[Boost-users] boost::numeric::interval - what are interval_holder and number_holder for?

Dear boost members! Perhaps the main boost developer mailing list would be the better place to ask this question, but I'll try it here first: I cannot find any references to interval_holder and number_holder, which are defined in boost/numerics/interval/interval.hpp in any other files of the boost library. Are those two structures deprecated remains of a previous boost release? (The last time I checked they were still in trunk of the svn repository.) regards Stephan