anchor.diff:  list_unification_1(Exp1, Exp2)->
       LEs1 = [E||E<-Exp1,is_list(E)],
       LEs2 = [E||E<-Exp2,is_list(E)],
  -    case LEs1==[] andalso LEs2==[] of 
  +    case LEs1==[] andalso LEs2==[] of
           false ->
               case  has_meta_list(Exp1) of
                   false ->
  
positive.code:     end;
  list_unification_3([], _) ->
      [false];
  list_unification_3(List1=[H1|T1], List2=[H2|T2]) ->
      case is_meta_list(H1) of
          true ->
              T11= [T||T<-T1, not is_meta_list(T)],
  
negative.code:         true ->
              list_unification_3(Exp1, Exp2)
      end.
  
  has_meta_list(NodeList) ->
      [E ||E<-NodeList, is_meta_list(E)]/=[].
  