Hi there, I have a slight problem with the construction of a map with fusion::as_map on an empty view: #include <boost/fusion/sequence/class/map.hpp> #include <boost/fusion/sequence/view/filter_view.hpp> #include <boost/fusion/sequence/conversion/as_map.hpp> #include <boost/fusion/core/pair.hpp> struct drop_all {template <typename A> struct apply : boost::mpl::false_ {};}; int main() { using namespace boost::fusion; typedef map<pair<int,int>,pair<float,int>, pair<short,int> > my_map; typedef filter_view<my_map, drop_all> empty_view; typedef meta::as_map<empty_view>::type empty_map; my_map source; empty_view empty_source( source ); empty_map obj( as_map( empty_source) ); } Should I check if the view is empty before running as_map? I had a related problem, which I am right now unable to minimize. Somehow filter and transform views seem to call the meta functions with mpl::void_ and fusion::void_. Regards, Andreas Pokorny