[Boost-users] [boost::variant] does 'incomplete<T>' still exist?

hi. i read a tutorial at http://electra.lbl.gov/stuff/variant/doc/tutorial.html which says a boost::variant type can be declared with an incomplete type in its typelist by using incomplete<T>. i'm using boost 1.33.1 & i can't find incomplete<T> anywhere. does it still exist? the tutorial is dated '14 February 2003'. can variants use incomplete types? i want to have a variant represent a type which has a variant member. can i do that? i'm working on a kind of envelope/letter idiom for dispatching operations on values. cheers jono