#9138: Categories for all rings
--------------------------+-------------------------------------------------
Reporter: jbandlow | Owner: nthiery
Type: defect | Status: needs_review
Priority: major | Milestone: sage-4.7.1
Component: categories | Keywords: introspection, categories for
rings
Work_issues: | Upstream: N/A
Reviewer: | Author: Simon King
Merged: | Dependencies: sage-4.7, #11268, #11139, #9976,
#9944, #11269
--------------------------+-------------------------------------------------
Changes (by SimonKing):
* status: needs_work => needs_review
* work_issues: doc test errors in sage/doc =>
Comment:
At last it seems to work! With the new first patch together with the
second patch, all doc tests (both sage/ and doc/) pass (at least for me)!
Here is the problem and its solution.
__First Problem__
Hecke algebras: _lmul_ for its elements returns None. The previous patch
version would thus register `from_base_ring` for coercion. However, in
that case, a default implementation of `from_base_ring` would be used,
which fails if _lmul_ returns None. Hence, it must not be registered as
coercion.
Solution: Use from_base_ring if it is a custom implementation , i.e., if
`self.from_base_ring` is not obtained from
`self.category().parent_class.from_base_ring`. If it is clear that the
default implementation won't work, then do not register from_base_ring as
coercion.
Additional advantage: If the user provides a fast custom `from_base_ring`
then it will be picked up.
__Second problem__
`SpecialCubicQuotientRing`: Here, self.one() had not been available during
initialisation
of coercion from the base ring. Hence, in the previous patch version,
from_base_ring
had been registered.
However, _lmul_ is returning None, again. Additional complication:
The initialisation of a `SpecialCubicQuotientRing` as a commutative
algebra happened
too early, namely ''before'' its hash was available. Hence, the attempt to
construct
a hom set containing the coercion from the base ring had failed.
Solution: Move `CommutativeAlgebra.__init__` nearer to the end of
`SpecialCubicQuotientRing.__init__`,
namely to a point where both self.one() and the hash are available.
__Conclusion__
Ready for Review!
Apply trac9138-categories_for_rings.patch
trac9138_categories_for_more_rings.rebase4.7.1.a1.patch
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9138#comment:80>
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