number_to_delimited_converter.rb

module ActiveSupport
  module NumberHelper
    class NumberToDelimitedConverter < NumberConverter #:nodoc:
      self.validate_float = true

      DELIMITED_REGEX = /(\d)(?=(\d\d\d)+(?!\d))/

      def convert
        parts.join(options[:separator])
      end

      private

        def parts
          left, right = number.to_s.split('.')
          left.gsub!(DELIMITED_REGEX) do |digit_to_delimit|
            "#{digit_to_delimit}#{options[:delimiter]}"
          end
          [left, right].compact
        end
    end
  end
end