anchor.diff:  							 | {error, string()}).
   fold_expr_by_loc(FName, Line, Col, SearchPaths) ->
       case check_undo_process() of
  -      ok -> wrangler:fold_expr_by_loc(FName, Line, Col, SearchPaths);
  +      ok -> Res = wrangler:fold_expr_by_loc(FName, Line, Col, SearchPaths),
  +	    check_wrangler_error_logger(),
  +	    Res;
         {error, Reason} -> {error, Reason}
       end.
   
  
positive.code: 	     {error, string()} | {ok, [filename()]}).
  rename_fun(Fname, Line, Col, NewName,SearchPaths) ->
      case check_undo_process() of
  	ok -> wrangler:rename_fun(Fname, Line, Col, NewName,SearchPaths);
  	{error, Reason} ->
  	   {error, Reason}
      end.
  
negative.code: register_pid(FileName, StartLine, StartCol, EndLine, EndCol, RegName, SearchPaths) ->
      case check_undo_process() of 
  	ok ->
  	    Res = wrangler:register_pid(FileName, {StartLine, StartCol}, {EndLine, EndCol}, RegName, SearchPaths),
  	    check_wrangler_error_logger(),
  	    Res;
  	{error, Reason} ->
  	    {error,Reason}
      end.
  