Bessel function with imaginary argument

Hello,

I get the following strange result for bessel_j(1,z) with purely imaginary
argument:

First, try numerical evaluation:

(%i127) bessel_j(1,1.0*%i);
(%o127) 0.56515910399249*%i
(%i128) realpart(bessel_j(1,1.0*%i));
(%o128) 0
(%i130) imagpart(bessel_j(1,1.0*%i));
(%o130) 0.56515910399249

This looks fine. Now, if I want to get the realpart / imagpart symbolically,
it is wired:

(%i131) realpart(bessel_j(1,1*%i));
(%o131) bessel_j(1,%i)
(%i132) imagpart(bessel_j(1,1*%i));
(%o132) 0

What am I doing wrong?


I am using the pre-built Windows release:

wxMaxima 0.8.1 http://wxmaxima.sourceforge.net
Maxima 5.17.1 http://maxima.sourceforge.net
Using Lisp GNU Common Lisp (GCL) GCL 2.6.8 (aka GCL)
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.

I am not an expert to maxima neither to lisp ...

Any hint is highly appreciated.

Thanks,

Rolf