
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 {
    private List buffer
 
    public Queue(List buffer =  new LinkedList()) {
        assert buffer != null
        assert buffer.empty
        this.buffer = buffer
    }
 
    def push (def item) { buffer << item }
    final enqueue = this.&push
 
    def pop() {
        if (this.empty) throw new NoSuchElementException('Empty Queue')
        buffer.remove(0)
    }
    final dequeue = this.&pop
 
    def getEmpty() { buffer.empty }
 
    String toString() { "Queue:${buffer}" }
}