Safe Haskell	None
Language	Haskell2010

Data.Tree.Util

Contents

Zipper on rose trees

Synopsis

data Zipper a = Zipper {
- focus :: Tree a
- ancestors :: [([Tree a], a, [Tree a])]
}
root :: Tree a -> Zipper a
up :: Zipper a -> Maybe (Zipper a)
firstChild :: Zipper a -> Maybe (Zipper a)
nextSibling :: Zipper a -> Maybe (Zipper a)
prevSibling :: Zipper a -> Maybe (Zipper a)
allChildren :: Zipper a -> [Zipper a]
allTrees :: Zipper a -> [Zipper a]
unZipperLocal :: Zipper a -> Tree a
constructTree :: [([Tree a], a, [Tree a])] -> Maybe (Tree a)
findEvert :: (a -> Bool) -> Tree a -> Maybe (Tree a)
findEvert' :: (Tree a -> Bool) -> Tree a -> Maybe (Tree a)
findPath :: (a -> Bool) -> (a -> Bool) -> Tree a -> Maybe [a]
findNode :: (a -> Bool) -> Tree a -> Maybe [a]
findNodes :: (Tree a -> Bool) -> Tree a -> [[a]]

Documentation

>>> :{
let myTree = Node 0 [ Node 1 []
                    , Node 2 []
                    , Node 3 [ Node 4 [] ]
                    ]
:}

Zipper on rose trees

data Zipper a Source #

Zipper for rose trees

Constructors

Zipper
Fields focus :: Tree a ancestors :: [([Tree a], a, [Tree a])]

Instances

Eq a => Eq (Zipper a) Source #
Instance details Defined in Data.Tree.Util Methods (==) :: Zipper a -> Zipper a -> Bool # (/=) :: Zipper a -> Zipper a -> Bool #
Show a => Show (Zipper a) Source #
Instance details Defined in Data.Tree.Util Methods showsPrec :: Int -> Zipper a -> ShowS # show :: Zipper a -> String # showList :: [Zipper a] -> ShowS #

root :: Tree a -> Zipper a Source #

Create a new zipper focussiong on the root.

up :: Zipper a -> Maybe (Zipper a) Source #

Move the focus to the parent of this node.

firstChild :: Zipper a -> Maybe (Zipper a) Source #

Move the focus to the first child of this node.

>>> firstChild $ root myTree
Just (Zipper {focus = Node {rootLabel = 1, subForest = []}, ancestors = [([],0,[Node {rootLabel = 2, subForest = []},Node {rootLabel = 3, subForest = [Node {rootLabel = 4, subForest = []}]}])]})

nextSibling :: Zipper a -> Maybe (Zipper a) Source #

Move the focus to the next sibling of this node

>>> (firstChild $ root myTree) >>= nextSibling
Just (Zipper {focus = Node {rootLabel = 2, subForest = []}, ancestors = [([Node {rootLabel = 1, subForest = []}],0,[Node {rootLabel = 3, subForest = [Node {rootLabel = 4, subForest = []}]}])]})

prevSibling :: Zipper a -> Maybe (Zipper a) Source #

Move the focus to the next sibling of this node

allChildren :: Zipper a -> [Zipper a] Source #

Given a zipper that focussses on some subtree t, construct a list with zippers that focus on each child.

allTrees :: Zipper a -> [Zipper a] Source #

Given a zipper that focussses on some subtree t, construct a list with zippers that focus on each of the nodes in the subtree of t.

unZipperLocal :: Zipper a -> Tree a Source #

Creates a new tree from the zipper that thas the current node as root. The ancestorTree (if there is any) forms the first child in this new root.

constructTree :: [([Tree a], a, [Tree a])] -> Maybe (Tree a) Source #

Constructs a tree from the list of ancestors (if there are any)

findEvert :: (a -> Bool) -> Tree a -> Maybe (Tree a) Source #

Given a predicate on an element, find a node that matches the predicate, and turn that node into the root of the tree.

running time: \(O(nT)\) where \(n\) is the size of the tree, and \(T\) is the time to evaluate a predicate.

>>> findEvert (== 4) myTree
Just (Node {rootLabel = 4, subForest = [Node {rootLabel = 3, subForest = [Node {rootLabel = 0, subForest = [Node {rootLabel = 1, subForest = []},Node {rootLabel = 2, subForest = []}]}]}]})
>>> findEvert (== 5) myTree
Nothing

findEvert' :: (Tree a -> Bool) -> Tree a -> Maybe (Tree a) Source #

Given a predicate matching on a subtree, find a node that matches the predicate, and turn that node into the root of the tree.

running time: \(O(nT(n))\) where \(n\) is the size of the tree, and \(T(m)\) is the time to evaluate a predicate on a subtree of size \(m\).

findPath Source #

Arguments

:: (a -> Bool)	is this node a starting node
-> (a -> Bool)	is this node an ending node
-> Tree a
-> Maybe [a]

Function to extract a path between a start node and an end node (if such a path exists). If there are multiple paths, no guarantees are given about which one is returned.

running time: \(O(n(T_p+T_s)\), where \(n\) is the size of the tree, and \(T_p\) and \(T_s\) are the times it takes to evaluate the isStartingNode and isEndingNode predicates.

>>> findPath (== 1) (==4) myTree
Just [1,0,3,4]
>>> findPath (== 1) (==2) myTree
Just [1,0,2]
>>> findPath (== 1) (==1) myTree
Just [1]
>>> findPath (== 1) (==2) myTree
Just [1,0,2]
>>> findPath (== 4) (==2) myTree
Just [4,3,0,2]

findNode :: (a -> Bool) -> Tree a -> Maybe [a] Source #

Given a predicate on a, find (the path to) a node that satisfies the predicate.

>>> findNode (== 4) myTree
Just [0,3,4]

findNodes :: (Tree a -> Bool) -> Tree a -> [[a]] Source #

Find all paths to nodes that satisfy the predicate

running time: \(O(nT(n))\) where \(n\) is the size of the tree, and \(T(m)\) is the time to evaluate a predicate on a subtree of size \(m\).

>>> findNodes ((< 4) . rootLabel) myTree
[[0],[0,1],[0,2],[0,3]]
>>> findNodes (even . rootLabel) myTree
[[0],[0,2],[0,3,4]]
>>> let size = length in findNodes ((> 1) . size) myTree
[[0],[0,3]]