Annotations.F.Zipper

Documentation

data Zipper a

A quasi-zipper, meant for O(1), fixed-memory stepping through a tree structure, but not meant for updates.

Constructors

Zipper

Fields

• zFocus :: a

  The current focus of this zipper.

• zUp :: Maybe (Zipper a)

  Move up to the parent.

• zLeft :: Maybe (Zipper a)

  Move to the left sibling.

• zRight :: Maybe (Zipper a)

  Move to the right sibling.

• zDown :: Maybe (Zipper a)

  Move down into the leftmost child.

enter :: Foldable f => Fix f -> Zipper (Fix f)

Move into the root of the fixed point. The returned zipper builds a data structure with optimal sharing and fixed memory usage. For example, zLeft >=> zRight (if successful) returns to the same node in memory.

leave :: Zipper a -> a

Walk back up to the root of the fixed point and leave the zipper structure.

child :: Int -> Zipper a -> Maybe (Zipper a)

Move down into a specific child.

allFoci :: Foldable f => Fix f -> [Zipper (Fix f)]

Traverses the tree in preorder, yielding all possible tree selections.

newtype Nav

Captures navigation steps in a Zipper. Its Monoid instance specifies the identity step (mempty) and step composition (mappend).

Constructors

Nav

Fields

• nav :: forall a. Zipper a -> Maybe (Zipper a)

Instances

Monoid Nav

Methods

mempty :: Nav

mappend :: Nav -> Nav -> Nav

mconcat :: [Nav] -> Nav