RUBY QUIZ: roman numerals

gistfile1.rb

class Converter

  ROMANS = {'M' => 1000, 'D' => 500, 'C' => 100, 'L' => 50, 'X' => 10, 'V' => 5, 'I' => 1} 

  def is_roman?(line)
    line = /[MDCLXVI]+/
  end

  def is_arabic?(line)
    line = /^(?:[123]\d{3}|[1-9]\d{0,2})$/
  end

  def enter(number, one, five, ten)
    t = String.new
    if number < 4 then (1..number).each {t += one}
    elsif number == 4 then t = one + five
    elsif number == 5 then t = five
    elsif (number > 5) && (number < 9) then t = five; (1..number-5).each {t += one}
    elsif number == 9 then t = one + ten
    end
    return t
  end

  def to_roman(number)
    roman = String.new
    (1..number/1000).each {roman += 'M'}; number %= 1000 if number/1000 > 0
    roman += enter(number/100, 'C', 'D', 'M'); number %= 100 if number/100 >0
    roman += enter(number/10, 'X', 'L', 'C'); number %= 10 if number/10 > 0
    roman += enter(number, 'I', 'V', 'X') if number > 0
  end

  def to_arabic(roman)
    sum = 0
    temp = false
    (0...roman.length).each do |i|
      add = min = 0
      if temp == false
        add = ROMANS[roman[i]]
        min = ROMANS[roman[i+1]] if !roman[i+1].nil?
        if add < min
          add = min - add
          temp = true
        end
        sum += add
      else
        temp = false
      end
    end
    return sum
  end
end

co = Converter.new

if __FILE__ == $0
  ARGF.each_line do |line|
  line.chomp!
    case line
    when co.is_arabic?(line) then puts co.to_roman(line.to_i)
    when co.is_roman?(line) then puts co.to_arabic(line)
    else raise "Wrong input:  #{line}"
    end
  end
end