Hello Newsgroup, I think that in "libs/tuple/doc/tuple_advanced_interface.html" there is a mistake: "The template access_traits defines three type functions. Let T be a type of an element in a tuple: 1. access_traits<T>::type maps T to the return type ... " There is no such member "::type". ¿Maybe it is "::non_const_type"? Best regards, Raúl.