(*
Copyright (c) 2013, Simon Cruanes
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(** {1 Functional queues (fifo)} *)

type 'a t
  (** Queue containing elements of type 'a *)

val empty : 'a t

val is_empty : 'a t -> bool

val push : 'a t -> 'a -> 'a t
  (** Push element at the end of the queue *)

val peek : 'a t -> 'a
  (** Get first element, or raise Invalid_argument *)

val pop : 'a t -> 'a * 'a t
  (** Get and remove the first element, or raise Invalid_argument *)

val junk : 'a t -> 'a t
  (** Remove first element. If queue is empty, do nothing. *)

val append : 'a t -> 'a t -> 'a t
  (** Append two queues. Elements from the second one come
      after elements of the first one *)

val size : 'a t -> int
  (** Number of elements in the queue (linear in time) *)

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

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

type 'a sequence = ('a -> unit) -> unit
val to_seq : 'a t -> 'a sequence
val of_seq : 'a sequence -> 'a t