1:  using Xint = System.Numerics.BigInteger;

   2:   

   3:   

   4:  namespace Luschny.Math.Factorial

   5:  {

   6:      public class FactorialProductNaive : IFactorialFunction

   7:      {

   8:          public FactorialProductNaive() { }

   9:   

  10:          public string Name

  11:          {

  12:              get { return "ProductNaive        "; }

  13:          }

  14:   

  15:          public Xint Factorial(int n)

  16:          {

  17:              if (n < 0)

  18:              {

  19:                  throw new System.ArgumentOutOfRangeException("n",

  20:                  Name + ": n >= 0 required, but was " + n);

  21:              }

  22:   

  23:              Xint nFact = Xint.One;

  24:   

  25:              for (int i = 2; i <= n; i++)

  26:              {

  27:                  nFact *= i;

  28:              }

  29:              return nFact;

  30:          }

  31:      }

  32:   

  33:  }   // endOfProductNaive