Opened 3 years ago
Closed 3 years ago
#23186 closed enhancement (fixed)
ZZ → QQ is not onto
| Reported by: | saraedum | Owned by: | |
|---|---|---|---|
| Priority: | minor | Milestone: | sage-8.0 |
| Component: | commutative algebra | Keywords: | sd86.5 |
| Cc: | Merged in: | ||
| Authors: | Julian Rüth | Reviewers: | Travis Scrimshaw |
| Report Upstream: | N/A | Work issues: | |
| Branch: | 79fd62a (Commits) | Commit: | 79fd62a8c40632891cf32502a3d80709edc68cf8 |
| Dependencies: | Stopgaps: |
Description (last modified by )
Currently, this fails
sage: QQ.coerce_map_from(ZZ).is_surjective() NotImplementedError
To fix this, we make the coercion morphism know it is not surjective.
Change History (6)
comment:1 Changed 3 years ago by
comment:2 Changed 3 years ago by
Why not do that at the category level?
comment:3 Changed 3 years ago by
- Branch set to u/saraedum/zz___qq_is_not_onto
comment:4 Changed 3 years ago by
- Branch u/saraedum/zz___qq_is_not_onto deleted
- Status changed from new to needs_review
comment:5 Changed 3 years ago by
- Branch set to u/saraedum/zz___qq_is_not_onto
- Commit set to 79fd62a8c40632891cf32502a3d80709edc68cf8
- Description modified (diff)
- Reviewers set to Travis Scrimshaw
- Status changed from needs_review to positive_review
Because to do something at the category level, you should be doing something for all objects in that category, not for one specific object (in a specific implementation). Now, if you wanted to have something in Rings checking if a morphism to ZZ was surjective returning True, then that would be good because it is true for all rings (of characteristic 0). Although map has a concrete implementation of is_surjective, which is a technical detail that would need to be worked around (which that method probably should be lifted to the category of set morphisms).
The fix LGTM.
New commits:
| 79fd62a | ZZ is not onto QQ
|
comment:6 Changed 3 years ago by
- Branch changed from u/saraedum/zz___qq_is_not_onto to 79fd62a8c40632891cf32502a3d80709edc68cf8
- Resolution set to fixed
- Status changed from positive_review to closed
You should never, ever give information about specific objects at the category level.
However, you can impart this information in the
Z_to_Qmorphism class.