Opened 12 years ago
Closed 10 years ago
#5367 closed defect (duplicate)
bug in composition of power series
Reported by: | AlexGhitza | Owned by: | tbd |
---|---|---|---|
Priority: | major | Milestone: | sage-duplicate/invalid/wontfix |
Component: | algebra | Keywords: | power series composition |
Cc: | Merged in: | ||
Authors: | Reviewers: | David Loeffler | |
Report Upstream: | N/A | Work issues: | |
Branch: | Commit: | ||
Dependencies: | Stopgaps: |
Description
The following returns an incorrect answer:
sage: S.<z> = QQ[[]] sage: p = 1 + O(z) sage: q = 1 + z sage: p(q) # should return O(z^0) 1
This was reported via "report a problem" from the notebook.
Change History (9)
comment:1 Changed 12 years ago by
comment:2 Changed 12 years ago by
I just came across this, which is presumably related:
sage: R.<x> = QQ[[]] sage: f = 1 + 24*x^11 + 24*x^22 + O(x^33) sage: f(x^2) 1 + 24*x^22 + 24*x^44 + O(x^86)
The answer should clearly be 1 + 24*x^{22 + 24*x}44 + O(x^{66). (This is causing some headaches in trying to sort out degeneracy maps for modular forms.) }
comment:4 Changed 11 years ago by
Since this is a duplicate of #3979, I think this ticket should be closed.
comment:5 in reply to: ↑ 3 Changed 10 years ago by
comment:6 Changed 10 years ago by
- Status changed from new to needs_review
I concur that this should be closed as duplicate. I'll set it to "positive review" to bring this to the attention of the release manager.
comment:7 Changed 10 years ago by
- Status changed from needs_review to positive_review
comment:8 Changed 10 years ago by
- Milestone changed from sage-4.7.1 to sage-duplicate/invalid/wontfix
comment:9 Changed 10 years ago by
- Resolution set to duplicate
- Reviewers set to David Loeffler
- Status changed from positive_review to closed
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As pointed out by Ralf Hemmecke on sage-devel, the correct behaviour is not to return 1, but rather to raise an error if q has a constant term.