expintegral_ei incorrect behavior at infinity

rtoy commented 3 months ago

Imported from SourceForge on 2024-07-06 18:10:17 Created by opfromthestart on 2024-03-21 21:08:04 Original: https://sourceforge.net/p/maxima/bugs/4276

Some behavior of expintegral_ei is not correct

(%i25) limit(((expintegral_ei(x)/%e^x)*x-1)*x,x,inf);
(%o25)                               minf

Bu this limit is known to be 1 (eg https://www.wolframalpha.com/input?i=limit+x+to+infinity+%28%28Ei%28x%29%2Fe%5Ex%29*x-1%29*x).

(%i29) taylor(expintegral_ei(x)*%e^-x,x,inf,10);

taylor: encountered an unfamiliar singularity in:
expintegral_ei(x)
 -- an error. To debug this try: debugmode(true);

But this Laurent series can be found (https://www.wolframalpha.com/input?i=Ei%28x%29e%5E-x+series+at+infinity).

Maxima version: "5.45.1"
Maxima build date: "2021-12-06 23:50:08"
Host type: "x86_64-pc-linux-gnu"
Lisp implementation type: "GNU Common Lisp (GCL)"
Lisp implementation version: "GCL 2.6.12"
User dir: "/home/opfromthestart/.maxima"
Temp dir: "/tmp"
Object dir: "/home/opfromthestart/.maxima/binary/5_45_1/gcl/GCL_2_6_12"
Frontend: false

I also have tried it on 5.47.0 and I get the same errors.

rtoy commented 3 months ago

Imported from SourceForge on 2024-07-06 18:10:18 Created by opfromthestart on 2024-03-21 21:13:47 Original: https://sourceforge.net/p/maxima/bugs/4276/#1f29

Sorry about the formatting, I'm not sure why it didn't work and I cant edit it.

rtoy commented 3 months ago

Imported from SourceForge on 2024-07-06 18:10:22 Created by robert_dodier on 2024-03-25 19:52:41 Original: https://sourceforge.net/p/maxima/bugs/4276/#1f29/da49

No worries, I got the formatting more or less straightened out.

rtoy / maxima

expintegral_ei incorrect behavior at infinity #2697