On Tue, Jan 13, 2026 at 10:12 AM kcrisman <[email protected]> wrote:
>
> Just FYI this has been fixed upstream: 
> https://sourceforge.net/p/maxima/bugs/4634/ so hopefully in a future version 
> of Maxima soon.
>
> Question to Nils or others: In the past we used to also open a ticket for 
> Sage to make our own doctest - is that still the practice?  I'm just making a 
> note at #40679 for now.
>
the practice is to open a PR with a fix.
For a trivial PR, all is needed is a GitHub account and a browser, by
the way. No need for a local Sage install, even.

> On Tuesday, November 18, 2025 at 12:55:27 PM UTC-5 [email protected] wrote:
>>
>> Thank you all for looking into this. I'm happy to hear that the bug has been 
>> fixed in Maxima. I'm sure the fix will work it's way into Sage soon enough.
>>
>> By the way, this sum did return "und" a few years ago, and later the answer 
>> changed to "ind" (before changing to -1/4). I agree that und is better than 
>> ind (as far as I understand the difference between these).
>>
>> Aaron
>>
>> On Tuesday, November 18, 2025 at 4:42:01 AM UTC-10 kcrisman wrote:
>>>
>>> Thanks for pointing that one out, that's great.
>>>
>>> (Though note that apparently the "correct" answer is "und" not "ind", 
>>> according to the latest comment on the Sourceforge ticket!)
>>>
>>> On Tuesday, November 18, 2025 at 8:14:01 AM UTC-5 Antonio Rojas wrote:
>>>>
>>>> This is fixed in maxima 5.48. The upgrade ticket is 
>>>> https://github.com/sagemath/sage/pull/40679
>>>>
>>>> El martes, 18 de noviembre de 2025 a las 13:59:27 UTC+1, kcrisman escribió:
>>>>>
>>>>> I've opened https://sourceforge.net/p/maxima/bugs/4634/ for this, and 
>>>>> hopefully we'll hear back.  Can someone open a corresponding Sage ticket 
>>>>> which will eventually get a doctest for the same?  Thanks!
>>>>>
>>>>> On Monday, November 17, 2025 at 10:38:54 PM UTC-5 Nils Bruin wrote:
>>>>>>
>>>>>> I can confirm the behaviour you're observing ... It's really 
>>>>>> unfortunate!. This would be a result produced by maxima, so most likely 
>>>>>> it's a change due to a change in maxima version. I would call it a bug. 
>>>>>> One should probably try to reproduce it in maxima proper and then report 
>>>>>> it to maxima. Hopefully they can fix it.
>>>>>>
>>>>>> In maxima 5.47.0 I get:
>>>>>>
>>>>>> (%i1) load(simplify_sum)$
>>>>>> (%i2) simplify_sum( sum(n*(-1)^n,n,1,inf));
>>>>>> -1/4
>>>>>>
>>>>>> This happens both on sage's ECL based one and on the system maxima 
>>>>>> (running on SBCL). So I think this behaviour tracks decisively to maxima.
>>>>>>
>>>>>> On Monday, 17 November 2025 at 19:23:53 UTC-8 [email protected] wrote:
>>>>>>>
>>>>>>> I have used SageMath within CoCalc for teaching Calculus 2 for several 
>>>>>>> years.
>>>>>>>
>>>>>>> In past semesters, the following code produced the output "ind":
>>>>>>>
>>>>>>>      var('n')
>>>>>>>      sum(n*(-1)^n,n,1,oo)
>>>>>>>
>>>>>>> This is expected, since the series diverges.
>>>>>>>
>>>>>>> However, this semester I changed the kernel from SageMath 10.4 to the 
>>>>>>> current SageMath 10.7. Now this same code produces the output "-1/4" [I 
>>>>>>> believe 10.5 and 10.6 behave the same way as 10.7.]
>>>>>>>
>>>>>>> I have my students compute the value of several similar series 
>>>>>>> (replacing the -1 in the code above with -2, -1/2, 1/2, 1, and 2), and 
>>>>>>> all the others are behaving the same way they always have. It is only 
>>>>>>> this series which is giving me an unexpected output.
>>>>>>>
>>>>>>> Has anyone else encountered this issue?
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Aaron
>
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