Unfinished Clojure puzzle for the purely functional newsletter

advanced-histogram.clj

user=> (require '[clojure.string :as str])
nil
user=> (def dictionary (->> (slurp "/home/arne/Downloads/purely functional - wordlist.txt")
  #_=>                      (str/split-lines)))
#'user/dictionary
user=> (defn frequency-histogram [phrase]
  #_=>   (->> (str/split (str/lower-case phrase) #"\s+")
  #_=>        (map frequencies)
  #_=>        (apply merge-with +)))
#'user/frequency-histogram
user=> (defn fits-perfectly? [p1 p2]
  #_=>   (->> (merge-with - (frequency-histogram p1) (frequency-histogram p2))
  #_=>        (vals)
  #_=>        (every? zero?)))
#'user/fits-perfectly?
user=> (defn fits-in-phrase? [phrase1 phrase2]
  #_=>   (let [freq1 (frequency-histogram phrase1)
  #_=>         freq2 (frequency-histogram phrase2)]
  #_=>     (every? (fn [[k v]]
  #_=>               (>= (get freq1 k 0) v)) freq2)))
#'user/fits-in-phrase?
user=> (defn find-anagram
  #_=>   [phrase]
  #_=>   (let [dictionary (filter (partial fits-in-phrase? phrase) dictionary)]
  #_=>     (loop [word (nth dictionary 0)
  #_=>            candidates dictionary
  #_=>            anagram []
  #_=>            found []
  #_=>            next-start 1]
  #_=>        (cond
  #_=>          ;; as long as our list of candidates isn't completely used up...
  #_=>          (some? word)
  #_=>          (let [guess (str/join " " (conj anagram word))]
  #_=>            (cond
  #_=>              ;; found an anagram :)
  #_=>              (fits-perfectly? phrase guess)
  #_=>              (recur (first candidates) dictionary anagram (conj found (conj anagram word))
  #_=>
  #_=>              ;; might still find one
  #_=>              (fits-in-phrase? phrase guess)
  #_=>              (recur (first candidates) dictionary (conj anagram word) found next-start)
  #_=>
  #_=>              ;; the current word doesn't fit
  #_=>              :else
  #_=>              (recur (first candidates) (rest candidates) anagram found next-start)))
  #_=>
  #_=>          ;; try again from a blank anagram if we weren't sucessful
  #_=>          (< next-start (count dictionary))
  #_=>          (recur (nth dictionary next-start) dictionary [] found (inc next-start)))
  #_=>
  #_=>          ;; we did everything we could :)
  #_=>          :else found))))
#'user/find-anagram
;; TODO: Find all anagrams, not just the first one alphabetically