Function helixiser::bessel_utils::nextBessel

pub fn nextBessel(n: u64, x: f64, Jn_minus_one: f64, Jn_minus_two: f64) -> f64

computes the next bessel "Jn(x)" using the values of Jn_minus_one(x) and Jn_minus_two(x) (at same x)

this makes use of the recurrence relation Jn(x) = 2*(n-1) / x * Jn_minus_one(x) - Jn_minus_two(x) as described in: Goldstein, M., and R. M. Thaler. "Recurrence techniques for the calculation of Bessel functions." Mathematics of Computation 13.66 (1959): 102-108.