number to Roman Numeral

roman.sh

#!/bin/bash -
#
# SCRIPT: romam
# AUTHOR: Luciano D. Cecere
# DATE: 2014
########################################################################
#
# roman - convert number (1-9999) to Roman numeral
# Copyright (C) 2014 Luciano D. Cecere <ldante86@aol.com>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
#########################################################################

base=(I II III IV V VI VII VIII IX)
tens=(X XX XXX XL L LX LXX LXXX XC)
hundreds=(C CC CCC CD D DC DCC DCCC CM)
thousands=(M MM MMM ^IV ^V ^VI ^VII ^VIII ^IX)

_roman()
{
case "$1" in
  [1-9]|[1-9][0-9]|[1-9][0-9][0-9][0-9]|[1-9][0-9][0-9])
    input="$1" ;;
  *)
    echo "Out of range [1-9999]"
    return
esac

subst_0=${input:0:1}
subst_1=${input:1:1}
subst_2=${input:2:1}
subst_3=${input:3:1}

base_0=${base[subst_0-1]}
base_1=${base[subst_1-1]}
base_2=${base[subst_2-1]}
base_3=${base[subst_3-1]}
tens_0=${tens[subst_0-1]}
tens_1=${tens[subst_1-1]}
tens_2=${tens[subst_2-1]}
hundreds_0=${hundreds[subst_0-1]}
hundreds_1=${hundreds[subst_1-1]}
thousands_0=${thousands[subst_0-1]}

case ${#input} in
  1)  echo $base_0
      ;;
  2)  [ $subst_1 -eq 0 ] && echo $tens_0
      [ $subst_1 -gt 0 ] && echo $tens_0$base_1
      ;;
  3)  [ $subst_1 -eq 0 -a $subst_2 -eq 0 ] && echo $hundreds_0
      [ $subst_1 -gt 0 -a $subst_2 -eq 0 ] && echo $hundreds_0$tens_1
      [ $subst_1 -eq 0 -a $subst_2 -gt 0 ] && echo $hundreds_0$base_2
      [ $subst_1 -gt 0 -a $subst_2 -gt 0 ] && echo $hundreds_0$tens_1$base_2
      ;;
  4)  [ $subst_1 -eq 0 -a $subst_2 -eq 0 -a $subst_3 -eq 0 ] && echo $thousands_0
      [ $subst_1 -eq 0 -a $subst_2 -eq 0 -a $subst_3 -gt 0 ] && echo $thousands_0$base_3
      [ $subst_1 -eq 0 -a $subst_2 -gt 0 -a $subst_3 -eq 0 ] && echo $thousands_0$tens_2
      [ $subst_1 -eq 0 -a $subst_2 -gt 0 -a $subst_3 -gt 0 ] && echo $thousands_0$tens_2$base_3
      [ $subst_1 -gt 0 -a $subst_2 -eq 0 -a $subst_3 -eq 0 ] && echo $thousands_0$hundreds_1
      [ $subst_1 -gt 0 -a $subst_2 -eq 0 -a $subst_3 -gt 0 ] && echo $thousands_0$hundreds_1$base_3
      [ $subst_1 -gt 0 -a $subst_2 -gt 0 -a $subst_3 -eq 0 ] && echo $thousands_0$hundreds_1$tens_2
      [ $subst_1 -gt 0 -a $subst_2 -gt 0 -a $subst_3 -gt 0 ] && echo $thousands_0$hundreds_1$tens_2$base_3
esac
}

if [ $# -eq 0 ]; then
  echo Usage: ${0##*/} 1-9999
  exit 1
fi

while [ $# -gt 0 ]; do
  _roman "$1"
  shift
done