Larry Evans wrote:
[...] I very much sympathize with you; however, I have no answers :( I went through the same confusion with my managed_ptr's nested ownership template class. It was discussed here:
http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&selm=1044dnuf7ojhpc0%40corp.supernews.com [...]
It looks like Gabriel gives the best answer in that thread. My understanding is now that non-deduced contexts occur partly because specializations may be defined after instantiations of a given template class. And this is why simply adding another operator won't work. One way to eliminate non-deducibility would be to require that all specializations be defined before any template of that type is instantiated. However, this would make certain types of code impossible. Another solution would be say that argument deduction proceeds with only the specializations visible at the point of instantiation. However, that would probably be confusing. Another solution would be to have instantiation occur in a separate pass, after all possible specializations have been seen. Then it seems that it should be possible to deduce many contexts that are only non-deducible because of possible specializations. But people are likely to say that that is too expensive for the benefit gained. Dave