anchor.diff:            undefined ->
                 Apply;
             Vid ->
  -              true = lists:member('V', Flags),  %% sanity check
                 ?CALL(setelement, [?INTEGER(3), Apply, ?INTEGER(Vid)])
         end]}.
   
  
positive.code: 
  %% ===========================================================================
  %% ===========================================================================
  
  choose(true, X, _)  -> X;
  choose(false, _, X) -> X.
  
  get_value(Key, Plist) ->
      proplists:get_value(Key, Plist, []).
  
negative.code: %%% ------------------------------------------------------------------------
  
  f_vendor_id(Spec) ->
      {?function, vendor_id, 0,
       [{?clause, [], [], [vendor_id(orddict:find(vendor, Spec))]}]}.
  
  vendor_id({ok, {Id, _}}) ->
      ?INTEGER(Id);
  vendor_id(error) ->
      ?APPLY(erlang, error, [?TERM(undefined)]).
  
  %%% ------------------------------------------------------------------------
  %%% # vendor_name/0
  %%% ------------------------------------------------------------------------
  
  f_vendor_name(Spec) ->
      {?function, vendor_name, 0,
       [{?clause, [], [], [vendor_name(orddict:find(vendor, Spec))]}]}.
  
  vendor_name({ok, {_, Name}}) ->
      ?Atom(Name);
  vendor_name(error) ->
      ?APPLY(erlang, error, [?TERM(undefined)]).
  
  %%% ------------------------------------------------------------------------
  %%% # msg_name/1
  