<?php

/****
 * ASCIIMathPHP and associated classes:
 * -- XMLNode
 * -- MathMLNode extends XMLNode
 *
 * These classes are a PHP port of ASCIIMath 
 * Version 1.3 Feb 19 2004, (c) Peter Jipsen http://www.chapman.edu/~jipsen
 *
 * ASCIIMathPHP Version 1.02, 02 Oct 2004, (c) Kee-Lin Steven Chan (kc56@cornell.edu)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or (at
 * your option) any later version.
 *
 * This program 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
 * General Public License (at http://www.gnu.org/copyleft/gpl.html) 
 * for more details.
 *
 * ChangeLog
 * Ver 1.02
 * -- Fixed bug with mbox and text
 * -- Fixed spacing bug with mbox and text
 *
 * Ver 1.01
 * -- Fixed Bug that did not parse symbols greater than a single character
 * correctly when appearing at end of expression.
 *
****/

class XMLNode
{
	// Private variables
	var $_id;
	var $_name;
	var $_content;
	var $_mt_elem_flg;
	var $_attr_arr;
	var $_child_arr;
	var $_nmspc;
	var $_nmspc_alias;
	var $_parent_id;
	var $_parent_node;
	
	function & XMLNode($id = NULL)
	{
		$this->_id = isset($id) ? $id : md5(uniqid(rand(),1));
		$this->_name = '';
		$this->_content = '';
		$this->_mt_elem_flg = FALSE;
		$this->_attr_arr = array();
		$this->_child_arr = array();
		$this->_nmspc = '';
		$this->_nmspc_alias = '';
		$this->_parent_id = FALSE;
		$this->_parent_node = NULL;
	}
	
	function addChild(&$node)
	{
		$this->_child_arr[$node->getId()] =& $node;
		$node->setParentId($this->_id);
		$node->setParentNode($this);
	}
	
	function addChildArr(&$node_arr)
	{
		$key_arr = array_keys($node_arr);
		$num_key = count($key_arr);
		
		for ($i = 0; $i < $num_key; $i++) {
			$node =& $node_arr[$key_arr[$i]];
			$this->addChild($node);
		}
	}
	
	function insertChildBefore($idx,&$node)
	{
		$key_arr = array_keys($this->_child_arr);
		$num_key = count($key_arr);
		$tmp_arr = arry();
		
		for ($i = 0;$i < $num_key;$i++) {
			if ($i == $idx) {
				$tmp_arr[$node->getId()] =& $node;
			}
			$tmp_arr[$key_arr[$i]] =& $this->_child_arr[$key_arr[$i]];
		}
		$this->_child_arr =& $tmp_arr;
	}
	
	function insertChildAfter($idx,&$node)
	{
		$key_arr = array_keys($this->_child_arr);
		$num_key = count($key_arr);
		$tmp_arr = arry();
		
		for ($i = 0;$i < $num_key;$i++) {
			$tmp_arr[$key_arr[$i]] =& $this->_child_arr[$key_arr[$i]];
			if ($i == $idx) {
				$tmp_arr[$node->getId()] =& $node;
			}
		}
		$this->_child_arr =& $tmp_arr;
	}
	
	function setId($id)
	{
		$this->_id = $id;
	}
	
	function setName($name)
	{
		$this->_name = $name;
	}
	
	function setNamepace($nmspc)
	{
		$this->_nmspc = $nmspc;
	}
	
	function setNamespaceAlias($nmspc_alias)
	{
		$this->_nmspc_alias = $nmspc_alias;
	}
	
	function setContent($content)
	{
		$this->_content = $content;
	}
	
	function setEmptyElem($mt_elem_flg)
	{
		$this->_mt_elem_flg = $mt_elem_flg;
	}
	
	function setAttr($attr_nm,$attr_val)
	{
		$this->_attr_arr[$attr_nm] = $attr_val;
	}
	
	function setAttrArr($attr_arr)
	{
		$this->_attr_arr = $attr_arr;
	}
	
	function setParentId($id)
	{
		$this->_parent_id = $id;
	}
	
	function setParentNode(&$node)
	{
		$this->_parent_node =& $node;
	}
	
	function getId()
	{
		return($this->_id);
	}
	
	function getName()
	{
		return($this->_name);
	}
	
	function getNamespace()
	{
		return($this->_nmspc);
	}
	
	function getNamespaceAlias()
	{
		return($this->_nmspc_alias);
	}
	
	function getContent()
	{
		return($this->_content);
	}
	
	function getAttr($attr_nm)
	{
		if (isset($this->_attr_arr[$attr_nm])) {
			return($this->_attr_arr[$attr_nm]);
		} else {
			return(NULL);
		}
	}
	
	function getAttrArr()
	{
		return($this->_attr_arr);
	}
	
	function getParentId()
	{
		return($this->parent_id);
	}
	
	function & getParentNode()
	{
		return($this->_parent_node);
	}
	
	function & getChild($id)
	{
		if (isset($this->_child_arr[$id])) {
			return($this->_child_arr[$id]);
		} else {
			return(FALSE);
		}
	}
	
	function & getFirstChild()
	{
		$id_arr = array_keys($this->_child_arr);
		$num_child = count($id_arr);
		
		if ($num_child > 0) {
			return($this->_child_arr[$id_arr[0]]);
		} else {
			return(FALSE);
		}
	}
	
	function & getLastChild()
	{
		$id_arr = array_keys($this->_child_arr);
		$num_child = count($id_arr);
		
		if ($num_child > 0) {
			return($this->_child_arr[$id_arr[$num_child - 1]]);
		} else {
			return(FALSE);
		}
	}
	
	function & getChildByIdx($idx)
	{
		$id_arr = array_keys($this->_child_arr);
		
		if (isset($this->_child_arr[$id_arr[$idx]])) {
			return($this->_child_arr[$id_arr[$idx]]);
		} else {
			return(FALSE);
		}
	}
	
	function getNumChild()
	{
		return(count($this->_child_arr));
	}
	
	function removeChild($id)
	{
		unset($this->_child_arr[$id]);
	}
	
	function removeChildByIdx($idx)
	{
		$key_arr = array_keys($this->_child_arr);
		unset($this->_child_arr[$key_arr[$idx]]);
	}
	
	function removeFirstChild()
	{
		$key_arr = array_keys($this->_child_arr);
		unset($this->_child_arr[$key_arr[0]]);
	}
	
	function removeLastChild()
	{
		$key_arr = array_keys($this->_child_arr);
		unset($this->_child_arr[$key_arr[count($key_arr)-1]]);
	}
	
	function dumpXML($indent_str = "\t")
	{
		$attr_txt = $this->_dumpAttr();
		$name = $this->_dumpName();
		$xmlns = $this->_dumpXmlns();
		$lvl = $this->_getCurrentLevel();
		$indent = str_pad('',$lvl,$indent_str);
		
		if ($this->_mt_elem_flg) {
			$tag = "$indent<$name$xmlns$attr_txt />";
			return($tag);
		} else {
			$key_arr = array_keys($this->_child_arr);
			$num_child = count($key_arr);
			
			$tag = "$indent<$name$xmlns$attr_txt>$this->_content";
			
			for ($i = 0;$i < $num_child;$i++) {
				$node =& $this->_child_arr[$key_arr[$i]];
				
				$child_txt = $node->dumpXML($indent_str);
				$tag .= "\n$child_txt";
			}
			
			$tag .= ($num_child > 0 ? "\n$indent</$name>" : "</$name>");
			return($tag);
		}
	}
	
	function _dumpAttr()
	{
		$id_arr = array_keys($this->_attr_arr);
		$id_arr_cnt = count($id_arr);
		$attr_txt = '';
		
		for($i = 0;$i < $id_arr_cnt;$i++) {
			$key = $id_arr[$i];
			$attr_txt .= " $key=\"{$this->_attr_arr[$key]}\"";
		}
		
		return($attr_txt);
	}
	
	function _dumpName()
	{
		$alias = $this->getNamespaceAlias();
		if ($alias == '') {
			return($this->getName());
		} else {
			return("$alias:" . $this->getName());
		}
	}
	
	function _dumpXmlns()
	{
		$nmspc = $this->getNamespace();
		$alias = $this->getNamespaceAlias();
		
		if ($nmspc != '') {
			if ($alias == '') {
				return(" xmlns=\"" . $nmspc . "\"");
			} else {
				return(" xmlns:$alias=\"" . $nmspc . "\"");
			}
		} else {
			return('');
		}
	}
	
	function _getCurrentLevel()
	{
		if ($this->_parent_id === FALSE) {
			return(0);
		} else {
			$node =& $this->getParentNode();
			$lvl = $node->_getCurrentLevel();
			$lvl++;
			return($lvl);
		}
	}
}

class MathMLNode extends XMLNode
{
	function & MathMLNode($id = NULL)
	{
		parent::XMLNode($id);
	}
	
	function removeBrackets()
	{
		if ($this->_name == 'mrow') {
			if ($c_node_0 =& $this->getFirstChild()) {
				$c_node_0->isLeftBracket() ? $this->removeFirstChild() : 0;
			}
			
			if ($c_node_0 =& $this->getLastChild()) {
				$c_node_0->isRightBracket() ? $this->removeLastChild() : 0;
			}
		}
	}
	
	function isLeftBracket()
	{
		switch ($this->_content) {
			case '{':
			case '[':
			case '(':
				return(TRUE);
				break;
		}
		return(FALSE);
	}
	
	function isRightBracket()
	{
		switch ($this->_content) {
			case '}':
			case ']':
			case ')':
				return(TRUE);
				break;
		}
		return(FALSE);
	}
}

class ASCIIMathPHP
{
	var $_expr;
	var $_curr_expr;
	var $_prev_expr;
	var $_symbol_arr;
	var $_node_arr;
	var $_node_cntr;
	
	function ASCIIMathPHP($symbol_arr,$expr = NULL)
	{
		$this->_symbol_arr = $symbol_arr;
		if (isset($expr)) {
			$this->setExpr($expr);
		}
	}
	
	function setExpr($expr)
	{
		$this->_expr = $expr;
		$this->_curr_expr = $expr;
		$this->_prev_expr = $expr;
		
		$this->_node_arr = array();
		$this->_node_cntr = 0;
	}
	
	function genMathML($attr_arr = NULL)
	{
		// <math> node
		$node_0 =& $this->createNode();
		$node_0->setName('math');
		$node_0->setNamepace('http://www.w3.org/1998/Math/MathML');
		
		// <mstyle> node
		if (isset($attr_arr)) {
			$node_1 =& $this->createNode();
			$node_1->setName('mstyle');
			$node_1->setAttrArr($attr_arr);
			
			$node_arr =& $this->parseExpr();
			
			$node_1->addChildArr($node_arr);
			$node_0->addChild($node_1);
		} else {
			$node_arr =& $this->parseExpr();
			$node_0->addChildArr($node_arr);
		}
		
		return(TRUE);
	}
	
	/*
	function & mergeNodeArr(&$node_arr_0,&$node_arr_1)
	{
		$key_arr_0 = array_keys($node_arr_0);
		$key_arr_1 = array_keys($node_arr_1);
		
		$num_key_0 = count($key_arr_0);
		$num_key_1 = count($key_arr_1);
		
		$merge_arr = array();
		
		for ($i = 0;$i < $num_key_0;$i++) {
			$merge_arr[$key_arr_0[$i]] =& $node_arr_0[$key_arr_0[$i]];
		}
		
		for ($j = 0;$j < $num_key_1;$i++) {
			$merge_arr[$key_arr_1[$i]] =& $node_arr_1[$key_arr_1[$i]];
		}
		
		return($merge_arr);
	}
	*/
	
	function & parseExpr()
	{
		// Child/Fragment array
		$node_arr = array();
		
		// Deal whole expressions like 'ax + by + c = 0' etc.
		do {
			$sym_0 = $this->getSymbol();
			$node_0 =& $this->parseSmplExpr();
			$sym = $this->getSymbol();
			// var_dump($sym);
			
			if (isset($sym['infix'])) {
				$this->chopExpr($sym['symlen']);
				$node_1 =& $this->parseSmplExpr();

				if ($node_1 === FALSE) {
					continue;
				}

				$node_1->removeBrackets();
				
				// If 'div' -- divide
				if ($sym['input'] == '/') { 
					$node_0->removeBrackets();
				}
				
				// If 'sub' -- subscript
				if ($sym['input'] == '_') { 
					$sym_1 = $this->getSymbol();
					
					// If 'sup' -- superscript
					if ($sym_1['input'] == '^') { 
						$this->chopExpr($sym_1['symlen']);
						$node_2 =& $this->parseSmplExpr();
						$node_2->removeBrackets();
						
						$node_3 =& $this->createNode();
						$node_3->setName(isset($sym_0['underover']) ? 'munderover' : 'msubsup');
						$node_3->addChild($node_0);
						$node_3->addChild($node_1);
						$node_3->addChild($node_2);
						
						$node_4 =& $this->createNode();
						$node_4->setName('mrow');
						$node_4->addChild($node_3);
						
						$node_arr[$node_4->getId()] =& $node_4;
					} else {
						$node_2 =& $this->createNode();
						$node_2->setName(isset($sym_0['underover']) ? 'munder' : 'msub');
						$node_2->addChild($node_0);
						$node_2->addChild($node_1);
						
						$node_arr[$node_2->getId()] =& $node_2;
					}
				} else {
					$node_2 =& $this->createNode();
					$node_2->setName($sym['tag']);
					$node_2->addChild($node_0);
					$node_2->addChild($node_1);
					
					$node_arr[$node_2->getId()] =& $node_2;
				}
				
			} elseif ($node_0 !== FALSE) {
				$node_arr[$node_0->getId()] =& $node_0;
			}
		} while (!isset($sym['right_bracket']) && $sym !== FALSE && $sym['output'] != '');
		
		//var_dump($sym);
		// Possibly to deal with matrices
		if (isset($sym['right_bracket'])) {
			$node_cnt = count($node_arr);
			$key_node_arr = array_keys($node_arr);
			
			if ($node_cnt > 1) {
				$node_5 =& $node_arr[$key_node_arr[$node_cnt-1]];
				$node_6 =& $node_arr[$key_node_arr[$node_cnt-2]];
			} else {
				$node_5 = FALSE;
				$node_6 = FALSE;
			}
			
			// Dealing with matrices
			if ($node_5 !== FALSE && $node_6 !== FALSE &&
				$node_cnt > 1 && 
				$node_5->getName() == 'mrow' && 
				$node_6->getName() == 'mo' &&
				$node_6->getContent() == ',') {
				
				// Checking if Node 5 has a LastChild
				if ($node_7 =& $node_5->getLastChild()) {
					$node_7_cntnt = $node_7->getContent();
				} else {
					$node_7_cntnt = FALSE;
				}
				
				// If there is a right bracket
				if ($node_7 !== FALSE && ($node_7_cntnt == ']' || $node_7_cntnt == ')')) {
					
					// Checking if Node 5 has a firstChild
					if ($node_8 =& $node_5->getFirstChild()) {
						$node_8_cntnt = $node_8->getContent();
					} else {
						$node_8_cntnt = FALSE;
					}
					
					// If there is a matching left bracket
					if ($node_8 !== FALSE && 
						(($node_8_cntnt == '(' && $node_7_cntnt == ')' && $sym['output'] != '}') ||
						($node_8_cntnt == '[' && $node_7_cntnt == ']'))) {
							
						$is_mtrx_flg = TRUE;
						$comma_pos_arr = array();
						
						$i = 0;
						
						while ($i < $node_cnt && $is_mtrx_flg) {
							$tmp_node =& $node_arr[$key_node_arr[$i]];
							
							if($tmp_node_first =& $tmp_node->getFirstChild()) {
								$tnfc = $tmp_node_first->getContent();
							} else {
								$tnfc = FALSE;
							}
							
							if($tmp_node_last =& $tmp_node->getLastChild()) {
								$tnlc = $tmp_node_last->getContent();
							} else {
								$tnlc = FALSE;
							}
							
							if (isset($key_node_arr[$i+1])) {
								$next_tmp_node =& $node_arr[$key_node_arr[$i+1]];
								$ntnn = $next_tmp_node->getName();
								$ntnc = $next_tmp_node->getContent();
							} else {
								$ntnn = FALSE;
								$ntnc = FALSE;
							}
							
							// Checking each node in node array for matrix criteria
							if ($is_mtrx_flg) {
								$is_mtrx_flg = $tmp_node->getName() == 'mrow' &&
									($i == $node_cnt-1 || $ntnn == 'mo' && $ntnc == ',') &&
									$tnfc == $node_8_cntnt && $tnlc == $node_7_cntnt;
							}

							if ($is_mtrx_flg) {
								for ($j = 0;$j < $tmp_node->getNumChild();$j++) {
									$tmp_c_node =& $tmp_node->getChildByIdx($j);
									
									if ($tmp_c_node->getContent() == ',') {
										$comma_pos_arr[$i][] = $j;
									}
								}
							}	
							
							if ($is_mtrx_flg && $i > 1) {
								
								$cnt_cpan = isset($comma_pos_arr[$i]) ? count($comma_pos_arr[$i]) : NULL;
								$cnt_cpap = isset($comma_pos_arr[$i-2]) ? count($comma_pos_arr[$i-2]) : NULL;
								$is_mtrx_flg = $cnt_cpan == $cnt_cpap;
							}
							
							$i += 2;
						}
						
						// If the node passes the matrix tests
						if ($is_mtrx_flg) {
							$tab_node_arr = array();
							
							for ($i = 0;$i < $node_cnt;$i += 2) {
								$tmp_key_node_arr = array_keys($node_arr);
								if (!($tmp_node =& $node_arr[$tmp_key_node_arr[0]])) {
									break;
								}
								$num_child = $tmp_node->getNumChild();
								$k = 0;
								
								$tmp_node->removeFirstChild();
								
								$row_node_arr = array();
								$row_frag_node_arr = array();
								
								for ($j = 1;$j < ($num_child-1);$j++) {
									if (isset($comma_pos_arr[$i][$k]) && 
										$j == $comma_pos_arr[$i][$k]) {
										
										$tmp_node->removeFirstChild();
										
										$tmp_c_node =& $this->createNode();
										$tmp_c_node->setName('mtd');
										$tmp_c_node->addChildArr($row_frag_node_arr);
										$row_frag_node_arr = array();
										
										$row_node_arr[$tmp_c_node->getId()] =& $tmp_c_node;
										
										$k++;
									} else {
										
										if ($tmp_c_node =& $tmp_node->getFirstChild()) {
											$row_frag_node_arr[$tmp_c_node->getId()] =& $tmp_c_node;
											$tmp_node->removeFirstChild();
										}
									}
								}
								
								$tmp_c_node =& $this->createNode();
								$tmp_c_node->setName('mtd');
								$tmp_c_node->addChildArr($row_frag_node_arr);
								
								$row_node_arr[$tmp_c_node->getId()] =& $tmp_c_node;
								
								if (count($node_arr) > 2) {
									$tmp_key_node_arr = array_keys($node_arr);
									unset($node_arr[$tmp_key_node_arr[0]]);
									unset($node_arr[$tmp_key_node_arr[1]]);
								}
								
								$tmp_c_node =& $this->createNode();
								$tmp_c_node->setName('mtr');
								$tmp_c_node->addChildArr($row_node_arr);
								
								$tab_node_arr[$tmp_c_node->getId()] =& $tmp_c_node;
							}
							
							$tmp_c_node =& $this->createNode();
							$tmp_c_node->setName('mtable');
							$tmp_c_node->addChildArr($tab_node_arr);
							
							if (isset($sym['invisible'])) {
								$tmp_c_node->setAttr('columnalign','left');
							}
							
							$key_node_arr = array_keys($node_arr);
							$tmp_c_node->setId($key_node_arr[0]);
							
							$node_arr[$tmp_c_node->getId()] =& $tmp_c_node;
						}
					}
				}
			}
			
			$this->chopExpr($sym['symlen']);
			if (!isset($sym['invisible'])) {
				$node_7 =& $this->createNode();
				$node_7->setName('mo');
				$node_7->setContent($sym['output']);
				$node_arr[$node_7->getId()] =& $node_7;
			}
		}
		
		return($node_arr);
	}
	
	function & parseSmplExpr()
	{
		$sym = $this->getSymbol();
		
		if (!$sym || isset($sym['right_bracket'])) {
			return(FALSE);
		}
		
		$this->chopExpr($sym['symlen']);
		
		if (isset($sym['left_bracket'])) {
			$node_arr =& $this->parseExpr();
			
			if (isset($sym['invisible'])) {
				$node_0 =& $this->createNode();
				$node_0->setName('mrow');
				$node_0->addChildArr($node_arr);
				
				return($node_0);
			} else {
				$node_0 =& $this->createNode();
				$node_0->setName('mo');
				$node_0->setContent($sym['output']);
				
				$node_1 =& $this->createNode();
				$node_1->setName('mrow');
				$node_1->addChild($node_0);
				$node_1->addChildArr($node_arr);
				
				return($node_1);
			}
		} elseif (isset($sym['unary'])) {
			
			if ($sym['input'] == 'sqrt') {
				$node_0 =& $this->parseSmplExpr();
				$node_0->removeBrackets();
				
				$node_1 =& $this->createNode();
				$node_1->setName($sym['tag']);
				$node_1->addChild($node_0);
				
				return($node_1);
			} elseif ($sym['input'] == 'text' || $sym['input'] == 'mbox') {
				$expr = ltrim($this->getCurrExpr());
				
				switch($expr{0}) {
					case '(':
						$end_brckt = ')';
						break;
					case '[':
						$end_brckt = ']';
						break;
					case '{':
						$end_brckt = '}';
						break;
					default:
						$end_brckt = chr(11); // A chracter that will never be matched.
						break;
				}
				
				$txt = substr($expr,1,strpos($expr,$end_brckt)-1);
				$len = strlen($txt);
				
				$node_0 =& $this->createNode();
				$node_0->setName('mrow');
				
				if ($len > 0) {
					if ($txt{0} == " ") {
						$node_1 =& $this->createNode();
						$node_1->setName('mspace');
						$node_1->setAttr('width','1ex');
						
						$node_0->addChild($node_1);
					}
					
					$node_3 =& $this->createNode();
					$node_3->setName($sym['tag']);
					$node_3->setContent(trim($txt));
					
					$node_0->addChild($node_3);
					
					if ($len > 1 && $txt{$len-1} == " ") {
						$node_2 =& $this->createNode();
						$node_2->setName('mspace');
						$node_2->setAttr('width','1ex');
						
						$node_0->addChild($node_2);
					}
					
					$this->chopExpr($len+2);
				}
				return($node_0);
				
			} elseif (isset($sym['acc'])) {
				$node_0 =& $this->parseSmplExpr();
				$node_0->removeBrackets();
				
				$node_1 =& $this->createNode();
				$node_1->setName($sym['tag']);
				$node_1->addChild($node_0);
				
				$node_2 =& $this->createNode();
				$node_2->setName('mo');
				$node_2->setContent($sym['output']);
				
				$node_1->addChild($node_2);
				return($node_1);
			} else {
				// Font change commands -- to complete
			}
		} elseif (isset($sym['binary'])) {
			$node_arr = array();
			
			$node_0 =& $this->parseSmplExpr();
			$node_0->removeBrackets();
			
			$node_1 =& $this->parseSmplExpr();
			$node_1->removeBrackets();
			
			if ($sym['input'] == 'root') {
				$node_arr[$node_1->getId()] =& $node_1;
				$node_arr[$node_0->getId()] =& $node_0;
			} elseif ($sym['input'] == 'frac') {
				$node_arr[$node_0->getId()] =& $node_0;
				$node_arr[$node_1->getId()] =& $node_1;
			}
			
			$node_2 =& $this->createNode();
			$node_2->setName($sym['tag']);
			$node_2->addChildArr($node_arr);
			
			return($node_2);
		} elseif (isset($sym['infix'])) {
			$node_0 =& $this->createNode();
			$node_0->setName('mo');
			$node_0->setContent($sym['output']);
			
			return($node_0);
		} elseif (isset($sym['space'])) {
			$node_0 =& $this->createNode();
			$node_0->setName('mrow');
			
			$node_1 =& $this->createNode();
			$node_1->setName('mspace');
			$node_1->setAttr('width',$sym['space']);
			
			$node_2 =& $this->createNode();
			$node_2->setName($sym['tag']);
			$node_2->setContent($sym['output']);
			
			$node_3 =& $this->createNode();
			$node_3->setName('mspace');
			$node_3->setAttr('width',$sym['space']);
			
			$node_0->addChild($node_1);
			$node_0->addChild($node_2);
			$node_0->addChild($node_3);
			
			return($node_0);
		} else {
			
			// A constant
			$node_0 =& $this->createNode();
			$node_0->setName($sym['tag']);
			$node_0->setContent($sym['output']);
			return($node_0);
		}
		
		return(FALSE);
	}
	
	function getMathML()
	{
		$root =& $this->_node_arr[0];
		return($root->dumpXML());
	}
	
	function getCurrExpr()
	{
		return($this->_curr_expr);
	}
	
	function getExpr()
	{
		return($this->_expr);
	}
	
	function getPrevExpr()
	{
		return($this->_prev_expr);
	}
	
	function & createNode()
	{
		$node =& new MathMLNode($this->_node_cntr);
		// $node->setNamespaceAlias('m');
		$this->_node_arr[$this->_node_cntr] =& $node;
		$this->_node_cntr++;
		return($node);
	}
	
	function getSymbol($chop_flg = FALSE)
	{
		$chr_cnt = strlen($this->_curr_expr);
		
		if ($chr_cnt == 0) {
			return(FALSE);
		}
		
		for ($i = 1; $i < $chr_cnt; $i++) {
			$sym_0 = substr($this->_curr_expr,0,$i);
			$sym_1 = substr($this->_curr_expr,0,$i+1);
			
			// Reading string for numeric values
			if (is_numeric($sym_0)) {
				
				if (!is_numeric($sym_1)) {
					$chop_flg ? $this->chopExpr($i) : 0;
					return(array('input'=>$sym_0, 'tag'=>'mn', 'output'=>$sym_0, 'symlen'=>$i));
				} elseif (is_numeric($sym_1) && $i == ($chr_cnt - 1)) {
					$chop_flg ? $this->chopExpr($i+1) : 0;
					return(array('input'=>$sym_1, 'tag'=>'mn', 'output'=>$sym_1, 'symlen'=>($i+1)));
				}
				
			} elseif (isset($this->_symbol_arr[$sym_0]) && !isset($this->_symbol_arr[$sym_1])) {
				
				$chop_flg ? $this->chopExpr($i) : 0;
				$sym_arr = $this->_symbol_arr[$sym_0];
				$sym_arr['symlen'] = $i;
				return($sym_arr);
			
			} elseif (isset($this->_symbol_arr[$sym_1]) && $i == ($chr_cnt - 1)) {
				
				$chop_flg ? $this->chopExpr($i+1) : 0;
				$sym_arr = $this->_symbol_arr[$sym_1];
				$sym_arr['symlen'] = $i+1;
				return($sym_arr);
			}
		}
		
		// Reading string for alphabetic constants and the minus sign
		$char = $this->_curr_expr{0};
		$len_left = $chop_flg ? $this->chopExpr(1) : strlen($this->_curr_expr)-1;
		
		// Deals with expressions of length 1
		if ($len_left == 0 && isset($this->_symbol_arr[$char])) {
			$sym_arr = $this->_symbol_arr[$char];
			$sym_arr['symlen'] = 1;
			return($sym_arr);
		} else {
			$tag = preg_match('/[a-z]/i',$char) ? 'mi' : 'mo';
			return(array('input'=>$char, 'tag'=>$tag, 'output'=>$char, 'symlen'=>1));
		}
	}
	
	function chopExpr($strlen)
	{
		$this->_prev_expr = $this->_curr_expr;
		
		if ($strlen == strlen($this->_curr_expr)) {
			$this->_curr_expr = '';
			return(0);
		} else {
			$this->_curr_expr = ltrim(substr($this->_curr_expr,$strlen));
			return(strlen($this->_curr_expr));
		}
	}	
}
?>