doubly-linked lists

Compared to other doubly-linked lists, in this one:

1. Calls to modification functions (insert*, move*, ...) detect if the list is being iterated over (iter, fold, ...), and if so raise an exception. For example, a use like the following would raise.

      iter t ~f:(fun _ -> ... remove t e ...)

2. There is a designated "front" and "back" of each list, rather than viewing each element as an equal in a ring.

3. Elements know which list they're in. Each operation that takes an Elt.t also takes a t, first checks that the Elt belongs to the t, and if not, raises.

4. Related to (3), lists cannot be split, though a sort of splicing is available as transfer. In other words, no operation will cause one list to become two. This makes this module unsuitable for maintaining the faces of a planar graph under edge insertion and deletion, for example.

5. Another property permitted by (3) and (4) is that length is O(1).

module Elt : sig .. end
type 'a t
val value : 'a t -> 'a
val equal : 'a t -> 'a t -> bool
val sexp_of_t : ('a -> Sexplib.Sexp.t) -> 'a t -> Sexplib.Sexp.t
type 'a t
include Container.S1 with type t := 'a t
val invariant : 'a t -> unit
val create : unit -> 'a t
creating doubly-linked lists
val of_list : 'a list -> 'a t
of_list l returns a doubly-linked list t with the same elements as l and in the same order (i.e. the first element of l is the first element of t). It is always the case that l = to_list (of_list l).
val equal : 'a t -> 'a t -> bool
val is_first : 'a t -> 'a Elt.t -> bool
val is_last : 'a t -> 'a Elt.t -> bool
val first_elt : 'a t -> 'a Elt.t option
constant-time extraction of first and last elements.
val last_elt : 'a t -> 'a Elt.t option
val first : 'a t -> 'a option
val last : 'a t -> 'a option
val next : 'a t -> 'a Elt.t -> 'a Elt.t option
constant-time retrieval of next or previous element.
val prev : 'a t -> 'a Elt.t -> 'a Elt.t option
val insert_before : 'a t -> 'a Elt.t -> 'a -> 'a Elt.t
constant-time insertion of a new element.
val insert_after : 'a t -> 'a Elt.t -> 'a -> 'a Elt.t
val insert_first : 'a t -> 'a -> 'a Elt.t
val insert_last : 'a t -> 'a -> 'a Elt.t
val move_to_front : 'a t -> 'a Elt.t -> unit
constant-time move of an element from and to positions in the same list. An exception is raised if elt is equal to anchor.
val move_to_back : 'a t -> 'a Elt.t -> unit
val move_after : 'a t -> 'a Elt.t -> anchor:'a Elt.t -> unit
val move_before : 'a t -> 'a Elt.t -> anchor:'a Elt.t -> unit
val remove : 'a t -> 'a Elt.t -> unit
constant-time removal of an element.
val remove_first : 'a t -> 'a option
val remove_last : 'a t -> 'a option
val fold_elt : 'a t -> init:'b -> f:('b -> 'a Elt.t -> 'b) -> 'b
fold_elt t ~init ~f is the same as fold, except f is called with the 'a Elt.t's from the list instead of the contained 'a values.

Note that like other iteration functions, it is an error to mutate t inside the fold. If you'd like to call remove on any of the 'a Elt.t's, accumulate them here and do so after fold_elt returns.

val iter_elt : 'a t -> f:('a Elt.t -> unit) -> unit
val fold_right : 'a t -> init:'b -> f:('a -> 'b -> 'b) -> 'b
val find_elt : 'a t -> f:('a -> bool) -> 'a Elt.t option
find_elt t ~f finds the first element in t that satisfies f, by testing each of element of t in turn until f succeeds.
val clear : 'a t -> unit
clear t removes all elements from the list in constant time.
val copy : 'a t -> 'a t
val transfer : src:'a t -> dst:'a t -> unit
transfer ~src ~dst has the same behavior as iter src ~f:(insert_last dst); clear src except that it runs in constant time.

If s = to_list src and d = to_list dst, then after transfer ~src ~dst: to_list src = [] to_list dst = d @ s

val filter_inplace : 'a t -> f:('a -> bool) -> unit
filter_inplace t ~f removes all elements of t that don't satisfy f.
val unchecked_iter : 'a t -> f:('a -> unit) -> unit
unchecked_iter t ~f behaves like iter t ~f except that f is allowed to modify t. Adding or removing elements before the element currently being visited has no effect on the traversal. Elements added after the element currently being visited will be traversed. Elements deleted after the element currently being visited will not be traversed. Deleting the element currently visited is an error that is not detected (presumably leading to an infinite loop) .
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