gistfile1.clj

(defn count-ways-to-make-change [coins sum]
  (defn sum-counts [counts]
    (reduce + (map * coins counts)))
  (defn next-counts [counts]
    (loop [counts counts
           digit 0]
      (if (>= digit (count counts))
        nil
        (let [next (assoc counts digit (inc (get counts digit)))]
          (if (<= (sum-counts next) sum)
            next
            (recur (assoc counts digit 0) (inc digit)))))))
  (loop [counts (vec (map (constantly 0) coins))
         ways 0]
    (if (nil? counts)
      ways
      (let [sum-counts (sum-counts counts)
            ways (if (= sum-counts sum) (inc ways) ways)
            counts (next-counts counts)]
        (recur counts ways)))))