Levenshtein Distance - 4clojure #101

Levenshtein

(fn f [a b]
  (letfn [(clear-string [a]
            (cond (string? a) a
                  (vector? a) (clojure.string/join (map str a))
                  :else (clojure.string/join
                         (filter #(not (= % \:))
                                 (clojure.string/join (map str a))))))
          (make-ls-d []
            (with-local-vars
                [ls-d (memoize
                       (fn f [a b]
                         (cond (empty? a) (count b)
                               (empty? b) (count a)
                               :else (let [cost (if (= (last a) (last b)) 0 1)
                                           a-1 (clojure.string/join (butlast a))
                                           b-1 (clojure.string/join (butlast b))]
                                       (min
                                        (inc (ls-d a-1 b))
                                        (inc (ls-d a b-1))
                                        (+ (ls-d a-1 b-1) cost))))))]
              (.bindRoot ls-d @ls-d)
              @ls-d))]
    (let [ls-d (make-ls-d)]
      (ls-d (clear-string a) (clear-string b)))))