boost 1.35 (boost::mpl::vector) models a front extensible sequence. of course this does not make sense, because inserting at front implies n operations, where the docu states it takes only constant compile time. boost 1.36 (boost::mpl::vector) so an compile time assertion tells, that push_front is not supported for vectors. (docu dont states so) boost 1.35 (boost::mpl::list ) is a front and back extensible sequence, so push_front and push_back are supported as for std::list (that ok). boost 1.36 (boost::mpl::list) is no longer back extensible, because a compile time assertion tells, that the push_back is no longer supported for lists. maybe its planned to change the implementation to a recursive list, then inserting at back, will take O(n), but a list must support push_back. please fix that. docu states, a list is front and back extensible (inconsitent to assertion). mfg, ingo.