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 output,

Comb = [[1,1],[1,2],[1,3],[2,1],[2,2],[2,3]]

Another example:

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

Comb = [[1,1,1],[1,1,2],[1,1,3],[1,2,1],[1,2,2],[1,2,3]….etc]

I know how to do it for a list with two sublists but it needs to work for any number of sublists.

I’m new to prolog, please help.

Answer 1

try([],[]).
try([L|Ls],[M|Ms]):-
    member(M,L),
    try(Ls,Ms).

all(L,All) :- findall(M, try(L,M), All).    

try returns one list composed of elements of the sublists of the first argument. all finds all such lists.