gistfile1.clj

(fn [n]
  (when (and (< n 4000) (> n 0))
    (loop [n n
           m {1000 "M"
              900  "CM"
              500  "D"
              400  "CD"
              100  "C"
              90   "XC"
              50   "L"
              40   "XL"
              10   "X"
              9    "IX"
              5    "V"
              4    "IV"
              1    "I"}
           [f & d] (reverse (sort (keys m)))
           r []]
      (if (zero? n)
        (apply str (flatten r))
        (recur (mod n f) m d (conj r (repeat (unchecked-divide-int n f) (m f))))))))

gistfile2.clj

(fn __
  ([coll]
     (let [coll (map {\I 1 \V 5 \X 10 \L 50 \C 100 \D 500 \M 1000} coll)]
       (__ coll 0)))
  ([coll acc]
     (if-not (seq coll)
       acc
       (let [a (first coll)
             b (second coll)
             f (if (and a b (< a b)) - +)]
         (__ (rest coll) (f acc a))))))

After several iterations, a version of Integer to Roman Numerals I'm somewhat happy with :)

And this is the reverse: Roman to Arabic converter :)