quo_rem fails for multivariate polynomial rings over function fields

[bhutz]

The quo_rem function fails for multivariate polynomial rings over function fields. This seems related to change #17033.

R.<c>=FunctionField(QQ)
S.<x,y>=R[]
f=x^4*y + 2*c*x^2*y^3 - x*y^4 + (c^2 + c)*y^5
g=x^2*y - x*y^2 + c*y^3
f.quo_rem(g)

CC: @bhutz

Component: algebraic geometry

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/17536

[bhutz]

comment:1

In working on #17535, I see that the failed example I list actually works with 6.5.beta3.
Perhaps this has already been fixed somewhere.

[tscrim]

comment:3

Do we want to add a doctest to prevent a regression since we don't know exactly what fixed this?

[bhutz]

comment:4

I wish I would have put what the failure was...

Looking at the code it does nothing put pass the input straight to singular and return the output from singular. Maybe the issue was the conversion of the singular output back to Sage or maybe it was issue with the Singular computation. I'm not sure at this point.

I don't think we need another specific test for this as it is tested implicitly in some of the schememorphism_polynomial functionality (for example in dynatomic_polynomial as well as in homogenize/dehomogenize). That is how I found the issue in the first place.

[tscrim]

comment:5

Okay. Then we can close as works-for-me.

[tscrim]

Reviewer: Travis Scrimshaw