See the C++ version of this page for documentation.

using System; // compute log(1+x) without losing precision for small values of x static double LogOnePlusX(double x) { if (x <= -1.0) { string msg = String.Format("Invalid input argument: {0}", x); throw new ArgumentOutOfRangeException(msg); } if (Math.Abs(x) > 1e-4) { // x is large enough that the obvious evaluation is OK return Math.Log(1.0 + x); } // Use Taylor approx. log(1 + x) = x - x^2/2 with error roughly x^3/3 // Since |x| < 10^-4, |x|^3 < 10^-12, relative error less than 10^-8 return (-0.5*x + 1.0)*x; }

This code is in the public domain. Do whatever you want to with it, no strings attached.

More stand-alone numerical code