Combinations of multiple lists - Prolog

Question

I need to find the combinations in a list of lists. For example, give the following list,

List = [[1, 2], [1, 2, 3]]

These should be the ou

Answer 1

A twist in @false's approach:

%list_comb( ++LL, -Ess)
list_comb( LL, Ess):-
    is_list( LL),
    maplist( is_list, LL),
    findall( Es, maplist( member, Es, LL), Ess).

Testing:

41 ?- list_comb( [[1,2],[1],[1]], X).
X = [[1, 1, 1], [2, 1, 1]].

42 ?- list_comb( [[1,2],[1],[1,2,3]], X).
X = [[1, 1, 1], [1, 1, 2], [1, 1, 3], [2, 1, 1], [2, 1, 2], [2, 1, 3]].

43 ?- list_comb( [[1,2],[],[1,2,3]], X).
X = [].

44 ?- list_comb( [[1,2],t,[1,2,3]], X).
false.

45 ?- list_comb( t, X).
false.