Jonathan Leto: May 2008 Archives

Previously I posted a graph of some Bessel functions on the interval zero to twenty, or [0,20] . Here is the same code but on the symmetric counterpart of the the previous interval, [-20, 20]. This allows use to plainly see that even-numbered Bessel functions are even functions (satisfy f(-x)=f(x)) while odd-numbered Bessel functions are odd ( satisfy f(-x)=-f(x) ).

View image

Evidently, this typemap was causing the issue with gcc 4.x:

 %typemap(freearg) double const [] {
    free($1);
}

What made it hard to track down was that I could not reproduce it on gcc 3.4.6. It was cargo-culted and unnecessary code. Have we learned our lesson?

There is now an examples/sf directory which has the Perl code to generate this graph with gnuplot. The function Math::GSL::SF::gsl_sf_bessel_Jn($n,$x) was used.