#10667: Morphisms and Objects of Categories
---------------------------+------------------------------------------------
Reporter: SimonKing | Owner: nthiery
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-5.0
Component: categories | Keywords: objects morphisms containment
Work_issues: doctests | Upstream: N/A
Reviewer: | Author: Simon King
Merged: | Dependencies: #9138, #11115
---------------------------+------------------------------------------------
Comment(by SimonKing):
I am making some progress.
Testsuites are really a good thing! By adding tests for morphisms, I found
a couple of bugs. And that's why my patch can not just be a short work-
around (unless I make the Testsuites skip some tests). It will contain
fixes in different parts of sage.
Just one example:
{{{
sage: E = CombinatorialFreeModule(ZZ, [1,2,3])
sage: F = CombinatorialFreeModule(ZZ, [2,3,4])
sage: H = Hom(E, F)
sage: TestSuite(H).run()
Failure in _test_additive_associativity:
Traceback (most recent call last):
File "/mnt/local/king/SAGE/broken/local/lib/python2.6/site-
packages/sage/misc/sage_unittest.py", line 275, in run
test_method(tester = tester)
File "/mnt/local/king/SAGE/broken/local/lib/python2.6/site-
packages/sage/categories/commutative_additive_semigroups.py", line 80, in
_test_additive_associativity
tester.assert_((x + y) + z == x + (y + z))
TypeError: unsupported operand type(s) for +: 'ModuleMorphismByLinearity'
and 'ModuleMorphismByLinearity'
------------------------------------------------------------
Failure in _test_an_element:
Traceback (most recent call last):
File "/mnt/local/king/SAGE/broken/local/lib/python2.6/site-
packages/sage/misc/sage_unittest.py", line 275, in run
test_method(tester = tester)
File "/mnt/local/king/SAGE/broken/local/lib/python2.6/site-
packages/sage/categories/sets_cat.py", line 388, in _test_an_element
tester.assertEqual(self(an_element), an_element, "element construction
is not idempotent")
...
}}}
The reason is that `dumps(H.zero())` fails:
{{{
sage: dumps(H.zero())
---------------------------------------------------------------------------
PicklingError Traceback (most recent call
last)
/home/king/SAGE/work/categories/objects/<ipython console> in <module>()
/mnt/local/king/SAGE/broken/local/lib/python2.6/site-
packages/sage/structure/sage_object.so in sage.structure.sage_object.dumps
(sage/structure/sage_object.c:8274)()
/mnt/local/king/SAGE/broken/local/lib/python2.6/site-
packages/sage/structure/sage_object.so in
sage.structure.sage_object.SageObject.dumps
(sage/structure/sage_object.c:2183)()
PicklingError: Can't pickle <type 'function'>: attribute lookup
__builtin__.function failed
}}}
There are more of those bugs.
The good news: I think I found a stable way to get the method resolution
order of hom category parent classes right.
I even tried to get rid of the odd explicit `__new__` method in
`sage.categories.rings.Rings.HomCategory.ParentMethods`. But I am not sure
if I will succeed.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10667#comment:42>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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