How do I find the longest list in a list of lists?

Question

I have a list of lists, and I need to find the longest one of them. If there are more than one with the same length it\'s the same which it returns. Thanks.

Answer 1

% Correct again.

longest(LL,LX) :-
        findmax(Len,(append(_,[L|_],LL),length(L,Len)),MaxLen),
        append(_,[LX|_],LL),
        length(LX,MaxLen).

findmax(V,P,Max) :-
        findall(V,P,L),
        max(L,Max).

max([N],N) :- !.
max([N|R],Max) :-
        max(R,Max2),
        max3(N,Max2,Max).

max3(N,Max2,N) :- N > Max2,!.
max3(N,Max2,Max2).