class RDoc::RubyLex

def ungetc(c = nil)
  if @here_readed.empty?
    c2 = @readed.pop
  else
    c2 = @here_readed.pop
  end
  c = c2 unless c
  @rests.unshift c #c =
  @seek -= 1
  if c == "\n"
    @line_no -= 1
    if idx = @readed.reverse.index("\n")
      @char_no = @readed.size - idx
    else
      @char_no = @base_char_no + @readed.size
    end
  else
    @char_no -= 1
  end
end