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bugs in LazySeries over non-integral domains #36154

Closed
2 tasks done
mantepse opened this issue Aug 29, 2023 · 0 comments · Fixed by #36156
Closed
2 tasks done

bugs in LazySeries over non-integral domains #36154

mantepse opened this issue Aug 29, 2023 · 0 comments · Fixed by #36156
Labels
c: algebra t: bug
Milestone
sage-10.2

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@mantepse
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Steps To Reproduce

sage: L.<z> = LazyPowerSeriesRing(Zmod(4))
sage: f = L(constant=2)
sage: f
2 + 2*z + 2*z^2 + O(z^3)
sage: 2*f
...
AssertionError: Stream_exact should only be used for non-zero streams

Expected Behavior

sage: L.<z> = LazyPowerSeriesRing(Zmod(4))
sage: f = L(constant=2)
sage: f
2 + 2*z + 2*z^2 + O(z^3)
sage: 2*f
0

Actual Behavior

There is an error.

Additional Information

No response

Environment

irrelevant

Checklist

  • I have searched the existing issues for a bug report that matches the one I want to file, without success.
  • I have read the documentation and troubleshoot guide
@mantepse mantepse mentioned this issue Aug 29, 2023
Merged
4 tasks
vbraun pushed a commit to vbraun/sage that referenced this issue Sep 1, 2023
09dd403 
sagemathgh-36156: detect the zero series when returning an exact stream
    
By definition, an exact stream is non-zero.  Therefore, we have to check
before constructing one.

Fixes sagemath#36154

### 📝 Checklist

- [X] The title is concise, informative, and self-explanatory.
- [X] The description explains in detail what this PR is about.
- [X] I have linked a relevant issue or discussion.
- [X] I have created tests covering the changes.
    
URL: sagemath#36156
Reported by: Martin Rubey
Reviewer(s): Frédéric Chapoton
@mkoeppe mkoeppe added this to the sage-10.2 milestone Sep 1, 2023
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c: algebra t: bug
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sage-10.2
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detect the zero series when returning an exact stream mantepse/sage
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@mkoeppe @mantepse