Enrique, you are right, that doesn't come from the interface, but directely from Singular. Above, I took the wrong ordering. Here the correction:
sage: R.<x,y>=PolynomialRing(QQ,order='neglex') sage: R._singular_init_() polynomial ring, over a field, local ordering // coefficients: QQ // number of vars : 2 // block 1 : ordering ls // : names x y // block 2 : ordering C SINGULAR / Development A Computer Algebra System for Polynomial Computations / version 4.1 .1 0< by: W. Decker, G.-M. Greuel, G. Pfister, H. Schoenemann \ Feb 2018 FB Mathematik der Universitaet, D-67653 Kaiserslautern \ > ring r = 0,(x, y),ls; > poly f,g = 1+x, x^2; > ideal I = (g); > reduce(f,I); 1 BTW: The ticket you mentioned doesn't seem to adress that problem properly. The example which Simon inserted is now working. Therefore the ticket just consists of a doctest for that (I guess that has been made on the Sage Days in Zaragozza). The only reason that it isn't closed has been a merge confict, which has disappeared in the meantime. On Thursday, April 9, 2020 at 9:28:07 AM UTC+2, Enrique Artal wrote: > > HI, > I think it is related with ticket #17638 > <https://trac.sagemath.org/ticket/17638>. There is a mathematical origin > in this situation. When considering a non local ordering, one is working in > a localized ideal, where any polynomial whose leading term is a non-zero > constant is invertible. Singular works silently in this new ring without > explicit declaration. I think that for Sage, a new structure should be > constructed, but I do not know how. Best, Enrique. > > El lunes, 6 de abril de 2020, 9:46:26 (UTC+2), Yang Zhou escribió: >> >> Hi, >> >> I am trying to truncate a multi-variable polynomial by moding out higher >> order term and found >> the following (simplified) example. I am wondering if it is a bug. >> >> >> *Reproducible Example: * >> >>> R.<x,y> = PolynomialRing(QQ, order='negdeglex') >>> >> f = 1 + x >>> I = R.ideal(x^2) >>> f.mod(I) >>> >> *Expected output:* >> >>> 1 + x >>> >> *Actual output:* >> >>> 1 >>> >> >> >> *Note: * >> The actual output will be 1+x when I omit the "order='negdeglex" >> parameter. >> >> *SageMath version:* >> SageMath version 9.0, Release Date: 2020-01-01 >> >> *Operating system:* >> OS: Ubuntu 19.10 x86_64 >> Kernel: 5.3.0-45-generic >> >> Best regards, >> Yang >> > -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sage-devel/2d4fa6e0-d819-4c9b-bd19-c73910096779%40googlegroups.com.