A double ended queue that can shrink and expand on both ends.

An index is assigned to an element when it enters the queue, and the index of an element is static (i.e. an index refers to a distinct element until that element is removed from the queue, no matter how many intervening push/pop operations occur).

One consequence of this is that the minimum index may be < 0.

The "front" is the smallest valid index, while the "back" is the largest.

All operations are amortized O(1) with a small constant.

type 'a t
include Binary_searchable.S1 with type t := 'a t
include Container.S1 with type t := 'a t
val create : ?initial_length:int -> ?never_shrink:bool -> unit -> 'a t
create ?initial_length ?never_shrink () create a new t. initial_length is the initial length of the dequeue; it will be able to hold initial_length elements without resizing. It must be positive. If never_shrink is true, the physical array will never shrink; only expand. If initial_length is given without never_shrink then never_shrink is presumed to be true, otherwise never_shrink defaults to false.
val front_index : 'a t -> int option
front_index t return the index of the front item in t.
val front_index_exn : 'a t -> int
front_index_exn t throws an exception if t is empty, otherwise returns the index of the front item in t
val back_index : 'a t -> int option
back_index t return the index of the back item in t.
val back_index_exn : 'a t -> int
back_index_exn t throws an exception if t is empty, otherwise returns the index of the back item in t
val get_opt : 'a t -> int -> 'a option
get_opt t i return the element at index i. Return None if i is invalid.
val get : 'a t -> int -> 'a
get t i return the element at index i. Raise an exception if i is invalid.
val peek : 'a t -> [ `back | `front ] -> 'a option
peek t back_or_front return the value at the back or front of the dequeue without removing it.
val peek_front : 'a t -> 'a option
val peek_front_exn : 'a t -> 'a
val peek_back : 'a t -> 'a option
val peek_back_exn : 'a t -> 'a
val set_exn : 'a t -> int -> 'a -> unit
set_exn t i v mutate the element at i.
val iter' : 'a t -> [ `back_to_front | `front_to_back ] -> f:('a -> unit) -> unit
iter' t ~f iter over the elements of t.
val iteri : 'a t -> f:(int -> 'a -> unit) -> unit
iteri t ~f iter over the elements of t `front_to_back passing in the index.
val iteri' : 'a t -> [ `back_to_front | `front_to_back ] -> f:(int -> 'a -> unit) -> unit
iteri' t ~f as iter, but also passes in the index of the current element.
val fold' : 'a t ->
[ `back_to_front | `front_to_back ] -> init:'b -> f:('b -> 'a -> 'b) -> 'b
fold' t ~init ~f fold over the elements of t
val foldi : 'a t -> init:'b -> f:(int -> 'b -> 'a -> 'b) -> 'b
foldi t ~init ~f as fold, but also passes in the index of the current element.
val foldi' : 'a t ->
[ `back_to_front | `front_to_back ] ->
init:'b -> f:(int -> 'b -> 'a -> 'b) -> 'b
foldi' t ~init ~f as fold', but also passes in the index of the current element to f.
val enqueue : 'a t -> [ `back | `front ] -> 'a -> unit
enqueue t back_or_front v push v onto the back_or_front of t.
val enqueue_front : 'a t -> 'a -> unit
val enqueue_back : 'a t -> 'a -> unit
val clear : 'a t -> unit
clear t removes all elements from t.
val drop : ?n:int -> 'a t -> [ `back | `front ] -> unit
drop ?n t back_or_front drop n elements (default 1) from the back_or_front of t. If t has fewer than n elements then it is cleared.
val drop_front : ?n:int -> 'a t -> unit
val drop_back : ?n:int -> 'a t -> unit
val dequeue : 'a t -> [ `back | `front ] -> 'a option
dequeue t back_or_front remove and return the back_or_front of t
val dequeue_exn : 'a t -> [ `back | `front ] -> 'a
val dequeue_front : 'a t -> 'a option
val dequeue_front_exn : 'a t -> 'a
val dequeue_back : 'a t -> 'a option
val dequeue_back_exn : 'a t -> 'a
val t_of_sexp : (Sexplib.Sexp.t -> 'a) -> Sexplib.Sexp.t -> 'a t
val sexp_of_t : ('a -> Sexplib.Sexp.t) -> 'a t -> Sexplib.Sexp.t
val bin_t : 'a Bin_prot.Type_class.t -> 'a t Bin_prot.Type_class.t
val bin_read_t : 'a Bin_prot.Read.reader -> 'a t Bin_prot.Read.reader
val __bin_read_t__ : 'a Bin_prot.Read.reader -> (int -> 'a t) Bin_prot.Read.reader
val bin_reader_t : 'a Bin_prot.Type_class.reader -> 'a t Bin_prot.Type_class.reader
val bin_size_t : 'a Bin_prot.Size.sizer -> 'a t Bin_prot.Size.sizer
val bin_write_t : 'a Bin_prot.Write.writer -> 'a t Bin_prot.Write.writer
val bin_writer_t : 'a Bin_prot.Type_class.writer -> 'a t Bin_prot.Type_class.writer