anchor.diff:  -spec(generalise/7::(filename(),integer(), integer(),integer(), integer(),string(), dir()) -> {ok, string()} | {error, string()}).
   generalise(Fname, StartLine, StartCol, EndLine, EndCol, ParName, SearchPaths)->
       case check_undo_process() of 
  -	ok -> wrangler:generalise(Fname, {StartLine, StartCol}, {EndLine, EndCol}, ParName, SearchPaths);
  +	ok -> Res =wrangler:generalise(Fname, {StartLine, StartCol}, {EndLine, EndCol}, ParName, SearchPaths),
  +	      check_wrangler_error_logger(),
  +	      Res;
   	{error, Reason} ->
   	    {error, Reason}
       end.
  
positive.code: instrument_prog(FName, SearchPaths) ->
      case check_undo_process() of 
  	ok ->
  	    wrangler:instrument_prog(FName, SearchPaths);
  	{error, Reason} ->
  	    {error, Reason}
      end.
  
negative.code: 	     {error, string()} | {ok, [filename()]}).
  tuple_funpar(Fname, Line, Col, Number, SearchPaths) ->
      case check_undo_process() of
  	ok -> Res = wrangler:tuple_funpar(Fname, Line, Col, Number, SearchPaths),
  	      check_wrangler_error_logger(),
  	      Res;
  	{error, Reason} ->
  	    {error, Reason}
      end.
  