
Data Structure

This illustrates a data structure, a means of storing data within a program.

You may see other such structures in the Data Structures category.
 Illustration of FIFO behavior
Task

Implement a FIFO queue.

Elements are added at one side and popped from the other in the order of insertion.



Operations:

   push   (aka enqueue)    - add element
   pop     (aka dequeue)    - pop first element
   empty                             - return truth value when empty


Errors:

   handle the error of trying to pop from an empty queue (behavior depends on the language and platform)


See

   Queue/Usage   for the built-in FIFO or queue of your language or standard library.


See also

 Array
 Associative array: Creation, Iteration
 Collections
 Compound data type
 Doubly-linked list: Definition, Element definition, Element insertion, List Traversal, Element Removal
 Linked list
 Queue: Definition, Usage
 Set
 Singly-linked list: Element definition, Element insertion, List Traversal, Element Removal
 Stack


class Fifo {
  private $data = array();
  public function push($element){
    array_push($this->data, $element);
  }
  public function pop(){
    if ($this->isEmpty()){
      throw new Exception('Attempt to pop from an empty queue');
    }
    return array_shift($this->data);
  }
 
  //Alias functions
  public function enqueue($element) { $this->push($element); }
  public function dequeue() { return $this->pop(); }
 
  //Note: PHP prevents a method name of 'empty'
  public function isEmpty(){
    return empty($this->data);
  }
}