Isn't this the real issue:
def is_VectorSpaceMorphism(x):
return isinstance(x, VectorSpaceMorphism)
With the category stuff the correct check is whether VectorSpaceMorphism in
x.__class__.__mro__. Is there a better way to express this? Whats the
..._with_category class if I want an isinstance() check?
On Saturday, November 3, 2012 3:44:19 PM UTC, jason wrote:
>
> On 11/3/12 9:56 AM, Jason Grout wrote:
> > sage: phi = (ZZ^2).hom(matrix(ZZ,2,[1..4]))
> > sage: h = (RR^2).hom(matrix(RR, 2, [1..4]))
> > sage: type(phi.parent())
> > sage.modules.free_module_homspace.FreeModuleHomspace_with_category
> > sage: type(h.parent())
> > sage.modules.vector_space_homspace.VectorSpaceHomspace_with_category
> >
> > Looking at the code, h.parent() is a direct subclass of phi.parent().
>
> Actually, maybe that's part of my confusion. The *_with_category
> classes are not subclasses.
>
> In fact, the error is boiled down to: the default implementation of
> _an_element_ works fine for phi.parent(), but not for h.parent(), since:
>
> sage: phi.parent()(2)
> Free module morphism defined by the matrix
> [2 0]
> [0 2]
> Domain: Ambient free module of rank 2 over the principal ideal domain
> Integer Ring
> Codomain: Ambient free module of rank 2 over the principal ideal domain
> Integer Ring
> sage: h.parent()(2)
> ---------------------------------------------------------------------------
>
> TypeError Traceback (most recent call
> last)
> <ipython-input-148-11d17a12ebdf> in <module>()
> ----> 1 h.parent()(Integer(2))
>
> /Users/grout/sage-trees/sage-5.4.rc1/local/lib/python2.7/site-packages/sage/modules/vector_space_homspace.pyc
>
>
> in __call__(self, A, check)
> 393 else:
> 394 msg = 'vector space homspace can only coerce
> matrices, vector space morphisms, functions or lists, not {0}'
> --> 395 raise TypeError(msg.format(A))
> 396 return vector_space_morphism.VectorSpaceMorphism(self, A)
> 397
>
> TypeError: vector space homspace can only coerce matrices, vector space
> morphisms, functions or lists, not 2
>
> So all we have to do is get h.parent()(i) working for some i in
> ['_an_element_', 'pi', 1.2, 2, 1, 0, infinity].
>
> Here is one way to do it: delete a bunch of the over-eager
> error-checking code:
>
> https://gist.github.com/4007685
>
> Rob Beezer, what do you think?
>
> Thanks,
>
> Jason
>
>
>
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