package btools.util;

/**
 * Some fast approximations to mathematical functions
 *
 * @author ab
 */
public class FastMath {
  /**
   * Approximation to Math.exp for small negative arguments
   */
  public static double exp(double e) {
    double x = e;
    double f = 1.;
    while (e < -1.) {
      e += 1.;
      f *= 0.367879;
    }
    return f * (1. + x * (1. + x * (0.5 + x * (0.166667 + 0.0416667 * x))));
  }
}