Programmation déclarative - Q4A - 06/2012

drop(L1, N, L2) :-
    drop(L1, N, L2, 1).

drop([], _, [], _).

drop([_|T], N, L2, N) :-
    drop(T, N, L2, 1).

drop([H|T], N, L2, I) :-
    I < N,
    J is I+1,
    drop(T, N, Tmp, J),
    append([H], Tmp, L2).

drop([H|T], N, L2, I) :-
    I > N,
    J is I+1,
    drop(T, N, Tmp, J),
    append([H], Tmp, L2).