WebBits.Data.Zipper

A zipper for Data.Tree.

Functional zipper

These are the core zipper functions.

data Tree a

Multi-way trees, also known as rose trees.

Constructors

Node

Fields

rootLabel :: a

label value

subForest :: Forest a

zero or more child trees

Instances

Monad Tree

Functor Tree

Typeable1 Tree

Applicative Tree

Foldable Tree

Traversable Tree

Eq a => Eq (Tree a)

Data a => Data (Tree a)

Read a => Read (Tree a)

Show a => Show (Tree a)

data Location a

toLocation :: Tree a -> Location a

fromLocation :: Location a -> Tree a

dfsFold

Arguments

:: (w -> v -> w)

transforms a node v using the accumulated value w from the root of the tree to v

-> w

the initial value of the accumulator at the root

-> Tree v

-> Tree w

dfsFoldM :: Monad m => (w -> v -> m w) -> w -> Tree v -> m (Tree w)

Similar to dfsFold, but the transformation is done in the monad m. The sequence of operations is depth-first, left-to-right.

showTree :: Show a => Tree a -> String

empty :: a -> Tree a

up :: Location a -> Location a

down :: Location a -> Location a

left :: Location a -> Location a

right :: Location a -> Location a

replace :: Location a -> Tree a -> Location a

change :: Location a -> a -> Location a

insertDown :: Location a -> Tree a -> Location a

insertLeft :: Location a -> Tree a -> Location a

insertRight :: Location a -> Tree a -> Location a

isTop :: Location a -> Bool

isChild :: Location a -> Bool

getValue :: Location a -> a

subTree :: Location a -> Tree a

top :: Location a -> Location a

Traverses to the top of the tree.

 up.top = undefined
 top.top = top

canGoLeft :: Location a -> Bool

canGoRight :: Location a -> Bool

canGoUp :: Location a -> Bool

canGoDown :: Location a -> Bool

Imperative tree construction

A state monad that carries a zipper. It provides convenient methods to imperatively create and update a tree.

The state monad's set method may be used to arbitrarily update the current location. However, such updates can break the behavior of nest and withCurrentChild. We recommend avoiding StateT.set.

type ZipperT v m a = StateT (Location v) m a

nest

Arguments

:: Monad m

=> v

value of the new right-most child

-> ZipperT v m a

computation applied to the new child

-> ZipperT v m a

returns the result of the nested computation

Creates a new node as the right-most child of the current node.

getNode :: Monad m => ZipperT v m v

setNode :: Monad m => v -> ZipperT v m ()

runZipperT :: Monad m => ZipperT v m a -> Location v -> m (a, Tree v)

evalZipperT :: Monad m => ZipperT v m a -> Location v -> m a

execZipperT :: Monad m => ZipperT v m a -> Location v -> m (Tree v)

shiftLeft :: Monad m => ZipperT v m ()

shiftRight :: Monad m => ZipperT v m ()

shiftLeft' :: Monad m => ZipperT v m ()

Silently fails to shift left if there is no left-child.

shiftRight' :: Monad m => ZipperT v m ()

Silently fails to shift right if there is no right-child.

withCurrentChild

Arguments

:: Monad m

=> ZipperT v m a

computation to apply to the current child

-> ZipperT v m a

returns the result of the nested computation