#10963: More functorial constructions
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Reporter: nthiery | Owner: stumpc5
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.1
Component: categories | Resolution:
Keywords: days54 | Merged in:
Authors: Nicolas M. Thiéry | Reviewers: Simon King, Frédéric
Report Upstream: N/A | Chapoton
Branch: | Work issues:
public/ticket/10963 | Commit:
Dependencies: #11224, #8327, | eb7b486c6fecac296052f980788e15e2ad1b59e4
#10193, #12895, #14516, #14722, | Stopgaps:
#13589, #14471, #15069, #15094, |
#11688, #13394, #15150, #15506 |
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Comment (by nbruin):
This [https://groups.google.com/forum/#!topic/sage-devel/lODVhZRT4RE sage-
devel thread] is probably a good real-world example for how careful one
should be messing about with attribute lookups and mro manipulations in
python:
To avoid the need to explicitly chain parts of the `__init__` process, the
category framework supplies `__init_extra__` hooks, which should get
executed for all the classes in the mro. It does so by looking for
`__init_extra__` entries in each of `[C.__dict__ for C in class.mro()]`,
or something roughly equivalent.
Problem: that doesn't test whether attributes are present if classes
implement a custom `__getattr__`. And Parent does that, to ensure that
dynamic classes get faked for `cdef` classes. So `__init_extra__` has
never worked properly for `cdef` classes.
It may well be that axioms defer to already-existing black magic for these
things, in which case this ticket doesn't really make things better or
worse in this respect, but it is clear that the scenario above was not
considered by the designers of the category framework before, so it's
worth checking how the code here is affected by it.
--
Ticket URL: <http://trac.sagemath.org/ticket/10963#comment:475>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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