Data.List.PointedList

An implementation of a zipper-like non-empty list structure that tracks an index position in the list (the focus).

Documentation

data PointedList a

The implementation of the pointed list structure which tracks the current position in the list structure.

Constructors

PointedList

Fields

reversedPrefix :: [a]

_focus :: a

suffix :: [a]

Instances

Functor PointedList

Foldable PointedList

Traversable PointedList

Eq a => Eq (PointedList a)

Show a => Show (PointedList a)

Binary a_1627403032 => Binary (PointedList a_1627403032)

lSuffix :: forall (~>) a. Arrow ~> => Lens ~> (PointedList a) [a]

lReversedPrefix :: forall (~>) a. Arrow ~> => Lens ~> (PointedList a) [a]

focus :: forall (~>) a. Arrow ~> => Lens ~> (PointedList a) a

singleton :: a -> PointedList a

Create a PointedList with a single element.

fromList :: [a] -> Maybe (PointedList a)

Possibly create a Just PointedList if the provided list has at least one element; otherwise, return Nothing.

The provided list's head will be the focus of the list, and the rest of list will follow on the right side.

fromListEnd :: [a] -> Maybe (PointedList a)

Possibly create a Just PointedList if the provided list has at least one element; otherwise, return Nothing.

The provided list's last element will be the focus of the list, following the rest of the list in order, to the left.

replace :: a -> PointedList a -> PointedList a

Replace the focus of the list, retaining the prefix and suffix.

next :: PointedList a -> Maybe (PointedList a)

Possibly move the focus to the next element in the list.

tryNext :: PointedList a -> PointedList a

Attempt to move the focus to the next element, or error if there are no more elements.

previous :: PointedList a -> Maybe (PointedList a)

Possibly move the focus to the previous element in the list.

tryPrevious :: PointedList a -> PointedList a

Attempt to move the focus to the previous element, or error if there are no more elements.

insert :: a -> PointedList a -> PointedList a

An alias for insertRight.

insertLeft :: a -> PointedList a -> PointedList a

Insert an element to the left of the focus, then move the focus to the new element.

insertRight :: a -> PointedList a -> PointedList a

Insert an element to the right of the focus, then move the focus to the new element.

delete :: PointedList a -> Maybe (PointedList a)

An alias of deleteRight.

deleteLeft :: PointedList a -> Maybe (PointedList a)

Possibly delete the element at the focus, then move the element on the left to the focus. If no element is on the left, focus on the element to the right. If the deletion will cause the list to be empty, return Nothing.

deleteRight :: PointedList a -> Maybe (PointedList a)

Possibly delete the element at the focus, then move the element on the right to the focus. If no element is on the right, focus on the element to the left. If the deletion will cause the list to be empty, return Nothing.

deleteOthers :: PointedList a -> PointedList a

Delete all elements in the list except the focus.

length :: PointedList a -> Int

The length of the list.

atStart :: PointedList a -> Bool

Whether the focus is the first element.

atEnd :: PointedList a -> Bool

Whether the focus is the last element.

positions :: PointedList a -> PointedList (PointedList a)

Create a PointedList of variations of the provided PointedList, in which each element is focused, with the provided PointedList as the focus of the sets.

contextMap :: (PointedList a -> b) -> PointedList a -> PointedList b

Map over the PointedLists created via positions, such that f is called with each element of the list focused in the provided PointedList. An example makes this easier to understand:

 contextMap atStart (fromJust $ fromList [1..5])

withFocus :: PointedList a -> PointedList (a, Bool)

Create a PointedList a of (a, Bool), in which the boolean values specify whether the current element has the focus. That is, all of the booleans will be False, except the focused element.

moveTo :: Int -> PointedList a -> Maybe (PointedList a)

Move the focus to the specified index. The first element is at index 0.

moveN :: Int -> PointedList a -> Maybe (PointedList a)

Move the focus by n, relative to the current index. Negative values move the focus backwards, positive values more forwards through the list.

find :: Eq a => a -> PointedList a -> Maybe (PointedList a)

Move the focus to the specified element, if it is present.

Patch with much faster algorithm provided by Runar Bjarnason for version 0.3.2. Improved again by Runar Bjarnason for version 0.3.3 to support infinite lists on both sides of the focus.

index :: PointedList a -> Int

The index of the focus, leftmost is 0.