On 18 November 2014 09:02, David Roe <roed.m...@gmail.com> wrote: > On Tue, Nov 18, 2014 at 5:57 AM, Bill Page <bill.p...@newsynthesis.org> wrote: >> >> > I think you are overly focused on trying to define a derivative that >> > reduces to the conventional derivative of non-analytic functions >> > over the reals. >> >> I've just been casually following this conversation, but I think it's >> important that the derivative of abs(x) be sign(x) not 2*sign(x) or >> 1/2*sign(x). >>
What makes it important that "the" derivative of abs(x) be sign(x)? An important point here is that there is no one single unique derivative of non-analytic functions like abs, but rather than all of their derivatives can be expressed in terms of just two. I am seriously interested in reasons for retaining the status quo. >> If you use a different function, like f.wirtinger_derivative(), then >> it doesn't matter so much. >> David >> On 18 November 2014 10:11, kcrisman <kcris...@gmail.com> wrote: > > +1 > Although I guess this would be consistent with the over all "assimilation philosophy" adopted by Sage, I am rather strongly against this in general. In my opinion it is in part what has lead to the rather confusing situation in most other computer algebra systems. I think rather that one should strive for the most general solution consistent with the mathematics. I suppose that to some extent this is conditioned by how the subject is taught. It came as a surprise to me that a solution of this problem (Wirtinger calculus or CR-calculus) was apparently "well-known" is some circles but considered only a marginal curiosity in others (if at all). > That notwithstanding, this conversation is really great to see and I hope > we get something that works for the usual cases in the original post > too! > Provided that one realizes its limitations I think the solution proposed by Vladimir V. Kisil for ginac and in more generality by Ondrej is quite good. I don't think a new name for this is desirable. Bill. -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at http://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
