Struct Zipper 

pub struct Zipper<A> {
    pub left: Vec<A>,
    pub focus: A,
    pub right: Vec<A>,
}

A zipper over a non-empty vector: models a focused list comonad.

The zipper is the canonical comonad for list-like structures: extract = current element, extend = apply f to each focus position.

Fields

left: Vec<A>

focus: A

right: Vec<A>

Implementations

impl<A: Clone> Zipper<A>

pub fn new(data: Vec<A>, i: usize) -> Option<Self>

Create a zipper focused on index i of data.

Returns None if data is empty or i is out of bounds.

pub fn extract(&self) -> &A

Extract the focused element (counit / extract).

pub fn extend<B: Clone>(&self, f: impl Fn(&Zipper<A>) -> B) -> Zipper<B>

Extend the zipper comonad: apply f at every position.

This implements extend f w for the zipper comonad.

pub fn move_left(&self) -> Option<Zipper<A>>

Move focus one step to the left.

pub fn move_right(&self) -> Option<Zipper<A>>

Move focus one step to the right.

pub fn to_vec(&self) -> Vec<A>

Collect all elements in order.

pub fn len(&self) -> usize

Length of the full sequence.

pub fn is_empty(&self) -> bool

A zipper always has at least one element (the focus), so it is never empty.

pub fn is_singleton(&self) -> bool

Returns true if the zipper has only one element.

Trait Implementations

impl<A: Clone> Clone for Zipper<A>

fn clone(&self) -> Zipper<A>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.