num-roman.lisp

;; -*- coding: utf-8; mode: common-lisp -*-
;; num-roman.lisp

(defun numeral (digito posicion)
  (setq matriz-numerales
        (make-array '(10 4)
                    :initial-contents '((""     ""     ""     "" )
                                        ("I"    "X"    "C"    "M")
                                        ("II"   "XX"   "CC"   "MM")
                                        ("III"  "XXX"  "CCC"  "MMM")
                                        ("IV"   "XL"   "CD"   "")
                                        ("V"    "L"    "D"    "")
                                        ("VI "  "LX"   "DC"   "")
                                        ("VII"  "LXX"  "DCC"  "")
                                        ("VIII" "LXXX" "DCCC" "")
                                        ("IX"   "XC"   "CM"   "")) ))

  (aref matriz-numerales digito posicion) )

(defun num-roman (n)
  (setq retval "")
  (setq cadena-num (reverse (write-to-string n)))
  (loop for pos from (- (length cadena-num) 1) downto 0 do
       (setq digito (parse-integer (string (elt cadena-num pos))))
       (setq retval (concatenate 'string
                                 retval
                                 (numeral digito pos))) )
  retval )