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QueueInterface.php
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QueueInterface.php
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<?php
declare(strict_types=1);
namespace Psl\DataStructure;
use Countable;
use Psl;
/**
* An interface representing a queue data structure ( FIFO ).
*
* @template T
*
* @see https://en.wikipedia.org/wiki/FIFO_(computing_and_electronics)
*/
interface QueueInterface extends Countable
{
/**
* Adds a node to the queue.
*
* @param T $node
*/
public function enqueue($node): void;
/**
* Retrieves, but does not remove, the node at the head of this queue,
* or returns null if this queue is empty.
*
* @return null|T
*/
public function peek();
/**
* Retrieves and removes the node at the head of this queue,
* or returns null if this queue is empty.
*
* @return null|T
*/
public function pull();
/**
* Retrieves and removes the node at the head of this queue.
*
* @throws Psl\Exception\InvariantViolationException If the Queue is invalid.
*
* @return T
*/
public function dequeue();
/**
* Count the nodes in the queue.
*/
public function count(): int;
}