Dave, I agree that it is quite possible that not all of them are correct
non-invertible elements in a ring. Of course, we would go through an
examine them more individually as David suggested.
I was originally thinking ValueError as well, but, as Martin pointed out,
ArithmeticError is a bit more specific. So that gets my vote.
Best,
Travis
On Tuesday, February 6, 2024 at 11:12:30 AM UTC+9 David Roe wrote:
> I agree that there are cases that shouldn't be changed to an
> ArithmeticError, and that grepping for "invertible" isn't sufficient. But
> I think with a narrower scope this change is a good idea: if the error
> arises from attempting to invert a non-invertible element of a ring.
>
> So +1 from me, with a manual check that the change seems appropriate.
> David
>
> On Mon, Feb 5, 2024 at 7:54 PM Dave Morris <dmo...@deductivepress.ca>
> wrote:
>
>> -1 from me.
>>
>> Looking at just a few uncovered some that I think are definitely not
>> ArithmeticError.
>>
>> Examples:
>> There is an occurrence of ValueError('{} is not invertible') in
>> the lift_isometry method of cliffordalgebra.py. Lifting an isometry is
>> clearly not an arithmetic operation. ValueError is correct here.
>> There is an occurrence of TypeError('the A-basis is defined only
>> when 2 is invertible') in the method to find an `A`-basis of an
>> Iwahori-Hecke algebra. Finding such a basis is clearly not an arithmetic
>> operation. Perhaps this should be a ValueError instead of a TypeError,
>> though.
>> RuntimeError("morphism is not invertible"). I think that finding
>> the inverse of a morphism between two objects of a category is clearly not
>> an arithmetic operation. Perhaps this should be a ValueError rather than a
>> RuntimeError.
>>
>> If you want to unify, I think ValueError might work. But I think they
>> all need to be inspected, not just assume a single error type fits.
>>
>> > On Feb 5, 2024, at 4:44 AM, 'Martin R' via sage-devel <
>> sage-...@googlegroups.com> wrote:
>> >
>> > Dear all,
>> >
>> > currently, when trying to invert a non-invertible element, one of the
>> following errors is raised (found using `grep -r --include=*.{py,pyx}
>> --color -nH --null -e "Error(.*invertible" *`):
>> > • 21 ValueError('{} is not invertible')
>> > • 11 ZeroDivisionError("element is not invertible")
>> > • 10 TypeError('the A-basis is defined only when 2 is invertible')
>> > • 8 ArithmeticError("self must be invertible to have a
>> multiplicative order")
>> > • 2 RuntimeError("morphism is not invertible")
>> > • 2 NotImplementedError("matrix must be invertible")
>> >
>> > Travis and I would like to propose to unify these to
>> "ArithmeticError". If nobody objects, I would prepare a PR within the next
>> few days.
>> >
>> > Best wishes,
>> >
>> > Martin
>> >
>> >
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