   (* 2 (nth i line))
			   (* 1 (nth (+ i 1) line))))
	    (dotimes (rule-idx 8)
	      (if (eq state rule-idx) 
		  (setf (nth i n-line) (nth rule-idx rule))))))
    n-line))

(defun run-it (rule iterations)
  (let ((current-line ())
	(width (+ 1 (* iterations 2))))
    (dotimes (i width)
      (setf current-line (append current-line '(0))))
    (setf (nth (floor (/ width 2)) current-line) 1)
    (print-line current-line)
    (dotimes (i iterations)
      (setf current-line (copy-list (next-line current-line rule)))
      (print-line current-line))))