
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


queue ← {
  data ← ⟨⟩
  Push ⇐ {data∾˜↩𝕩}
  Pop ⇐ {
    𝕊𝕩:
    0=≠data ? •Show "Cannot pop from empty queue";
    (data↓˜↩¯1)⊢⊑⌽data
  }
  Empty ⇐ {𝕊𝕩: 0=≠data}
  Display ⇐ {𝕊𝕩: •Show data}
}
 
q1 ← queue
 
•Show q1.Empty@
q1.Push 3
q1.Push 4
q1.Display@
•Show q1.Pop@
q1.Display@