(= nth (fn (n lst)
  (while (< 0 n)
    (= n (- n 1))
    (= lst (cdr lst)))
  (if (is n 0) (car lst))
))


(= rev (fn (lst)
  (let res nil)
  (while lst
    (= res (cons (car lst) res))
    (= lst (cdr lst))
  )
  res
))


(= map (fn (f lst)
  (let res nil)
  (while lst
    (= res (cons (f (car lst)) res))
    (= lst (cdr lst))
  )
  (rev res)
))


(= print-grid (fn (grid)
  (map
    (fn (row)
      (print (map (fn (x) (if (is x 0) '- '#)) row))
    )
    grid
  )
))


(= get-cell (fn (grid x y)
  (or (nth x (nth y grid)) 0)
))


(= next-cell (fn (grid cell x y)
  (let n (+
    (get-cell grid (- x 1)  (- y 1))
    (get-cell grid (- x 1)  y      )
    (get-cell grid (- x 1)  (+ y 1))
    (get-cell grid x        (- y 1))
    (get-cell grid x        (+ y 1))
    (get-cell grid (+ x 1)  (- y 1))
    (get-cell grid (+ x 1)  y      )
    (get-cell grid (+ x 1)  (+ y 1))
  ))
  (if
    (and (is cell 1) (or (is n 2) (is n 3))) 1
    (and (is cell 0) (is n 3)) 1
    0
  )
))


(= next-grid (fn (grid)
  (let y -1)
  (map
    (fn (row)
      (= y (+ y 1))
      (let x -1)
      (map
        (fn (cell)
          (= x (+ x 1))
          (next-cell grid cell x y)
        )
        row
      )
    )
    grid
  )
))


(= life (fn (n grid)
  (let i 1)
  (while (<= i n)
    (print ">> iteration" i)
    (print-grid grid)
    (print)
    (= grid (next-grid grid))
    (= i (+ i 1))
  )
))


; blinker in a 3x3 universe
(life 5 '(
  (0 1 0)
  (0 1 0)
  (0 1 0)
))


; glider in an 8x8 universe
(life 22 '(
  (0 0 1 0 0 0 0 0)
  (0 0 0 1 0 0 0 0)
  (0 1 1 1 0 0 0 0)
  (0 0 0 0 0 0 0 0)
  (0 0 0 0 0 0 0 0)
  (0 0 0 0 0 0 0 0)
  (0 0 0 0 0 0 0 0)
  (0 0 0 0 0 0 0 0)
))