Generics.Regular.Zipper

Locations

data Loc :: * -> * where

Abstract type of locations. A location contains the current focus and its context. A location is parameterized over the family of datatypes and over the type of the complete value.

Constructors

Loc :: (Regular a, Zipper (PF a)) => a -> [Ctx (PF a) a] -> Loc a

Context frames

data family Ctx f :: * -> *

Abstract type of context frames. Not required for the high-level navigation functions.

Instances

Zipper f => Functor (Ctx f)

data Ctx I = CId

data Ctx U

data Ctx (K a)

data Ctx ((:+:) f g)

• = CL (Ctx f r)
• | CR (Ctx g r)

data Ctx ((:*:) f g)

• = C1 (Ctx f r) (g r)
• | C2 (f r) (Ctx g r)

data Ctx (C c f) = CC (Ctx f r)

data Ctx (S s f) = CS (Ctx f r)

Generic zipper class

class Functor f => Zipper f where

It is in general not necessary to use the generic navigation functions directly. The functions listed in the ``Interface'' section below are more user-friendly.

Methods

cmap :: (a -> b) -> Ctx f a -> Ctx f b

fill :: Ctx f a -> a -> f a

first, last :: f a -> Maybe (a, Ctx f a)

next, prev :: Ctx f a -> a -> Maybe (a, Ctx f a)

Instances

Zipper I

Zipper U

Zipper (K a)

(Zipper f, Zipper g) => Zipper ((:+:) f g)

(Zipper f, Zipper g) => Zipper ((:*:) f g)

Zipper f => Zipper (C c f)

Zipper f => Zipper (S s f)

Interface

enter :: (Regular a, Zipper (PF a)) => a -> Loc a

Start navigating a datastructure. Returns a location that focuses the entire value and has an empty context.

down :: Loc a -> Maybe (Loc a)

Move down to the leftmost child. Returns Nothing if the current focus is a leaf.

down' :: Loc a -> Maybe (Loc a)

Move down to the rightmost child. Returns Nothing if the current focus is a leaf.

up :: Loc a -> Maybe (Loc a)

Move up to the parent. Returns Nothing if the current focus is the root.

right :: Loc a -> Maybe (Loc a)

Move to the right sibling. Returns Nothing if the current focus is the rightmost sibling.

left :: Loc a -> Maybe (Loc a)

Move to the left sibling. Returns Nothing if the current focus is the leftmost sibling.

leave :: Loc a -> a

Return the entire value, independent of the current focus.

on :: Loc a -> a

Operate on the current focus. This function can be used to extract the current point of focus.

update :: (a -> a) -> Loc a -> Loc a

Update the current focus without changing its type.

updateM :: Monad m => (a -> m a) -> Loc a -> m (Loc a)

Update the current focus without changing its type.