roman_numerals.rb

class RomanNumerals
  NUMBERS = {
    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",
  }

  def convert number
    amount, symbol = NUMBERS.detect {|k,v| k <= number }
    amount == number ? symbol : symbol + convert(number - amount)
  end
end