David Abrahams wrote:
template <class OuterSequence, InnerSequence> struct includes : boost::is_same< typename mpl::find_if< InnerSequence , mpl::not_< mpl::contains<OuterSequence, _1> > >::type , typename mpl::end<SubSequence>::type > {};
Okay, thanks very much. This works for me, and I even pretty much understand it :-). Unfortunately, I can't make the leap from this to what I really want, which is to provide a predicate to contains for determining whether two types are the same. I think I need to do something like this, and I apologize in advance for what will probably strike you as appalling: // returns whether Seq1 includes each of the elements in Seq2. // Pred defines whether 2 types are the same. template<typename Seq1, // the putative superset typename Seq2, // the putative subset typename Pred> // whether T1 from Seq1 == T2 from Seq2 struct includes_if : boost::is_same< typename find_if< Seq2, not_< is_same< find_if<Seq1, Pred::apply<_1 from outer find_if, _1 from inner find_if> > typename end<Seq1>::type > >::type, typename end<Seq2>::type
{}; I don't know how to refer to the current elements of the two calls to find_if, and I don't know whether it's a syntax issue or if I'm just approaching this incorrectly. Help? Thanks, Scott