anchor.diff:      X == undefined.
   
   
  -% check_term_seq
  +%% check_term_seq
   check_term_seq([], [], _Level, _Mod) ->
       true;
   check_term_seq(_Args, [], _Level, _Mod) ->
  
positive.code: check_term_predef({tuple,Attrs}, X) ->
      is_tuple(X) andalso check_term_attrlist(tuple,Attrs,X).
  
  %% check_term_attrlist
  check_term_attrlist(Type, Attrs, Val) ->
      [] == [ {Type,Attr,Val} || Attr <- Attrs, not check_term_attr(Type,Attr,Val) ].
  
negative.code: %% alt
  check_term({alt, A, B}, X, Level, Mod) ->
      case check_term(A, X, Level, Mod) of
          ok ->
              ok;
          _   ->
              check_term(B, X, Level, Mod)
  