gistfile1.txt

def separate_comma(number)
  @interjects = (number.to_s.length - 1) / 3
  @number = number.to_s.split('')
  @comma_number = []
  @number = @number.reverse
  @number.each_slice(3) do |slice|
    @comma_number << slice
    if @interjects > 0
      @comma_number << ","
      @interjects -= 1
    end
  end
  @comma_number.flatten.reverse.join
end