conversion in multivariate polynomial ring fails

[dkrenn]

Trying to "group" the coefficients like

sage: P.<a, b, n> = QQ[]
sage: N = PolynomialRing(QQ, 'n')
sage: AB = PolynomialRing(N, 'a, b')
sage: AB(a*n + a*n^2)

fails with

TypeError: not a constant polynomial

but the result should be

(n + n^2)*a

As an interesting side note, the Laurent polynomial ring can do it:

sage: L = LaurentPolynomialRing(QQ, 'a, b, n')
sage: LN = LaurentPolynomialRing(QQ, 'n')
sage: LAB = LaurentPolynomialRing(LN, 'a, b')
sage: LAB(L(a*n + a*n^2))
(n + n^2)*a

The Laurent polynomial ring can do this since #21855. And #22333 is about reusing this code, so there is a good chance that #22333 fixes this as well.

Depends on #22333

Component: algebra

Issue created by migration from https://trac.sagemath.org/ticket/27255

[jdemeyer]

comment:2

This might be fixed by #25558 (which is work in progress).

[embray]

comment:3

Ticket retargeted after milestone closed (if you don't believe this ticket is appropriate for the Sage 8.8 release please retarget manually)

[embray]

comment:4

As the Sage-8.8 release milestone is pending, we should delete the sage-8.8 milestone for tickets that are not actively being worked on or that still require significant work to move forward. If you feel that this ticket should be included in the next Sage release at the soonest please set its milestone to the next release milestone (sage-8.9).

[dkrenn]

Bug still in 10.0