On Mar 21, 2007, at 1:38 AM, William Stein wrote:
> That said, we simply can't require > (*) "a == b ==> hash(a) == hash(b)" > in SAGE, because mathematics is simply too complicated for this sort > of rule. So what is done in SAGE is to _attempt_ to satisfy (*) > when it > is reasonably easy to do so, but use judgment and not go overboard. > E.g., > sage: hash(Mod(2,7)) > 2 > I.e., we get 2. That's better than some weird random hash that also > involves the moduli, but it's of course not right from the Python > point > of view, since 9 == Mod(2,7). Long ago before we ever had this > discussion about hashing, I think Mod(2,7) was the hash of some > combination of 2 and 7. The only way we could "fix" this problem for good is to abandon using the "==" operator for "SAGE equality", and implement SAGE equality as a new method attached to each object. Then we could follow python rules for "==" and our rules for everything else, and all SAGE code would become completely unreadable (and for that matter unwriteable). So I think what you've said above is perfectly reasonable, and we just have to live with it. David --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://sage.scipy.org/sage/ and http://modular.math.washington.edu/sage/ -~----------~----~----~----~------~----~------~--~---
