#lang racket
(define (number->list n)
  (for/fold ([result null])
    ([decimal '(1000 900 500 400 100 90 50 40 10 9  5 4  1)]
     [roman   '(M    CM  D   CD  C   XC L  XL X  IX V IV I)])
    #:break (= n 0)
    (let-values ([(q r) (quotient/remainder n decimal)])
      (set! n r)
      (append result (make-list q roman)))))

(define (encode/roman number)
  (string-join (map symbol->string (number->list number)) ""))

(for ([n '(1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 25 30 40
           50 60 69 70 80 90 99 100 200 300 400 500 600 666 700 800 900
           1000 1009 1444 1666 1945 1997 1999 2000 2008 2010 2011 2500
           3000 3999)])
  (printf "~a ~a\n" n (encode/roman n)))