package batteries

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Module type
Class type

First-in first-out queues.

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

  • author Xavier Leroy (Base module)
  • author David Teller
type 'a t = 'a Queue.t

The type of queues containing elements of type 'a.

exception Empty

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

val create : unit -> 'a t

Return a new queue, initially empty.

val add : 'a -> 'a t -> unit

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

val push : 'a -> 'a t -> unit

push is a synonym for add.

val take : 'a t -> 'a

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

val pop : 'a t -> 'a

pop is a synonym for take.

val peek : 'a t -> 'a

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

val top : 'a t -> 'a

top is a synonym for peek.

val clear : 'a t -> unit

Discard all elements from a queue.

val copy : 'a t -> 'a t

Return a copy of the given queue.

val is_empty : 'a t -> bool

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

val length : 'a t -> int

Return the number of elements in a queue.

val iter : ('a -> unit) -> 'a t -> 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.

val map : ('a -> 'b) -> 'a t -> 'b t

map f q applies function f to each element of the queue and returns a new queue q' with the results returned by f. Order is preserved and q is not consumed. So that if take q returns x take q' will return f x.

  • since 2.3.0
val filter : ('a -> bool) -> 'a t -> 'a t

filter p q returns a new queue that contain the elements of q that satisfy the predicate p, in the same order.

  • since 2.4
val filter_map : ('a -> 'b option) -> 'a t -> 'b t

filter_map f q applies f to the elements a0, of q in order, and returns the queue of the elements bi such that f ai = Some bi, in the corresponding order.

  • since 2.4
val filter_inplace : ('a -> bool) -> 'a t -> unit

filter_inplace p q removes all the elements of the queue q that don't satisfy the predicate p. The order of the elements in the queue is preserved.

  • since 2.4
val fold : ('b -> 'a -> 'b) -> 'b -> 'a t -> '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.

val transfer : 'a t -> 'a t -> 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.

type 'a enumerable = 'a t
val enum : 'a t -> 'a BatEnum.t

enum q returns a destructive enumeration of the elements of queue q, from the least recently entered to the most recently entered. Reading the enumeration will progressively empty q.

val of_enum : 'a BatEnum.t -> 'a t

of_enum e returns a new queue containing all the elements of e. This is equivalent to calling push with the first element of the enumeration, then with the second, etc.

Boilerplate code
val print : ?first:string -> ?last:string -> ?sep:string -> ('a BatInnerIO.output -> 'b -> unit) -> 'a BatInnerIO.output -> 'b t -> unit
val compare : 'a BatOrd.comp -> 'a t BatOrd.comp
val equal : 'a BatOrd.eq -> 'a t BatOrd.eq
module Exceptionless : sig ... end

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