num-roman.rkt

;; -*- coding: utf-8; mode: scheme -*-
;; $Id: num-roman.rkt,v 1.6 2012/02/04 21:44:33 alcides_fp Exp $
#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 dec->list)

(define (dec->list numero)
  (let ((retval '())
        (base 10)
        (residuo 0))
    (do ((cantidad numero)) ((= cantidad 0) retval)
      (set! residuo (remainder cantidad base))
      (set! retval (append retval (list residuo) ))
      (set! cantidad (quotient cantidad base)) ) ) )
;;------------------------------------------------------------------------
(provide num-roman)

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

    (set! lista-cifras (dec->list arabigo))
    (set! longitud (length lista-cifras))

    (for ((posicion longitud))
         (set! digito (list-ref lista-cifras posicion))
         (set! retval (string-append (numeral digito posicion) retval)) )

    retval ))
;;------------------------------------------------------------------------