anchor.diff:  %%                {ok, none}
   %% @end
   %%--------------------------------------------------------------------
  -select_focus(_Args) -> 
  -    {ok, none}.
  +select_focus(_Args=#args{current_file_name=File,
  +                         cursor_pos=Pos}) -> 
  +    case api_interface:pos_to_fun_def(File, Pos) of 
  +        {ok, FunDef} -> 
  +            {_M, F, A} = api_refac:fun_define_info(FunDef),
  +            {ok, {F, A}};
  +        {error, Msg} ->
  +            throw({error, Msg})
  +    end. 
       
   %%--------------------------------------------------------------------
   %% @private
  
positive.code: %% ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  %%@author  Huiqing Li <H.Li@kent.ac.uk>
  %% @hidden
  %% @private
  -module(refac_add_op_arg).
  
  -behaviour(gen_refac).
  
negative.code:               ?TO_AST("{call, M@, F@, [Args1@@,"++NewArgGen++"(), Args2@@]}",
                       wrangler_syntax:get_pos(_This@))
            end,
            ?PP(F@)==Op andalso length(Args@@)==Arity andalso 
            api_refac:is_expr(_This@) andalso Style==non_tuple).
  
  
  add_op_arg(FileName, OpName, NewArgName, Index, NewArgGen, SearchPaths, Editor, TabWidth) ->
  