num-roman.rkt

;; -*- coding: utf-8; mode: scheme -*-
;; num-roman.rkt
#lang racket

(provide numeral)

(define (numeral digito posicion)
  (let ((matriz-numerales
         #(#("" "I" "II" "III" "IV" "V" "VI" "VII" "VIII" "IX")
           #("" "X" "XX" "XXX" "XL" "L" "LX" "LXX" "LXXX" "XC")
           #("" "C" "CC" "CCC" "CD" "D" "DC" "DCC" "DCCC" "CM")
           #("" "M" "MM" "MMM"))))
    (vector-ref (vector-ref matriz-numerales posicion) digito) ))

(provide num-roman)

(define (num-roman arabigo)
  (let ((retval "")
        (cadena-num '())
        (longitud 0)
        (digito 0))

    (set! cadena-num (reverse (string->list (number->string arabigo))))
    (set! longitud (length cadena-num))

    (for ((posicion longitud))
         (set! digito (- (char->integer (list-ref cadena-num posicion)) 48))
         (set! retval (string-append (numeral digito posicion) retval)) )

    retval ))