roman.clj

(ns roman.core)

(declare roman)

(defn -main [& args]
  (if (= (count args) 1)
    (let [arabic (read-string (first args))]
      (if (number? arabic)
        (println (roman arabic ""))
        (println "Must enter a number")))
    (println "Must pass exactly one parameter")))

(defn roman [arabic acc]
  (cond
    (<= arabic 0) acc
    (< arabic 4) (roman (- arabic 1) (str acc "I"))
    (< arabic 5) (roman (- arabic 4) (str acc "IV"))
    (< arabic 9) (roman (- arabic 5) (str acc "V"))
    (< arabic 10) (roman (- arabic 9) (str acc "IX"))
    (< arabic 40) (roman (- arabic 10) (str acc "X"))
    (< arabic 50) (roman (- arabic 40) (str acc "XL"))
    (< arabic 90) (roman (- arabic 50) (str acc "L"))
    (< arabic 100) (roman (- arabic 90) (str acc "XC"))
    (< arabic 400) (roman (- arabic 100) (str acc "C"))
    (< arabic 500) (roman (- arabic 400) (str acc "CD"))
    (< arabic 900) (roman (- arabic 500) (str acc "D"))
    (< arabic 1000) (roman (- arabic 900) (str acc "CM"))
    :else (roman (- arabic 1000) (str acc "M"))))