Dear Martin Albrecht,
Thanks for your quick answer.
> > So my question is the following: is there a specific reason why this test
> > has been written ?
>
> I wrote that doctest, because that behaviour is consistent with other
> matrices.
>
> sage: A = random_matrix(GF(127),0,0)
> sage: A^(-1)
> Traceback (most recent call last)
> ...
> ZeroDivisionError:
>
> sage: A = random_matrix(QQ,0,0)
> sage: A^(-1)
> ---------------------------------------------------------------------------
> Traceback (most recent call last)
> ...
> ZeroDivisionError:
>
>
> I have no strong feelings about how things should behave as long as it is
> consistent.
Neither do I. Actually, As you pointed out, the main problem was more that
this behavior was only tested for Matrix_mod2_dense, and not for the other
type of matrices. Moreover you made me realize something even worse.
For any type of matrices, sage were completely inconsistent since ~a and
a^(-1) did not returns the same result:
sage: A = random_matrix(QQ,0,0)
sage:
sage: A^(-1)
---------------------------------------------------------------------------
ZeroDivisionError Traceback (most recent call last)
wheras:
sage: ~A
[]
Basically my patch delegate the choice to ~ to raise an error or not.
> I suggest, to add doctests to catch these for the various matrix
> types while you're changing the behaviour.
Ok... I'll try not to forget any kind of matrices.
I also hope there will be not too much kind where this case is not properly
handled. One community question : suppose that this happen and that I don't
find the correct way to fix it (no one knows about strange data structure :-))
is this ok to post a patch that test the problem and raise a doc error and to
add a trac ticket for this specific problem ?
Cheers,
Florent
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