1% create a list omitting all instances of Something
    2without(_, [], []).
    3without(Something, [Something|T], NT) :-
    4	without(Something, T, NT).
    5without(Something, [H|T], [H|NT]) :-
    6	Something \= H,
    7	without(Something, T, NT).
    8
    9
   10unique([],[]).
   11unique([H|T],[H|UNT]) :-
   12	without(H, T, NT),
   13	unique(NT, UNT)