List.Zipper

A zipper for List.

The `Zipper` type

type Zipper a

= Zipper (List a) a (List a)

The Zipper type.

fromList : List a -> Maybe (Zipper a)

Construct a Zipper from a list. The Zipper will focus on the first element (if there is a first element).

before : Zipper a -> List a

Returns all elements before the element the Zipper is focussed on.

get : Zipper a -> a

Returns the element the Zipper is focussed on.

after : Zipper a -> List a

Returns all elements after the element the Zipper is focussed on

toList : Zipper a -> List a

Reconstruct the list.

updateBefore : (List a -> List a) -> Zipper a -> Zipper a

Update all elements before the element the Zipper is focussed on.

update : (a -> a) -> Zipper a -> Zipper a

Updat the element the Zipper is focussed on.

updateAfter : (List a -> List a) -> Zipper a -> Zipper a

Update all elements after the element the Zipper is focussed on.

first : Zipper a -> Zipper a

Move the focus to the first element of the list.

previous : Zipper a -> Maybe (Zipper a)

Move the focus to the element before the element the Zipper is currently focussed on (if there is such an element).

next : Zipper a -> Maybe (Zipper a)

Move the focus to the element after the element the Zipper is currently focussed on (if there is such an element).

last : Zipper a -> Zipper a

Move the focus to the last element of the list.

find : (a -> Bool) -> Zipper a -> Maybe (Zipper a)

Returns a Zipper focussed on the first element for which the predicate returns True (starting from a given Zipper).