christophe henry wrote:

Hi Eric,

...

You could use reverse_fold instead of reversing the whole list after the transform. Or you could use reverse_fold_tree to get the vector and then pop the attribute_ off the front. That's probably fastest and simplest.

I must be doing something wrong (I suppose it has something to do with my second "when") because parsing: attributes_ << int() << bool() << string()

With the above given grammar gives me a mpl::vector<string,bool,int>, which is normal, but if I simply and naively replace fold by reverse_fold, all I get is a mpl::vector<int>.

Am I missing something obvious?

Please see below: #include <string> #include <boost/mpl/vector.hpp> #include <boost/mpl/push_back.hpp> #include <boost/mpl/pop_front.hpp> #include <boost/proto/core.hpp> #include <boost/proto/transform.hpp> namespace proto = boost::proto; namespace mpl = boost::mpl; using proto::_; namespace My { struct my_tag {}; template<class X = proto::is_proto_expr> struct attribute_ { BOOST_PROTO_BASIC_EXTENDS( proto::terminal<my_tag>::type , attribute_ , proto::default_domain ) }; attribute_<> const attribute = {{}}; struct BuildAttributes : proto::make< mpl::pop_front< proto::fold_tree< _ , mpl::vector0<>() , mpl::push_back<proto::_state, proto::_value>() > > > {}; } int main() { mpl::vector3<int, std::string, bool> x = My::BuildAttributes()( My::attribute << int() << std::string() << bool() ); } HTH, -- Eric Niebler BoostPro Computing http://www.boostpro.com