Language.GroteTrap.Trees

A class for tree types and representations of selections on tree types, as well as functions for converting between text and tree selections.

Paths and navigation

type Path = [Int]

A path in a tree. Each integer denotes the selection of a child; these indices are 0-relative.

root :: Path

root is the empty path.

type Nav = Path -> Path

Navigation transforms one path to another.

up :: Nav

Move up to parent node. Moving up from root has no effect.

into :: Int -> Nav

Move down into the nth child node.

down :: Nav

Move down into first child node.

left :: Nav

Move left one sibling.

right :: Nav

Move right one sibling.

sibling :: Int -> Nav

Move n siblings (n can be negative).

Tree types

class Tree p where

Tree types.

Methods

children :: p -> [p]

Yields this tree's subtrees.

Instances

Tree ParseTree

followM :: (Monad m, Tree t) => t -> Path -> m t

Follows a path in a tree, returning the result in a monad.

follow :: Tree t => t -> Path -> t

Follows a path in a tree.

depth :: Tree t => t -> Int

Yields the depth of the tree.

selectDepth :: Tree t => Int -> t -> [t]

Yields all ancestors at the specified depth.

flatten :: Tree t => t -> [t]

Breadth-first, pre-order traversal.

Tree selections

class Tree t => Selectable t where

Selectable trees.

Methods

allowSubranges :: t -> Bool

Tells whether complete subranges of children may be selected in this tree. If not, valid TreeSelections in this tree always have a second element 0.

Instances

Selectable ParseTree

type TreeSelection = (Path, Int)

Selection in a tree. The path indicates the left side of the selection; the int tells how many siblings to the right are included in the selection.

select :: (Monad m, Tree t) => t -> TreeSelection -> m [t]

Selects part of a tree.

allSelections :: Selectable a => a -> [TreeSelection]

Enumerates all possible selections of a tree.

selectionToRange :: (Tree a, KnowsPosition a) => a -> TreeSelection -> Range

Computes the range of a valid selection.

rangeToSelection :: (Tree a, KnowsPosition a, Monad m) => a -> Range -> m TreeSelection

Converts a specified range to a corresponding selection and returns it in a monad.

posToPath :: (Tree a, KnowsPosition a) => a -> Pos -> Path

Returns the path to the deepest descendant whose range contains the specified position.

isValidRange :: (KnowsPosition a, Selectable a) => a -> Range -> Bool

Tells whether the text selection corresponds to a tree selection.

Suggesting and fixing

suggest :: (Selectable a, KnowsPosition a) => a -> Range -> [TreeSelection]

Yields all possible selections, ordered by distance to the specified range, closest first.

repair :: (KnowsPosition a, Selectable a) => a -> Range -> Range

Takes suggest's first suggestion and yields its range.