Lexicase Parent selection implementation for clojush

gistfile1.clj

(defn lexicase-selection
  "Returns an individual that does the best on a randomly selected set of fitness cases"
  [pop tournament-size]
  (loop [survivors pop
         cases (shuffle (range (count (:errors (first pop)))))]
    (if (or (empty? cases)
            (empty? (rest survivors)))
      (first survivors)
      (let [min-err-for-case (apply min (map #(nth % (first cases))
                                             (map #(:errors %) survivors)))]
        (recur (filter #(= (nth (:errors %) (first cases)) min-err-for-case)
                       survivors)
               (rest cases))))))