Dear David, dear Javier,
On Fri, Oct 23, 2009 at 05:23:15PM +0200, David R. Kohel wrote:
> I put of positive review of most of the assigned category files.
Excellent! Thanks much!
> Note that I hadn't downloaded those attributed to Javier, so these
> are still outstanding.
Feel free to beat him to it, starting from the end of the list :-)
> I made a few comments (mostly regarding the lines "TODO" in the
> files). Some are probably historical, but I guess the examples might
> crash if the relevant implementations are not in place in Sage
> upstream.
Thanks for reminding me about this. For the modules file, I just
removed all (but one) "todo: not implemented", since #6136 is now
ready, and can get into Sage at the same time as the category code.
I am now having a look at your comments on the wiki.
> I am also still not comfortable with the "with_basis" categories. I
> think there are already classes which handle these
Concrete classes sure. But not abstract classes for factoring generic
code out of the many concrete implementations of modules with basis:
(Combinatorial)FreeModule, matrix spaces, polynomials, ...
> and the "with_basis" is redundant if it is not a structure to be
> preserved by morphisms (like for pointed sets as distinct from
> sets).
It's not redundant, because it specifies how the elements are
represented by expanding them on the basis, which is not always
desirable or even possible (lazy power series, or functions from R to
R definitely form a module, but the basis is not constructive). In
turn, this information on the representation of elements yields
generic algorithms.
For another example of extra information carried by those *with_basis
categories, an object in GradedAlgebrasWithBasis is not just a graded
algebra; the elements of the distinguished basis must also be
homogeneous.
Yeah, I know; all of that should be stated explicitly in the doc. We
haven't yet finished porting all of this info from MuPAD's doc.
Best,
Nicolas
PS:
> Doing sage -combinat install I get the following error on start-up:
>
> SyntaxError: Non-ASCII character '\xc2' in file
> /usr/local/sage-4.1.2/local/lib/python2.6/site-packages/sage/combinat/__init__.py
> on line
> 22, but no encoding declared; see http://www.python.org/peps/pep-0263.html
> for details
> (__init__.py, line 21)
Good catch. Should be fixed in a couple minutes.
--
Nicolas M. Thiéry "Isil" <[email protected]>
http://Nicolas.Thiery.name/
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