I want to call a GSL function, which writes data to a pointer to be provided
(Regular Spherical Bessel Functions, array version) it has prototype
int gsl_sf_bessel_jl_steed_array (int lmax, double x, double * jl_x_array)
so the 'array' is a pointer and no specific length (though only lmax + 1 of
the space is used, I think).
I tried the below, but the actual call results in a crash:
arrB_GSL := define_external(
GSL sits in my system directory, so it is found and NO_COPY for updates into
arrB_GSL(nTst, 1.0, steedArr); # now that does not work ... :-(
Any suggestions how to proceed here? I have tried with length or Fortan as
ordering and this and that ... nada ... and the 'Advanced Prog Guide' does
not illuminate me.
PS: the underlying function is sqrt(2*Pi/x)*BesselJ(n+1/2,x)/2, n in IN and
the GSL should provide all the values for k=0 ... n and 0 <= x given - for
which I want a fast numerical solution. However I do not want to compile
the GSL code for my special needs again (using fixed length).
PPS: the GSL docu for that: