#14793: Unique representation for homsets
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Reporter: nthiery | Owner: nthiery
Type: enhancement | Status: new
Priority: major | Milestone: sage-5.12
Component: categories | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Simon King | Merged in:
Dependencies: | Stopgaps:
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Comment (by nbruin):
Replying to [comment:12 SimonKing]:
> Here is the problem and a potential solution.
>
> While unpickling of the modular symbols M, we need to construct a homset
with domain and codomain M. At this point, calling M.category() results in
an error, since M.base() returns None and M.category() wants to return
Modules(M.base()).
Is `None` ever a valid value for `M.base()`? At this point, is there
enough information available on `M` to derive what `base()` should return?
In that case, I'd think the cleanest way would be to make `base()` a
caching routine: return a stored value if available and otherwise derive
the correct value, store it, and return that. Whenever someone asks for
`base` they're probably not interested in an invalid value. Or is
computing `base` possibly expensive and not really necessary for the
unpickling?
[...]
> Do you think this is a feasible idea?
If you can't easily fix the category determination then, yes. However,
what you're proposing is a hack, so solving it properly should really be
preferred. (Other people more knowledgeable on category stuff will
probably have a more informed opinion than this generic remark)
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/14793#comment:13>
Sage <http://www.sagemath.org>
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