Module Queue

module Queue: sig .. end

First-in first-out queues.

This module implements queues (FIFOs), with in-place modification.

Warning This module is not thread-safe: each Queue.t value must be protected from concurrent access (e.g. with a Mutex.t). Failure to do so can lead to a crash.

type t('a);

The type of queues containing elements of type 'a.

exception Empty;

Raised when Queue.take or Queue.peek is applied to an empty queue.

let create: unit => t('a);

Return a new queue, initially empty.

let add: ('a, t('a)) => unit;

add x q adds the element x at the end of the queue q.

let push: ('a, t('a)) => unit;

push is a synonym for add.

let take: t('a) => 'a;

take q removes and returns the first element in queue q, or raises Queue.Empty if the queue is empty.

let take_opt: t('a) => option('a);

take_opt q removes and returns the first element in queue q, or returns None if the queue is empty.

Since 4.08

let pop: t('a) => 'a;

pop is a synonym for take.

let peek: t('a) => 'a;

peek q returns the first element in queue q, without removing it from the queue, or raises Queue.Empty if the queue is empty.

let peek_opt: t('a) => option('a);

peek_opt q returns the first element in queue q, without removing it from the queue, or returns None if the queue is empty.

Since 4.08

let top: t('a) => 'a;

top is a synonym for peek.

let clear: t('a) => unit;

Discard all elements from a queue.

let copy: t('a) => t('a);

Return a copy of the given queue.

let is_empty: t('a) => bool;

Return true if the given queue is empty, false otherwise.

let length: t('a) => int;

Return the number of elements in a queue.

let iter: ('a => unit, t('a)) => unit;

iter f q applies f in turn to all elements of q, from the least recently entered to the most recently entered. The queue itself is unchanged.

let fold: (('b, 'a) => 'b, 'b, t('a)) => 'b;

fold f accu q is equivalent to List.fold_left f accu l, where l is the list of q's elements. The queue remains unchanged.

let transfer: (t('a), t('a)) => unit;

transfer q1 q2 adds all of q1's elements at the end of the queue q2, then clears q1. It is equivalent to the sequence iter (fun x -> add x q2) q1; clear q1, but runs in constant time.

Iterators

let to_seq: t('a) => Seq.t('a);

Iterate on the queue, in front-to-back order. The behavior is not defined if the queue is modified during the iteration.

Since 4.07

let add_seq: (t('a), Seq.t('a)) => unit;

Add the elements from the generator to the end of the queue

Since 4.07

let of_seq: Seq.t('a) => t('a);

Create a queue from the generator

Since 4.07