Hi Mark!
On Thu, Jun 11, 2015 at 06:44:04PM -0400, Mark Shimozono wrote:
> I require a method which, given a sage category of a module,
> returns the ring which acts upon it.
>
> There is a method :meth:`ModulesWithBasis.base_ring`
> which is supposed to give the base ring of a module (rather than
> that of a category of modules) but it is broken.
>
> The base ring is stored as an attribute. However unlike methods,
> attributes are not inherited by sage subcategories.
> Thus it is necessary to search the category tree to find
> a suitable leaf which possesses the base ring attribute.
Following the issues you had mentioned in Davis, since #11111
Modules.SubcategoryMethods.base_ring provides a default implementation
of base_ring so that A(XXX).base_ring() returns XXX for any
subcategory A(XXX) of Modules(XXX).
XXX may indeed be either a ring or a category thereof, depending on
how the category was created.
> At any rate, in the given example, passage to the category has the
> effect of forgetting needed information.
Can you describe more precisely your use case? Do you have an example
where you only have the category under hand, and still need to know
explicitly the base ring?
Cheers,
Nicolas
--
Nicolas M. Thiéry "Isil" <nthi...@users.sf.net>
http://Nicolas.Thiery.name/
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