<?php

/*
 * Copyleft 2002 Johann Hanne
 *
 * This 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 software 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 software; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place,
 * Suite 330, Boston, MA  02111-1307 USA
 */

/* This file contains source from the PEAR::Spreadsheet class Parser.php file version 0.4 .
   The raiseError was replaced by triggerError function.
   The PEAR::isError was imported to keep compatibility to PEAR::Spreadsheet class

   Imported and adapted by Andreas Brodowski 2003 (andreas.brodowski@oscar-gmbh.com).

   There should be no license rights in question because the Parser.php from PEAR class is
   published under GNU License the same way like this class.

   Changes:	03/08/27 Added SPREADSHEET_EXCEL_WRITER_SCOLON for arg seperation in excel functions
 */

/*
 * This is the Spreadsheet::WriteExcel Perl package ported to PHP
 * Spreadsheet::WriteExcel was written by John McNamara, jmcnamara@cpan.org
 */

define('SPREADSHEET_EXCEL_WRITER_ADD',"+");
    // @const SPREADSHEET_EXCEL_WRITER_ADD token identifier for character "+"
define('SPREADSHEET_EXCEL_WRITER_SUB',"-");
    // @const SPREADSHEET_EXCEL_WRITER_SUB token identifier for character "-"
define('SPREADSHEET_EXCEL_WRITER_MUL',"*");
    // @const SPREADSHEET_EXCEL_WRITER_MUL token identifier for character "*"
define('SPREADSHEET_EXCEL_WRITER_DIV',"/");
    // @const SPREADSHEET_EXCEL_WRITER_DIV token identifier for character "/"
define('SPREADSHEET_EXCEL_WRITER_OPEN',"(");
   // @const SPREADSHEET_EXCEL_WRITER_OPEN token identifier for character "("
define('SPREADSHEET_EXCEL_WRITER_CLOSE',")");
 // @const SPREADSHEET_EXCEL_WRITER_CLOSE token identifier for character ")"
define('SPREADSHEET_EXCEL_WRITER_COMA',",");
   // @const SPREADSHEET_EXCEL_WRITER_COMA token identifier for character ","
define('SPREADSHEET_EXCEL_WRITER_SCOLON',";");
// @const SPREADSHEET_EXCEL_WRITER_SCOLON token identifier for character ";"
define('SPREADSHEET_EXCEL_WRITER_GT',">");
     // @const SPREADSHEET_EXCEL_WRITER_GT token identifier for character ">"
define('SPREADSHEET_EXCEL_WRITER_LT',"<");
     // @const SPREADSHEET_EXCEL_WRITER_LT token identifier for character "<"
define('SPREADSHEET_EXCEL_WRITER_LE',"<=");
    // @const SPREADSHEET_EXCEL_WRITER_LE token identifier for character "<="
define('SPREADSHEET_EXCEL_WRITER_GE',">=");
    // @const SPREADSHEET_EXCEL_WRITER_GE token identifier for character ">="
define('SPREADSHEET_EXCEL_WRITER_EQ',"=");
     // @const SPREADSHEET_EXCEL_WRITER_EQ token identifier for character "="
define('SPREADSHEET_EXCEL_WRITER_NE',"<>");
    // @const SPREADSHEET_EXCEL_WRITER_NE token identifier for character "<>"


class writeexcel_formula {

###############################################################################
#
# Class data.
#
var $parser;
var $ptg;
var $_functions;
var $_current_char;
var $_current_token;
var $_lookahead;
var $_debug;
var $_byte_order;
var $_volatile;
var $_workbook;
var $_ext_sheets;
var $_formula;

###############################################################################
#
# new()
#
# Constructor
#
function writeexcel_formula($byte_order) {

    $this->parser          = false;
    $this->ptg             = array();
    $this->_functions       = array();
    $this->_debug          = 0;
    $this->_byte_order     = $byte_order;
    $this->_volatile       = 0;
    $this->_workbook       = "";
    $this->_ext_sheets     = array();
    $this->_current_token  = '';
    $this->_lookahead	   = '';
    $this->_current_char   = 0;
    $this->_formula	   = '';
}

###############################################################################
#
# _init_parser()
#
# There is a small overhead involved in generating the parser. Therefore, the
# initialisation is delayed until a formula is required. TODO: use a pre-
# compiled header.
#
function _init_parser() {

    $this->_initializeHashes();


    if ($this->_debug) {
        print "Init_parser.\n\n";
    }
}

###############################################################################
#
# parse_formula()
#
# This is the only public method. It takes a textual description of a formula
# and returns a RPN encoded byte string.
#
function parse_formula() {

    $_=func_get_args();

    # Initialise the parser if this is the first call
    if ($this->parser===false) {
        $this->_init_parser();
    }

    $formula = array_shift($_);
    //$str;
    //$tokens;

    if ($this->_debug) {
        print "$formula\n";
    }

    # Build the parse tree for the formula

    $this->_formula	 = $formula;
    $this->_current_char = 0;
    $this->_lookahead    = $this->_formula[1];
    $this->_advance($formula);
    $parsetree = $this->_condition();

    $str = $this->toReversePolish($parsetree);

    return $str;
}

function isError($data) {
    return (bool)(is_object($data) &&
                  (get_class($data) == 'pear_error' ||
                  is_subclass_of($data, 'pear_error')));
}

/**
* Class for parsing Excel formulas
*
* @author   Xavier Noguer <xnoguer@rezebra.com>
* @category FileFormats
* @package  Spreadsheet_Excel_Writer
*/


/**
* 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 ),
        'ROUNDUP'         => array( 212,    2,    1,    0 ),
        'ROUNDDOWN'       => array( 213,    2,    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 ),
        'ROMAN'           => array( 354,   -1,    1,    0 )
        );
}

/**
* Convert a token to the proper ptg value.
*
* @access private
* @param mixed $token The token to convert.
* @return mixed the converted token on success. PEAR_Error if the token
*               is not recognized
*/
function _convert($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:Sheet2!A1
    elseif (preg_match("/^[A-Za-z0-9_]+(\:[A-Za-z0-9_]+)?\![A-Ia-i]?[A-Za-z](\d+)$/",$token))
 {

        return $this->_convertRef3d($token);
    }
    // match ranges like A1:B2
    elseif (preg_match('/^\$?[A-Ia-i]?[A-Za-z]\$?\d+\:\$?[A-Ia-i]?[A-Za-z]\$?\d+$/',$token))
 {
        return $this->_convertRange2d($token);
    }
    // match ranges like A1..B2
    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:Sheet2!A1:B2
    elseif (preg_match("/^[A-Za-z0-9_]+(\:[A-Za-z0-9_]+)?\!([A-Ia-i]?[A-Za-z])?(\d+)\:([A-Ia-i]?[A-Za-z])?(\d+)$/",$token))
 {
        return $this->_convertRange3d($token);
    }
    // match external ranges like 'Sheet1:Sheet2'!A1:B2
    elseif (preg_match("/^'[A-Za-z0-9_ ]+(\:[A-Za-z0-9_ ]+)?'\!([A-Ia-i]?[A-Za-z])?(\d+)\:([A-Ia-i]?[A-Za-z])?(\d+)$/",$token))
 {
        return $this->_convertRange3d($token);
    }
    elseif (isset($this->ptg[$token])) // operators (including parentheses)
 {
        return pack("C", $this->ptg[$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
    trigger_error("Unknown token $token", E_USER_ERROR);
}

/**
* 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'], $num));
    }
 else { // A float
        if ($this->_byte_order) { // 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 $string A string for conversion to its ptg value
*/
function _convertString($string)
 {
    // chop away beggining and ending quotes
    $string = substr($string, 1, strlen($string) - 2);
    return pack("CC", $this->ptg['ptgStr'], strlen($string)).$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 $range An Excel range in the A1:A2 or A1..A2 format.
*/
function _convertRange2d($range)
 {
    $class = 2; // as far as I know, this is magick.

    // 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(':', $range);
    }
 elseif (preg_match('/^\$?([A-Ia-i]?[A-Za-z])\$?(\d+)\.\.\$?([A-Ia-i]?[A-Za-z])\$?(\d+)$/',$range)) {
        list($cell1, $cell2) = preg_split('/\.\./', $range);
    }
 else {
        // TODO: use real error codes
        trigger_error("Unknown range separator", E_USER_ERROR);
    }

    // Convert the cell references
    $cell_array1 = $this->_cellToPackedRowcol($cell1);
    if ($this->isError($cell_array1)) {
        return $cell_array1;
    }
    list($row1, $col1) = $cell_array1;
    $cell_array2 = $this->_cellToPackedRowcol($cell2);
    if ($this->isError($cell_array2)) {
        return $cell_array2;
    }
    list($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
        trigger_error("Unknown class $class", E_USER_ERROR);
    }
    return $ptgArea . $row1 . $row2 . $col1. $col2;
}

/**
* Convert an Excel 3d range such as "Sheet1!A1:D4" or "Sheet1:Sheet2!A1:D4" to
* a ptgArea3dV.
*
* @access private
* @param string $token An Excel range in the Sheet1!A1:A2 format.
*/
function _convertRange3d($token)
 {
    $class = 2; // as far as I know, this is magick.

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

    // Convert the external reference part
    $ext_ref = $this->_packExtRef($ext_ref);
    if ($this->isError($ext_ref)) {
        return $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);
        if ($this->isError($cell_array1)) {
            return $cell_array1;
        }
	list($row1, $col1) = $cell_array1;
        $cell_array2 = $this->_cellToPackedRowcol($cell2);
        if ($this->isError($cell_array2)) {
	    return $cell_array2;
        }
        list($row2, $col2) = $cell_array2;
    }
 else { // It's a columns range (like 26:27)
	$cells_array = $this->_rangeToPackedRange($cell1.':'.$cell2);
	if ($this->isError($cells_array)) {
    	    return $cells_array;
        }
	list($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 {
        trigger_error("Unknown class $class", E_USER_ERROR);
    }

    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);
    if ($this->isError($cell_array)) {
        return $cell_array;
    }
    list($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
        trigger_error("Unknown class $class",E_USER_ERROR);
    }
    return $ptgRef.$row.$col;
}

/**
* Convert an Excel 3d reference such as "Sheet1!A1" or "Sheet1:Sheet2!A1" to a
* ptgRef3dV.
*
* @access private
* @param string $cell An Excel cell reference
* @return string The cell in packed() format with the corresponding ptg
*/
function _convertRef3d($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
    $ext_ref = $this->_packExtRef($ext_ref);
    if ($this->isError($ext_ref)) {
        return $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 {
        trigger_error("Unknown class $class", E_USER_ERROR);
    }

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

/**
* 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) {
            trigger_error("Unknown sheet name $sheet_name1 in formula",E_USER_ERROR);
        }
        $sheet2 = $this->_getSheetIndex($sheet_name2);
        if ($sheet2 == -1) {
            trigger_error("Unknown sheet name $sheet_name2 in formula",E_USER_ERROR);
        }

        // 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) {
            trigger_error("Unknown sheet name $ext_ref in formula",E_USER_ERROR);
        }
        $sheet2 = $sheet1;
    }

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

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

/**
* Look up the index that corresponds to an external sheet name. The hash of
* sheet names is updated by the addworksheet() method of the
* Spreadsheet_Excel_Writer_Workbook class.
*
* @access private
* @return integer
*/
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 Spreadsheet_Excel_Writer_Workbook class.
*
* @access private
* @param string  $name  The name of the worksheet being added
* @param integer $index The index of the worksheet being added
*/
function set_ext_sheet($name, $index)
 {
    $this->_ext_sheets[$name] = $index;
}

/**
* pack() row and column into the required 3 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) {
        trigger_error("Column in: $cell greater than 255", E_USER_ERROR);
    }
    if ($row >= 16384) {
        trigger_error("Row in: $cell greater than 16384 ", E_USER_ERROR);
    }

    // Set the high bits to indicate if row or col are relative.
    $row    |= $col_rel << 14;
    $row    |= $row_rel << 15;

    $row     = pack('v', $row);
    $col     = pack('C', $col);

    return array($row, $col);
}

/**
* pack() row range into the required 3 byte format.
* Just using maximun 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; // maximum possible value for Excel 5 (change this!!!)

    //list($row, $col, $row_rel, $col_rel) = $this->_cellToRowcol($cell);
    if (($row1 >= 16384) or ($row2 >= 16384)) {
        trigger_error("Row in: $range greater than 16384 ",E_USER_ERROR);
    }

    // Set the high bits to indicate if rows are relative.
    $row1    |= $row1_rel << 14;
    $row2    |= $row2_rel << 15;

    $row1     = pack('v', $row1);
    $row2     = pack('v', $row2);
    $col1     = pack('C', $col1);
    $col2     = pack('C', $col2);

    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;
    $col    = 0;
    for ($i=0; $i < strlen($col_ref); $i++)
 {
        $col += (ord($col_ref[$i]) - ord('A') + 1) * 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 = $this->_current_char;
    // eat up white spaces
    if ($i < strlen($this->_formula))
 {
        while ($this->_formula[$i] == " ") {
            $i++;
        }
        if ($i < strlen($this->_formula) - 1) {
            $this->_lookahead = $this->_formula[$i+1];
        }
        $token = "";
    }
    while ($i < strlen($this->_formula))
 {
        $token .= $this->_formula[$i];
        if ($i < strlen($this->_formula) - 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 < strlen($this->_formula) - 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($token)
 {
        case SPREADSHEET_EXCEL_WRITER_ADD:
            return($token);
            break;
        case SPREADSHEET_EXCEL_WRITER_SUB:
            return($token);
            break;
        case SPREADSHEET_EXCEL_WRITER_MUL:
            return($token);
            break;
        case SPREADSHEET_EXCEL_WRITER_DIV:
            return($token);
            break;
        case SPREADSHEET_EXCEL_WRITER_OPEN:
            return($token);
            break;
        case SPREADSHEET_EXCEL_WRITER_CLOSE:
            return($token);
            break;
        case SPREADSHEET_EXCEL_WRITER_SCOLON:
            return($token);
            break;
        case SPREADSHEET_EXCEL_WRITER_COMA:
            return($token);
            break;
        case SPREADSHEET_EXCEL_WRITER_GT:
            if ($this->_lookahead == '=') { // it's a GE token
                break;
            }
            return($token);
            break;
        case SPREADSHEET_EXCEL_WRITER_LT:
            // it's a LE or a NE token
            if (($this->_lookahead == '=') or ($this->_lookahead == '>')) {
                break;
            }
            return($token);
            break;
        case SPREADSHEET_EXCEL_WRITER_GE:
            return($token);
            break;
        case SPREADSHEET_EXCEL_WRITER_LE:
            return($token);
            break;
        case SPREADSHEET_EXCEL_WRITER_EQ:
            return($token);
            break;
        case SPREADSHEET_EXCEL_WRITER_NE:
            return($token);
            break;
        default:
            // if it's a reference
            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 $token;
            }
            // If it's an external reference (Sheet1!A1 or Sheet1:Sheet2!A1)
            elseif (preg_match("/^[A-Za-z0-9_]+(\:[A-Za-z0-9_]+)?\![A-Ia-i]?[A-Za-z][0-9]+$/",$token) and
                   !preg_match("/[0-9]/",$this->_lookahead) and
                   ($this->_lookahead != ':') and ($this->_lookahead != '.'))
 {
                return $token;
            }
            // if it's a range (A1:A2)
            elseif (preg_match("/^(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+:(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+$/",$token) and
                   !preg_match("/[0-9]/",$this->_lookahead))
 {
                return $token;
            }
            // if it's a range (A1..A2)
            elseif (preg_match("/^(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+\.\.(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+$/",$token) and
                   !preg_match("/[0-9]/",$this->_lookahead))
 {
                return $token;
            }
            // If it's an external range like Sheet1:Sheet2!A1:B2
            elseif (preg_match("/^[A-Za-z0-9_]+(\:[A-Za-z0-9_]+)?\!([A-Ia-i]?[A-Za-z])?[0-9]+:([A-Ia-i]?[A-Za-z])?[0-9]+$/",$token) and
                   !preg_match("/[0-9]/",$this->_lookahead))
 {
                return $token;
            }
	    // If it's an external range like 'Sheet1:Sheet2'!A1:B2
            elseif (preg_match("/^'[A-Za-z0-9_ ]+(\:[A-Za-z0-9_ ]+)?'\!([A-Ia-i]?[A-Za-z])?[0-9]+:([A-Ia-i]?[A-Za-z])?[0-9]+$/",$token) and
                   !preg_match("/[0-9]/",$this->_lookahead))
 {
                return $token;
            }
            // If it's a number (check that it's not a sheet name or range)
            elseif (is_numeric($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))
 {
                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 $formula The formula to parse, without the initial equal sign (=).
*/
function parse($formula)
 {
    $this->_current_char = 0;
    $this->_formula      = $formula;
    $this->_lookahead    = $formula[1];
    $this->_advance();
    $this->_parse_tree   = $this->_condition();
    if ($this->isError($this->_parse_tree)) {
        return $this->_parse_tree;
    }
}

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

/**
* It parses a expression. It assumes the following rule:
* Expr -> Term [("+" | "-") Term]
*
* @access private
* @return mixed The parsed ptg'd tree
*/
function _expression()
 {
    // If it's a string return a string node
    if (preg_match("/^\"[^\"]{0,255}\"$/", $this->_current_token))
 {
        $result = $this->_createTree($this->_current_token, '', '');
        $this->_advance();
        return $result;
    }
    $result = $this->_term();
    if ($this->isError($result)) {
        return $result;
    }
    while (($this->_current_token == SPREADSHEET_EXCEL_WRITER_ADD) or
           ($this->_current_token == SPREADSHEET_EXCEL_WRITER_SUB))
 {
        if ($this->_current_token == SPREADSHEET_EXCEL_WRITER_ADD)

{
            $this->_advance();
            $result2 = $this->_term();
            if ($this->isError($result2)) {
                return $result2;
            }
            $result = $this->_createTree('ptgAdd', $result, $result2);
        }
 else
{
            $this->_advance();
            $result2 = $this->_term();
            if ($this->isError($result2)) {
                return $result2;
            }
            $result = $this->_createTree('ptgSub', $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 mixed 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
*/
function _term()
 {
    $result = $this->_fact();
    if ($this->isError($result)) {
        return $result;
    }
    while (($this->_current_token == SPREADSHEET_EXCEL_WRITER_MUL) or
           ($this->_current_token == SPREADSHEET_EXCEL_WRITER_DIV)) {
        if ($this->_current_token == SPREADSHEET_EXCEL_WRITER_MUL)

{
            $this->_advance();
            $result2 = $this->_fact();
            if ($this->isError($result2)) {
                return $result2;
            }
            $result = $this->_createTree('ptgMul', $result, $result2);
        }
 else
{
            $this->_advance();
            $result2 = $this->_fact();
            if ($this->isError($result2)) {
                return $result2;
            }
            $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
*/
function _fact()
 {
    if ($this->_current_token == SPREADSHEET_EXCEL_WRITER_OPEN)
 {
        $this->_advance();         // eat the "("
        $result = $this->_parenthesizedExpression();
        if ($this->_current_token != SPREADSHEET_EXCEL_WRITER_CLOSE) {
            trigger_error("')' token expected.",E_USER_ERROR);
        }
        $this->_advance();         // eat the ")"
        return $result;
    }
 if (preg_match('/^\$?[A-Ia-i]?[A-Za-z]\$?[0-9]+$/',$this->_current_token))
 {
    // if it's a reference
        $result = $this->_createTree($this->_current_token, '', '');
        $this->_advance();
        return $result;
    }
 elseif (preg_match("/^[A-Za-z0-9_]+(\:[A-Za-z0-9_]+)?\![A-Ia-i]?[A-Za-z][0-9]+$/",$this->_current_token))
 {
    // If it's an external reference (Sheet1!A1 or Sheet1:Sheet2!A1)
        $result = $this->_createTree($this->_current_token, '', '');
        $this->_advance();
        return $result;
    }
 elseif (preg_match("/^(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+:(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+$/",$this->_current_token) or
              preg_match("/^(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+\.\.(\$)?[A-Ia-i]?[A-Za-z](\$)?[0-9]+$/",$this->_current_token))
 {
    // if it's a range
        $result = $this->_current_token;
        $this->_advance();
        return $result;
    }
 elseif (preg_match("/^[A-Za-z0-9_]+(\:[A-Za-z0-9_]+)?\!([A-Ia-i]?[A-Za-z])?[0-9]+:([A-Ia-i]?[A-Za-z])?[0-9]+$/",$this->_current_token))
 {
    // If it's an external range (Sheet1!A1:B2)
        $result = $this->_current_token;
        $this->_advance();
        return $result;
    }
 elseif (preg_match("/^'[A-Za-z0-9_ ]+(\:[A-Za-z0-9_ ]+)?'\!([A-Ia-i]?[A-Za-z])?[0-9]+:([A-Ia-i]?[A-Za-z])?[0-9]+$/",$this->_current_token))
 {
    // If it's an external range ('Sheet1'!A1:B2)
        $result = $this->_current_token;
        $this->_advance();
        return $result;
    }
 elseif (is_numeric($this->_current_token))
 {
        $result = $this->_createTree($this->_current_token, '', '');
        $this->_advance();
        return $result;
    }
 elseif (preg_match("/^[A-Z0-9\xc0-\xdc\.]+$/i",$this->_current_token))
 {
    // if it's a function call
        $result = $this->_func();
        return $result;
    }
    trigger_error("Sintactic error: ".$this->_current_token.", lookahead: ".
                          $this->_lookahead.", current char: ".$this->_current_char, E_USER_ERROR);
}

/**
* It parses a function call. It assumes the following rule:
* Func -> ( Expr [,Expr]* )
*
* @access private
*/
function _func()
 {
    $num_args = 0; // number of arguments received
    $function = $this->_current_token;
    $this->_advance();
    $this->_advance();         // eat the "("
    while ($this->_current_token != ')')
 {
        if ($num_args > 0)
 {
            if ($this->_current_token == SPREADSHEET_EXCEL_WRITER_COMA ||
		$this->_current_token == SPREADSHEET_EXCEL_WRITER_SCOLON) {
                $this->_advance();  // eat the ","
            }
 else {
                trigger_error("Sintactic error: coma expected in ".
                                  "function $function, {$num_args}?arg", E_USER_ERROR);
            }
            $result2 = $this->_condition();
            if ($this->isError($result2)) {
                return $result2;
            }
            $result = $this->_createTree('arg', $result, $result2);
        }
 else { // first argument
            $result2 = $this->_condition();
            if ($this->isError($result2)) {
                return $result2;
            }
            $result = $this->_createTree('arg', '', $result2);
        }
        $num_args++;
    }
    $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)) {
        trigger_error("Incorrect number of arguments in function $function() ",E_USER_ERROR);
    }

    $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 $right The right array (sub-tree) or a final node.
*/
function _createTree($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']);
        if ($this->isError($converted_tree)) {
            return $converted_tree;
        }
        $polish .= $converted_tree;
    }
 elseif ($tree['left'] != '') { // It's a final node
        $converted_tree = $this->_convert($tree['left']);
        if ($this->isError($converted_tree)) {
            return $converted_tree;
        }
        $polish .= $converted_tree;
    }
    if (is_array($tree['right']))
 {
        $converted_tree = $this->toReversePolish($tree['right']);
        if ($this->isError($converted_tree)) {
            return $converted_tree;
        }
        $polish .= $converted_tree;
    }
 elseif ($tree['right'] != '') { // It's a final node
        $converted_tree = $this->_convert($tree['right']);
        if ($this->isError($converted_tree)) {
            return $converted_tree;
        }
        $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 {
            $left_tree = '';
        }
        if ($this->isError($left_tree)) {
            return $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']);
        if ($this->isError($converted_tree)) {
            return $converted_tree;
        }
    }
    $polish .= $converted_tree;
    return $polish;
}

}