using System;

namespace BrazilTimestampReconstruction
{
	/// <summary>
	/// Returns the incomplete gamma function P(a, x) evaluated by its series representation as gamser.
	/// Also returns ln\Gamma(a) as gln.
	/// </summary>
	public class Gser
	{
		private double gamser, gln;
		public double Gamser
		{
			get{return gamser;}
		}
		public double Gln
		{
			get{return gln;}
		}
		public Gser()
		{
		}
        private int ITMAX = 100;
        private double EPS = 3.0e-7;
		public void gser(double a, double x)
		{
			Gammln gam = new Gammln();
			int n;
			double sum,del,ap;

			gln=gam.gammln(a);
			if (x <= 0.0) 
			{
				if (x < 0.0) try{throw new Exception();}
							 catch (Exception)
							 {
								 
							 } 
				gamser=0.0;
				return;
			} 
			else 
			{
				ap=a;
				del=sum=1.0/a;
				for (n=1;n<=ITMAX;n++) 
				{
					++ap;
					del *= x/ap;
					sum += del;
					if (Math.Abs(del) < Math.Abs(sum)*EPS) 
					{
						gamser=sum*Math.Exp(-x+a*Math.Log(x)-gln);
						return;
					}
				}
				try{throw new Exception();}
				catch (Exception)
				{
				}
				return;
			}
		}
	}
}