[Boost-users] [traits, fusion, mpl] Basic question about is_base_of and template ancestors

Hello List! I have an issue understanding how to combine CRTP with the "is_base_of" trait when iterating over a fusion vector. I have tried to illustrate my problem in the test program below. The idea is to first "do stuff" to all instances of types derived from A and then "do stuff" to the ones derived from B. I just don't know what to write instead of "WHAT_GOES_HERE?" below. I have tried to use "::boost::mpl::_" in different ways to get the "type" type of B but failed miserably every time. I'm also curious about how to negate the "is_base_of" predicate. I tried using "not_<>" but that didn't work at all... Very thankful for any and all help! // Magnus P.S. Sorry if this question has been answered already! I have looked at the documentation, searched archives and the web but couldn't find the solution. Maybe I searched using the wrong keywords... #include #include #include #include #include #include #include struct dostuff { template<typename T> void operator()(T const & x) const { // Do stuff here! } }; template<class D> struct A { }; template struct B { typedef T type; }; struct derived_from_A : public A { }; struct derived_from_B : public B { }; typedef ::boost::mpl::vector::type typelist_type; ::boost::fusion::result_of::as_set::type typeset_; int main(int argc, char ** argv) { dostuff ds; // This seems to be working! ::boost::fusion::for_each( ::boost::fusion::filter_if < ::boost::is_base_of, ::boost::mpl::_> > (typeset_), ds); #if(0) // Don't know how to do this! Preferably I'd like to check for inheritance from B. // If that isn't possible I'll settle for "not inheriting from A". ::boost::fusion::for_each( ::boost::fusion::filter_if < ::boost::is_base_of, ::boost::mpl::_> > (typeset_), ds); #endif }