Opened 3 years ago

Closed 3 years ago

#29469 closed enhancement (fixed)

Have method is_unit of QuotientRingElement and PolynomialQuotientRingElement return True in more cases

Reported by: soehms Owned by:
Priority: major Milestone: sage-9.2
Component: commutative algebra Keywords: quotient ring, polynomial, is_unit, invert
Cc: Merged in:
Authors: Sebastian Oehms Reviewers: Travis Scrimshaw
Report Upstream: N/A Work issues:
Branch: 0beccc8 (Commits, GitHub, GitLab) Commit: 0beccc8a6aa2d4074241137f6d264a9d1d9f98bb
Dependencies: Stopgaps:

Status badges


In the case of both classes there are examples where is_unit raises a NotImplementedError even though the answer True could easily be given:

sage: P.<x,y> = QQ[]
sage: Q = P.quo([1-x*y])
sage: Q.inject_variables()
Defining xbar, ybar
sage: ybar.is_unit()
Traceback (most recent call last):


sage: ~ybar


sage: Z16x.<x> = Integers(16)[]
sage: S.<y> =  Z16x.quotient(x^2 + x + 1)
sage: S(3).is_unit()
Traceback (most recent call last):
NotImplementedError: The base ring (=Ring of integers modulo 16) is not a field


sage: Z16x(3).is_unit()

This will be improved here. Se also this sage-devel thread.

Change History (7)

comment:1 Changed 3 years ago by soehms

Branch: u/soehms/is_unit_quotient_ring_elemnts_29469

comment:2 Changed 3 years ago by soehms

Authors: Sebastian Oehms
Commit: 85afe0a2ba045263981814a4f913dd2ff82fd9ba
Status: newneeds_review

New commits:

85afe0a29469: initial

comment:3 Changed 3 years ago by git

Commit: 85afe0a2ba045263981814a4f913dd2ff82fd9ba0beccc8a6aa2d4074241137f6d264a9d1d9f98bb

Branch pushed to git repo; I updated commit sha1. New commits:

0beccc829469: fix doctest in matrix0

comment:4 Changed 3 years ago by mkoeppe

Milestone: sage-9.1sage-9.2

Moving tickets to milestone sage-9.2 based on a review of last modification date, branch status, and severity.

comment:5 Changed 3 years ago by tscrim

Reviewers: Travis Scrimshaw
Status: needs_reviewpositive_review


comment:6 Changed 3 years ago by soehms


comment:7 Changed 3 years ago by vbraun

Branch: u/soehms/is_unit_quotient_ring_elemnts_294690beccc8a6aa2d4074241137f6d264a9d1d9f98bb
Resolution: fixed
Status: positive_reviewclosed
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