The limit program in Maxima was (is?) based on part of Paul Wang's PhD
dissertation.
An alternative, the tlimit program has a lot to recommend it, when it is
applicable.
There is
a more recent method described in PhD by D.Gruntz and (an undocumented
amount of this?) was
apparently implemented
by Dan Gildea circa 2007, but is apparently not a top-level call. I
have not tried to track down where it
is called.
There is a lisp function though that can be called directly. It
?gruntz1((-1)^n,n,inf) gives an error -- taylor: canot determine
mrv-sign log(-1).
and returns similarly for the expression in the bug report.
RJF
On 11/9/2013 6:54 AM, Stavros Macrakis wrote:
> Thank you for the bug report.
>
> This is indeed a bug in limit. A workaround until it is fixed is to
> use tlimit instead.
>
> BTW, when reporting a bug, it's best if you can include the exact
> version of Maxima you're running (the bug_report() command tells you
> that).
>
> -s
>
>
> On Fri, Nov 8, 2013 at 5:05 PM, Dan Drake <ddrake at math.wisc.edu
> <mailto:ddrake at math.wisc.edu>> wrote:
>
> Hello,
>
> A Sage user encountered a problem that seems to come from Maxima. See
> https://groups.google.com/forum/#!topic/sage-support/dwR4kuBmiQo
> <https://groups.google.com/forum/#%21topic/sage-support/dwR4kuBmiQo>;.
> In
> Sage:
>
> sage: n = var('n')
> sage: assume(n>0)
> sage: series = -(3*n^2 + 1)*(-1)^n/sqrt(n^5 + 8*n^3 + 8)
> sage: limit(series, n=infinity)
> 38/25*pi^2*und
>
> And in Maxima:
>
> (%i6) display2d:false;
>
> (%o6) false
> (%i7) limit(-(3*n^2 + 1)*(-1)^n/sqrt(n^5 + 8*n^3 + 8),n,inf);
>
> (%o7) -38*und*log(-1)^2/25
>
> I would expect Maxima to evaluate the limit and get zero.
> (Possibly with
> some encouragement?)
>
> (I'm not on the mailing list, I'm just reporting a bug -- further
> discussion can be directed to the sage-support mailing list or to our
> trac ticket: http://trac.sagemath.org/ticket/15386.)
>
> Thanks,
>
> Dan
>
> --
> --- Dan Drake
> ----- www.math.wisc.edu/~ddrake/ <http://www.math.wisc.edu/%7Eddrake/>;
> -------
>
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