Hi Corrado,
I think the best would be to have a reusable "(typed) argument list" structure, around which the factories can be built as free functions (or we could have a generic apply taking the argument list and a functor, so every factory will just become a different functor). Moreover, once the argument list is decoupled from the factory, it could be interoperable with fusion, enabling more freedom in how they are used.
Indeed, I agree that the best factorization is to decouple the factory applicator from the argument list. In fact, the applicator should handle a generic tuple as the argument list (with at most some custom made tuple if dependency with fusion is a problem) Now that's a major make up for the factories, though one worth doing it IMO, so the big quesion is: would you be interested in doing that yourself? Best -- Fernando Cacciola SciSoft http://fcacciola.50webs.com