Weasel in Clojure

weasel.clj

;; weasel
(def TARGET "ME THINKS IT IS LIKE A WEASEL")
(def ALPHABET "ABCDEFGHIJKLMNOPQRSTUVWXYZ ")
(def RATE 0.05)


(def rand-seed
  "Generate a random seed as long as the target."
  (take (count TARGET) (repeatedly #(rand-nth ALPHABET))))


(defn mutate?
  "Mutates a string `s` if rand is less than the rate."
  [c]
  (if (< (rand) RATE) (rand-nth ALPHABET) c))


(defn check-fitness
  "Checks the fitness of a string `s` against the target. Returns 0 for
  perfect matches, otherwise a postive integer."
  [s]
  (count (filter #(not= (first %) (last %)) (map list s TARGET))))


(defn generate-candidate
  "Generates a candidate over a seed `s`."
  [s]
  (let [candidate (map mutate? s)]
    {:score (check-fitness candidate), :candidate candidate}))


(defn best-candidate
  "Finds the best candidate in a pool of `n`."
  [seed n]
  (apply min-key :score (take n (repeatedly #(generate-candidate seed)))))


(defn run-weasel
  "Runs a pool of `n` number of candidates and loops until a match is found."
  [n]
  (loop [generation 0 seed rand-seed]
    (let [candidate (best-candidate seed n)]
      (println generation (apply str (:candidate candidate)))
      (if (zero? (:score candidate))
        nil
        (recur (inc generation) (:candidate candidate))))))

Run with:

(run-weasel 1000)