[CLN-list] [GiNaC-devel] evalf() on cube roots

[Jan Rheinländer]

Hi,

maybe I should explain why I am considering this. My background is in
engineering (mechanical) and here complex numbers are considered as
extremely exotic. For me as an engineer the idea that the cubic root of
-1 should be complex sounds absurd. Most engineers probably have the
opinion that -1 has only one cubic root anyway!

I am using GiNaC for programming a tool that I use in engineering.

Am 21.09.19 um 18:00 schrieb Richard B. Kreckel:
> Hi,
>
> This is a CLN topic. Let's take this thread to cln-list.
>
> Your proposal seems to suggest that CLN pick another branch cut for
> roots if a certain global flag is set.
>
> I'm sceptical about introducing global flags which control the
> computation in a way that results in very different numerical results -
> it looks like calling for problems. Admitted, there are global flags
> (cl_inhibit_floating_point_underflow and those dealing with I/O), and
> rounding control is well known from IEEE754. But returning a complex
> number which is far away from the conventional result in the complex
> plane is a different thing. I'm not aware of any such flag in another
> system; is there one?
>
> I'ld like to hear what others think.
>
>   -richy.