Conway's Game of Life in Clojure (with Venkat at CodeRetreat, Uncubed, 2012/01/21)

conway.clj

(ns game
  (:use clojure.test))

(defn vitality [cell-state live-neighbors]
  (or (= live-neighbors 3) (and cell-state (= live-neighbors 2))))

(defn count-live-neighbors [grid position]
  (let [row (first position)
   column (last position)]
  (def neighbors
    (list
      (list (- row 1) (- column 1)) (list (- row 1) column) (list (- row 1) (+ column 1))
      (list row (- column 1)) (list row (+ column 1))
      (list (+ row 1) (- column 1)) (list (+ row 1) column) (list (+ row 1) (+ column 1))))

  (count (filter #(get grid %)  neighbors))))

(defn tick [grid]
  (defn new-state-for-cell [result-grid map-entry]
    (assoc result-grid (key map-entry) (vitality (get grid (key map-entry)) (count-live-neighbors grid (key map-entry)))))

  (reduce new-state-for-cell (hash-map) grid))

(def test-canary
  (is true))

(def test-dead-cell-w-3-live-neighbors-alive
  (is (vitality false 3)))

(def test-dead-cell-w-1-live-neighbors-alive
  (is (not (vitality false 1))))

(def test-dead-cell-w-5-live-neighbors-alive
  (is (not (vitality false 5))))

(def test-live-cell-w-2-live-neighbors-alive
  (is (vitality true 2)))

(def test-live-cell-w-3-live-neighbors-alive
  (is (vitality true 3)))

(def test-live-cell-w-1-live-neighbors-dead
  (is (not (vitality true 1))))

(def test-live-cell-w-5-live-neighbors-dead
 (is (not (vitality true 5))))

(def test-zero-live-neighbors
  (let [grid (hash-map
    '(0 0) false '(0 1) false '(0 2) false
    '(1 0) false '(1 1) false '(1 2) false
    '(2 0) false '(2 1) false '(2 2) false
    )
    position '(1 1)]
  (is (= 0 (count-live-neighbors grid position)))))

(def test-two-live-neighbors
  (let [grid (hash-map
    '(0 0) false '(0 1) false '(0 2) false
    '(1 0) true '(1 1) true '(1 2) true
    '(2 0) false '(2 1) false '(2 2) false
    )
    position '(1 1)]
  (is (= 2 (count-live-neighbors grid position)))))

(def test-two-live-neighbors-for-corner-cell
  (let [grid (hash-map
    '(0 0) false '(0 1) true '(0 2) false
    '(1 0) true '(1 1) false '(1 2) true
    '(2 0) false '(2 1) false '(2 2) false
    )
    position '(0 0)]
  (is (= 2 (count-live-neighbors grid position)))))

(def test-tick
  (let [grid (hash-map
    '(0 0) false '(0 1) false '(0 2) false
    '(1 0) true '(1 1) true '(1 2) true
    '(2 0) false '(2 1) false '(2 2) false
    )
    position '(0 0)
    result-grid (hash-map
      '(0 0) false '(0 1) true '(0 2) false
      '(1 0) false '(1 1) true '(1 2) false
      '(2 0) false '(2 1) true '(2 2) false
      )]
  (is (= result-grid (tick grid)))))