/// <summary>
/// Compute n!, the <a href="http://mathworld.wolfram.com/Factorial.html">
/// factorial</a> of <c>n</c> (the product of the numbers 1 to n), as a
/// <c>double</c>.
/// The result should be small enough to fit into a <c>double</c>: The
/// largest <c>n</c> for which <c>n! < Double.MaxValue</c> is 170.
/// If the computed value exceeds <c>Double.MaxValue</c>,
/// <c>Double.PositiveInfinity</c> is returned.
/// </summary>
/// <param name="n">Argument.</param>
/// <returns><c>n!</c></returns>
/// <exception cref="NotPositiveException"> if <c>n < 0</c>.</exception>
public static double factorialDouble(int n)
{
if (n < 0)
{
throw new NotPositiveException <Int32>(new LocalizedFormats("FACTORIAL_NEGATIVE_PARAMETER"), n);
}
if (n < 21)
{
return(FACTORIALS[n]);
}
return(FastMath.floor(FastMath.exp(CombinatoricsUtils.factorialLog(n)) + 0.5));
}
public static double factorialLog(int n)
{
return(CombinatoricsUtils.factorialLog(n));
}
