CodeMirror

(ns game-of-life

  "Conway's Game of Life, based on the work of

  Christophe Grand (http://clj-me.cgrand.net/2011/08/19/conways-game-of-life)

  and Laurent Petit (https://gist.github.com/1200343).")

​

;;; Core game of life's algorithm functions

​

(defn neighbors

  "Given a cell's coordinates `[x y]`, returns the coordinates of its

  neighbors."

  [[x y]]

  (for [dx [-1 0 1]

        dy (if (zero? dx)

             [-1 1]

             [-1 0 1])]

    [(+ dx x) (+ dy y)]))

​

(defn step

  "Given a set of living `cells`, computes the new set of living cells."

  [cells]

  (set (for [[cell n] (frequencies (mapcat neighbors cells))

             :when (or (= n 3)

                       (and (= n 2)

                            (cells cell)))]

         cell)))

​

;;; Utility methods for displaying game on a text terminal

​

(defn print-grid

  "Prints a `grid` of `w` columns and `h` rows, on *out*, representing a

  step in the game."

  [grid w h]

  (doseq [x (range (inc w))

          y (range (inc h))]

    (when (= y 0) (println))

    (print (if (grid [x y])

             "[X]"

             " . "))))

​

(defn print-grids

  "Prints a sequence of `grids` of `w` columns and `h` rows on *out*,

  representing several steps."

  [grids w h]

  (doseq [grid grids]

    (print-grid grid w h)

    (println)))

​

;;; Launches an example grid

​

(def grid

  "`grid` represents the initial set of living cells"

  #{[2 1] [2 2] [2 3]})

​

(print-grids (take 3 (iterate step grid)) 5 5)