Roman Numeral Converter

module Z
  ROMAN = {
       1  => "I",
       5  => "V",
      10  => "X",
      50  => "L",
     100  => "C",
     500  => "D",
    1000  => "M",
    5000  => "",
   10000  => ""
  }
end
class Integer

  def to_roman
    value = self
    if value < 4000
      base = ""
      for key in Z::ROMAN.keys.sort.reverse
        a = value / key
        case a
        when 0; next
        when 1, 2, 3
          base += Z::ROMAN[key]*a
        when 4
          base += Z::ROMAN[key]
          base += Z::ROMAN[key*5]
        when 5, 6, 7, 8
          base += Z::ROMAN[key*5]
          base += Z::ROMAN[key]*a-5
        when 9
          base += Z::ROMAN[key*10]
          base += Z::ROMAN[key]
        end
        value -= a * key
      end
      return base
    else
      return "---"
    end
  end

end

print 3000.to_roman
print 252.to_roman
print 99.to_roman
print 44.to_roman