
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 Queue
{
  List queue := [,]
 
  public Void push (Obj obj)
  {
    queue.add (obj)  // add to right of list
  }
 
  public Obj pop ()
  {
    if (queue.isEmpty)
      throw (Err("queue is empty"))
    else
    {
      return queue.removeAt(0) // removes left-most item 
    }
  }
 
  public Bool isEmpty ()
  {
    queue.isEmpty
  }
}
 