On Sat, Oct 28, 2023 at 1:02 AM John H Palmieri <jhpalmier...@gmail.com> wrote:
> Yes, I noticed that, too. It also fails to provide any information about what > ``v`` should be (beyond saying that it should be a "valid object"): there is > no INPUT block. I've left a comment here: https://github.com/sagemath/sage/commit/977ace651af9b99689f7b6507f91f8b4e2588ae9#r131117132 fortunately, the author, @kwankyu is active I can't locate the ticket, but it was merged in 9.0.beta9 > > > On Friday, October 27, 2023 at 3:51:10 PM UTC-7 Dima Pasechnik wrote: >> >> By the way, the docstring of divisor() misses an example, it's >> >> def divisor(self, v, base_ring=None, check=True, reduce=True): >> r""" >> Return the divisor specified by ``v``. >> >> .. WARNING:: >> >> The coefficients of the divisor must be in the base ring >> and the terms must be reduced. If you set ``check=False`` >> and/or ``reduce=False`` it is your responsibility to pass >> a valid object ``v``. >> >> EXAMPLES:: >> >> sage: x,y,z = PolynomialRing(QQ, 3, names='x,y,z').gens() >> sage: C = Curve(y^2*z - x^3 - 17*x*z^2 + y*z^2) >> >> """ >> >> Is there an issue for this? >> >> On Sat, Oct 28, 2023 at 12:42 AM Nils Bruin <nbr...@sfu.ca> wrote: >> > >> > A canonical divisor is the divisor of any differential on C so the >> > following does the trick: >> > >> > sage: kC=C.function_field() >> > sage: kC(kC.base_field().gen(0)).differential().divisor() >> > >> > It doesn't look like we quite have computation of Riemann-Roch spaces >> > natively in sage yet, so finding effective representatives requires a >> > little more work. In the RiemannSurface code this is done using singular's >> > adjoint ideal code (or by Baker's theorem in cases where it applies). For >> > this curve the canonical class is of degree -2, so there are no effective >> > representatives in this case. >> > >> > On Friday, 27 October 2023 at 15:14:00 UTC-7 John H Palmieri wrote: >> >> >> >> If anyone here knows anything about canonical divisors and their >> >> implementation in Sage, please see >> >> https://ask.sagemath.org/question/74034/converting-algebraic-geometry-magmas-code-to-sage/. >> >> The setup: >> >> >> >> sage: P2.<x,y,z> = ProjectiveSpace(QQ, 2) >> >> sage: f = 2*x^5 - 4*x^3*y*z + x^2*y*z^2 + 2*x*y^3*z + 2*x*y^2*z^2+ y^5 >> >> sage: C = P2.curve(f) >> >> >> >> How do you get the canonical divisor for C? >> >> >> >> (I encourage you to post answers directly to ask.sagemath.org, if you're >> >> willing.) >> >> >> >> -- >> >> John >> >> >> > -- >> > You received this message because you are subscribed to the Google Groups >> > "sage-support" group. >> > To unsubscribe from this group and stop receiving emails from it, send an >> > email to sage-support...@googlegroups.com. >> > To view this discussion on the web visit >> > https://groups.google.com/d/msgid/sage-support/91b14570-b83e-4dbf-8bca-0a2eff538a50n%40googlegroups.com. > > -- > You received this message because you are subscribed to the Google Groups > "sage-support" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sage-support+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sage-support/391d8ee7-0329-4a15-bc88-4b84973389abn%40googlegroups.com. -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sage-support/CAAWYfq3o5nCfF5b4Lr1NHV4c_uN9G4SPtxBttt5tPmtqjT1FAw%40mail.gmail.com.
