I submitted bug 3114 (https://svn.boost.org/trac/boost/ticket/3114) with a preliminary patch to implement my feature request several days ago, and have not yet received a response. I believe that this feature would make Boost.Parameter much more useful for certain use cases, especially in libraries such as Boost.Graph where the defaults for named parameters may use templates that cannot be instantiated or do not include required members in some cases when users specify explicit arguments to a function. I made sure not to change the interface for existing default handlers by requiring a special tag to enable the new interface on a handler-by-handler basis. Could I please have the patch examined, generalized to more platforms, and possibly applied? Thank you. -- Jeremiah Willcock