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diff --git a/microbe/traverser.h b/microbe/traverser.h
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+/***************************************************************************
+ *   Copyright (C) 2004-2005 by Daniel Clarke                              *
+ *   daniel.jc@gmail.com                                               *
+ *                                                                         *
+ *   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 for more details.                          *
+ *                                                                         *
+ *   You should have received a copy of the GNU General Public License     *
+ *   along with this program; if not, write to the                         *
+ *   Free Software Foundation, Inc.,                                       *
+ *   51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.             *
+ ***************************************************************************/
+#ifndef TRAVERSER_H
+#define TRAVERSER_H
+
+#include "btreenode.h"
+
+/**
+Keeps persistant information needed and the algorithm for traversing the binary trees made of BTreeNodes, initialise either by passing a BTreeBase or BTreeNode to traverse a sub tree.
+
+Note that this is designed for traversing in the *reverse* way starting at the end of each branch
+in order to calculate the expression contained in the tree.
+
+@author Daniel Clarke
+*/
+class Traverser
+{
+public:
+	Traverser(BTreeNode *root);
+	~Traverser();
+	
+	/** Find where to start in the tree and return it also resets all the data related to the traversal. */
+	BTreeNode *start();
+	
+	/** Finds the next node to move to and returns it. */
+	BTreeNode *next();
+	
+	/** Returns true if we are on the left branch, false otherwise. */
+	bool onLeftBranch();
+	
+	/** Returns the node on the opposite branch of the parent. */
+	BTreeNode * oppositeNode();
+	
+	BTreeNode * current() const { return m_current; }
+
+	void setCurrent(BTreeNode *current){m_current = current;}
+	
+	/** From the current position, go down the tree taking a left turn always, 
+	 and stopping when reaching the left terminal node.
+	 */
+	void descendLeftwardToTerminal();
+	
+	/** It might occur in the future that next() does not just move to the parent,
+	 so use this for moving to parent
+	 */
+	void moveToParent();
+	
+	BTreeNode *root() const {return m_root;}
+	
+protected:
+	BTreeNode *m_root;
+	BTreeNode *m_current;
+};
+
+#endif