Roman <> Arabic converter

gistfile1.rb

roman = %w(M CM D CD C XC L XL X IX V IV I)
arabic = [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1]
@roman_arabic = Hash[*roman.zip(arabic).flatten]

def arabic2roman(arabic)
  roman = ""
  @roman_arabic.each do |symbol,value|
    while arabic/value > 0
      roman << symbol
      arabic -= value
    end
  end
  roman
end

def roman2arabic(roman)
  arabic = 0
  while roman.size > 0
    current_char = @roman_arabic[roman[0..1]] ? roman[0..1] : roman[0]
    arabic += @roman_arabic[current_char]
    roman.sub!(current_char,'')
  end
  arabic
end

ARGF.each_line do |raw_line|
  line = raw_line.chop!
  break if line.empty?
  line =~ /\A[0-9]+\z/ ? puts(arabic2roman(line.to_i)) : puts(roman2arabic(line))
end