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:  sage9.2 
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: 
Description
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([1x*y]) sage: Q.inject_variables() Defining xbar, ybar sage: ybar.is_unit() Traceback (most recent call last): ... NotImplementedError:
but:
sage: ~ybar xbar
or:
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
but:
sage: Z16x(3).is_unit() True
This will be improved here. Se also this sagedevel thread.
Change History (7)
comment:1 Changed 3 years ago by
Branch:  → u/soehms/is_unit_quotient_ring_elemnts_29469 

comment:2 Changed 3 years ago by
Authors:  → Sebastian Oehms 

Commit:  → 85afe0a2ba045263981814a4f913dd2ff82fd9ba 
Status:  new → needs_review 
comment:3 Changed 3 years ago by
Commit:  85afe0a2ba045263981814a4f913dd2ff82fd9ba → 0beccc8a6aa2d4074241137f6d264a9d1d9f98bb 

Branch pushed to git repo; I updated commit sha1. New commits:
0beccc8  29469: fix doctest in matrix0

comment:4 Changed 3 years ago by
Milestone:  sage9.1 → sage9.2 

Moving tickets to milestone sage9.2 based on a review of last modification date, branch status, and severity.
comment:5 Changed 3 years ago by
Reviewers:  → Travis Scrimshaw 

Status:  needs_review → positive_review 
LGTM.
comment:7 Changed 3 years ago by
Branch:  u/soehms/is_unit_quotient_ring_elemnts_29469 → 0beccc8a6aa2d4074241137f6d264a9d1d9f98bb 

Resolution:  → fixed 
Status:  positive_review → closed 
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New commits:
29469: initial