Power set: Difference between revisions

=={{header|Logtalk}}==

<lang logtalk>:- object(set).

:- public(powerset/2).

powerset(Set, PowerSet) :-

reverse(Set, RSet),

powerset_1(RSet, [[]], PowerSet).

powerset_1([], PowerSet, PowerSet).

powerset_1([X| Xs], Yss0, Yss) :-

powerset_2(Yss0, X, Yss1),

powerset_1(Xs, Yss1, Yss).

powerset_2([], _, []).

powerset_2([Zs| Zss], X, [Zs, [X| Zs]| Yss]) :-

powerset_2(Zss, X, Yss).

reverse(List, Reversed) :-

reverse(List, [], Reversed).

reverse([], Reversed, Reversed).

reverse([Head| Tail], List, Reversed) :-

reverse(Tail, [Head| List], Reversed).

:- end_object.</lang>

Usage example:

<lang logtalk>| ?- set::powerset([1, 2, 3, 4], PowerSet).

PowerSet = [[],[1],[2],[1,2],[3],[1,3],[2,3],[1,2,3],[4],[1,4],[2,4],[1,2,4],[3,4],[1,3,4],[2,3,4],[1,2,3,4]]

yes</lang>