def digits_text(digit_values, options={})
      insignificant_digits = options[:insignificant_digits] || 0
      num_digits = digit_values.reduce(0) { |num, digit|
        digit.nil? ? num : num + 1
      }
      num_digits -= insignificant_digits
      digit_values.map { |d|
        if d.nil?
          options[:separator]
        else
          num_digits -= 1
          if num_digits >= 0
            digit_symbol(d, options)
          else
            options[:insignificant_symbol]
          end
        end
      }.join
    end
def digits_text(digit_values, options={})
      insignificant_digits = options[:insignificant_digits] || 0
      num_digits = digit_values.reduce(0) { |num, digit|
        digit.nil? ? num : num + 1
      }
      num_digits -= insignificant_digits
      digit_values.map { |d|
        if d.nil?
          options[:separator]
        else
          num_digits -= 1
          if num_digits >= 0
            digit_symbol(d, options)
          else
            options[:insignificant_symbol]
          end
        end
      }.join
    end
Convert sequence of digits to its text representation.
 The nil value can be used in the digits sequence to
 represent the group separator.