On Mon, Sep 15, 2008 at 10:25 PM, Waldek Hebisch wrote: > > Bill Page wrote: >> Supoose I say: please consider the domain RomainNumeral. >> You can use >> >> )show RomanNumeral >> >> and discover what it exports. Maybe I would like to "extend" this >> list of exports to include new functions such as 'five', 'ten', 'fifty', >> 'hundred' etc. It seems to me that I should be able to do this >> without looking at the source code for RomanNumeral. This is >> exactly what you *can* do with Aldor's extend. The only reason >> you cannot do it some other way is because you cannot determine >> exactly the category to which RomanNumeral belongs. >> > > I think you misunderstood how Aldor extend works: when you extend > D you effectively change category to which D belong.
I think I do understand how Aldor extend works. 'extend' is an operation with some input and some result. When I *extend* D I specifically intend to change D. There is an "old D" before the extend operation, and a "new D" after the extend. Yes, "new D" belongs to some new category. > In Aldor you _can_ not change category after it is defined (extend > is limited to ordinary domains). I am not sure what you mean by "change category". Certainly I can change which domains belong to a given category. Perhaps you mean that I cannot change which operations a category exports? That is true but it is not something that I am discussing here. > So in Aldor you can extend D only because you _can not_ determine > exactly the category to which D belong -- ??? Every domain belongs to at least one category - even if it is anonymous (not given a name). > if you have Cat(D) in hand and you extend D than > either Cat(D) will be out of date The old value of Cat(D) will be out of date. If I use Cat(D) after using extend then Cat(D) will evaluate to some new category. > or you need to also extend Cat(D). I do not understand what you mean by "extend Cat(D)". All that is necessary is to evaluate it again in the new context. > IMHO either will break a lot in Aldor design. > Actually I was not proposing this for Aldor since Aldor already has extend, although I do not see any problem with doing so. My intention was to propose a mechanism by which something equivalent to Aldor's extend could be added to Spad. Regards, Bill Page. --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
