Copyright	(c) 2008--2009 Universiteit Utrecht
License	BSD3
Maintainer	generics@haskell.org
Stability	experimental
Portability	non-portable
Safe Haskell	Safe-Inferred
Language	Haskell98

Generics.MultiRec.Zipper

Contents

Locations and context stacks
Context frames
Contexts and locations are functors
Generic navigation functions
Internal functions

Description

The generic zipper.

Synopsis

Locations and context stacks

data Loc :: (* -> *) -> (* -> *) -> * -> * where Source

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 :: (Fam phi, Zipper phi (PF phi)) => phi ix -> r ix -> Ctxs phi ix r a -> Loc phi r a

Instances

HFunctor phi (Loc phi)

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

Constructors

Empty :: Ctxs phi a r a
Push :: phi a -> Ctx (PF phi) a r ix -> Ctxs phi b r a -> Ctxs phi b r ix

Instances

Zipper phi (PF phi) => HFunctor phi (Ctxs phi b)
ShowPath (PF phi) => Show (Path phi t i)

Context frames

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

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) where CId :: Ctx (I xi) xi r ix
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) where CTag :: Ctx f b r ix -> Ctx ((:>:) f ix) b r ix
data Ctx ((:.:) [] g) = CCL [g r ix] (Ctx g b r ix) [g r ix]
data Ctx ((:.:) Maybe g) = CCM (Ctx g b r ix)
data Ctx (C c f) = CC (Ctx f b r ix)

Contexts and locations are functors

Generic navigation functions

class HFunctor phi f => Zipper phi f where Source

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) Source

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

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

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 Source

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 g => Zipper phi ((:.:) Maybe g)
Zipper phi g => Zipper phi ((:.:) [] g)
(Zipper phi f, Zipper phi g) => Zipper phi ((:*:) f g)
(Zipper phi f, Zipper phi g) => Zipper phi ((:+:) f g)

Internal functions

impossible :: a -> b Source