Number to Roman

roman_converter.rb

class RomanConverter
  Dictionary = {
    1000 => 'M',
    900  => 'CM',
    500  => 'D',
    400  => 'CD',
    100  => 'C',
    90   => 'XC',
    50   => 'L',
    40   => 'XL',
    10   => 'X',
    9    => 'IX',
    5    => 'V',
    4    => 'IV',
    1    => 'I'
  }.freeze

  def self.call(num)
    Dictionary.each_with_object('') do |(arabic, roman), result|
      while num >= arabic
        result << roman
        num -= arabic
      end
    end
  end
end

class Fixnum
  def to_roman
    RomanConverter.call(self)
  end
end