nearest-vowels Clojure kata

nearest-vowels.clj

(def vowels "aeiou")

(defn is-vowel [ch] (not (nil? (some #{ch} vowels))))

(defn abs [n] (max n (- n)))

(defn distance
  "Returns the distance from the number x to the closest number in xs"
  [xs x]
  (apply min (map (fn [y] (abs (- y x))) xs)))

(defn nearest-vowels [string]
  (let [vowel-indices (->> string
                           (map-indexed vector)
                           (filter #(is-vowel (second %)))
                           (map first))]
    (if (not-empty vowel-indices)
      (map-indexed (fn [index ch] (distance vowel-indices index)) string)
      (map #{nil} string))))

(nearest-vowels "babbba") ;; (1 0 1 2 1 0)
(nearest-vowels "hjkl") ;; (nil nil nil nil)