simple-life.core.clj

(ns simple-life.core
  "Simplified game of life. Random universe consists of ones and
   zeros. For every iteration we calculate current cell value
   depending on it's own value and values of it's left and right
   neighbours.  When exactly one of those cells is 1 the resulting
   value for next generation is 1, otherwise it's 0. For edge
   elements the absent neighbour counts as 0.")

(defn next-cell [coll]
  "takes collection and returns 1 only if one of collection's
   elements equals 1"
  (if (= 1 (reduce + coll))
    1
    0))

(defn next-gen [coll]
  "takes collection and expands it's left and right edges with
   zeros to avoid edge checking. then partitions it by 3 elements
   with step of 1. then maps it with next-cell function. ie.
   initial collection: (0 1 1 0)
   expanded:           (0 0 1 1 0 0)
   partitioned:        ((0 0 1) (0 1 1) (1 1 0) (1 0 0))
   result:             (1 0 0 1)
   "
  (map next-cell (partition 3 1 (concat '(0) coll '(0)))))

(defn age [num-gens universe]
  (def u (atom universe))
  (dotimes [n num-gens]
    (swap! u next-gen))
  (deref u))

(defn universe [num-cells]
  "generates random universe consisting of ones and zeros with
   num-cells length"
  (take num-cells (repeatedly #(rand-int 2))))

(println (age 30 (universe 40)))