(ns ^{:doc "Conway's Game of Life."}
game-of-life)
(defn neighbours
"Given a cell's coordinates, returns the coordinates of its neighbours."
[[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 neighbours cells))
:when (or (= n 3) (and (= n 2) (cells cell)))]
cell)))
(defn print-board
"Prints a board on *out*, representing a step in the game."
[board w h]
(doseq [x (range (inc w)) y (range (inc h))]
(if (= y 0) (print "\n"))
(print (if (board [x y]) "[X]" " . "))))
(defn display-grids