1member(X, [X |Xs]).
    2member(X, [_ |Xs]):- member(X, Xs).
    3
    4list([1,2,3]).
    5
    6not_in_list(A) :-
    7    list(A), 
    8    not member(B, A). 
    9
   10
   11?- not_in_list(A).