/**
* This method returns the element at the head of the queue, but does not remove it.
*
* @access public
* @throws Throwable\EmptyCollection\Exception indicates no element could be dequeued
* @return mixed the element at the head of the queue
*/
public function peek()
{
if ($this->list->isEmpty()) {
throw new Throwable\EmptyCollection\Exception('Unable to peek at next element in the queue. Collection contains no elements.');
}
return $this->list->getValue(0);
}
/**
* This method pops the top element off the stack.
*
* @access public
* @return mixed the element at the top of the stack
* @throws Throwable\EmptyCollection\Exception indicates that no more elements are
* on the stack
*/
public function pop()
{
if ($this->list->isEmpty()) {
throw new Throwable\EmptyCollection\Exception('Unable to pop an element off the stack. Collection contains no elements.');
}
$index = $this->list->count() - 1;
$value = $this->list->getValue($index);
$this->list->removeIndex($index);
return $value;
}
/**
* This method pops off the element at the back of the deque.
*
* @access public
* @return mixed the element from the back of the deque
* @throws Throwable\EmptyCollection\Exception indicates that no more elements are
* on the deque
*/
public function popBack()
{
if ($this->isEmpty()) {
throw new Throwable\EmptyCollection\Exception('Trying to pop element from empty deque');
}
$index = $this->list->count() - 1;
$value = $this->list->getValue($index);
$this->list->removeIndex($index);
return $value;
}
