# Module Batteries.FingerTree

    module FingerTree: BatFingerTree

    type 'a monoid = {

`` | `zero :`'a`;` | `(*` | The neutral element of the monoid. | `*)`
`` | `combine :`'a -> 'a -> 'a`;` | `(*` | `combine` should be associative, and have `zero` as neutral element. | `*)`

}
The type of the element of a monoid.

    exception Empty

An exception that is thrown by various operations when trying to get a non existing element.

    module type S = sig .. end

    module Generic: sig .. end

    type 'a t

    include BatFingerTree.S

    val size : 'a t -> int

`size t` returns the number of elements in the sequence.

Unlike the generic `size` on finger trees, this one has complexity O(1).

    val split_at : 'a t -> int -> 'a t * 'a t

`split_at` is equivalent to `List.split_at`.
Raises `Invalid_argument` when the index is out of bounds.

O(log(n)).

    val get : 'a t -> int -> 'a

`get t i` returns the `i`-th element of `t`.
Raises `Invalid_argument` when the index is out of bounds.

O(log(n)).

    val set : 'a t -> int -> 'a -> 'a t

`set t i v` returns `t` where the `i`-th element is now `v`.
Raises `Invalid_argument` when the index is out of bounds.

O(log(n)).

    val update : 'a t -> int -> ('a -> 'a) -> 'a t

`update t i f` returns `t` where the `i`-th element is now `f (get i t)`.
Raises `Invalid_argument` when the index is out of bounds.

O(log(n)).