head2tail.clj

  (:use [clojure.string :only [lower-case split-lines replace-first]]))

  (def dictionary
    (into #{}
      (map lower-case
        (split-lines (slurp "/usr/share/dict/words")))))

  (def alphabet "abcdefghijklmnopqrstuvwxyz")

  (defn neighbor-words [^String word]
    "Return a lazy-seq with words which differ from
    the input word by only the first letter"
    (remove #{word} (into []
      (filter dictionary
        (let [[f & r] word]
          (for [abc alphabet]
            (replace-first word f (str abc))))))))