reginaldojunior / winners

	 * @TODO Better handling of the approximation method to support the differences between Excel/Gnumeric and Open/Libre Office

	 *

	 */

	public static function BESSELK($x, $ord) {

		$x		= (is_null($x))		? 0.0 :	PHPExcel_Calculation_Functions::flattenSingleValue($x);

		$ord	= (is_null($ord))	? 0.0 :	PHPExcel_Calculation_Functions::flattenSingleValue($ord);

		if ((is_numeric($x)) && (is_numeric($ord))) {

			if (($ord < 0) || ($x == 0.0)) {

				return PHPExcel_Calculation_Functions::NaN();

			}

			switch(floor($ord)) {

				case 0 :	return self::_Besselk0($x);

							break;

				case 1 :	return self::_Besselk1($x);

							break;

				default :	$fTox	= 2 / $x;

							$fBkm	= self::_Besselk0($x);

							$fBk	= self::_Besselk1($x);

							for ($n = 1; $n < $ord; ++$n) {

								$fBkp	= $fBkm + $n * $fTox * $fBk;

								$fBkm	= $fBk;

								$fBk	= $fBkp;

							}

			}

			return (is_nan($fBk)) ? PHPExcel_Calculation_Functions::NaN() : $fBk;

		}

		return PHPExcel_Calculation_Functions::VALUE();

	}	//	function BESSELK()

	private static function _Bessely0($fNum) {

	 *

	 * @return	float

	 */

	public static function BESSELY($x, $ord) {

		$x		= (is_null($x))		? 0.0 :	PHPExcel_Calculation_Functions::flattenSingleValue($x);

		$ord	= (is_null($ord))	? 0.0 :	PHPExcel_Calculation_Functions::flattenSingleValue($ord);

		if ((is_numeric($x)) && (is_numeric($ord))) {

			if (($ord < 0) || ($x == 0.0)) {

				return PHPExcel_Calculation_Functions::NaN();

			}

			switch(floor($ord)) {

				case 0 :	return self::_Bessely0($x);

							break;

				case 1 :	return self::_Bessely1($x);

							break;

				default:	$fTox	= 2 / $x;

							$fBym	= self::_Bessely0($x);

							$fBy	= self::_Bessely1($x);

							for ($n = 1; $n < $ord; ++$n) {

								$fByp	= $n * $fTox * $fBy - $fBym;

								$fBym	= $fBy;

								$fBy	= $fByp;

							}

			}

			return (is_nan($fBy)) ? PHPExcel_Calculation_Functions::NaN() : $fBy;

		}

		return PHPExcel_Calculation_Functions::VALUE();

	}	//	function BESSELY()

	/**