Re: [GiNaC-devel] [GiNaC-list] Issue with derivative of "abs"

Hello! 17.06.2020, 00:30, "Vladimir V. Kisil" <v.kisil@leeds.ac.uk>:

       Dear Developers,

        To support Pierangelo's suggestion from here:

https://www.ginac.de/pipermail/ginac-list/2020-June/002301.html

I'm afraid the patch is wrong. abs(x) is not differentiable at x = 0, and there's no way to "fix" that. x*abs(x) is differentiable at x = 0 (with derivative being zero). Unfortunately GiNaC can't automatically compute that. For now one can manually substitute x^2 -> abs(x)^2 which will reduce x^2/abs(x) + abs(x) to 2*abs(x) Best regards,       Alexey