# Module BatDllist

    module BatDllist: sig .. end

A mutable, imperative, circular, doubly linked list library

This module implements a doubly linked list in a mutable or imperitive style (changes to the list are visible to all copies of the list).

Note This implementation of doubly-linked lists does not support empty lists.
Author(s): Brian Hurt, Jesse Guardiani, David Teller

    type 'a node_t

    type 'a t = 'a node_t

The type of a non-empty doubly-linked list.

    include BatInterfaces.Mappable

    include BatEnum.Enumerable

    exception Empty

###### node functions

    val create : 'a -> 'a node_t

Creates a node. This is an O(1) operation.

    val copy : 'a node_t -> 'a node_t

Copy the list attached to the given node and return the copy of the given node. This is an O(N) operation.

    val length : 'a node_t -> int

Returns the length of the list. This is an O(N) operation.

    val rev : 'a node_t -> unit

List reversal. This is an O(N) operation. The given node still points to the same element, so `to_list (rev (of_list [1;2;3;4])) = [1;4;3;2]`

    val add : 'a node_t -> 'a -> unit

`add n a` Creates a new node containing data `a` and inserts it into the list after node `n`. This is an O(1) operation.

    val append : 'a node_t -> 'a -> 'a node_t

`append n a` Creates a new node containing data `a` and inserts it into the list after node `n`. Returns new node. This is an O(1) operation.

    val prepend : 'a node_t -> 'a -> 'a node_t

`prepend n a` Creates a new node containing data `a` and inserts it into the list before node `n`. Returns new node. This is an O(1) operation.

    val promote : 'a node_t -> unit

`promote n` Swaps `n` with `next n`. This is an O(1) operation.

    val demote : 'a node_t -> unit

`demote n` Swaps `n` with `prev n`. This is an O(1) operation.

    val remove : 'a node_t -> unit

Remove node from the list no matter where it is. This is an O(1) operation.
Raises `Empty` when trying to remove an element from a list of length one.

    val drop : 'a node_t -> 'a node_t

Remove node from the list no matter where it is. Return next node. This is an O(1) operation.
Raises `Empty` when trying to remove an element from a list of length one.

    val rev_drop : 'a node_t -> 'a node_t

Remove node from the list no matter where it is. Return previous node. This is an O(1) operation.
Raises `Empty` when trying to remove an element from a list of length one.

    val splice : 'a node_t -> 'a node_t -> unit

`splice n1 n2` Connects `n1` and `n2` so that `next n1 == n2 && prev n2 == n1`. This can be used to connect two discrete lists, or, if used on two nodes within the same list, it can be used to separate the nodes between `n1` and `n2` from the rest of the list. In this case, those nodes become a discrete list by themselves. This is an O(1) operation.

    val get : 'a node_t -> 'a

Given a node, get the data associated with that node. This is an O(1) operation.

    val set : 'a node_t -> 'a -> unit

Given a node, set the data associated with that node. This is an O(1) operation.

    val next : 'a node_t -> 'a node_t

Given a node, get the next element in the list after the node.

The list is circular, so the last node of the list returns the first node of the list as it's next node.

This is an O(1) operation.

    val prev : 'a node_t -> 'a node_t

Given a node, get the previous element in the list before the node.

The list is circular, so the first node of the list returns the last element of the list as it's previous node.

This is an O(1) operation.

    val skip : 'a node_t -> int -> 'a node_t

`skip n i` Return the node that is `i` nodes after node `n` in the list. If `i` is negative then return the node that is `i` nodes before node `n` in the list. This is an O(N) operation.

    val iter : ('a -> unit) -> 'a node_t -> unit

`iter f n` Apply `f` to every element in the list, starting at `n`. This is an O(N) operation.

    val fold_left : ('a -> 'b -> 'a) -> 'a -> 'b node_t -> 'a

Accumulate a value over the entire list. This works like List.fold_left. This is an O(N) operation.

    val fold_right : ('a -> 'b -> 'b) -> 'a node_t -> 'b -> 'b

Accumulate a value over the entire list. This works like List.fold_right, but since the list is bidirectional, it doesn't suffer the performance problems of List.fold_right. This is an O(N) operation.

    val find : ('a -> bool) -> 'a node_t -> 'a node_t

`find p l` returns the first element, `l` or after, for which `p` returns true.
Raises `Not_found` if no such element exists

    val for_all : ('a -> bool) -> 'a node_t -> bool

Test whether a given predicate returns true for all members of the given list. O(N)

    val exists : ('a -> bool) -> 'a node_t -> bool

Test whether there exists an element of the given list for which the predicate returns true. O(N)

    val map : ('a -> 'b) -> 'a node_t -> 'b node_t

Allocate a new list, with entirely new nodes, whose values are the transforms of the values of the original list. Note that this does not modify the given list. This is an O(N) operation.

    val filter : ('a -> bool) -> 'a node_t -> 'a node_t

`filter p l` returns a new list, with entirely new nodes, whose values are all the elements of the list `l` that satisfy the predicate `p`. The order of the elements in the input list is preserved.
Raises `Empty` if the resulting list is empty.

    val filter_map : ('a -> 'b option) -> 'a node_t -> 'b node_t

`filter_map f l` calls `(f a0) (f a1) ... (f an)` where `a0,a1...an` are the elements of `l`. It returns a new list of elements `bi` such as `f ai = Some bi` (when `f` returns `None`, the corresponding element of `l` is discarded).
Raises `Empty` if the resulting list is empty.

###### list conversion

    val to_list : 'a node_t -> 'a list

Converts a dllist to a normal list. This is an O(N) operation.

    val of_list : 'a list -> 'a node_t

Converts from a normal list to a Dllist and returns the first node.
Raises `Empty` if given list is empty. This is an O(N) operation.

###### enums

    val enum : 'a node_t -> 'a BatEnum.t

Create an enum of the list. Note that modifying the list while the enum exists will have undefined effects. This is an O(1) operation.

    val rev_enum : 'a node_t -> 'a BatEnum.t

Create a reverse enum of the list. The enumeration starts with the current element of the list: `rev_enum (of_list [1;2;3;4])` will generate the enumeration `[1;4;3;2]`.

If you want it to start with the last one, see `backwards`.

Note that modifying the list while the enum exists will have undefined effects. This is an O(1) operation.

    val backwards : 'a node_t -> 'a BatEnum.t

`backwards t` is similar to `rev_enum t` except that the enumeration starts at the node before the current one:

`backwards (of_list [1;2;3;4])` will generate the enumeration `[4;3;2;1]`.

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

Create a dllist from an enum. This consumes the enum, and allocates a whole new dllist.
Raises `Empty` if given enum is empty. This is an O(N) operation.

###### Boilerplate code

Printing

    val print : ?first:string ->
           ?last:string ->
           ?sep:string ->
           ('a BatInnerIO.output -> 'b -> unit) ->
           'a BatInnerIO.output -> 'b t -> unit