Following some ideas discussed about a year ago, I've added a new boost::multi_index::key construct allowing for a very terse specification of predefined key extractors in C++17 compliant environments. For instance, given struct phonebook_entry { std::string family_name; std::string given_name; std::string phone_number()const; }; int num_calls(const phonebook_entry&); a classical definition like typedef multi_index_container< phonebook_entry, indexed_by< ordered_unique< const_mem_fun<phonebook_entry,std::string,&phonebook_entry::phone_number> >, ordered_unique< global_fun<const phonebook_entry&,int,num_calls> >, ordered_non_unique< composite_key< phonebook_entry, member<phonebook_entry,std::string,&phonebook_entry::family_name>, member<phonebook_entry,std::string,&phonebook_entry::given_name> > > > > phonebook; can now be written as typedef multi_index_container< phonebook_entry, indexed_by< ordered_unique< key<&phonebook_entry::phone_number> >, ordered_unique< key<num_calls> >, ordered_non_unique< key<&phonebook_entry::family_name,&phonebook_entry::given_name> > > > phonebook; If you have a C++17 compiler, you can play with this new feature by simply copying https://github.com/boostorg/multi_index/blob/develop/include/boost/multi_ind... into your local Boost installation. More info at https://www.boost.org/doc/libs/develop/libs/multi_index/doc/tutorial/key_ext... https://www.boost.org/doc/libs/develop/libs/multi_index/doc/reference/key_ex... Comments and suggestions, specially before Boost 1.69 ships and this becomes more or less frozen, are most welcome. Best regards, Joaquín M López Muñoz