Opened 9 years ago
Closed 6 years ago
#13682 closed defect (fixed)
No coercion map with quotients of ring quotients
Reported by: | tscrim | Owned by: | tscrim |
---|---|---|---|
Priority: | major | Milestone: | sage-6.4 |
Component: | coercion | Keywords: | ideal, quotient, coercion |
Cc: | boerner, saraedum | Merged in: | |
Authors: | Travis Scrimshaw | Reviewers: | Michel Boerner, Julian Rueth |
Report Upstream: | N/A | Work issues: | |
Branch: | d935124 (Commits, GitHub, GitLab) | Commit: | d93512419089b35d11d0c05a3533a80eb41a5790 |
Dependencies: | Stopgaps: |
Description
If you take the quotient ring of a quotient ring, I would expect there to be a coercion map corresponding to the natural surjection. However this does not occur:
sage: R.<x,y> = PolynomialRing(QQ) sage: S = R.quotient_ring(x^2+y^2) sage: S Quotient of Multivariate Polynomial Ring in x, y over Rational Field by the ideal (x^2 + y^2) sage: S.has_coerce_map_from(R) True sage: T = S.quotient_ring(x^3 - y) sage: T Quotient of Multivariate Polynomial Ring in x, y over Rational Field by the ideal (-x*y^2 - y, x^2 + y^2) sage: T.has_coerce_map_from(R) True sage: T.has_coerce_map_from(S) # this should be true False
I suspect the following does not occur either (and is where the problem lies). If an ideal I
is contained in an ideal J
, there is not a coercion from R/I -> R/J
.
Change History (9)
comment:1 Changed 8 years ago by
- Milestone changed from sage-5.11 to sage-5.12
comment:2 Changed 7 years ago by
- Milestone changed from sage-6.1 to sage-6.2
comment:3 Changed 7 years ago by
- Milestone changed from sage-6.2 to sage-6.3
comment:4 Changed 7 years ago by
- Milestone changed from sage-6.3 to sage-6.4
comment:5 Changed 7 years ago by
- Branch set to public/coercion/between_quotient_rings-13682
- Commit set to d93512419089b35d11d0c05a3533a80eb41a5790
- Status changed from new to needs_review
comment:6 Changed 6 years ago by
- Cc boerner saraedum added
comment:7 Changed 6 years ago by
- Reviewers set to Michel Boerner, Julian Rueth
- Status changed from needs_review to positive_review
comment:8 Changed 6 years ago by
Thanks for the review!
comment:9 Changed 6 years ago by
- Branch changed from public/coercion/between_quotient_rings-13682 to d93512419089b35d11d0c05a3533a80eb41a5790
- Resolution set to fixed
- Status changed from positive_review to closed
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We have to do an ideal membership test, which means computing Groebner bases. However it now returns the correct (or at least more intuitive) answer. Needs review.
New commits:
Expanded coercions between quotient rings.