Opened 5 years ago
Last modified 20 months ago
#15411 new defect
is_nilpotent on multivariate power series gives baloney
Reported by: | darij | Owned by: | |
---|---|---|---|
Priority: | minor | Milestone: | sage-6.4 |
Component: | algebra | Keywords: | multivariate power series, rings, nilpotent |
Cc: | hivert, chapoton, nthiery, jakobkroeker | Merged in: | |
Authors: | Reviewers: | ||
Report Upstream: | N/A | Work issues: | |
Branch: | Commit: | ||
Dependencies: | #14814 | Stopgaps: |
Description
From sage/rings/multi_power_series_ring_element.py
(I added the warning/todo in #14814):
def is_nilpotent(self): """ Return ``True`` if ``self`` is nilpotent. This occurs if - ``self`` has finite precision and positive valuation, or - ``self`` is constant and nilpotent in base ring. Otherwise, return ``False``. .. WARNING:: This is so far just a sufficient condition, so don't trust a ``False`` output to be legit! .. TODO:: What should we do about this method? Is nilpotency of a power series even decidable (assuming a nilpotency oracle in the base ring)? And I am not sure that returning ``True`` just because the series has finite precision and zero constant term is a good idea.
How shall we fix this?
Notice that is_nilpotent
is NotImplemented? for univariate power series. Maybe we can just follow that example -- or does something rely on this method?
Change History (4)
comment:1 Changed 5 years ago by
- Milestone changed from sage-6.1 to sage-6.2
comment:2 Changed 4 years ago by
- Milestone changed from sage-6.2 to sage-6.3
comment:3 Changed 4 years ago by
- Milestone changed from sage-6.3 to sage-6.4
comment:4 Changed 20 months ago by
- Cc jakobkroeker added
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