I think we have a consensus that we should do *something* but unless I am
very much mistaken, the suggestion from Vincent Delecroix and Nils Bruin
that we make a symbolic function has advantages.
I was looking at Nils's code, but I have to confess that I don't understand
that code. Actually, I wasn't able to get the following to work, but I have
a feeling that I am making a minor and stupid mistake with the syntax.
################
from sage.symbolic.function import SymbolicFunction
class nth_root(SymbolicFunction):
def __init__(self):
SymbolicFunction.__init__(self, 'nth_root', nargs=2)
def _evalf_(self, n, x, parent=None):
return parent(x).nth_root(n)
plot( nth_root( x, 3), -5, 5 )
################
Maybe someone here could explain exactly what the distinction is or what
the pros/cons are for my approach versus Nils's? I have no idea.
I have also posted this on Sage-Edu, but perhaps all future replies should
be restricted to Sage-Devel and not Sage-Edu?
---Greg
On Wednesday, June 25, 2014 1:10:06 AM UTC-4, Gregory Bard wrote:
>
> As Vincent and Niles have brought up, there might be advantages to it
> being a symbolic function. How does one actually go about making that
> happen? Is this an intrusive change, or an easy one? I really have no
> idea...
> ---Greg
>
>
> On Sun, Jun 22, 2014 at 5:00 PM, Vincent Delecroix
> <20100.delecr...@gmail.com> wrote:
> > As Niles already said it would be better to have it as a symbolic
> function
> >
> > sage: f(x) = real_nth_root(x, 5)
> > sage: f
> > x |--> real_nth_root(x,5)
> >
> > 2014-06-22 22:36 UTC+02:00, Gregory Bard <gregory.bard1...@gmail.com>:
> >> Yes, that is reasonable. Let us call it "real_nth_root" instead, as
> >> suggested by Nicolas Thiery. Any other requests/comments?
> >>
> >> It would be superb if this could be resolved by June 30th, when my
> >> book goes to the American Mathematical Society for publication...
> >> ---Greg
> >>
> >> On Sun, Jun 22, 2014 at 9:02 AM, William Stein <wst...@gmail.com>
> wrote:
> >>> On Sun, Jun 22, 2014 at 8:27 AM, Nicolas M. Thiery
> >>> <nicolas.thi...@u-psud.fr> wrote:
> >>>> On Fri, Jun 20, 2014 at 06:33:52PM -0700, Gregory Bard wrote:
> >>>>> It seems that the consensus on both Sage-devel and Sage-edu is to go
> >>>>> with some sort of nth_real_root function. I propose the following,
> >>>>> which I have tested for evaluation, plotting, differentiation, and
> >>>>> integration. Sadly, the derivative has a Dirac delta in it, which is
> >>>>> ... perhaps unavoidable because of the vertical tangency of the
> >>>>> cuberoot function at x=0. (Naturally, we can remove the asserts once
> >>>>> testing is completed.
> >>>>> ---Greg
> >>>>>
> >>>>> def nth_real_root( x, n ):
> >>>>
> >>>> Just 2 cents of outsider feedback since I have not followed the
> >>>> discussion, and am not knowledgeable on the topic. This names
> suggests
> >>>> to me that we look at all the real roots of n (for whatever this
> >>>> means), and then take the n-th one. So maybe real_nth_root instead?
> >>>
> >>> +1
> >>>
> >>>>
> >>>> Cheers,
> >>>> Nicolas
> >>>> --
> >>>> Nicolas M. Thiéry "Isil" <nthi...@users.sf.net>
> >>>> http://Nicolas.Thiery.name/
> >>>>
> >>>> --
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> >>>
> >>>
> >>> --
> >>> William Stein
> >>> Professor of Mathematics
> >>> University of Washington
> >>> http://wstein.org
> >>>
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