factorial.h

// Description: Factorial
// Documentation: math_functions.txt

#ifndef PASTELSYS_FACTORIAL_H
#define PASTELSYS_FACTORIAL_H

#include "pastel/sys/mytypes.h"

namespace Pastel
{

    //! Returns the factorial.
    /*!
   Preconditions:
   i >= 0

   A table look-up is used for i in [0, 20].
   The gamma() function is used for larger i.
   Note that 20! < 2^64 - 1 < 21!.
   */
    template <typename Real>
    Real factorial(integer i);

    //! Returns the logarithm of the factorial.
    /*!
   Preconditions:
   i >= 0

   A table look-up is used for i in [0, 256].
   The gamma() function is used for larger i.
   */
    template <typename Real>
    Real lnFactorial(integer i);

}

#include "pastel/sys/math/factorial.hpp"

#endif