Hi there, next metaprogramming problem. Is it possible to extract a tagged type from a map? namespace fields { struct _id_; struct _name_; struct _birthday_; struct _address_id_; } namespace tags { struct _primary_key_; struct _foreign_key_; struct _value_; } typedef fusion::map< fusion::vector< fields::_id_ , std::string, tags::_primary_key_ > , fusion::vector< fields::_name_ , std::string, tags::_value_ > , fusion::vector< fields::_birthday_ , std::string, tags::_value_ > , fusion::vector< fields::_address_id_, std::string, tags::_foreign_key_ > > table_type; int main() { /// how to get the primary key type vector } I was looking at fusion's filter_view but that is only available for non-metaprogramming. Any ideas? Christian