On Feb 7, 3:37 pm, Florent Hivert <florent.hiv...@univ-rouen.fr>
wrote:
> Dear William
Hi Florent,
<SNIP>
> Yes... This was perfectly clear to me. And that's why I volunteered to makes
> things coherent.
Thanks. It is very important to make all the various classes of Sage
more consistent. Some work has been done in that direction to
systematically check methods, but much remains to be done. That is why
Nicolas' check framework will come in very handy because it enforces
discipline and can easily find regressions for new code being added.
> > is that it suggests there is exactly one exception for all types of
> > errors involving linear algebra. But I can at least see situations
> > where ValueError and ZeroDivisionError at least both make sense, so
> > doing the above would presumably merge them.
>
> > So I'm definitely not a priori convinced that LinAlgError is
> > necessarily better.
>
> Ok ! You get the point. I'm really sorry to encumber the mailing list, but I
> think, to ensure the quality of sage, things like that should be discussed and
> fixed once for all. Moreover since I'm new to sage, I don't want to make a
> decision which goes against the usual behavior of sage.
Cool, that is why technical decisions should and are discussed in the
open and I think in this case you are definitely on the right track.
And don't worry about the volume of emails you send to sage-devel
since this is a high volume list :)
> So let me summarize the decisions. For any rings
>
> 1. The 0x0 matrix is its self inverse and has 1 for determinant.
>
> 2. Any nx0 or 0xn (n != 0) matrix is not invertible and should raise a
> ValueError "matrix must be square" if one tries to invert it. I'll add
> support for this in the file matrix0.pyx. I'll also try to make generic
> test for this behavior.
>
> 3. Any singular matrix when inverted should raise a DivisionByZero Error. In
> numpy case this probably means catching an exception to launch a different
> one. Am I right ?
>
> Any last comment ?
>
> After dealing with this I'll have go back to combinatorics otherwise I'll
> never be able to use sage for my own research :-).
Hehe, as long as everyone contributes a little to the generic low
level code the end result is much better :). Ever since the combinat
meeting last months you guys seems to have exploded with activity on
the patch server, so I am looking forward to many pushes from the
combinat team in the coming releases.
> Cheers,
>
> Florent
Cheers,
Michael
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