Queue

A queue is a data structure sometimes used in esoteric programming languages.

Operations

A queue works by the principle of First In, First Out (FIFO). What is enqueued onto the queue first, will be dequeued first. This leads to the operations ENQUEUE, which puts a value at the back of the queue, and DEQUEUE, which takes a value from the front, removes it, and returns it.

Additional Operations

In addition to ENQUEUE and DEQUEUE, there are a few other queue manipulation operations, many of which are the queue equivalent of stack operations, that queues can use that are generally accomplished through scalar variables.

The following table lists them, including the operation, its name, its traditional (or completely made up) laconic representation, its meaning, and an example in "Generic Queue Language" (GQL), a language used solely for example purposes.

Op	Laconic	Name	Meaning	GQL
PEEK	N/A	Peek	Get the value at the front of the queue without removing it	Not possible due to the FIFO nature of queues
DROP	$	Drop	Remove the value from the front of the queue and discard it	DEQUEUE;
ROLL	N/A	Roll	Move the value from the front of the queue to the back	DEQUEUE→a; ENQUEUE a;
DUP	:	Duplicate	Duplicate the value at the front of the queue to the back	PEEK→a; ENQUEUE a;

Use in esolangs

Here are some examples of esoteric programming languages that use queues:

• Q-BAL works like a stack-based language, except using queues instead of stacks.
• Qdeql uses a single queue.
• NULL uses three queues.
• Fueue uses a single queue.
• 0815 uses a single queue and 3 registers.
• Bitwise Cyclic Tag uses two queues, one for program and one for data.

See Also

• Category:Queue-based
• Stack
• Deque, a double-ended queue