I omited to show the definition of those templates TreeImplBase.They would have the map as a private member,as protected members, functions to insert instances in the map, called by the ctors of derived templates. I will look at boost::fusion thanks, ----- Original Message ----- From: "Ovanes Markarian" To: boost-users@lists.boost.org Subject: Re: [Boost-users] Multiple templates singletons Date: Thu, 24 Jan 2008 00:02:01 +0100 Hello! I have a question to this construct: template class TreeImplBase; Each specialization of these holds a static std::map< boost::tuple, const TreeImplBase* >; which contains the list of the derived template classes. How can you instantiate a pointer to the class temlate? Class template is an incomplete type. You will not be able to specify a pointer to it. I think you should use boost::fusion inplace. This lib, offers a compile time map (if you map the same time to an instance of it, use a fusion set), which can map a type to an instance. This is what you need. http://spirit.sourceforge.net/dl_more/fusion_v2/libs/fusion/doc/html/fusion/... http://spirit.sourceforge.net/dl_more/fusion_v2/libs/fusion/doc/html/fusion/... Any comments are appreciated, Perhaps this is a known design pattern, perhaps there is an easier way of doing this, perhaps there is a boost library which helps with this, Good Luck, Ovanes _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users