Actually, this case is fully covered by
https://trac.sagemath.org/ticket/32161
which is, unfortunately, stalled on what looks like a non-trivial problem
with a more general solution. Given that the problem arises again here,
perhaps it's worth accepting first a more limited solution and just stick
with errors on non-constant summation bounds.
On Saturday, 28 May 2022 at 08:51:37 UTC+2 Nils Bruin wrote:
> The bug is perhaps concisely illustrated with the following:
>
> sage: var('k,n')
> (k, n)
> sage: function('f')
> f
> sage: sum(f(x,k),k,1,n).diff(x)
> diff(f(x, k), x)*D[0](sum)(f(x, k), k, 1, n)
>
> it shows that sage doesn't have a differentiation rule in place for
> symbolic sums and just applies the chain rule on the first argument (and
> undoubtedly on the others, but those are constants in x). I would expect
> that there is a ticket lying around about this (some care needs to be taken
> to do something sensible with the other arguments as well), but I wasn't
> able to locate one.
> On Saturday, 28 May 2022 at 00:41:07 UTC+2 summers...@gmail.com wrote:
>
>> Hello, Sage Developers,
>>
>> I want to calculate the symbolic differentiation of a variable in an
>> expression with a sum of N unknown variables, and it seems sage cannot
>> handle it. I posted my question in
>> https://ask.sagemath.org/question/62451/how-to-symbolic-differentiate-a-sum-of-n-unknown-variables/
>>
>> , and the answer says it is a bug in sage. How can I report a bug? Is this
>> bug already reported somewhere?
>>
>> Thanks,
>>
>
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