The html page fragment: http://steven_watanabe.users.sourceforge.net/type_erasure/libs/type_erasure/... contains a link, CopyConstructible, which sends my browser to: http://steven_watanabe.users.sourceforge.net/trunk/doc/html/CopyConstructibl... which is not there. Maybe it should go to: http://www.boost.org/doc/libs/1_50_0/libs/utility/CopyConstructible.html or something similar? Also, why couldn't there be any number of arguments, something like: template<typename Map, class... U> explicit any(const static_binding< Map > & binding, U &&... arg); I think this would then allow any constructor to be used for the contained type. Of course then the requirement would have to be modified to be something like: The underlying type has a constructor accepting arguments, U&... arg. -regards, Larry