Add example of cyclic reference calculation

Classes/PHPExcel/CalcEngine/CyclicReferenceStack.new.php

@@ -0,0 +1,122 @@
+<?php
+/**
+ * PHPExcel
+ *
+ * Copyright (c) 2006 - 2014 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_Calculation
+ * @copyright  Copyright (c) 2006 - 2014 PHPExcel (http://www.codeplex.com/PHPExcel)
+ * @license	http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt	LGPL
+ * @version	##VERSION##, ##DATE##
+ */
+
+
+/**
+ * PHPExcel_CalcEngine_CyclicReferenceStack
+ *
+ * @category	PHPExcel_CalcEngine_CyclicReferenceStack
+ * @package		PHPExcel_Calculation
+ * @copyright	Copyright (c) 2006 - 2014 PHPExcel (http://www.codeplex.com/PHPExcel)
+ */
+class PHPExcel_CalcEngine_CyclicReferenceStack {
+
+	/**
+	 *  The call stack for calculated cells
+	 *
+	 *  @var mixed[]
+	 */
+	private $_stack = array();
+
+    private $_values = array();
+
+
+	/**
+	 * Return the number of entries on the stack
+	 *
+	 * @return  integer
+	 */
+	public function count() {
+		return count($this->_stack);
+	}
+
+	/**
+	 * Push a new entry onto the stack
+	 *
+	 * @param  mixed  $value
+	 */
+	public function push($value) {
+		$this->_stack[] = $value;
+	}	//	function push()
+
+	/**
+	 * Pop the last entry from the stack
+	 *
+	 * @return  mixed
+	 */
+	public function pop() {
+		return array_pop($this->_stack);
+	}	//	function pop()
+
+	/**
+	 * Test to see if a specified entry exists on the stack
+	 *
+	 * @param  mixed  $value  The value to test
+	 */
+	public function onStack($value) {
+		return in_array($value, $this->_stack);
+	}
+
+	/**
+	 * Clear the stack
+	 */
+	public function clear() {
+		$this->_stack = array();
+	}	//	function push()
+
+	/**
+	 * Return an array of all entries on the stack
+	 *
+	 * @return  mixed[]
+	 */
+	public function showStack() {
+		return $this->_stack;
+	}
+
+    public function setValueByKey($key, $value) {
+        $this->_values[$key] = $value;
+    }
+
+    public function getValueByKey($key, &$value) {
+        if (isset($this->_values[$key])) {
+            $value = $this->_values[$key];
+            return true;
+        }
+        return false;
+    }
+
+    public function removeValueByKey($key) {
+        if (isset($this->_values[$key])) {
+            unset($this->_values[$key]);
+        }
+    }
+
+    public function showValues() {
+        return $this->_values;
+    }
+
+}	//	class PHPExcel_CalcEngine_CyclicReferenceStack