pub fn integral(x: f64, n: u64) -> Option<f64>Expand description
Computes the generalized Exponential Integral function
where x is the argument and n is the integer power of the
denominator term.
Returns None if x < 0.0 or the computation could not
converge after 100 iterations
§Remarks
This implementation follows the derivation in
“Handbook of Mathematical Functions, Applied Mathematics Series, Volume 55” - Abramowitz, M., and Stegun, I.A 1964
AND
“Advanced mathematical methods for scientists and engineers” - Bender, Carl M.; Steven A. Orszag (1978). page 253
The continued fraction approach is used for x > 1.0 while the taylor
series expansions is used for 0.0 < x <= 1.