#10963: More functorial constructions
-------------------------------------+-------------------------------------
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, | ec340363a811bbafbb8cd5ff8f39e75db9872f9f
#10193, #12895, #14516, #14722, | Stopgaps:
#13589, #14471, #15069, #15094, |
#11688, #13394, #15150, #15506 |
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Comment (by SimonKing):
Aha, it is not so easy. It turns out that the lazy attribute is involved
much more often, but not during startup of Sage.
For example, when you start Sage, then `FinitePermutationGroups` are not
constructed by means of applying an axiom. Hence, the attribute is not
available. Hence, things crash.
{{{
sage: FinitePermutationGroups()
# Note: Here I have replaced the lazy axiom by something that just raises
an error
Traceback (most recent call last):
...
AttributeError: <class
'sage.categories.finite_permutation_groups.FinitePermutationGroups'> does
not know its base category and axiom
}}}
If one then constructs the category ''class'' (not instance!) by means of
an axiom, thing work:
{{{
sage: PermutationGroups.Finite
<class
'sage.categories.finite_permutation_groups.FinitePermutationGroups'>
sage: FinitePermutationGroups()
Category of finite permutation groups
}}}
So, it seems that we have to live with the guesswork. But I wonder if we
can simplify the logic, and can make it so that categories with axiom can
be defined interactively.
--
Ticket URL: <http://trac.sagemath.org/ticket/10963#comment:309>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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