Создать предикат нахождения множества объединения трех множеств

domains
   r=real
   list=real*
 
predicates
   union(list,list,list)
   intersection(list,list,list)
   member(r,list)
   example(list,list,list,list)
   list_set(list,list)
   delete_all(r,list,list)
 
clauses
   union([],S2,S2).
   union([H|T],S2,S):-member(H,S2),!,union(T,S2,S).
   union([H|T],S2,[H|S]):-union(T,S2,S).
 
   member(X,[X|_]):-!.
   member(X,[_|T]):-member(X,T).
 
   intersection([],_,[]).
   intersection([H|T1],S2,[H|T]):-member(H,S2),!,intersection(T1,S2,T).
   intersection([_|T],S2,S):-intersection(T,S2,S).
 
   delete_all(_,[],[]).
   delete_all(X,[X|L],L1):-delete_all(X,L,L1).
   delete_all(X,[Y|L],[Y|L1]):-X<>Y,delete_all(X,L,L1).
 
   list_set([],[]).
   list_set([H|T],[H|T1]):-delete_all(H,T,T2),list_set(T2,T1).
 
   example(T1,T2,T3,Res):-union(T1,T2,H),union(H,T3,Res).
 
goal
   write("vvedite A "),readterm(list,List1),
   write("vvedite B "),readterm(list,List2),
   write("vvedite C "),readterm(list,List3),
   list_set(List1,T1), list_set(List2,T2), list_set(List3,T3),
   example(T1,T2,T3,Res), write("A: ",T1), write(" B: ",T2),
   write(" C: ",T3), write(" result: ",Res).