[Boost-users] [fusion][docs] is_sequence *isnt* true for std::vector ?

Hi all. I've been looking thru the documentation at boost.org to try to understand Boost.Spirit.  That documentation refers to Boost.Fusion, and at http://www.boost.org/doc/libs/1_45_0/libs/fusion/doc/html/fusion/support/is_... there's something I think needs clarification (at the very least), or is mistaken.  The first line of the last paragraph of that page contains the following line:BOOST_MPL_ASSERT_NOT(( traits::is_sequence< std::vector<int> > )); I don't understand.  How can a std::vector *not* be considered a sequence? Martin