Accord.Math.Beta.PowerSeries C# (CSharp) Method

        public static double PowerSeries(double a, double b, double x)
        {
            double s, t, u, v, n, t1, z, ai;

            ai = 1.0 / a;
            u = (1.0 - b) * x;
            v = u / (a + 1.0);
            t1 = v;
            t = u;
            n = 2.0;
            s = 0.0;
            z = Constants.DoubleEpsilon * ai;
            while (System.Math.Abs(v) > z)
            {
                u = (n - b) * x / n;
                t *= u;
                v = t / (a + n);
                s += v;
                n += 1.0;
            }
            s += t1;
            s += ai;

            u = a * System.Math.Log(x);
            if ((a + b) < Gamma.GammaMax && System.Math.Abs(u) < Constants.LogMax)
            {
                t = Gamma.Function(a + b) / (Gamma.Function(a) * Gamma.Function(b));
                s = s * t * System.Math.Pow(x, a);
            }
            else
            {
                t = Gamma.Log(a + b) - Gamma.Log(a) - Gamma.Log(b) + u + System.Math.Log(s);
                if (t < Constants.LogMin) s = 0.0;
                else s = System.Math.Exp(t);
            }
            return s;
        }