Hi! At present I learn what it means not to have strong typing: I play around with boost::any. A new and healing experience. Thank You, Bjarne, for insisting on strong typing for C++ ;-) Never made so much use of the debugger ... So now I found out that any_cast does not promote types that may be promoted like for int->double conversions. Any workaround in the lib I overlooked or is this the time for my_any_cast<T>(boost::any const &)? Markus -- Compile time analytic differentiation? Yes, at http://daixtrose.sourceforge.net/