gistfile1.clj

(defn lazy-compare 
  [& s] 
  (-> (some #{-1 1} (apply map compare s)) (or 0)))

(defn canonical?
  [cards]
  (if (not (= (sort cards) cards))
    false
    (let [by-suits (reduce (fn [a-map suit] 
                             (let [new-val (for [card cards
                                                 :when (and (>= card suit)
                                                            (< card (+ suit 13)))]
                                             (mod card 13))]
                               (if (= (count (into #{} new-val)) (count new-val))
                                 (merge-with concat a-map {suit new-val})
                                 (reduced false))))
                           {}
                           (range 0 52 13))]
      (and by-suits
           (not-any? (fn [suit]
                       (let [suit1 (by-suits (- suit 13))
                             suit2 (by-suits suit)]
                         (and (not (empty? suit2)) 
                              (or (< (count suit1) (count suit2))
                                  (and (= (count suit1) (count suit2)) 
                                       (pos? (lazy-compare suit1 suit2)))))))
                     (range 13 52 13))))))

(defn generate-isomorphs
  [n]
  (filter canonical? (c/combinations (range 52) n)))