<?php
/**
 * PHPExcel
 *
 * Copyright (c) 2006 - 2011 PHPExcel
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * @category   PHPExcel
 * @package    PHPExcel_Writer_Excel5
 * @copyright  Copyright (c) 2006 - 2011 PHPExcel (http://www.codeplex.com/PHPExcel)
 * @license    http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt	LGPL
 * @version    1.7.6, 2011-02-27
 */

// Original file header of PEAR::Spreadsheet_Excel_Writer_Parser (used as the base for this class):
// -----------------------------------------------------------------------------------------
// *  Class for parsing Excel formulas
// *
// *  License Information:
// *
// *    Spreadsheet_Excel_Writer:  A library for generating Excel Spreadsheets
// *    Copyright (c) 2002-2003 Xavier Noguer xnoguer@rezebra.com
// *
// *    This library is free software; you can redistribute it and/or
// *    modify it under the terms of the GNU Lesser General Public
// *    License as published by the Free Software Foundation; either
// *    version 2.1 of the License, or (at your option) any later version.
// *
// *    This library is distributed in the hope that it will be useful,
// *    but WITHOUT ANY WARRANTY; without even the implied warranty of
// *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// *    Lesser General Public License for more details.
// *
// *    You should have received a copy of the GNU Lesser General Public
// *    License along with this library; if not, write to the Free Software
// *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
// */


/**
 * PHPExcel_Writer_Excel5_Parser
 *
 * @category   PHPExcel
 * @package    PHPExcel_Writer_Excel5
 * @copyright  Copyright (c) 2006 - 2011 PHPExcel (http://www.codeplex.com/PHPExcel)
 */
class PHPExcel_Writer_Excel5_Parser
{
	/**	Constants				*/
	// Sheet title in unquoted form
	// Invalid sheet title characters cannot occur in the sheet title:
	// 		*:/\?[]
	// Moreover, there are valid sheet title characters that cannot occur in unquoted form (there may be more?)
	// +-% '^&<>=,;#()"{}
	const REGEX_SHEET_TITLE_UNQUOTED = '[^\*\:\/\\\\\?\[\]\+\-\% \\\'\^\&\<\>\=\,\;\#\(\)\"\{\}]+';

	// Sheet title in quoted form (without surrounding quotes)
	// Invalid sheet title characters cannot occur in the sheet title:
	// *:/\?[]					(usual invalid sheet title characters)
	// Single quote is represented as a pair ''
	const REGEX_SHEET_TITLE_QUOTED = '(([^\*\:\/\\\\\?\[\]\\\'])+|(\\\'\\\')+)+';

	/**
	 * The index of the character we are currently looking at
	 * @var integer
	 */
	public $_current_char;

	/**
	 * The token we are working on.
	 * @var string
	 */
	public $_current_token;

	/**
	 * The formula to parse
	 * @var string
	 */
	public $_formula;

	/**
	 * The character ahead of the current char
	 * @var string
	 */
	public $_lookahead;

	/**
	 * The parse tree to be generated
	 * @var string
	 */
	public $_parse_tree;

	/**
	 * Array of external sheets
	 * @var array
	 */
	public $_ext_sheets;

	/**
	 * Array of sheet references in the form of REF structures
	 * @var array
	 */
	public $_references;

	/**
	 * The BIFF version for the workbook
	 * @var integer
	 */
	public $_BIFF_version;

	/**
	 * The class constructor
	 *
	 * @param integer $byte_order The byte order (Little endian or Big endian) of the architecture
	 *                           (optional). 1 => big endian, 0 (default) little endian.
	 */
	public function __construct($biff_version)
	{
		$this->_current_char  = 0;
		$this->_BIFF_version  = $biff_version;
		$this->_current_token = '';       // The token we are working on.
		$this->_formula       = '';       // The formula to parse.
		$this->_lookahead     = '';       // The character ahead of the current char.
		$this->_parse_tree    = '';       // The parse tree to be generated.
		$this->_initializeHashes();      // Initialize the hashes: ptg's and function's ptg's
		$this->_ext_sheets = array();
		$this->_references = array();
	}

	/**
	 * Initialize the ptg and function hashes.
	 *
	 * @access private
	 */
	function _initializeHashes()
	{
		// The Excel ptg indices
		$this->ptg = array(
			'ptgExp'       => 0x01,
			'ptgTbl'       => 0x02,
			'ptgAdd'       => 0x03,
			'ptgSub'       => 0x04,
			'ptgMul'       => 0x05,
			'ptgDiv'       => 0x06,
			'ptgPower'     => 0x07,
			'ptgConcat'    => 0x08,
			'ptgLT'        => 0x09,
			'ptgLE'        => 0x0A,
			'ptgEQ'        => 0x0B,
			'ptgGE'        => 0x0C,
			'ptgGT'        => 0x0D,
			'ptgNE'        => 0x0E,
			'ptgIsect'     => 0x0F,
			'ptgUnion'     => 0x10,
			'ptgRange'     => 0x11,
			'ptgUplus'     => 0x12,
			'ptgUminus'    => 0x13,
			'ptgPercent'   => 0x14,
			'ptgParen'     => 0x15,
			'ptgMissArg'   => 0x16,
			'ptgStr'       => 0x17,
			'ptgAttr'      => 0x19,
			'ptgSheet'     => 0x1A,
			'ptgEndSheet'  => 0x1B,
			'ptgErr'       => 0x1C,
			'ptgBool'      => 0x1D,
			'ptgInt'       => 0x1E,
			'ptgNum'       => 0x1F,
			'ptgArray'     => 0x20,
			'ptgFunc'      => 0x21,
			'ptgFuncVar'   => 0x22,
			'ptgName'      => 0x23,
			'ptgRef'       => 0x24,
			'ptgArea'      => 0x25,
			'ptgMemArea'   => 0x26,
			'ptgMemErr'    => 0x27,
			'ptgMemNoMem'  => 0x28,
			'ptgMemFunc'   => 0x29,
			'ptgRefErr'    => 0x2A,
			'ptgAreaErr'   => 0x2B,
			'ptgRefN'      => 0x2C,
			'ptgAreaN'     => 0x2D,
			'ptgMemAreaN'  => 0x2E,
			'ptgMemNoMemN' => 0x2F,
			'ptgNameX'     => 0x39,
			'ptgRef3d'     => 0x3A,
			'ptgArea3d'    => 0x3B,
			'ptgRefErr3d'  => 0x3C,
			'ptgAreaErr3d' => 0x3D,
			'ptgArrayV'    => 0x40,
			'ptgFuncV'     => 0x41,
			'ptgFuncVarV'  => 0x42,
			'ptgNameV'     => 0x43,
			'ptgRefV'      => 0x44,
			'ptgAreaV'     => 0x45,
			'ptgMemAreaV'  => 0x46,
			'ptgMemErrV'   => 0x47,
			'ptgMemNoMemV' => 0x48,
			'ptgMemFuncV'  => 0x49,
			'ptgRefErrV'   => 0x4A,
			'ptgAreaErrV'  => 0x4B,
			'ptgRefNV'     => 0x4C,
			'ptgAreaNV'    => 0x4D,
			'ptgMemAreaNV' => 0x4E,
			'ptgMemNoMemN' => 0x4F,
			'ptgFuncCEV'   => 0x58,
			'ptgNameXV'    => 0x59,
			'ptgRef3dV'    => 0x5A,
			'ptgArea3dV'   => 0x5B,
			'ptgRefErr3dV' => 0x5C,
			'ptgAreaErr3d' => 0x5D,
			'ptgArrayA'    => 0x60,
			'ptgFuncA'     => 0x61,
			'ptgFuncVarA'  => 0x62,
			'ptgNameA'     => 0x63,
			'ptgRefA'      => 0x64,
			'ptgAreaA'     => 0x65,
			'ptgMemAreaA'  => 0x66,
			'ptgMemErrA'   => 0x67,
			'ptgMemNoMemA' => 0x68,
			'ptgMemFuncA'  => 0x69,
			'ptgRefErrA'   => 0x6A,
			'ptgAreaErrA'  => 0x6B,
			'ptgRefNA'     => 0x6C,
			'ptgAreaNA'    => 0x6D,
			'ptgMemAreaNA' => 0x6E,
			'ptgMemNoMemN' => 0x6F,
			'ptgFuncCEA'   => 0x78,
			'ptgNameXA'    => 0x79,
			'ptgRef3dA'    => 0x7A,
			'ptgArea3dA'   => 0x7B,
			'ptgRefErr3dA' => 0x7C,
			'ptgAreaErr3d' => 0x7D
			);

		// Thanks to Michael Meeks and Gnumeric for the initial arg values.
		//
		// The following hash was generated by "function_locale.pl" in the distro.
		// Refer to function_locale.pl for non-English function names.
		//
		// The array elements are as follow:
		// ptg:   The Excel function ptg code.
		// args:  The number of arguments that the function takes:
		//           >=0 is a fixed number of arguments.
		//           -1  is a variable  number of arguments.
		// class: The reference, value or array class of the function args.
		// vol:   The function is volatile.
		//
		$this->_functions = array(
			  // function                  ptg  args  class  vol
			  'COUNT'           => array(   0,   -1,    0,    0 ),
			  'IF'              => array(   1,   -1,    1,    0 ),
			  'ISNA'            => array(   2,    1,    1,    0 ),
			  'ISERROR'         => array(   3,    1,    1,    0 ),
			  'SUM'             => array(   4,   -1,    0,    0 ),
			  'AVERAGE'         => array(   5,   -1,    0,    0 ),
			  'MIN'             => array(   6,   -1,    0,    0 ),
			  'MAX'             => array(   7,   -1,    0,    0 ),
			  'ROW'             => array(   8,   -1,    0,    0 ),
			  'COLUMN'          => array(   9,   -1,    0,    0 ),
			  'NA'              => array(  10,    0,    0,    0 ),
			  'NPV'             => array(  11,   -1,    1,    0 ),
			  'STDEV'           => array(  12,   -1,    0,    0 ),
			  'DOLLAR'          => array(  13,   -1,    1,    0 ),
			  'FIXED'           => array(  14,   -1,    1,    0 ),
			  'SIN'             => array(  15,    1,    1,    0 ),
			  'COS'             => array(  16,    1,    1,    0 ),
			  'TAN'             => array(  17,    1,    1,    0 ),
			  'ATAN'            => array(  18,    1,    1,    0 ),
			  'PI'              => array(  19,    0,    1,    0 ),
			  'SQRT'            => array(  20,    1,    1,    0 ),
			  'EXP'             => array(  21,    1,    1,    0 ),
			  'LN'              => array(  22,    1,    1,    0 ),
			  'LOG10'           => array(  23,    1,    1,    0 ),
			  'ABS'             => array(  24,    1,    1,    0 ),
			  'INT'             => array(  25,    1,    1,    0 ),
			  'SIGN'            => array(  26,    1,    1,    0 ),
			  'ROUND'           => array(  27,    2,    1,    0 ),
			  'LOOKUP'          => array(  28,   -1,    0,    0 ),
			  'INDEX'           => array(  29,   -1,    0,    1 ),
			  'REPT'            => array(  30,    2,    1,    0 ),
			  'MID'             => array(  31,    3,    1,    0 ),
			  'LEN'             => array(  32,    1,    1,    0 ),
			  'VALUE'           => array(  33,    1,    1,    0 ),
			  'TRUE'            => array(  34,    0,    1,    0 ),
			  'FALSE'           => array(  35,    0,    1,    0 ),
			  'AND'             => array(  36,   -1,    0,    0 ),
			  'OR'              => array(  37,   -1,    0,    0 ),
			  'NOT'             => array(  38,    1,    1,    0 ),
			  'MOD'             => array(  39,    2,    1,    0 ),
			  'DCOUNT'          => array(  40,    3,    0,    0 ),
			  'DSUM'            => array(  41,    3,    0,    0 ),
			  'DAVERAGE'        => array(  42,    3,    0,    0 ),
			  'DMIN'            => array(  43,    3,    0,    0 ),
			  'DMAX'            => array(  44,    3,    0,    0 ),
			  'DSTDEV'          => array(  45,    3,    0,    0 ),
			  'VAR'             => array(  46,   -1,    0,    0 ),
			  'DVAR'            => array(  47,    3,    0,    0 ),
			  'TEXT'            => array(  48,    2,    1,    0 ),
			  'LINEST'          => array(  49,   -1,    0,    0 ),
			  'TREND'           => array(  50,   -1,    0,    0 ),
			  'LOGEST'          => array(  51,   -1,    0,    0 ),
			  'GROWTH'          => array(  52,   -1,    0,    0 ),
			  'PV'              => array(  56,   -1,    1,    0 ),
			  'FV'              => array(  57,   -1,    1,    0 ),
			  'NPER'            => array(  58,   -1,    1,    0 ),
			  'PMT'             => array(  59,   -1,    1,    0 ),
			  'RATE'            => array(  60,   -1,    1,    0 ),
			  'MIRR'            => array(  61,    3,    0,    0 ),
			  'IRR'             => array(  62,   -1,    0,    0 ),
			  'RAND'            => array(  63,    0,    1,    1 ),
			  'MATCH'           => array(  64,   -1,    0,    0 ),
			  'DATE'            => array(  65,    3,    1,    0 ),
			  'TIME'            => array(  66,    3,    1,    0 ),
			  'DAY'             => array(  67,    1,    1,    0 ),
			  'MONTH'           => array(  68,    1,    1,    0 ),
			  'YEAR'            => array(  69,    1,    1,    0 ),
			  'WEEKDAY'         => array(  70,   -1,    1,    0 ),
			  'HOUR'            => array(  71,    1,    1,    0 ),
			  'MINUTE'          => array(  72,    1,    1,    0 ),
			  'SECOND'          => array(  73,    1,    1,    0 ),
			  'NOW'             => array(  74,    0,    1,    1 ),
			  'AREAS'           => array(  75,    1,    0,    1 ),
			  'ROWS'            => array(  76,    1,    0,    1 ),
			  'COLUMNS'         => array(  77,    1,    0,    1 ),
			  'OFFSET'          => array(  78,   -1,    0,    1 ),
			  'SEARCH'          => array(  82,   -1,    1,    0 ),
			  'TRANSPOSE'       => array(  83,    1,    1,    0 ),
			  'TYPE'            => array(  86,    1,    1,    0 ),
			  'ATAN2'           => array(  97,    2,    1,    0 ),
			  'ASIN'            => array(  98,    1,    1,    0 ),
			  'ACOS'            => array(  99,    1,    1,    0 ),
			  'CHOOSE'          => array( 100,   -1,    1,    0 ),
			  'HLOOKUP'         => array( 101,   -1,    0,    0 ),
			  'VLOOKUP'         => array( 102,   -1,    0,    0 ),
			  'ISREF'           => array( 105,    1,    0,    0 ),
			  'LOG'             => array( 109,   -1,    1,    0 ),
			  'CHAR'            => array( 111,    1,    1,    0 ),
			  'LOWER'           => array( 112,    1,    1,    0 ),
			  'UPPER'           => array( 113,    1,    1,    0 ),
			  'PROPER'          => array( 114,    1,    1,    0 ),
			  'LEFT'            => array( 115,   -1,    1,    0 ),
			  'RIGHT'           => array( 116,   -1,    1,    0 ),
			  'EXACT'           => array( 117,    2,    1,    0 ),
			  'TRIM'            => array( 118,    1,    1,    0 ),
			  'REPLACE'         => array( 119,    4,    1,    0 ),
			  'SUBSTITUTE'      => array( 120,   -1,    1,    0 ),
			  'CODE'            => array( 121,    1,    1,    0 ),
			  'FIND'            => array( 124,   -1,    1,    0 ),
			  'CELL'            => array( 125,   -1,    0,    1 ),
			  'ISERR'           => array( 126,    1,    1,    0 ),
			  'ISTEXT'          => array( 127,    1,    1,    0 ),
			  'ISNUMBER'        => array( 128,    1,    1,    0 ),
			  'ISBLANK'         => array( 129,    1,    1,    0 ),
			  'T'               => array( 130,    1,    0,    0 ),
			  'N'               => array( 131,    1,    0,    0 ),
			  'DATEVALUE'       => array( 140,    1,    1,    0 ),
			  'TIMEVALUE'       => array( 141,    1,    1,    0 ),
			  'SLN'             => array( 142,    3,    1,    0 ),
			  'SYD'             => array( 143,    4,    1,    0 ),
			  'DDB'             => array( 144,   -1,    1,    0 ),
			  'INDIRECT'        => array( 148,   -1,    1,    1 ),
			  'CALL'            => array( 150,   -1,    1,    0 ),
			  'CLEAN'           => array( 162,    1,    1,    0 ),
			  'MDETERM'         => array( 163,    1,    2,    0 ),
			  'MINVERSE'        => array( 164,    1,    2,    0 ),
			  'MMULT'           => array( 165,    2,    2,    0 ),
			  'IPMT'            => array( 167,   -1,    1,    0 ),
			  'PPMT'            => array( 168,   -1,    1,    0 ),
			  'COUNTA'          => array( 169,   -1,    0,    0 ),
			  'PRODUCT'         => array( 183,   -1,    0,    0 ),
			  'FACT'            => array( 184,    1,    1,    0 ),
			  'DPRODUCT'        => array( 189,    3,    0,    0 ),
			  'ISNONTEXT'       => array( 190,    1,    1,    0 ),
			  'STDEVP'          => array( 193,   -1,    0,    0 ),
			  'VARP'            => array( 194,   -1,    0,    0 ),
			  'DSTDEVP'         => array( 195,    3,    0,    0 ),
			  'DVARP'           => array( 196,    3,    0,    0 ),
			  'TRUNC'           => array( 197,   -1,    1,    0 ),
			  'ISLOGICAL'       => array( 198,    1,    1,    0 ),
			  'DCOUNTA'         => array( 199,    3,    0,    0 ),
			  'USDOLLAR'        => array( 204,   -1,    1,    0 ),
			  'FINDB'           => array( 205,   -1,    1,    0 ),
			  'SEARCHB'         => array( 206,   -1,    1,    0 ),
			  'REPLACEB'        => array( 207,    4,    1,    0 ),
			  'LEFTB'           => array( 208,   -1,    1,    0 ),
			  'RIGHTB'          => array( 209,   -1,    1,    0 ),
			  'MIDB'            => array( 210,    3,    1,    0 ),
			  'LENB'            => array( 211,    1,    1,    0 ),
			  'ROUNDUP'         => array( 212,    2,    1,    0 ),
			  'ROUNDDOWN'       => array( 213,    2,    1,    0 ),
			  'ASC'             => array( 214,    1,    1,    0 ),
			  'DBCS'            => array( 215,    1,    1,    0 ),
			  'RANK'            => array( 216,   -1,    0,    0 ),
			  'ADDRESS'         => array( 219,   -1,    1,    0 ),
			  'DAYS360'         => array( 220,   -1,    1,    0 ),
			  'TODAY'           => array( 221,    0,    1,    1 ),
			  'VDB'             => array( 222,   -1,    1,    0 ),
			  'MEDIAN'          => array( 227,   -1,    0,    0 ),
			  'SUMPRODUCT'      => array( 228,   -1,    2,    0 ),
			  'SINH'            => array( 229,    1,    1,    0 ),
			  'COSH'            => array( 230,    1,    1,    0 ),
			  'TANH'            => array( 231,    1,    1,    0 ),
			  'ASINH'           => array( 232,    1,    1,    0 ),
			  'ACOSH'           => array( 233,    1,    1,    0 ),
			  'ATANH'           => array( 234,    1,    1,    0 ),
			  'DGET'            => array( 235,    3,    0,    0 ),
			  'INFO'            => array( 244,    1,    1,    1 ),
			  'DB'              => array( 247,   -1,    1,    0 ),
			  'FREQUENCY'       => array( 252,    2,    0,    0 ),
			  'ERROR.TYPE'      => array( 261,    1,    1,    0 ),
			  'REGISTER.ID'     => array( 267,   -1,    1,    0 ),
			  'AVEDEV'          => array( 269,   -1,    0,    0 ),
			  'BETADIST'        => array( 270,   -1,    1,    0 ),
			  'GAMMALN'         => array( 271,    1,    1,    0 ),
			  'BETAINV'         => array( 272,   -1,    1,    0 ),
			  'BINOMDIST'       => array( 273,    4,    1,    0 ),
			  'CHIDIST'         => array( 274,    2,    1,    0 ),
			  'CHIINV'          => array( 275,    2,    1,    0 ),
			  'COMBIN'          => array( 276,    2,    1,    0 ),
			  'CONFIDENCE'      => array( 277,    3,    1,    0 ),
			  'CRITBINOM'       => array( 278,    3,    1,    0 ),
			  'EVEN'            => array( 279,    1,    1,    0 ),
			  'EXPONDIST'       => array( 280,    3,    1,    0 ),
			  'FDIST'           => array( 281,    3,    1,    0 ),
			  'FINV'            => array( 282,    3,    1,    0 ),
			  'FISHER'          => array( 283,    1,    1,    0 ),
			  'FISHERINV'       => array( 284,    1,    1,    0 ),
			  'FLOOR'           => array( 285,    2,    1,    0 ),
			  'GAMMADIST'       => array( 286,    4,    1,    0 ),
			  'GAMMAINV'        => array( 287,    3,    1,    0 ),
			  'CEILING'         => array( 288,    2,    1,    0 ),
			  'HYPGEOMDIST'     => array( 289,    4,    1,    0 ),
			  'LOGNORMDIST'     => array( 290,    3,    1,    0 ),
			  'LOGINV'          => array( 291,    3,    1,    0 ),
			  'NEGBINOMDIST'    => array( 292,    3,    1,    0 ),
			  'NORMDIST'        => array( 293,    4,    1,    0 ),
			  'NORMSDIST'       => array( 294,    1,    1,    0 ),
			  'NORMINV'         => array( 295,    3,    1,    0 ),
			  'NORMSINV'        => array( 296,    1,    1,    0 ),
			  'STANDARDIZE'     => array( 297,    3,    1,    0 ),
			  'ODD'             => array( 298,    1,    1,    0 ),
			  'PERMUT'          => array( 299,    2,    1,    0 ),
			  'POISSON'         => array( 300,    3,    1,    0 ),
			  'TDIST'           => array( 301,    3,    1,    0 ),
			  'WEIBULL'         => array( 302,    4,    1,    0 ),
			  'SUMXMY2'         => array( 303,    2,    2,    0 ),
			  'SUMX2MY2'        => array( 304,    2,    2,    0 ),
			  'SUMX2PY2'        => array( 305,    2,    2,    0 ),
			  'CHITEST'         => array( 306,    2,    2,    0 ),
			  'CORREL'          => array( 307,    2,    2,    0 ),
			  'COVAR'           => array( 308,    2,    2,    0 ),
			  'FORECAST'        => array( 309,    3,    2,    0 ),
			  'FTEST'           => array( 310,    2,    2,    0 ),
			  'INTERCEPT'       => array( 311,    2,    2,    0 ),
			  'PEARSON'         => array( 312,    2,    2,    0 ),
			  'RSQ'             => array( 313,    2,    2,    0 ),
			  'STEYX'           => array( 314,    2,    2,    0 ),
			  'SLOPE'           => array( 315,    2,    2,    0 ),
			  'TTEST'           => array( 316,    4,    2,    0 ),
			  'PROB'            => array( 317,   -1,    2,    0 ),
			  'DEVSQ'           => array( 318,   -1,    0,    0 ),
			  'GEOMEAN'         => array( 319,   -1,    0,    0 ),
			  'HARMEAN'         => array( 320,   -1,    0,    0 ),
			  'SUMSQ'           => array( 321,   -1,    0,    0 ),
			  'KURT'            => array( 322,   -1,    0,    0 ),
			  'SKEW'            => array( 323,   -1,    0,    0 ),
			  'ZTEST'           => array( 324,   -1,    0,    0 ),
			  'LARGE'           => array( 325,    2,    0,    0 ),
			  'SMALL'           => array( 326,    2,    0,    0 ),
			  'QUARTILE'        => array( 327,    2,    0,    0 ),
			  'PERCENTILE'      => array( 328,    2,    0,    0 ),
			  'PERCENTRANK'     => array( 329,   -1,    0,    0 ),
			  'MODE'            => array( 330,   -1,    2,    0 ),
			  'TRIMMEAN'        => array( 331,    2,    0,    0 ),
			  'TINV'            => array( 332,    2,    1,    0 ),
			  'CONCATENATE'     => array( 336,   -1,    1,    0 ),
			  'POWER'           => array( 337,    2,    1,    0 ),
			  'RADIANS'         => array( 342,    1,    1,    0 ),
			  'DEGREES'         => array( 343,    1,    1,    0 ),
			  'SUBTOTAL'        => array( 344,   -1,    0,    0 ),
			  'SUMIF'           => array( 345,   -1,    0,    0 ),
			  'COUNTIF'         => array( 346,    2,    0,    0 ),
			  'COUNTBLANK'      => array( 347,    1,    0,    0 ),
			  'ISPMT'           => array( 350,    4,    1,    0 ),
			  'DATEDIF'         => array( 351,    3,    1,    0 ),
			  'DATESTRING'      => array( 352,    1,    1,    0 ),
			  'NUMBERSTRING'    => array( 353,    2,    1,    0 ),
			  'ROMAN'           => array( 354,   -1,    1,    0 ),
			  'GETPIVOTDATA'    => array( 358,   -1,    0,    0 ),
			  'HYPERLINK'       => array( 359,   -1,    1,    0 ),
			  'PHONETIC'        => array( 360,    1,    0,    0 ),
			  'AVERAGEA'        => array( 361,   -1,    0,    0 ),
			  'MAXA'            => array( 362,   -1,    0,    0 ),
			  'MINA'            => array( 363,   -1,    0,    0 ),
			  'STDEVPA'         => array( 364,   -1,    0,    0 ),
			  'VARPA'           => array( 365,   -1,    0,    0 ),
			  'STDEVA'          => array( 366,   -1,    0,    0 ),
			  'VARA'            => array( 367,   -1,    0,    0 ),
			  'BAHTTEXT'        => array( 368,    1,    0,    0 ),
			  );
	}

	/**
	 * Convert a token to the proper ptg value.
	 *
	 * @access private
	 * @param mixed $token The token to convert.
	 * @return mixed the converted token on success
	 */
	function _convert($token)
	{
		if (preg_match("/\"([^\"]|\"\"){0,255}\"/", $token)) {
			return $this->_convertString($token);

		} elseif (is_numeric($token)) {
			return $this->_convertNumber($token);

		// match references like A1 or $A$1
		} elseif (preg_match('/^\$?([A-Ia-i]?[A-Za-z])\$?(\d+)$/',$token)) {
			return $this->_convertRef2d($token);

		// match external references like Sheet1!A1 or Sheet1:Sheet2!A1 or Sheet1!$A$1 or Sheet1:Sheet2!$A$1
		} elseif (preg_match("/^" . self::REGEX_SHEET_TITLE_UNQUOTED . "(\:" . self::REGEX_SHEET_TITLE_UNQUOTED . ")?\!\\$?[A-Ia-i]?[A-Za-z]\\$?(\d+)$/u",$token)) {
			return $this->_convertRef3d($token);

		// match external references like 'Sheet1'!A1 or 'Sheet1:Sheet2'!A1 or 'Sheet1'!$A$1 or 'Sheet1:Sheet2'!$A$1
		} elseif (preg_match("/^'" . self::REGEX_SHEET_TITLE_QUOTED . "(\:" . self::REGEX_SHEET_TITLE_QUOTED . ")?'\!\\$?[A-Ia-i]?[A-Za-z]\\$?(\d+)$/u",$token)) {
			return $this->_convertRef3d($token);

		// match ranges like A1:B2 or $A$1:$B$2
		} elseif (preg_match('/^(\$)?[A-Ia-i]?[A-Za-z](\$)?(\d+)\:(\$)?[A-Ia-i]?[A-Za-z](\$)?(\d+)$/', $token)) {
			return $this->_convertRange2d($token);

		// match external ranges like Sheet1!A1:B2 or Sheet1:Sheet2!A1:B2 or Sheet1!$A$1:$B$2 or Sheet1:Sheet2!$A$1:$B$2
		} elseif (preg_match("/^" . self::REGEX_SHEET_TITLE_UNQUOTED . "(\:" . self::REGEX_SHEET_TITLE_UNQUOTED . ")?\!\\$?([A-Ia-i]?[A-Za-z])?\\$?(\d+)\:\\$?([A-Ia-i]?[A-Za-z])?\\$?(\d+)$/u",$token)) {
			return $this->_convertRange3d($token);

		// match external ranges like 'Sheet1'!A1:B2 or 'Sheet1:Sheet2'!A1:B2 or 'Sheet1'!$A$1:$B$2 or 'Sheet1:Sheet2'!$A$1:$B$2
		} elseif (preg_match("/^'" . self::REGEX_SHEET_TITLE_QUOTED . "(\:" . self::REGEX_SHEET_TITLE_QUOTED . ")?'\!\\$?([A-Ia-i]?[A-Za-z])?\\$?(\d+)\:\\$?([A-Ia-i]?[A-Za-z])?\\$?(\d+)$/u",$token)) {
			return $this->_convertRange3d($token);

		// operators (including parentheses)
		} elseif (isset($this->ptg[$token])) {
			return pack("C", $this->ptg[$token]);

        // match error codes
		} elseif (preg_match("/^#[A-Z0\/]{3,5}[!?]{1}$/", $token) or $token == '#N/A') {
		    return $this->_convertError($token);

		// commented so argument number can be processed correctly. See toReversePolish().
		/*elseif (preg_match("/[A-Z0-9\xc0-\xdc\.]+/",$token))
		{
			return($this->_convertFunction($token,$this->_func_args));
		}*/

		// if it's an argument, ignore the token (the argument remains)
		} elseif ($token == 'arg') {
			return '';
		}

		// TODO: use real error codes
		throw new Exception("Unknown token $token");
	}

	/**
	 * Convert a number token to ptgInt or ptgNum
	 *
	 * @access private
	 * @param mixed $num an integer or double for conversion to its ptg value
	 */
	function _convertNumber($num)
	{
		// Integer in the range 0..2**16-1
		if ((preg_match("/^\d+$/", $num)) and ($num <= 65535)) {
			return pack("Cv", $this->ptg['ptgInt'], $num);
		} else { // A float
			if (PHPExcel_Writer_Excel5_BIFFwriter::getByteOrder()) { // if it's Big Endian
				$num = strrev($num);
			}
			return pack("Cd", $this->ptg['ptgNum'], $num);
		}
	}

	/**
	 * Convert a string token to ptgStr
	 *
	 * @access private
	 * @param string $string A string for conversion to its ptg value.
	 * @return mixed the converted token on success
	 */
	function _convertString($string)
	{
		// chop away beggining and ending quotes
		$string = substr($string, 1, strlen($string) - 2);
		if (strlen($string) > 255) {
			throw new Exception("String is too long");
		}

		if ($this->_BIFF_version == 0x0500) {
			return pack("CC", $this->ptg['ptgStr'], strlen($string)).$string;
		} elseif ($this->_BIFF_version == 0x0600) {
			return pack('C', $this->ptg['ptgStr']) . PHPExcel_Shared_String::UTF8toBIFF8UnicodeShort($string);
		}
	}

	/**
	 * Convert a function to a ptgFunc or ptgFuncVarV depending on the number of
	 * args that it takes.
	 *
	 * @access private
	 * @param string  $token    The name of the function for convertion to ptg value.
	 * @param integer $num_args The number of arguments the function receives.
	 * @return string The packed ptg for the function
	 */
	function _convertFunction($token, $num_args)
	{
		$args     = $this->_functions[$token][1];
		$volatile = $this->_functions[$token][3];

		// Fixed number of args eg. TIME($i,$j,$k).
		if ($args >= 0) {
			return pack("Cv", $this->ptg['ptgFuncV'], $this->_functions[$token][0]);
		}
		// Variable number of args eg. SUM($i,$j,$k, ..).
		if ($args == -1) {
			return pack("CCv", $this->ptg['ptgFuncVarV'], $num_args, $this->_functions[$token][0]);
		}
	}

	/**
	 * Convert an Excel range such as A1:D4 to a ptgRefV.
	 *
	 * @access private
	 * @param string $range An Excel range in the A1:A2
	 */
	function _convertRange2d($range, $class=0)
	{

		// TODO: possible class value 0,1,2 check Formula.pm
		// Split the range into 2 cell refs
		if (preg_match('/^(\$)?([A-Ia-i]?[A-Za-z])(\$)?(\d+)\:(\$)?([A-Ia-i]?[A-Za-z])(\$)?(\d+)$/', $range)) {
			list($cell1, $cell2) = explode(':', $range);
		} else {
			// TODO: use real error codes
			throw new Exception("Unknown range separator");
		}

		// Convert the cell references
		$cell_array1 = $this->_cellToPackedRowcol($cell1);
		list($row1, $col1) = $cell_array1;
		$cell_array2 = $this->_cellToPackedRowcol($cell2);
		list($row2, $col2) = $cell_array2;

		// The ptg value depends on the class of the ptg.
		if ($class == 0) {
			$ptgArea = pack("C", $this->ptg['ptgArea']);
		} elseif ($class == 1) {
			$ptgArea = pack("C", $this->ptg['ptgAreaV']);
		} elseif ($class == 2) {
			$ptgArea = pack("C", $this->ptg['ptgAreaA']);
		} else {
			// TODO: use real error codes
			throw new Exception("Unknown class $class");
		}
		return $ptgArea . $row1 . $row2 . $col1. $col2;
	}

	/**
	 * Convert an Excel 3d range such as "Sheet1!A1:D4" or "Sheet1:Sheet2!A1:D4" to
	 * a ptgArea3d.
	 *
	 * @access private
	 * @param string $token An Excel range in the Sheet1!A1:A2 format.
	 * @return mixed The packed ptgArea3d token on success.
	 */
	function _convertRange3d($token)
	{
		$class = 0; // formulas like Sheet1!$A$1:$A$2 in list type data validation need this class (0x3B)

		// Split the ref at the ! symbol
		list($ext_ref, $range) = explode('!', $token);

		// Convert the external reference part (different for BIFF8)
		if ($this->_BIFF_version == 0x0500) {
			$ext_ref = $this->_packExtRef($ext_ref);
		} elseif ($this->_BIFF_version == 0x0600) {
			 $ext_ref = $this->_getRefIndex($ext_ref);
		}

		// Split the range into 2 cell refs
		list($cell1, $cell2) = explode(':', $range);

		// Convert the cell references
		if (preg_match("/^(\\$)?[A-Ia-i]?[A-Za-z](\\$)?(\d+)$/", $cell1)) {
			$cell_array1 = $this->_cellToPackedRowcol($cell1);
			list($row1, $col1) = $cell_array1;
			$cell_array2 = $this->_cellToPackedRowcol($cell2);
			list($row2, $col2) = $cell_array2;
		} else { // It's a rows range (like 26:27)
			 $cells_array = $this->_rangeToPackedRange($cell1.':'.$cell2);
			 list($row1, $col1, $row2, $col2) = $cells_array;
		}

		// The ptg value depends on the class of the ptg.
		if ($class == 0) {
			$ptgArea = pack("C", $this->ptg['ptgArea3d']);
		} elseif ($class == 1) {
			$ptgArea = pack("C", $this->ptg['ptgArea3dV']);
		} elseif ($class == 2) {
			$ptgArea = pack("C", $this->ptg['ptgArea3dA']);
		} else {
			throw new Exception("Unknown class $class");
		}

		return $ptgArea . $ext_ref . $row1 . $row2 . $col1. $col2;
	}

	/**
	 * Convert an Excel reference such as A1, $B2, C$3 or $D$4 to a ptgRefV.
	 *
	 * @access private
	 * @param string $cell An Excel cell reference
	 * @return string The cell in packed() format with the corresponding ptg
	 */
	function _convertRef2d($cell)
	{
		$class = 2; // as far as I know, this is magick.

		// Convert the cell reference
		$cell_array = $this->_cellToPackedRowcol($cell);
		list($row, $col) = $cell_array;

		// The ptg value depends on the class of the ptg.
		if ($class == 0) {
			$ptgRef = pack("C", $this->ptg['ptgRef']);
		} elseif ($class == 1) {
			$ptgRef = pack("C", $this->ptg['ptgRefV']);
		} elseif ($class == 2) {
			$ptgRef = pack("C", $this->ptg['ptgRefA']);
		} else {
			// TODO: use real error codes
			throw new Exception("Unknown class $class");
		}
		return $ptgRef.$row.$col;
	}

	/**
	 * Convert an Excel 3d reference such as "Sheet1!A1" or "Sheet1:Sheet2!A1" to a
	 * ptgRef3d.
	 *
	 * @access private
	 * @param string $cell An Excel cell reference
	 * @return mixed The packed ptgRef3d token on success.
	 */
	function _convertRef3d($cell)
	{
		$class = 2; // as far as I know, this is magick.

		// Split the ref at the ! symbol
		list($ext_ref, $cell) = explode('!', $cell);

		// Convert the external reference part (different for BIFF8)
		if ($this->_BIFF_version == 0x0500) {
			$ext_ref = $this->_packExtRef($ext_ref);
		} elseif ($this->_BIFF_version == 0x0600) {
			$ext_ref = $this->_getRefIndex($ext_ref);
		}

		// Convert the cell reference part
		list($row, $col) = $this->_cellToPackedRowcol($cell);

		// The ptg value depends on the class of the ptg.
		if ($class == 0) {
			$ptgRef = pack("C", $this->ptg['ptgRef3d']);
		} elseif ($class == 1) {
			$ptgRef = pack("C", $this->ptg['ptgRef3dV']);
		} elseif ($class == 2) {
			$ptgRef = pack("C", $this->ptg['ptgRef3dA']);
		} else {
			throw new Exception("Unknown class $class");
		}

		return $ptgRef . $ext_ref. $row . $col;
	}

    /**
     * Convert an error code to a ptgErr
     *
     * @access private
     * @param mixed $num an error codefor conversion to its ptg value
     */
    function _convertError($errorCode)
    {
        switch ($errorCode) {
            case '#NULL!':	return pack("C", 0x00);
            case '#DIV/0!':	return pack("C", 0x07);
            case '#VALUE!':	return pack("C", 0x0F);
            case '#REF!':	return pack("C", 0x17);
            case '#NAME?':	return pack("C", 0x1D);
            case '#NUM!':	return pack("C", 0x24);
            case '#N/A':	return pack("C", 0x2A);
        }
        return pack("C", 0xFF);
    }

	/**
	 * Convert the sheet name part of an external reference, for example "Sheet1" or
	 * "Sheet1:Sheet2", to a packed structure.
	 *
	 * @access private
	 * @param string $ext_ref The name of the external reference
	 * @return string The reference index in packed() format
	 */
	function _packExtRef($ext_ref)
	{
		$ext_ref = preg_replace("/^'/", '', $ext_ref); // Remove leading  ' if any.
		$ext_ref = preg_replace("/'$/", '', $ext_ref); // Remove trailing ' if any.

		// Check if there is a sheet range eg., Sheet1:Sheet2.
		if (preg_match("/:/", $ext_ref)) {
			list($sheet_name1, $sheet_name2) = explode(':', $ext_ref);

			$sheet1 = $this->_getSheetIndex($sheet_name1);
			if ($sheet1 == -1) {
				throw new Exception("Unknown sheet name $sheet_name1 in formula");
			}
			$sheet2 = $this->_getSheetIndex($sheet_name2);
			if ($sheet2 == -1) {
				throw new Exception("Unknown sheet name $sheet_name2 in formula");
			}

			// Reverse max and min sheet numbers if necessary
			if ($sheet1 > $sheet2) {
				list($sheet1, $sheet2) = array($sheet2, $sheet1);
			}
		} else { // Single sheet name only.
			$sheet1 = $this->_getSheetIndex($ext_ref);
			if ($sheet1 == -1) {
				throw new Exception("Unknown sheet name $ext_ref in formula");
			}
			$sheet2 = $sheet1;
		}

		// References are stored relative to 0xFFFF.
		$offset = -1 - $sheet1;

		return pack('vdvv', $offset, 0x00, $sheet1, $sheet2);
	}

	/**
	 * Look up the REF index that corresponds to an external sheet name
	 * (or range). If it doesn't exist yet add it to the workbook's references
	 * array. It assumes all sheet names given must exist.
	 *
	 * @access private
	 * @param string $ext_ref The name of the external reference
	 * @return mixed The reference index in packed() format on success
	 */
	function _getRefIndex($ext_ref)
	{
		$ext_ref = preg_replace("/^'/", '', $ext_ref); // Remove leading  ' if any.
		$ext_ref = preg_replace("/'$/", '', $ext_ref); // Remove trailing ' if any.
		$ext_ref = str_replace('\'\'', '\'', $ext_ref); // Replace escaped '' with '

		// Check if there is a sheet range eg., Sheet1:Sheet2.
		if (preg_match("/:/", $ext_ref)) {
			list($sheet_name1, $sheet_name2) = explode(':', $ext_ref);

			$sheet1 = $this->_getSheetIndex($sheet_name1);
			if ($sheet1 == -1) {
				throw new Exception("Unknown sheet name $sheet_name1 in formula");
			}
			$sheet2 = $this->_getSheetIndex($sheet_name2);
			if ($sheet2 == -1) {
				throw new Exception("Unknown sheet name $sheet_name2 in formula");
			}

			// Reverse max and min sheet numbers if necessary
			if ($sheet1 > $sheet2) {
				list($sheet1, $sheet2) = array($sheet2, $sheet1);
			}
		} else { // Single sheet name only.
			$sheet1 = $this->_getSheetIndex($ext_ref);
			if ($sheet1 == -1) {
				throw new Exception("Unknown sheet name $ext_ref in formula");
			}
			$sheet2 = $sheet1;
		}

		// assume all references belong to this document
		$supbook_index = 0x00;
		$ref = pack('vvv', $supbook_index, $sheet1, $sheet2);
		$total_references = count($this->_references);
		$index = -1;
		for ($i = 0; $i < $total_references; ++$i) {
			if ($ref == $this->_references[$i]) {
				$index = $i;
				break;
			}
		}
		// if REF was not found add it to references array
		if ($index == -1) {
			$this->_references[$total_references] = $ref;
			$index = $total_references;
		}

		return pack('v', $index);
	}

	/**
	 * Look up the index that corresponds to an external sheet name. The hash of
	 * sheet names is updated by the addworksheet() method of the
	 * PHPExcel_Writer_Excel5_Workbook class.
	 *
	 * @access private
	 * @return integer The sheet index, -1 if the sheet was not found
	 */
	function _getSheetIndex($sheet_name)
	{
		if (!isset($this->_ext_sheets[$sheet_name])) {
			return -1;
		} else {
			return $this->_ext_sheets[$sheet_name];
		}
	}

	/**
	 * This method is used to update the array of sheet names. It is
	 * called by the addWorksheet() method of the
	 * PHPExcel_Writer_Excel5_Workbook class.
	 *
	 * @access public
	 * @see PHPExcel_Writer_Excel5_Workbook::addWorksheet()
	 * @param string  $name  The name of the worksheet being added
	 * @param integer $index The index of the worksheet being added
	 */
	function setExtSheet($name, $index)
	{
		$this->_ext_sheets[$name] = $index;
	}

	/**
	 * pack() row and column into the required 3 or 4 byte format.
	 *
	 * @access private
	 * @param string $cell The Excel cell reference to be packed
	 * @return array Array containing the row and column in packed() format
	 */
	function _cellToPackedRowcol($cell)
	{
		$cell = strtoupper($cell);
		list($row, $col, $row_rel, $col_rel) = $this->_cellToRowcol($cell);
		if ($col >= 256) {
			throw new Exception("Column in: $cell greater than 255");
		}
		// FIXME: change for BIFF8
		if ($row >= 16384) {
			throw new Exception("Row in: $cell greater than 16384 ");
		}

		// Set the high bits to indicate if row or col are relative.
		if ($this->_BIFF_version == 0x0500) {
			$row    |= $col_rel << 14;
			$row    |= $row_rel << 15;
			$col     = pack('C', $col);
		} elseif ($this->_BIFF_version == 0x0600) {
			$col    |= $col_rel << 14;
			$col    |= $row_rel << 15;
			$col     = pack('v', $col);
		}
		$row     = pack('v', $row);

		return array($row, $col);
	}

	/**
	 * pack() row range into the required 3 or 4 byte format.
	 * Just using maximum col/rows, which is probably not the correct solution
	 *
	 * @access private
	 * @param string $range The Excel range to be packed
	 * @return array Array containing (row1,col1,row2,col2) in packed() format
	 */
	function _rangeToPackedRange($range)
	{
		preg_match('/(\$)?(\d+)\:(\$)?(\d+)/', $range, $match);
		// return absolute rows if there is a $ in the ref
		$row1_rel = empty($match[1]) ? 1 : 0;
		$row1     = $match[2];
		$row2_rel = empty($match[3]) ? 1 : 0;
		$row2     = $match[4];
		// Convert 1-index to zero-index
		--$row1;
		--$row2;
		// Trick poor inocent Excel
		$col1 = 0;
		$col2 = 16383; // FIXME: maximum possible value for Excel 5 (change this!!!)

		// FIXME: this changes for BIFF8
		if (($row1 >= 16384) or ($row2 >= 16384)) {
			throw new Exception("Row in: $range greater than 16384 ");
		}

		// Set the high bits to indicate if rows are relative.
		if ($this->_BIFF_version == 0x0500) {
			$row1    |= $row1_rel << 14; // FIXME: probably a bug
			$row2    |= $row2_rel << 15;
			$col1     = pack('C', $col1);
			$col2     = pack('C', $col2);
		} elseif ($this->_BIFF_version == 0x0600) {
			$col1    |= $row1_rel << 15;
			$col2    |= $row2_rel << 15;
			$col1     = pack('v', $col1);
			$col2     = pack('v', $col2);
		}
		$row1     = pack('v', $row1);
		$row2     = pack('v', $row2);

		return array($row1, $col1, $row2, $col2);
	}

	/**
	 * Convert an Excel cell reference such as A1 or $B2 or C$3 or $D$4 to a zero
	 * indexed row and column number. Also returns two (0,1) values to indicate
	 * whether the row or column are relative references.
	 *
	 * @access private
	 * @param string $cell The Excel cell reference in A1 format.
	 * @return array
	 */
	function _cellToRowcol($cell)
	{
		preg_match('/(\$)?([A-I]?[A-Z])(\$)?(\d+)/',$cell,$match);
		// return absolute column if there is a $ in the ref
		$col_rel = empty($match[1]) ? 1 : 0;
		$col_ref = $match[2];
		$row_rel = empty($match[3]) ? 1 : 0;
		$row     = $match[4];

		// Convert base26 column string to a number.
		$expn   = strlen($col_ref) - 1;
		$col    = 0;
		$col_ref_length = strlen($col_ref);
		for ($i = 0; $i < $col_ref_length; ++$i) {
			$col += (ord($col_ref{$i}) - 64) * pow(26, $expn);
			--$expn;
		}

		// Convert 1-index to zero-index
		--$row;
		--$col;

		return array($row, $col, $row_rel, $col_rel);
	}

	/**
	 * Advance to the next valid token.
	 *
	 * @access private
	 */
	function _advance()
	{
		$i = $this->_current_char;
		$formula_length = strlen($this->_formula);
		// eat up white spaces
		if ($i < $formula_length) {
			while ($this->_formula{$i} == " ") {
				++$i;
			}

			if ($i < ($formula_length - 1)) {
				$this->_lookahead = $this->_formula{$i+1};
			}
			$token = '';
		}

		while ($i < $formula_length) {
			$token .= $this->_formula{$i};
			if ($i < ($formula_length - 1)) {
				$this->_lookahead = $this->_formula{$i+1};
			} else {
				$this->_lookahead = '';
			}

			if ($this->_match($token) != '') {
				//if ($i < strlen($this->_formula) - 1) {
				//    $this->_lookahead = $this->_formula{$i+1};
				//}
				$this->_current_char = $i + 1;
				$this->_current_token = $token;
				return 1;
			}

			if ($i < ($formula_length - 2)) {
				$this->_lookahead = $this->_formula{$i+2};
			} else { // if we run out of characters _lookahead becomes empty
				$this->_lookahead = '';
			}
			++$i;
		}
		//die("Lexical error ".$this->_current_char);
	}

	/**
	 * Checks if it's a valid token.
	 *
	 * @access private
	 * @param mixed $token The token to check.
	 * @return mixed       The checked token or false on failure
	 */
	function _match($token)
	{
		switch($token) {
			case "+":
			case "-":
			case "*":
			case "/":
			case "(":
			case ")":
			case ",":
			case ";":
			case ">=":
			case "<=":
			case "=":
			case "<>":
			case "^":
			case "&":
			case "%":
				return $token;
				break;
			case ">":
				if ($this->_lookahead == '=') { // it's a GE token
					break;
				}
				return $token;
				break;
			case "<":
				// it's a LE or a NE token
				if (($this->_lookahead == '=') or ($this->_lookahead == '>')) {
					break;
				}
				return $token;
				break;
			default:
				// if it's a reference A1 or $A$1 or $A1 or A$1
				if (preg_match('/^\$?[A-Ia-i]?[A-Za-z]\$?[0-9]+$/',$token) and
				   !preg_match("/[0-9]/",$this->_lookahead) and
				   ($this->_lookahead != ':') and ($this->_lookahead != '.') and
				   ($this->_lookahead != '!'))
				{
					return $token;
				}
				// If it's an external reference (Sheet1!A1 or Sheet1:Sheet2!A1 or Sheet1!$A$1 or Sheet1:Sheet2!$A$1)
				elseif (preg_match("/^" . self::REGEX_SHEET_TITLE_UNQUOTED . "(\:" . self::REGEX_SHEET_TITLE_UNQUOTED . ")?\!\\$?[A-Ia-i]?[A-Za-z]\\$?[0-9]+$/u",$token) and
					   !preg_match("/[0-9]/",$this->_lookahead) and
					   ($this->_lookahead != ':') and ($this->_lookahead != '.'))
				{
					return $token;
				}
				// If it's an external reference ('Sheet1'!A1 or 'Sheet1:Sheet2'!A1 or 'Sheet1'!$A$1 or 'Sheet1:Sheet2'!$A$1)
				elseif (preg_match("/^'" . self::REGEX_SHEET_TITLE_QUOTED . "(\:" . self::REGEX_SHEET_TITLE_QUOTED . ")?'\!\\$?[A-Ia-i]?[A-Za-z]\\$?[0-9]+$/u",$token) and
					   !preg_match("/[0-9]/",$this->_lookahead) and
					   ($this->_lookahead != ':') and ($this->_lookahead != '.'))
				{
					return $token;
				}
				// if it's a range A1:A2 or $A$1:$A$2
				elseif (preg_match('/^(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+:(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+$/', $token) and
					   !preg_match("/[0-9]/",$this->_lookahead))
				{
					return $token;
				}
				// If it's an external range like Sheet1!A1:B2 or Sheet1:Sheet2!A1:B2 or Sheet1!$A$1:$B$2 or Sheet1:Sheet2!$A$1:$B$2
				elseif (preg_match("/^" . self::REGEX_SHEET_TITLE_UNQUOTED . "(\:" . self::REGEX_SHEET_TITLE_UNQUOTED . ")?\!\\$?([A-Ia-i]?[A-Za-z])?\\$?[0-9]+:\\$?([A-Ia-i]?[A-Za-z])?\\$?[0-9]+$/u",$token) and
					   !preg_match("/[0-9]/",$this->_lookahead))
				{
					return $token;
				}
				// If it's an external range like 'Sheet1'!A1:B2 or 'Sheet1:Sheet2'!A1:B2 or 'Sheet1'!$A$1:$B$2 or 'Sheet1:Sheet2'!$A$1:$B$2
				elseif (preg_match("/^'" . self::REGEX_SHEET_TITLE_QUOTED . "(\:" . self::REGEX_SHEET_TITLE_QUOTED . ")?'\!\\$?([A-Ia-i]?[A-Za-z])?\\$?[0-9]+:\\$?([A-Ia-i]?[A-Za-z])?\\$?[0-9]+$/u",$token) and
					   !preg_match("/[0-9]/",$this->_lookahead))
				{
					return $token;
				}
				// If it's a number (check that it's not a sheet name or range)
				elseif (is_numeric($token) and
						(!is_numeric($token.$this->_lookahead) or ($this->_lookahead == '')) and
						($this->_lookahead != '!') and ($this->_lookahead != ':'))
				{
					return $token;
				}
				// If it's a string (of maximum 255 characters)
				elseif (preg_match("/\"([^\"]|\"\"){0,255}\"/",$token) and $this->_lookahead != '"' and (substr_count($token, '"')%2 == 0))
				{
					return $token;
				}
			    // If it's an error code
			    elseif (preg_match("/^#[A-Z0\/]{3,5}[!?]{1}$/", $token) or $token == '#N/A')
			    {
			        return $token;
			    }
				// if it's a function call
				elseif (preg_match("/^[A-Z0-9\xc0-\xdc\.]+$/i",$token) and ($this->_lookahead == "("))
				{
					return $token;
				}
				return '';
		}
	}

	/**
	 * The parsing method. It parses a formula.
	 *
	 * @access public
	 * @param string $formula The formula to parse, without the initial equal
	 *                        sign (=).
	 * @return mixed true on success
	 */
	function parse($formula)
	{
		$this->_current_char = 0;
		$this->_formula      = $formula;
		$this->_lookahead    = isset($formula{1}) ? $formula{1} : '';
		$this->_advance();
		$this->_parse_tree   = $this->_condition();
		return true;
	}

	/**
	 * It parses a condition. It assumes the following rule:
	 * Cond -> Expr [(">" | "<") Expr]
	 *
	 * @access private
	 * @return mixed The parsed ptg'd tree on success
	 */
	function _condition()
	{
		$result = $this->_expression();
		if ($this->_current_token == "<") {
			$this->_advance();
			$result2 = $this->_expression();
			$result = $this->_createTree('ptgLT', $result, $result2);
		} elseif ($this->_current_token == ">") {
			$this->_advance();
			$result2 = $this->_expression();
			$result = $this->_createTree('ptgGT', $result, $result2);
		} elseif ($this->_current_token == "<=") {
			$this->_advance();
			$result2 = $this->_expression();
			$result = $this->_createTree('ptgLE', $result, $result2);
		} elseif ($this->_current_token == ">=") {
			$this->_advance();
			$result2 = $this->_expression();
			$result = $this->_createTree('ptgGE', $result, $result2);
		} elseif ($this->_current_token == "=") {
			$this->_advance();
			$result2 = $this->_expression();
			$result = $this->_createTree('ptgEQ', $result, $result2);
		} elseif ($this->_current_token == "<>") {
			$this->_advance();
			$result2 = $this->_expression();
			$result = $this->_createTree('ptgNE', $result, $result2);
		} elseif ($this->_current_token == "&") {
		    $this->_advance();
		    $result2 = $this->_expression();
		    $result = $this->_createTree('ptgConcat', $result, $result2);
		}
		return $result;
	}

	/**
	 * It parses a expression. It assumes the following rule:
	 * Expr -> Term [("+" | "-") Term]
	 *      -> "string"
	 *      -> "-" Term : Negative value
	 *      -> "+" Term : Positive value
	 *      -> Error code
	 *
	 * @access private
	 * @return mixed The parsed ptg'd tree on success
	 */
	function _expression()
	{
		// If it's a string return a string node
		if (preg_match("/\"([^\"]|\"\"){0,255}\"/", $this->_current_token)) {
			$tmp = str_replace('""', '"', $this->_current_token);
			if (($tmp == '"') || ($tmp == '')) $tmp = '""';	//	Trap for "" that has been used for an empty string
			$result = $this->_createTree($tmp, '', '');
			$this->_advance();
			return $result;
        // If it's an error code
        } elseif (preg_match("/^#[A-Z0\/]{3,5}[!?]{1}$/", $this->_current_token) or $this->_current_token == '#N/A'){
		    $result = $this->_createTree($this->_current_token, 'ptgErr', '');
		    $this->_advance();
		    return $result;
		// If it's a negative value
        } elseif ($this->_current_token == "-") {
			// catch "-" Term
			$this->_advance();
			$result2 = $this->_expression();
			$result = $this->_createTree('ptgUminus', $result2, '');
			return $result;
        // If it's a positive value
		} elseif ($this->_current_token == "+") {
			// catch "+" Term
			$this->_advance();
			$result2 = $this->_expression();
			$result = $this->_createTree('ptgUplus', $result2, '');
			return $result;
		}
		$result = $this->_term();
		while (($this->_current_token == "+") or
			   ($this->_current_token == "-") or
			   ($this->_current_token == "^")) {
		/**/
			if ($this->_current_token == "+") {
				$this->_advance();
				$result2 = $this->_term();
				$result = $this->_createTree('ptgAdd', $result, $result2);
			} elseif ($this->_current_token == "-") {
				$this->_advance();
				$result2 = $this->_term();
				$result = $this->_createTree('ptgSub', $result, $result2);
			} else {
				$this->_advance();
				$result2 = $this->_term();
				$result = $this->_createTree('ptgPower', $result, $result2);
			}
		}
		return $result;
	}

	/**
	 * This function just introduces a ptgParen element in the tree, so that Excel
	 * doesn't get confused when working with a parenthesized formula afterwards.
	 *
	 * @access private
	 * @see _fact()
	 * @return array The parsed ptg'd tree
	 */
	function _parenthesizedExpression()
	{
		$result = $this->_createTree('ptgParen', $this->_expression(), '');
		return $result;
	}

	/**
	 * It parses a term. It assumes the following rule:
	 * Term -> Fact [("*" | "/") Fact]
	 *
	 * @access private
	 * @return mixed The parsed ptg'd tree on success
	 */
	function _term()
	{
		$result = $this->_fact();
		while (($this->_current_token == "*") or
			   ($this->_current_token == "/")) {
		/**/
			if ($this->_current_token == "*") {
				$this->_advance();
				$result2 = $this->_fact();
				$result = $this->_createTree('ptgMul', $result, $result2);
			} else {
				$this->_advance();
				$result2 = $this->_fact();
				$result = $this->_createTree('ptgDiv', $result, $result2);
			}
		}
		return $result;
	}

	/**
	 * It parses a factor. It assumes the following rule:
	 * Fact -> ( Expr )
	 *       | CellRef
	 *       | CellRange
	 *       | Number
	 *       | Function
	 *
	 * @access private
	 * @return mixed The parsed ptg'd tree on success
	 */
	function _fact()
	{
		if ($this->_current_token == "(") {
			$this->_advance();         // eat the "("
			$result = $this->_parenthesizedExpression();
			if ($this->_current_token != ")") {
				throw new Exception("')' token expected.");
			}
			$this->_advance();         // eat the ")"
			return $result;
		}
		// if it's a reference
		if (preg_match('/^\$?[A-Ia-i]?[A-Za-z]\$?[0-9]+$/',$this->_current_token))
		{
			$result = $this->_createTree($this->_current_token, '', '');
			$this->_advance();
			return $result;
		}
		// If it's an external reference (Sheet1!A1 or Sheet1:Sheet2!A1 or Sheet1!$A$1 or Sheet1:Sheet2!$A$1)
		elseif (preg_match("/^" . self::REGEX_SHEET_TITLE_UNQUOTED . "(\:" . self::REGEX_SHEET_TITLE_UNQUOTED . ")?\!\\$?[A-Ia-i]?[A-Za-z]\\$?[0-9]+$/u",$this->_current_token))
		{
			$result = $this->_createTree($this->_current_token, '', '');
			$this->_advance();
			return $result;
		}
		// If it's an external reference ('Sheet1'!A1 or 'Sheet1:Sheet2'!A1 or 'Sheet1'!$A$1 or 'Sheet1:Sheet2'!$A$1)
		elseif (preg_match("/^'" . self::REGEX_SHEET_TITLE_QUOTED . "(\:" . self::REGEX_SHEET_TITLE_QUOTED . ")?'\!\\$?[A-Ia-i]?[A-Za-z]\\$?[0-9]+$/u",$this->_current_token))
		{
			$result = $this->_createTree($this->_current_token, '', '');
			$this->_advance();
			return $result;
		}
		// if it's a range A1:B2 or $A$1:$B$2
		elseif (preg_match('/^(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+:(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+$/',$this->_current_token) or
				preg_match('/^(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+\.\.(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+$/',$this->_current_token))
		{
			// must be an error?
			$result = $this->_createTree($this->_current_token, '', '');
			$this->_advance();
			return $result;
		}
		// If it's an external range (Sheet1!A1:B2 or Sheet1:Sheet2!A1:B2 or Sheet1!$A$1:$B$2 or Sheet1:Sheet2!$A$1:$B$2)
		elseif (preg_match("/^" . self::REGEX_SHEET_TITLE_UNQUOTED . "(\:" . self::REGEX_SHEET_TITLE_UNQUOTED . ")?\!\\$?([A-Ia-i]?[A-Za-z])?\\$?[0-9]+:\\$?([A-Ia-i]?[A-Za-z])?\\$?[0-9]+$/u",$this->_current_token))
		{
			// must be an error?
			//$result = $this->_current_token;
			$result = $this->_createTree($this->_current_token, '', '');
			$this->_advance();
			return $result;
		}
		// If it's an external range ('Sheet1'!A1:B2 or 'Sheet1'!A1:B2 or 'Sheet1'!$A$1:$B$2 or 'Sheet1'!$A$1:$B$2)
		elseif (preg_match("/^'" . self::REGEX_SHEET_TITLE_QUOTED . "(\:" . self::REGEX_SHEET_TITLE_QUOTED . ")?'\!\\$?([A-Ia-i]?[A-Za-z])?\\$?[0-9]+:\\$?([A-Ia-i]?[A-Za-z])?\\$?[0-9]+$/u",$this->_current_token))
		{
			// must be an error?
			//$result = $this->_current_token;
			$result = $this->_createTree($this->_current_token, '', '');
			$this->_advance();
			return $result;
		}
		// If it's a number or a percent
		elseif (is_numeric($this->_current_token))
		{
		    if($this->_lookahead == '%'){
		        $result = $this->_createTree('ptgPercent', $this->_current_token, '');
		    } else {
		        $result = $this->_createTree($this->_current_token, '', '');
		    }
		    $this->_advance();
		    return $result;
		}
		// if it's a function call
		elseif (preg_match("/^[A-Z0-9\xc0-\xdc\.]+$/i",$this->_current_token))
		{
			$result = $this->_func();
			return $result;
		}
		throw new Exception("Syntax error: ".$this->_current_token.
								 ", lookahead: ".$this->_lookahead.
								 ", current char: ".$this->_current_char);
	}

	/**
	 * It parses a function call. It assumes the following rule:
	 * Func -> ( Expr [,Expr]* )
	 *
	 * @access private
	 * @return mixed The parsed ptg'd tree on success
	 */
	function _func()
	{
		$num_args = 0; // number of arguments received
		$function = strtoupper($this->_current_token);
		$result   = ''; // initialize result
		$this->_advance();
		$this->_advance();         // eat the "("
		while ($this->_current_token != ')') {
		/**/
			if ($num_args > 0) {
				if ($this->_current_token == "," or
					$this->_current_token == ";")
				{
					$this->_advance();  // eat the "," or ";"
				} else {
					throw new Exception("Syntax error: comma expected in ".
									  "function $function, arg #{$num_args}");
				}
				$result2 = $this->_condition();
				$result = $this->_createTree('arg', $result, $result2);
			} else { // first argument
				$result2 = $this->_condition();
				$result = $this->_createTree('arg', '', $result2);
			}
			++$num_args;
		}
		if (!isset($this->_functions[$function])) {
			throw new Exception("Function $function() doesn't exist");
		}
		$args = $this->_functions[$function][1];
		// If fixed number of args eg. TIME($i,$j,$k). Check that the number of args is valid.
		if (($args >= 0) and ($args != $num_args)) {
			throw new Exception("Incorrect number of arguments in function $function() ");
		}

		$result = $this->_createTree($function, $result, $num_args);
		$this->_advance();         // eat the ")"
		return $result;
	}

	/**
	 * Creates a tree. In fact an array which may have one or two arrays (sub-trees)
	 * as elements.
	 *
	 * @access private
	 * @param mixed $value The value of this node.
	 * @param mixed $left  The left array (sub-tree) or a final node.
	 * @param mixed $right The right array (sub-tree) or a final node.
	 * @return array A tree
	 */
	function _createTree($value, $left, $right)
	{
		return array('value' => $value, 'left' => $left, 'right' => $right);
	}

	/**
	 * Builds a string containing the tree in reverse polish notation (What you
	 * would use in a HP calculator stack).
	 * The following tree:
	 *
	 *    +
	 *   / \
	 *  2   3
	 *
	 * produces: "23+"
	 *
	 * The following tree:
	 *
	 *    +
	 *   / \
	 *  3   *
	 *     / \
	 *    6   A1
	 *
	 * produces: "36A1*+"
	 *
	 * In fact all operands, functions, references, etc... are written as ptg's
	 *
	 * @access public
	 * @param array $tree The optional tree to convert.
	 * @return string The tree in reverse polish notation
	 */
	function toReversePolish($tree = array())
	{
		$polish = ""; // the string we are going to return
		if (empty($tree)) { // If it's the first call use _parse_tree
			$tree = $this->_parse_tree;
		}

		if (is_array($tree['left'])) {
			$converted_tree = $this->toReversePolish($tree['left']);
			$polish .= $converted_tree;
		} elseif ($tree['left'] != '') { // It's a final node
			$converted_tree = $this->_convert($tree['left']);
			$polish .= $converted_tree;
		}
		if (is_array($tree['right'])) {
			$converted_tree = $this->toReversePolish($tree['right']);
			$polish .= $converted_tree;
		} elseif ($tree['right'] != '') { // It's a final node
			$converted_tree = $this->_convert($tree['right']);
			$polish .= $converted_tree;
		}
		// if it's a function convert it here (so we can set it's arguments)
		if (preg_match("/^[A-Z0-9\xc0-\xdc\.]+$/",$tree['value']) and
			!preg_match('/^([A-Ia-i]?[A-Za-z])(\d+)$/',$tree['value']) and
			!preg_match("/^[A-Ia-i]?[A-Za-z](\d+)\.\.[A-Ia-i]?[A-Za-z](\d+)$/",$tree['value']) and
			!is_numeric($tree['value']) and
			!isset($this->ptg[$tree['value']]))
		{
			// left subtree for a function is always an array.
			if ($tree['left'] != '') {
				$left_tree = $this->toReversePolish($tree['left']);
			} else {
				$left_tree = '';
			}
			// add it's left subtree and return.
			return $left_tree.$this->_convertFunction($tree['value'], $tree['right']);
		} else {
			$converted_tree = $this->_convert($tree['value']);
		}
		$polish .= $converted_tree;
		return $polish;
	}

}