report/src/hs.pl

   1 isHittingSetTree(_, leaf).
   2 isHittingSetTree(_, node([], [])).
   3 isHittingSetTree(VisitedLabels, node([CurLabel|Labels], [CurChild|Children])) :-
   4         not(member(CurLabel, VisitedLabels)),
   5         append(VisitedLabels, [CurChild], UpdatedVisitedLabels),
   6         isHSTree(UpdatedVisitedLabels, CurChild),
   7         isHSTree(VisitedLabels, node(Labels, Children)).