Hi Dima, 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.
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.
