anchor.diff:  
   ensure_escaped_amp(<<>>, Acc) ->
       Acc;
  +ensure_escaped_amp(<<"<!--", Rest/binary>>, Acc) ->
  +    case try_comment(Rest, <<Acc/binary, "<!--">>) of
  +        false -> Acc;
  +        {Rest1, Acc1} -> ensure_escaped_amp(Rest1, Acc1)
  +    end;
   ensure_escaped_amp(<<$&, Rest/binary>>, Acc) ->
       case try_amp(Rest, in_amp, <<>>) of
           {Amp,Rest1} -> ensure_escaped_amp(Rest1, <<Acc/binary, $&, Amp/binary>>);
  
positive.code: try_amp(_B, _, _Acc) -> 
      false.
  
  
  is_valid_ent_char(C) ->
      (C >= $a andalso C =< $z) orelse (C >= $A andalso C =< $Z).
  
negative.code: flatten({nop, Enclosed}) ->
      flatten(Enclosed);
  flatten({comment, Text}) ->
      Comment = binary:replace(Text, <<"-->">>, <<"-- >">>, [global]),
      <<"<!--", Comment/binary, "-->">>;
  flatten({sanitized_html, Html}) ->
      Html;
  