Evaluates the exponential integral (E1), based on the polynomial and rational approximations of Abramowitz and Stegun (1964).
Abramowitz, Milton, and Irene A. Stegun. Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables. National Bureau of Standards. (1964): 1046 p.
function exponentialIntegralE1 extends Modelica.Icons.Function; input Real x "Independent variable"; output Real E1 "Exponential integral E1(x)"; end exponentialIntegralE1;