* Prado 3.3.0

1 files changed, 741 insertions, 0 deletions

diff --git a/lib/prado/framework/Collections/TPriorityList.php b/lib/prado/framework/Collections/TPriorityList.php
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+++ b/lib/prado/framework/Collections/TPriorityList.php
@@ -0,0 +1,741 @@
+<?php
+/**
+ * TPriorityList, TPriorityListIterator classes
+ *
+ * @author Brad Anderson <javalizard@gmail.com>
+ * @link https://github.com/pradosoft/prado
+ * @copyright Copyright &copy; 2005-2015 The PRADO Group
+ * @license https://github.com/pradosoft/prado/blob/master/COPYRIGHT
+ * @package System.Collections
+ */
+
+/**
+ * TPriorityList class
+ *
+ * TPriorityList implements a priority ordered list collection class.  It allows you to specify
+ * any numeric for priorities down to a specific precision.  The lower the numeric, the high the priority of the item in the
+ * list.  Thus -10 has a higher priority than -5, 0, 10 (the default), 18, 10005, etc.  Per {@link round}, precision may be negative and
+ * thus rounding can go by 10, 100, 1000, etc, instead of just .1, .01, .001, etc. The default precision allows for 8 decimal
+ * places. There is also a default priority of 10, if no different default priority is specified or no item specific priority is indicated.
+ * If you replace TList with this class it will  work exactly the same with items inserted set to the default priority, until you start
+ * using different priorities than the default priority.
+ *
+ * As you access the PHP array features of this class, it flattens and caches the results.  If at all possible, this
+ * will keep the cache fresh even when manipulated.  If this is not possible the cache is cleared.
+ * When an array of items are needed and the cache is outdated, the cache is recreated from the items and their priorities
+ *
+ * You can access, append, insert, remove an item by using
+ * {@link itemAt}, {@link add}, {@link insertAt}, and {@link remove}.
+ * To get the number of the items in the list, use {@link getCount}.
+ * TPriorityList can also be used like a regular array as follows,
+ * <code>
+ * $list[]=$item;  // append with the default priority.  It may not be the last item if other items in the list are prioritized after the default priority
+ * $list[$index]=$item; // $index must be between 0 and $list->Count-1.  This sets the element regardless of priority.  Priority stays the same.
+ * $list[$index]=$item; // $index is $list->Count.  This appends the item to the end of the list with the same priority as the last item in the list.
+ * unset($list[$index]); // remove the item at $index
+ * if(isset($list[$index])) // if the list has an item at $index
+ * foreach($list as $index=>$item) // traverse each item in the list in proper priority order and add/insert order
+ * $n=count($list); // returns the number of items in the list
+ * </code>
+ *
+ * To extend TPriorityList for doing your own operations with each addition or removal,
+ * override {@link insertAtIndexInPriority()} and {@link removeAtIndexInPriority()} and then call the parent.
+ *
+ * @author Brad Anderson <javalizard@gmail.com>
+ * @package System.Collections
+ * @since 3.2a
+ */
+class TPriorityList extends TList
+{
+	/**
+	 * @var array internal data storage
+	 */
+	private $_d=array();
+	/**
+	 * @var boolean indicates if the _d is currently ordered.
+	 */
+	private $_o=false;
+	/**
+	 * @var array cached flattened internal data storage
+	 */
+	private $_fd=null;
+	/**
+	 * @var integer number of items contain within the list
+	 */
+	private $_c=0;
+	/**
+	 * @var numeric the default priority of items without specified priorities
+	 */
+	private $_dp=10;
+	/**
+	 * @var integer the precision of the numeric priorities within this priority list.
+	 */
+	private $_p=8;
+
+	/**
+	 * Constructor.
+	 * Initializes the list with an array or an iterable object.
+	 * @param array|Iterator the intial data. Default is null, meaning no initial data.
+	 * @param boolean whether the list is read-only
+	 * @param numeric the default priority of items without specified priorities.
+	 * @param integer the precision of the numeric priorities
+	 * @throws TInvalidDataTypeException If data is not null and is neither an array nor an iterator.
+	 */
+	public function __construct($data=null,$readOnly=false,$defaultPriority=10,$precision=8)
+	{
+		parent::__construct();
+		if($data!==null)
+			$this->copyFrom($data);
+		$this->setReadOnly($readOnly);
+		$this->setPrecision($precision);
+		$this->setDefaultPriority($defaultPriority);
+	}
+
+	/**
+	 * Returns the number of items in the list.
+	 * This method is required by Countable interface.
+	 * @return integer number of items in the list.
+	 */
+	public function count()
+	{
+		return $this->getCount();
+	}
+
+	/**
+	 * Returns the total number of items in the list
+	 * @return integer the number of items in the list
+	 */
+	public function getCount()
+	{
+		return $this->_c;
+	}
+
+	/**
+	 * Gets the number of items at a priority within the list
+	 * @param numeric optional priority at which to count items.  if no parameter, it will be set to the default {@link getDefaultPriority}
+	 * @return integer the number of items in the list at the specified priority
+	 */
+	public function getPriorityCount($priority=null)
+	{
+		if($priority===null)
+			$priority=$this->getDefaultPriority();
+		$priority=(string)round(TPropertyValue::ensureFloat($priority),$this->_p);
+
+		if(!isset($this->_d[$priority]) || !is_array($this->_d[$priority]))
+			return false;
+		return count($this->_d[$priority]);
+	}
+
+	/**
+	 * @return numeric gets the default priority of inserted items without a specified priority
+	 */
+	public function getDefaultPriority()
+	{
+		return $this->_dp;
+	}
+
+	/**
+	 * This must be called internally or when instantiated.
+	 * @param numeric sets the default priority of inserted items without a specified priority
+	 */
+	protected function setDefaultPriority($value)
+	{
+		$this->_dp=(string)round(TPropertyValue::ensureFloat($value),$this->_p);
+	}
+
+	/**
+	 * @return integer The precision of numeric priorities, defaults to 8
+	 */
+	public function getPrecision()
+	{
+		return $this->_p;
+	}
+
+	/**
+	 * This must be called internally or when instantiated.
+	 * @param integer The precision of numeric priorities.
+	 */
+	protected function setPrecision($value)
+	{
+		$this->_p=TPropertyValue::ensureInteger($value);
+	}
+
+	/**
+	 * Returns an iterator for traversing the items in the list.
+	 * This method is required by the interface IteratorAggregate.
+	 * @return Iterator an iterator for traversing the items in the list.
+	 */
+	public function getIterator()
+	{
+		return new ArrayIterator($this->flattenPriorities());
+	}
+
+	/**
+	 * This returns a list of the priorities within this list, ordered lowest to highest.
+	 * @return array the array of priority numerics in decreasing priority order
+	 */
+	public function getPriorities()
+	{
+		$this->sortPriorities();
+		return array_keys($this->_d);
+	}
+
+
+	/**
+	 * This orders the priority list internally.
+	 */
+	protected function sortPriorities() {
+		if(!$this->_o) {
+			ksort($this->_d,SORT_NUMERIC);
+			$this->_o=true;
+		}
+	}
+
+	/**
+	 * This flattens the priority list into a flat array [0,...,n-1]
+	 * @return array array of items in the list in priority and index order
+	 */
+	protected function flattenPriorities() {
+		if(is_array($this->_fd))
+			return $this->_fd;
+
+		$this->sortPriorities();
+		$this->_fd=array();
+		foreach($this->_d as $priority => $itemsatpriority)
+			$this->_fd=array_merge($this->_fd,$itemsatpriority);
+		return $this->_fd;
+	}
+
+
+	/**
+	 * Returns the item at the index of a flattened priority list.
+	 * {@link offsetGet} calls this method.
+	 * @param integer the index of the item to get
+	 * @return mixed the element at the offset
+	 * @throws TInvalidDataValueException Issued when the index is invalid
+	 */
+	public function itemAt($index)
+	{
+		if($index>=0&&$index<$this->getCount()) {
+			$arr=$this->flattenPriorities();
+			return $arr[$index];
+		} else
+			throw new TInvalidDataValueException('list_index_invalid',$index);
+	}
+
+	/**
+	 * Gets all the items at a specific priority.
+	 * @param numeric priority of the items to get.  Defaults to null, filled in with the default priority, if left blank.
+	 * @return array all items at priority in index order, null if there are no items at that priority
+	 */
+	public function itemsAtPriority($priority=null)
+	{
+		if($priority===null)
+			$priority=$this->getDefaultPriority();
+		$priority=(string)round(TPropertyValue::ensureFloat($priority),$this->_p);
+
+		return isset($this->_d[$priority])?$this->_d[$priority]:null;
+	}
+
+	/**
+	 * Returns the item at an index within a priority
+	 * @param integer the index into the list of items at priority
+	 * @param numeric the priority which to index.  no parameter or null will result in the default priority
+	 * @return mixed the element at the offset, false if no element is found at the offset
+	 */
+	public function itemAtIndexInPriority($index,$priority=null)
+	{
+		if($priority===null)
+			$priority=$this->getDefaultPriority();
+		$priority=(string)round(TPropertyValue::ensureFloat($priority), $this->_p);
+
+		return !isset($this->_d[$priority])?false:(
+				isset($this->_d[$priority][$index])?$this->_d[$priority][$index]:false
+			);
+	}
+
+	/**
+	 * Appends an item into the list at the end of the specified priority.  The position of the added item may
+	 * not be at the end of the list.
+	 * @param mixed item to add into the list at priority
+	 * @param numeric priority blank or null for the default priority
+	 * @return int the index within the flattened array
+	 * @throws TInvalidOperationException if the map is read-only
+	 */
+	public function add($item,$priority=null)
+	{
+		if($this->getReadOnly())
+			throw new TInvalidOperationException('list_readonly',get_class($this));
+
+		return $this->insertAtIndexInPriority($item,false,$priority,true);
+	}
+
+	/**
+	 * Inserts an item at an index.  It reads the priority of the item at index within the flattened list
+	 * and then inserts the item at that priority-index.
+	 * @param integer the specified position in the flattened list.
+	 * @param mixed new item to add
+	 * @throws TInvalidDataValueException If the index specified exceeds the bound
+	 * @throws TInvalidOperationException if the list is read-only
+	 */
+	public function insertAt($index,$item)
+	{
+		if($this->getReadOnly())
+			throw new TInvalidOperationException('list_readonly',get_class($this));
+
+		if(($priority=$this->priorityAt($index,true))!==false)
+			$this->insertAtIndexInPriority($item,$priority[1],$priority[0]);
+		else
+			throw new TInvalidDataValueException('list_index_invalid',$index);
+	}
+
+	/**
+	 * Inserts an item at the specified index within a priority.  Override and call this method to
+	 * insert your own functionality.
+	 * @param mixed item to add within the list.
+	 * @param integer index within the priority to add the item, defaults to false which appends the item at the priority
+	 * @param numeric priority priority of the item.  defaults to null, which sets it to the default priority
+	 * @param boolean preserveCache specifies if this is a special quick function or not. This defaults to false.
+	 * @throws TInvalidDataValueException If the index specified exceeds the bound
+	 * @throws TInvalidOperationException if the list is read-only
+	 */
+	public function insertAtIndexInPriority($item,$index=false,$priority=null,$preserveCache=false)
+	{
+		if($this->getReadOnly())
+			throw new TInvalidOperationException('list_readonly',get_class($this));
+
+		if($priority===null)
+			$priority=$this->getDefaultPriority();
+		$priority=(string)round(TPropertyValue::ensureFloat($priority), $this->_p);
+
+		if($preserveCache) {
+			$this->sortPriorities();
+			$cc=0;
+			foreach($this->_d as $prioritykey=>$items)
+				if($prioritykey>=$priority)
+					break;
+				else
+					$cc+=count($items);
+
+			if($index===false&&isset($this->_d[$priority])) {
+				$c=count($this->_d[$priority]);
+				$c+=$cc;
+				$this->_d[$priority][]=$item;
+			} else if(isset($this->_d[$priority])) {
+				$c=$index+$cc;
+				array_splice($this->_d[$priority],$index,0,array($item));
+			} else {
+				$c = $cc;
+				$this->_o = false;
+				$this->_d[$priority]=array($item);
+			}
+
+			if($this->_fd&&is_array($this->_fd)) // if there is a flattened array cache
+				array_splice($this->_fd,$c,0,array($item));
+		} else {
+			$c=null;
+			if($index===false&&isset($this->_d[$priority])) {
+				$cc=count($this->_d[$priority]);
+				$this->_d[$priority][]=$item;
+			} else if(isset($this->_d[$priority])) {
+				$cc=$index;
+				array_splice($this->_d[$priority],$index,0,array($item));
+			} else {
+				$cc=0;
+				$this->_o=false;
+				$this->_d[$priority]=array($item);
+			}
+			if($this->_fd&&is_array($this->_fd)&&count($this->_d)==1)
+				array_splice($this->_fd,$cc,0,array($item));
+			else
+				$this->_fd=null;
+		}
+
+		$this->_c++;
+
+		return $c;
+
+	}
+
+
+	/**
+	 * Removes an item from the priority list.
+	 * The list will search for the item.  The first matching item found will be removed from the list.
+	 * @param mixed item the item to be removed.
+	 * @param numeric priority of item to remove. without this parameter it defaults to false.
+	 * A value of false means any priority. null will be filled in with the default priority.
+	 * @return integer index within the flattened list at which the item is being removed
+	 * @throws TInvalidDataValueException If the item does not exist
+	 */
+	public function remove($item,$priority=false)
+	{
+		if($this->getReadOnly())
+			throw new TInvalidOperationException('list_readonly',get_class($this));
+
+		if(($p=$this->priorityOf($item,true))!==false)
+		{
+			if($priority!==false) {
+				if($priority===null)
+					$priority=$this->getDefaultPriority();
+				$priority=(string)round(TPropertyValue::ensureFloat($priority),$this->_p);
+
+				if($p[0]!=$priority)
+					throw new TInvalidDataValueException('list_item_inexistent');
+			}
+			$this->removeAtIndexInPriority($p[1],$p[0]);
+			return $p[2];
+		}
+		else
+			throw new TInvalidDataValueException('list_item_inexistent');
+	}
+
+	/**
+	 * Removes an item at the specified index in the flattened list.
+	 * @param integer index of the item to be removed.
+	 * @return mixed the removed item.
+	 * @throws TInvalidDataValueException If the index specified exceeds the bound
+	 * @throws TInvalidOperationException if the list is read-only
+	 */
+	public function removeAt($index)
+	{
+		if($this->getReadOnly())
+			throw new TInvalidOperationException('list_readonly',get_class($this));
+
+		if(($priority=$this->priorityAt($index, true))!==false)
+			return $this->removeAtIndexInPriority($priority[1],$priority[0]);
+		throw new TInvalidDataValueException('list_index_invalid',$index);
+	}
+
+	/**
+	 * Removes the item at a specific index within a priority.  Override
+	 * and call this method to insert your own functionality.
+	 * @param integer index of item to remove within the priority.
+	 * @param numeric priority of the item to remove, defaults to null, or left blank, it is then set to the default priority
+	 * @return mixed the removed item.
+	 * @throws TInvalidDataValueException If the item does not exist
+	 */
+	public function removeAtIndexInPriority($index, $priority=null)
+	{
+		if($this->getReadOnly())
+			throw new TInvalidOperationException('list_readonly',get_class($this));
+
+		if($priority===null)
+			$priority=$this->getDefaultPriority();
+		$priority=(string)round(TPropertyValue::ensureFloat($priority),$this->_p);
+
+		if(!isset($this->_d[$priority])||$index<0||$index>=count($this->_d[$priority]))
+			throw new TInvalidDataValueException('list_item_inexistent');
+
+		// $value is an array of elements removed, only one
+		$value=array_splice($this->_d[$priority],$index,1);
+		$value=$value[0];
+
+		if(!count($this->_d[$priority]))
+			unset($this->_d[$priority]);
+
+		$this->_c--;
+		$this->_fd=null;
+		return $value;
+	}
+
+	/**
+	 * Removes all items in the priority list by calling removeAtIndexInPriority from the last item to the first.
+	 */
+	public function clear()
+	{
+		if($this->getReadOnly())
+			throw new TInvalidOperationException('list_readonly',get_class($this));
+
+		$d=array_reverse($this->_d,true);
+		foreach($this->_d as $priority=>$items) {
+			for($index=count($items)-1;$index>=0;$index--)
+				$this->removeAtIndexInPriority($index,$priority);
+			unset($this->_d[$priority]);
+		}
+	}
+
+	/**
+	 * @param mixed item
+	 * @return boolean whether the list contains the item
+	 */
+	public function contains($item)
+	{
+		return $this->indexOf($item)>=0;
+	}
+
+	/**
+	 * @param mixed item
+	 * @return integer the index of the item in the flattened list (0 based), -1 if not found.
+	 */
+	public function indexOf($item)
+	{
+		if(($index=array_search($item,$this->flattenPriorities(),true))===false)
+			return -1;
+		else
+			return $index;
+	}
+
+	/**
+	 * Returns the priority of a particular item
+	 * @param mixed the item to look for within the list
+	 * @param boolean withindex this specifies if the full positional data of the item within the list is returned.
+	 * 		This defaults to false, if no parameter is provided, so only provides the priority number of the item by default.
+	 * @return numeric|array the priority of the item in the list, false if not found.
+	 *   if withindex is true, an array is returned of [0 => $priority, 1 => $priorityIndex, 2 => flattenedIndex,
+	 * 'priority' => $priority, 'index' => $priorityIndex, 'absindex' => flattenedIndex]
+	 */
+	public function priorityOf($item,$withindex = false)
+	{
+		$this->sortPriorities();
+
+		$absindex = 0;
+		foreach($this->_d as $priority=>$items) {
+			if(($index=array_search($item,$items,true))!==false) {
+				$absindex+=$index;
+				return $withindex?array($priority,$index,$absindex,
+						'priority'=>$priority,'index'=>$index,'absindex'=>$absindex):$priority;
+			} else
+				$absindex+=count($items);
+		}
+
+		return false;
+	}
+
+	/**
+	 * Retutrns the priority of an item at a particular flattened index.
+	 * @param integer index of the item within the list
+	 * @param boolean withindex this specifies if the full positional data of the item within the list is returned.
+	 * 		This defaults to false, if no parameter is provided, so only provides the priority number of the item by default.
+	 * @return numeric|array the priority of the item in the list, false if not found.
+	 *   if withindex is true, an array is returned of [0 => $priority, 1 => $priorityIndex, 2 => flattenedIndex,
+	 * 'priority' => $priority, 'index' => $priorityIndex, 'absindex' => flattenedIndex]
+	 */
+	public function priorityAt($index,$withindex = false)
+	{
+		if($index<0||$index>=$this->getCount())
+			throw new TInvalidDataValueException('list_index_invalid',$index);
+
+		$absindex=$index;
+		$this->sortPriorities();
+		foreach($this->_d as $priority=>$items) {
+			if($index>=($c=count($items)))
+				$index-=$c;
+			else
+				return $withindex?array($priority,$index,$absindex,
+						'priority'=>$priority,'index'=>$index,'absindex'=>$absindex):$priority;
+		}
+		return false;
+	}
+
+	/**
+	 * This inserts an item before another item within the list.  It uses the same priority as the
+	 * found index item and places the new item before it.
+	 * @param mixed indexitem the item to index
+	 * @param mixed the item to add before indexitem
+	 * @return integer where the item has been inserted in the flattened list
+	 * @throws TInvalidDataValueException If the item does not exist
+	 */
+	public function insertBefore($indexitem, $item)
+	{
+		if($this->getReadOnly())
+			throw new TInvalidOperationException('list_readonly',get_class($this));
+
+		if(($priority=$this->priorityOf($indexitem,true))===false)
+			throw new TInvalidDataValueException('list_item_inexistent');
+
+		$this->insertAtIndexInPriority($item,$priority[1],$priority[0]);
+
+		return $priority[2];
+	}
+
+	/**
+	 * This inserts an item after another item within the list.  It uses the same priority as the
+	 * found index item and places the new item after it.
+	 * @param mixed indexitem the item to index
+	 * @param mixed the item to add after indexitem
+	 * @return integer where the item has been inserted in the flattened list
+	 * @throws TInvalidDataValueException If the item does not exist
+	 */
+	public function insertAfter($indexitem, $item)
+	{
+		if($this->getReadOnly())
+			throw new TInvalidOperationException('list_readonly',get_class($this));
+
+		if(($priority=$this->priorityOf($indexitem,true))===false)
+			throw new TInvalidDataValueException('list_item_inexistent');
+
+		$this->insertAtIndexInPriority($item,$priority[1]+1,$priority[0]);
+
+		return $priority[2]+1;
+	}
+
+	/**
+	 * @return array the priority list of items in array
+	 */
+	public function toArray()
+	{
+		return $this->flattenPriorities();
+	}
+
+	/**
+	 * @return array the array of priorities keys with values of arrays of items.  The priorities are sorted so important priorities, lower numerics, are first.
+	 */
+	public function toPriorityArray()
+	{
+		$this->sortPriorities();
+		return $this->_d;
+	}
+
+	/**
+	 * Combines the map elements which have a priority below the parameter value
+	 * @param numeric the cut-off priority.  All items of priority less than this are returned.
+	 * @param boolean whether or not the input cut-off priority is inclusive.  Default: false, not inclusive.
+	 * @return array the array of priorities keys with values of arrays of items that are below a specified priority.
+	 *  The priorities are sorted so important priorities, lower numerics, are first.
+	 */
+	public function toArrayBelowPriority($priority,$inclusive=false)
+	{
+		$this->sortPriorities();
+		$items=array();
+		foreach($this->_d as $itemspriority=>$itemsatpriority)
+		{
+			if((!$inclusive&&$itemspriority>=$priority)||$itemspriority>$priority)
+				break;
+			$items=array_merge($items,$itemsatpriority);
+		}
+		return $items;
+	}
+
+	/**
+	 * Combines the map elements which have a priority above the parameter value
+	 * @param numeric the cut-off priority.  All items of priority greater than this are returned.
+	 * @param boolean whether or not the input cut-off priority is inclusive.  Default: true, inclusive.
+	 * @return array the array of priorities keys with values of arrays of items that are above a specified priority.
+	 *  The priorities are sorted so important priorities, lower numerics, are first.
+	 */
+	public function toArrayAbovePriority($priority,$inclusive=true)
+	{
+		$this->sortPriorities();
+		$items=array();
+		foreach($this->_d as $itemspriority=>$itemsatpriority)
+		{
+			if((!$inclusive&&$itemspriority<=$priority)||$itemspriority<$priority)
+				continue;
+			$items=array_merge($items,$itemsatpriority);
+		}
+		return $items;
+	}
+
+
+	/**
+	 * Copies iterable data into the priority list.
+	 * Note, existing data in the map will be cleared first.
+	 * @param mixed the data to be copied from, must be an array or object implementing Traversable
+	 * @throws TInvalidDataTypeException If data is neither an array nor an iterator.
+	 */
+	public function copyFrom($data)
+	{
+		if($data instanceof TPriorityList)
+		{
+			if($this->getCount()>0)
+				$this->clear();
+			foreach($data->getPriorities() as $priority)
+			{
+				foreach($data->itemsAtPriority($priority) as $index=>$item)
+					$this->insertAtIndexInPriority($item,$index,$priority);
+			}
+		} else if(is_array($data)||$data instanceof Traversable) {
+			if($this->getCount()>0)
+				$this->clear();
+			foreach($data as $key=>$item)
+				$this->add($item);
+		} else if($data!==null)
+			throw new TInvalidDataTypeException('map_data_not_iterable');
+	}
+
+	/**
+	 * Merges iterable data into the priority list.
+	 * New data will be appended to the end of the existing data.  If another TPriorityList is merged,
+	 * the incoming parameter items will be appended at the priorities they are present.  These items will be added
+	 * to the end of the existing items with equal priorities, if there are any.
+	 * @param mixed the data to be merged with, must be an array or object implementing Traversable
+	 * @throws TInvalidDataTypeException If data is neither an array nor an iterator.
+	 */
+	public function mergeWith($data)
+	{
+		if($data instanceof TPriorityList)
+		{
+			foreach($data->getPriorities() as $priority)
+			{
+				foreach($data->itemsAtPriority($priority) as $index=>$item)
+					$this->insertAtIndexInPriority($item,false,$priority);
+			}
+		}
+		else if(is_array($data)||$data instanceof Traversable)
+		{
+			foreach($data as $priority=>$item)
+				$this->add($item);
+
+		}
+		else if($data!==null)
+			throw new TInvalidDataTypeException('map_data_not_iterable');
+	}
+
+	/**
+	 * Returns whether there is an element at the specified offset.
+	 * This method is required by the interface ArrayAccess.
+	 * @param mixed the offset to check on
+	 * @return boolean
+	 */
+	public function offsetExists($offset)
+	{
+		return ($offset>=0&&$offset<$this->getCount());
+	}
+
+	/**
+	 * Returns the element at the specified offset.
+	 * This method is required by the interface ArrayAccess.
+	 * @param integer the offset to retrieve element.
+	 * @return mixed the element at the offset, null if no element is found at the offset
+	 */
+	public function offsetGet($offset)
+	{
+		return $this->itemAt($offset);
+	}
+
+	/**
+	 * Sets the element at the specified offset. This method is required by the interface ArrayAccess.
+	 * Setting elements in a priority list is not straight forword when appending and setting at the
+	 * end boundary.  When appending without an offset (a null offset), the item will be added at
+	 * the default priority.  The item may not be the last item in the list.  When appending with an
+	 * offset equal to the count of the list, the item will get be appended with the last items priority.
+	 *
+	 * All together, when setting the location of an item, the item stays in that location, but appending
+	 * an item into a priority list doesn't mean the item is at the end of the list.
+	 * @param integer the offset to set element
+	 * @param mixed the element value
+	 */
+	public function offsetSet($offset,$item)
+	{
+		if($offset===null)
+			return $this->add($item);
+		if($offset===$this->getCount()) {
+			$priority=$this->priorityAt($offset-1,true);
+			$priority[1]++;
+		} else {
+			$priority=$this->priorityAt($offset,true);
+			$this->removeAtIndexInPriority($priority[1],$priority[0]);
+		}
+		$this->insertAtIndexInPriority($item,$priority[1],$priority[0]);
+	}
+
+	/**
+	 * Unsets the element at the specified offset.
+	 * This method is required by the interface ArrayAccess.
+	 * @param mixed the offset to unset element
+	 */
+	public function offsetUnset($offset)
+	{
+		$this->removeAt($offset);
+	}
+}