> One can hardly say that these two domains differ only in the representation of > their elements.
Well, what about Dom1, Dom2, and DomS on http://axiom-wiki.newsynthesis.org/SandboxIsomorphic ? They are in some sense isomorphic. At least that is my intention. > So, I should have been more precise: > There are categories (like for example UPOLYC), where it makes sense to have > for any two domains A and B of that category. > A has CoercibleTo B and B has CoercibleTo A. I don't think you can state that for any two A and B. As in my previous example, I can certainly give a domain that doesn't work well. How do I map a domain with 3 variables into one with 2 variables. And back? Do you assume that mapping back and forth is the identity? > However, it seems that this cannot be expressed in SPAD or Aldor. To me it seems that you still have not made the task fully precise. > Somehow, it might be nice to have the possibility to say > with CoercibleTo B where B has SomeCategory See http://axiom-wiki.newsynthesis.org/SandboxIsomorphic . define IsIsomorphicTo(C: Category, T: C): Category == with { coerce: % -> T } If you want to remove the C from above then that is something that Gaby and Stephen talked about at the Aldor & Axiom Workshop (http://axiom-wiki.newsynthesis.org/uploads/WattDosReis-MultisortedAlgebras.pdf) and which indeed is not yet in Aldor. But I somehow believe that even if it were possible, it wouldn't help you in what you are thinking about. Can you be even more explicit. I am asking for it, because besides the categories one also has to think of how one actually could implement the respective coercion functions. Ralf --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "FriCAS - computer algebra system" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/fricas-devel?hl=en -~----------~----~----~----~------~----~------~--~---
