On 2014-06-23, Dima Pasechnik <[email protected]> wrote:
> On 2014-06-23, Karl Schultheisz <[email protected]> wrote:
>> I'm using Sage 6.2 on Arch Linux. I have posted before about sums being
>> wrong
>><https://groups.google.com/d/msg/sage-support/IgC78rcdO7c/qTWzpA9f-P8J>,
>> and I am happy to see that the community took action. Thanks! I have been
>> seeing other errors that may or may not be related to those addressed in
>> the link above.
>>
>> I open a new Sage session (command line). The following code ought to
>> return (e^x - 1)/x.
>>
>> sage: k = var('k')
>> sage: sum(x^k/factorial(k+1),k,0,oo)
>> 1/4*sqrt(pi)*sqrt(x)*e^(1/2*x)
>>
>> This looks similar to the sort of nonsense it was spitting out when
>> misinterpreting
>> Bessel functions from Maxima <http://trac.sagemath.org/ticket/16224>. In
>> the same session, if I run the summation command again, the result is
>
> did you try applying the patch from #16224 ?
Note that on Sage 6.3.beta4, which contains the fix from #16224, I get
sage: sum(x^k/factorial(k+1),k,0,oo)
2*sqrt(pi)*sqrt(1/(pi*x))*e^(1/2*x)*sinh(1/2*x)/sqrt(x)
which is correct (up to a failure to get obvious simplifications)
>
>> different.
>>
>> sage: sum(x^k/factorial(k+1),k,0,oo)
>> sum(x^k/factorial(k + 1), k, 0, +Infinity)
>>
>> And after this it will not simplify any sums, even ones it would have done
>> correctly on the first try:
>>
>> sage: sum(x^k/factorial(k),k,0,oo)
>> sum(x^k/factorial(k), k, 0, +Infinity)
>>
>> Even a reset doesn't help. (As a side-note, the exit command doesn't
>> survive reset.)
>>
>> sage: reset()
>> sage: k = var('k')
>> sage: sum(x^k/factorial(k),k,0,oo)
>> sum(x^k/factorial(k), k, 0, +Infinity)
>> sage: exit
>>
>> ---------------------------------------------------------------------------
>> NameError Traceback (most recent call
>> last)
>> /opt/sage/local/lib/python2.7/site-packages/sage/all_cmdline.py in
>><module>()
>> ----> 1 exit
>>
>> NameError: name 'exit' is not defined
>>
>> Finite sums seem to be ok.
>>
>> sage: sum(x^k,k,0,3)
>> x^3 + x^2 + x + 1
>> sage: m = var('m')
>> sage: sum(x^k,k,0,m)
>> (x^(m + 1) - 1)/(x - 1)
>>
>> Any help is greatly appreciated.
>>
>
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