#10963: More functorial constructions
-------------------------------------+-------------------------------------
Reporter: nthiery | Owner: stumpc5
Type: enhancement | Status: needs_work
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: Detect and fix
public/ticket/10963 | Heisenbugs
Dependencies: #11224, #8327, | Commit:
#10193, #12895, #14516, #14722, | 8eaf51a82c4e2194769db13457979ae601ebbc04
#13589, #14471, #15069, #15094, | Stopgaps:
#11688, #13394, #15150, #15506 |
-------------------------------------+-------------------------------------
Comment (by SimonKing):
Here is my attempt at explaining the interrelation of the cached function
`base_category_class_and_axiom`, the `__classget__`, and the lazy
attribute
`_base_category_class_and_axiom`.
- The lazy attribute needs the cached function to compute its value.
- If the classget is invoked, then the value of the lazy attribute does
not
need to be guessed, but can be put explicitly (but then: Why is
`cls._base_category_class_and_axiom_was_guessed = True`? It should be
False,
since the value is in fact ''not'' guessed by classget).
- The cached function invokes the classget to do a consistency test.
Now, it can obviously happen that everything starts by calling the lazy
attribute. Then, classget is called, and overrides the lazy attribute
''before
its computation is finished''. Then, the lazy attribute finishes its
computation, and is overridden again (by the value it just computed).
I guess this is why the lazy attribute / cached function is called twice
for
some classes, even with our fixes.
--
Ticket URL: <http://trac.sagemath.org/ticket/10963#comment:266>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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