/// Spherical Bessel functions.
double
bessel_jl(unsigned int n, double x)
{
gsl_sf_result result;
int stat = gsl_sf_bessel_jl_e(static_cast<int>(n), x, &result);
if (stat != GSL_SUCCESS)
{
std::ostringstream msg("Error in bessel_jl:");
msg << " n=" << n << " x=" << x;
throw std::runtime_error(msg.str());
}
else
return result.val;
}
int
gsl_sf_bessel_jl_array(const int lmax, const double x, double * result_array)
{
/* CHECK_POINTER(result_array) */
if(lmax < 0 || x < 0.0) {
int j;
for(j=0; j<=lmax; j++) result_array[j] = 0.0;
GSL_ERROR ("error", GSL_EDOM);
}
else if(x == 0.0) {
int j;
for(j=1; j<=lmax; j++) result_array[j] = 0.0;
result_array[0] = 1.0;
return GSL_SUCCESS;
}
else {
gsl_sf_result r_jellp1;
gsl_sf_result r_jell;
int stat_0 = gsl_sf_bessel_jl_e(lmax+1, x, &r_jellp1);
int stat_1 = gsl_sf_bessel_jl_e(lmax, x, &r_jell);
double jellp1 = r_jellp1.val;
double jell = r_jell.val;
double jellm1;
int ell;
result_array[lmax] = jell;
for(ell = lmax; ell >= 1; ell--) {
jellm1 = -jellp1 + (2*ell + 1)/x * jell;
jellp1 = jell;
jell = jellm1;
result_array[ell-1] = jellm1;
}
return GSL_ERROR_SELECT_2(stat_0, stat_1);
}
}
double gsl_sf_bessel_jl(const int l, const double x)
{
EVAL_RESULT(gsl_sf_bessel_jl_e(l, x, &result));
}
