I posted this in http://rosettacode.org/wiki/Roman_Numerals#Clojure

`1: (def arabic-roman-map`

2: {1 "I", 5 "V",

3: 10 "X", 50 "L",

4: 100 "C", 500 "D",

5: 1000 "M",

6: 4 "IV", 9 "IX",

7: 40 "XL", 90 "XC",

8: 400 "CD", 900 "CM" })

9: (def arabic-roman-map-sorted-keys

10: (sort (keys arabic-roman-map)))

11: (defn find-value-in-coll

12: [coll k]

13: (let [aval (find coll k)]

14: (if (nil? aval) "" (val aval))))

15: (defn to-roman

16: [result n]

17: (let

18: [closest-key-for-n (last (filter #(> n %) arabic-roman-map-sorted-keys))

19: roman-value-for-n (find-value-in-coll arabic-roman-map n)

20: roman-value-for-closet-to-n (find-value-in-coll arabic-roman-map

21: closest-key-for-n)]

22: (if (or (<= n 0) (contains? arabic-roman-map n))

23: (conj result roman-value-for-n)

24: (recur (conj result roman-value-for-closet-to-n)

25: (- n closest-key-for-n)))))

26: Usage: >(to-roman [] 1999)

27: result: ["M" "CM" "XC" "IX"]