%query: sublist(o,i). append([],Ys,Ys). append([X|Xs],Ys,[X|Zs]) :- append(Xs,Ys,Zs). sublist(X,Y) :- append(P,_,Y), append(_,X,P). /*TWDESC The sublist/2 relation */ /*TWDEMO selected_norms([listlength]). */