/// <summary>
 /// Creates an instance.
 /// </summary>
 /// <param name="a">  the value </param>
 public IncompleteGammaFunction(double a)
 {
     ArgChecker.notNegativeOrZero(a, "a");
     _maxIter = 100000;
     _eps     = 1e-12;
     _a       = a;
 }
 /// <summary>
 /// Creates an instance.
 /// </summary>
 /// <param name="a">  the value </param>
 /// <param name="maxIter">  the maximum iterations </param>
 /// <param name="eps">  the epsilon </param>
 public IncompleteGammaFunction(double a, int maxIter, double eps)
 {
     ArgChecker.notNegativeOrZero(a, "a");
     ArgChecker.notNegative(eps, "eps");
     if (maxIter < 1)
     {
         throw new System.ArgumentException("Must have at least one iteration");
     }
     _maxIter = maxIter;
     _eps     = eps;
     _a       = a;
 }