Roman Numerals Kata written in clojure by @Serchinastico

roman.cj

(def table-number->roman
  [{:number 1000 :roman "M"}
   {:number 900 :roman "CM"}
   {:number 500 :roman "D"}
   {:number 400 :roman "CD"}
   {:number 100 :roman "C"}
   {:number 90 :roman "XC"}
   {:number 50 :roman "L"}
   {:number 40 :roman "XL"}
   {:number 10 :roman "X"}
   {:number 9 :roman "IX"}
   {:number 5 :roman "V"}
   {:number 4 :roman "IV"}
   {:number 3 :roman "III"}
   {:number 2 :roman "II"}
   {:number 1 :roman "I"}])

(defn first-matching
  [number]
  (first (filter #(= 1 (quot number (:number %))) table-number->roman)))

(defn number->roman
  [number]
  (loop [roman ""
         number number]
    (if (> number 0)
      (let [translation (first-matching number)]
        (recur (str roman (:roman translation)) (- number (:number translation))))
      roman)))

(= "" (number->roman -50))
(= "" (number->roman 0))
(= "I" (number->roman 1))
(= "II" (number->roman 2))
(= "III" (number->roman 3))
(= "XV" (number->roman 15))
(= "XVI" (number->roman 16))
(= "IV" (number->roman 4))
(= "VIII" (number->roman 8))
(= "XIV" (number->roman 14))
(= "XLIV" (number->roman 44))
(= "C" (number->roman 100))
(= "CXLIV" (number->roman 144))
(= "D" (number->roman 500))
(= "CD" (number->roman 400))
(= "M" (number->roman 1000))
(= "CM" (number->roman 900))
(= "CMXLIV" (number->roman 944))