# File lib/maruku/input/linesource.rb, line 39
    def describe
      s = "At line #{original_line_number(@lines_index)}\n"

      context = 3 # lines
      from = [@lines_index - context, 0].max
      to   = [@lines_index + context, @lines.size - 1].min

      from.upto(to) do |i|
        prefix = (i == @lines_index) ? '--> ' : '    ';
        l = @lines[i]
        s += "%10s %4s|%s" %
          [@lines[i].md_type.to_s, prefix, l]

        s += "|\n"
      end

      s
    end