Annotations.MultiRec.Zipper

The generic 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 :: phi ix -> r ix -> Ctxs phi f ix r a -> Loc phi f r a

Instances

Zipper phi f => HFunctor phi (Loc phi f)

Context frames

data family Ctx f :: * -> (* -> *) -> * -> *

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

Instances

Zipper phi f => HFunctor phi (Ctx f b)

data Ctx U

data Ctx (I xi) = CId ((:=:) b xi)

data Ctx (K a)

data Ctx ((:+:) f g)

• = CL (Ctx f b r ix)
• | CR (Ctx g b r ix)

data Ctx ((:*:) f g)

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

data Ctx ((:>:) f xi) = CTag ((:=:) ix xi) (Ctx f b r ix)

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

data Ctxs :: (* -> *) -> ((* -> *) -> * -> *) -> * -> (* -> *) -> * -> * where

Constructors

Empty :: Ctxs phi f a r a

Push :: phi ix -> Ctx f b r ix -> Ctxs phi f ix r a -> Ctxs phi f b r a

Instances

Zipper phi f => HFunctor phi (Ctxs phi f b)

Generic zipper class

class HFunctor phi f => Zipper phi 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

cmapA :: Applicative a => (forall ix. phi ix -> r ix -> a (r' ix)) -> phi ix -> Ctx f b r ix -> a (Ctx f b r' ix)

fill :: phi b -> Ctx f b r ix -> r b -> f r ix

first, last :: (forall b. phi b -> r b -> Ctx f b r ix -> a) -> f r ix -> Maybe a

next, prev :: (forall b. phi b -> r b -> Ctx f b r ix -> a) -> phi b -> Ctx f b r ix -> r b -> Maybe a

Instances

Zipper phi U

Zipper phi (K a)

El phi xi => Zipper phi (I xi)

(Constructor c, Zipper phi f) => Zipper phi (C c f)

Zipper phi f => Zipper phi ((:>:) f xi)

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

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

Interface

enter :: Zipper phi f => phi ix -> r ix -> Loc phi f r ix

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

on :: (forall xi. phi xi -> r xi -> a) -> Loc phi f r ix -> a

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

update :: (forall xi. phi xi -> r xi -> r xi) -> Loc phi f r ix -> Loc phi f r ix

Update the current focus without changing its type.