Wrong limit(x / (x + 2^x + cos(x)), x=-oo)

[pelegm]

Up to Sage 8.7 this limit returns "und" for "undefined":

sage: limit(x / (x + 2^x + cos(x)), x=-infinity)
und

while it should clearly be 1.

SymPy returns the correct result:

sage: limit(x / (x+2^x + cos(x)), x=-infinity, algorithm='sympy')
1

Reported to Maxima on 2018-08-15
as Maxima bug 3459,
fixed there
by Maxima commit 0c5c018
on 2018-08-30, fix included
in Maxima 5.42.2
to which we upgrade in #26625, merged in Sage 8.8.beta7.

In Sage >= 8.8 we get the correct value for this limit:

sage: limit(x / (x + 2^x + cos(x)), x=-infinity)
1

This ticket adds a doctest for that limit computation.

Depends on #26625

Upstream: Fixed upstream, in a later stable release.

CC: @slel

Component: calculus

Keywords: limit, maxima

Author: Samuel Lelièvre

Branch/Commit: 7f96496

Reviewer: Karl-Dieter Crisman

Issue created by migration from https://trac.sagemath.org/ticket/26060

[kcrisman]

Upstream: Reported upstream. No feedback yet.

[kcrisman]

comment:1

Apparently yes.

$ sage --maxima
<snip>
Maxima 5.41.0 http://maxima.sourceforge.net
using Lisp ECL 16.1.2
Distributed under the GNU Public License. See the file COPYING.
Dedicated to the memory of William Schelter.
The function bug_report() provides bug reporting information.
(%i1) limit(x / (x+2^x+cos(x)),x,-inf)       ;
(%o1)                                 und

I've reported this at Maxima bug 3459.

[kcrisman]

Changed upstream from Reported upstream. No feedback yet. to Reported upstream. Developers acknowledge bug.

[kcrisman]

Changed upstream from Reported upstream. Developers acknowledge bug. to Fixed upstream, but not in a stable release.

[kcrisman]

comment:4

(That was pretty fast work!)

[slel]

Changed upstream from Fixed upstream, but not in a stable release. to Fixed upstream, in a later stable release.

[slel]

Dependencies: #26625

[slel]

comment:5

After the upgrade to Maxima 5.42.2 in #26625, we should add a doctest here.

[embray]

comment:6

Ticket retargeted after milestone closed (if you don't believe this ticket is appropriate for the Sage 8.8 release please retarget manually)

[embray]

comment:7

As the Sage-8.8 release milestone is pending, we should delete the sage-8.8 milestone for tickets that are not actively being worked on or that still require significant work to move forward. If you feel that this ticket should be included in the next Sage release at the soonest please set its milestone to the next release milestone (sage-8.9).

[mkoeppe]

comment:8

Works in 9.2.beta10

[kcrisman]

comment:9

Doctest

[slel]

comment:10

Doctest added. Please review.

---

New commits:

7f96496

26060: doctest for limit after Maxima upgrade

[slel]

Branch: public/ticket/26060

[slel]

Commit: 7f96496

[kcrisman]

comment:14

Looks fine to me (assuming patchbot says it's fine), though all the other changes in typesetting could have occurred on another ticket. Thanks for doctesting!

[kcrisman]

Reviewer: Karl-Dieter Crisman

[kcrisman]

Author: Samuel Lelievre

[slel]

Changed author from Samuel Lelievre to Samuel Lelièvre

[kcrisman]

comment:18

Sorry! Haven't been keeping "Trac" as much lately.

[vbraun]

Changed branch from public/ticket/26060 to 7f96496