amalloy-4clojure-solution94.clj

;; amalloy's solution to Game of Life
;; https://4clojure.com/problem/94

(fn [board]
  (let [board (vec (map vec board))
        [h w] (map count ((juxt identity first) board))
        cell (fn [y x]
               (get-in board (map mod [y x] [h w])))
        alive? (comp #{\#} cell)
        neighbors (let [offsets [-1 0 1]
                        deltas (for [y offsets, x offsets
                                     :when (not= y x 0)]
                                 [y x])]
                    (fn [y x]
                      (count
                       (for [[dy dx] deltas
                             :when (alive? (+ y dy) (+ x dx))]
                         true))))
        new-state (fn [y x]
                    (let [nbr-count (neighbors y x)]
                      (if (or (= 3 nbr-count)
                              (and (= 2 nbr-count)
                                   (alive? y x)))
                        \#
                        \space)))]
    (for [y (range h)]
      (apply str (for [x (range w)]
                   (new-state y x))))))