Hi Everyone, I'm not sure whether this is more appropriate for the users list or the developers list so I sent the email to both. I'm using Boost's SVN Trunk r66609 and I tried to compile the (attached) file to follow the pattern described by the Boost.Parameter tutorial (http://www.boost.org/doc/libs/1_44_0/libs/parameter/doc/html/index.html#para...) but unfortunately I get an error deep in the preprocessor code that Boost.Parameter uses. What I'm trying to do is to make a template class support parameterized constructors, and only have optional parameters and no required ones. The idea is: template <class Tag> struct base; template <class Tag> struct derived : base<Tag> { BOOST_PARAMETER_CONSTRUCTOR(...); }; Has anybody been able to make this work? Thanks and I definitely hope to hear from you soon. PS. I am also going to file this as a bug in Boost.Parameter so that it doesn't get lost in the mailing list churn. ;) -- Dean Michael Berris deanberris.com