# tags: roman, numbers, awk, code
#
# Arabic to Roman Number Conversion
# Michael Sanders 2023
# https://busybox.neocities.org/notes/arabic-to-roman.txt
#
# example usage: echo 6 | awk -f arabic-to-roman.txt
#
# note: using standard Roman numerals, the largest number
# that can be represented is 3,999 written as MMMCMXCIX

function toRoman(n) {
  if (n !~ /^[0-9]+$/ || n < 1 || n > 3999) return "invalid input"
  split("I IV V IX X XL L XC C CD D CM M", roman)
  split("1 4 5 9 10 40 50 90 100 400 500 900 1000", arabic)
  # loop through array in reverse order building romanNum
  for (x = 13; x >= 1; x--) {
    while (n >= arabic[x]) {
      romanNum = romanNum roman[x]
      n -= arabic[x]
    }
  }
  return romanNum
}

{ print toRoman($1) }

# eof