Hi! Even for the more correct typedef I get lost: typedef bm::multi_index_container <data_t, bm::indexed_by <bm::sequenced<>, bm::ordered_unique <bm::const_mem_fun<data_t, std::string const &, &data_t::get<0> > > > > storage_t; this fails due to probably disallowed standard conversions (or a cobfused gcc-4.0.3): Cleaned up error message: '&boost::tuples::cons<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::tuples::cons<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::tuples::null_type> >::get' is not a valid template argument for type 'const std::string& (boost::tuples::tuple<string, string, ...>::*)()const' because it is of type 'const string& (boost::tuples::cons<string, boost::tuples::cons<string, boost::tuples::null_type> >::*)()const' note: standard conversions are not allowed in this context