Solution to http://www.4clojure.com/problem/82

chainable.clj

(defn chainable?
  ([words]
     ((complement not-any?) #(chainable? % (clojure.set/difference words %)) words))
  ([word others]
     (letfn [(levenshtein [str1 str2]
               (cond (empty? str1) (count str2)
                     (empty? str2) (count str1)
                     :else
                     (let [cost (if (= (first str1) (first str2)) 0 1)]
                       (min (inc (levenshtein (rest str1) str2))
                            (inc (levenshtein str1 (rest str2)))
                            (+ cost (levenshtein (rest str1) (rest str2)))))))]
       (let [candidates (set (filter #(= 1 (levenshtein word %)) others))]
         (cond (empty? others) true
               (empty? candidates) false
               :else
               (some #(chainable? % (clojure.set/difference others #{%})) candidates))))))

Wow. I can't quite read this but I look forward to you explaining it to me someday. I'm impressed you cracked it!