legal.clj

(defn suicide? [board point color size]
  (let [board (assoc board point color)
        enemy (find-enemy board point color size)
        ally  (find-ally board point color size)]
    (and (reduce #(and %1 (> (count (find-liberty %2)) 0)) true enemy)
         (= (count (find-liberty ally)) 0))))

(defn legal? [board point color size ko]
  (and (not (= ko point))
       (not (out-of-bound point size))
       (gray? board point size)
       (not (suicide? board point color size))))