anchor.diff:          digit ->
               scan(T, [{number_literal, {Row, Column}, [H]} | Scanned], {Row, Column + 1}, {in_number, Closer});
           _ ->
  -            {error, io:format("Illegal character line ~p column ~p", [Row, Column])}
  +            {error, io_lib:format("Illegal character line ~p column ~p", [Row, Column])}
       end;
   
   scan([H | T], Scanned, {Row, Column}, {in_number, Closer}) ->
  
positive.code:         digit ->
              scan(T, append_char(Scanned, H), {Row, Column + 1}, {in_identifier, Closer});
          _ ->
              {error, io:format("Illegal character line ~p column ~p", [Row, Column])}
      end.
  
  % internal functions
  
negative.code:         digit ->
              scan(T, append_char(Scanned, H), {Row, Column + 1}, {in_number, Closer});
          _ ->
              {error, io_lib:format("Illegal character line ~p column ~p", [Row, Column])}
      end;
  
  scan([H | T], Scanned, {Row, Column}, {in_identifier, Closer}) ->
  