Hi, Some algorithms doesn't work with empty boost::tuple. See... #include <boost/fusion/algorithm/query/find.hpp> #include <boost/tuple/tuple.hpp> #include <boost/fusion/sequence/container/vector.hpp> #include <boost/fusion/sequence/adapted/boost_tuple.hpp> #include <boost/fusion/algorithm/query/count.hpp> int main() { { boost::fusion::vector<> v; boost::fusion::begin(v); boost::fusion::find<int>(v); boost::fusion::count(v, 1); } { boost::tuples::tuple<> t; boost::fusion::begin(t); //boost::fusion::count(t, 1); // doesn't compile. //boost::fusion::find<int>(t);// doesn't compile. } } (tested on msvc-8.0 and gcc3.4) I don't know why; errors are very complicated :-( Regards, -- Shunsuke Sogame