[Boost-users] [MultiIndex] is it possible to create multi-key key-extractors?

Hi, For the following struct: struct Flower { int type; string name; std::list<string> aliases; }; I want to create a multiindexed container that indexes Flower objects by type, name, and aliases, where aliases is some iteratable collection of strings. I just don't know if it's possible to create a multi-key key-extractor for aliases. So far I've come up with the following: typedef boost::multi_index_container< Flower, indexed_by< ordered_unique< member<Flower, int, &Flower::type> >, ordered_unique< member<Flower, string, &Flower::name> >, ordered_unique< //What goes here ... ? >

FlowerMngr;

Thanks, -Mostafa