四則ソルバー in Clojure

sisoku.clj

(use 'clojure.contrib.combinatorics)


(def seeds [7 7 7 9 11 11])
(def answer 218/100)


(defn drop-nth [n coll]
  (concat (take n coll)
          (drop (inc n) coll)))

(defn comb [n m]
  (combinations (range n) m))

(def comb (memoize comb))

(defn choose-2 [coll n m]
  (let [a (nth coll n)
        b (nth coll m)
        rest (drop-nth n (drop-nth m coll))]
    [a b rest]))

(defn choose-random-2 [coll]
  (for [[a b] (comb (count coll) 2)]
    (choose-2 coll a b)))

(defn single? [coll]
  (empty? (rest coll)))

(defmacro concatfor [seq-exprs body-expr]
  `(apply concat (for ~seq-exprs ~body-expr)))

(defmacro go [op a b coll]
  `(let [r# (~op ~a ~b)
         n# (conj ~coll r#)
         s# (sisoku (sort n#))]
     (if (empty? s#)
       s#
       (map #(conj % (str '~op) ~a ~b) s#))))

(defn sisoku [seeds]
  "Return a sequence of answers"
  (if (single? seeds)
    (if (= (first seeds) answer)
      [seeds]
      [])
    (concatfor [[a b r] (choose-random-2 seeds)]
       (concat (go + a b r)
               (go - a b r)
               (go - b a r)
               (go * a b r)
               (when-not (zero? b)
                 (go / a b r))
               (when-not (zero? a)
                 (go / b a r))))))

(def sisoku (memoize sisoku))                       

; REPLから(sisoku seeds)ってしてね♡