Modulelens-family-core-2.1.3Haskell2010

Lens.Family.Clone

This module is provided for "Haskell 2022" compatibility. If you are able to use Rank2Types, I advise you to instead use the rank 2 aliases

Adapter, Adapter'
Prism, Prism'
Lens, Lens'
Traversal, Traversal'
Setter, Setter'
Grate, Grate'
Resetter, Resetter'
Grid, Grid'
Fold, Fold'
Getter, Getter'
Reviewer, Reviewer'

from the lens-family package instead.

cloneLens allows one to circumvent the need for rank 2 types by allowing one to take a universal monomorphic lens instance and rederive a polymorphic instance. When you require a lens family parameter you use the type ALens s t a b (or ALens' s a). Then, inside a where clause, you use cloneLens to create a Lens type.

For example.

example :: ALens s t a b -> Example
example l = ... x^.cl ... cl .~ y ...
 where
  cl x = cloneLens l x

Note: It is important to eta-expand the definition of cl to avoid the dreaded monomorphism restriction.

cloneAdapter, cloneGrate, cloneTraversal, cloneSetter, cloneResetter, cloneGetter, and cloneFold provides similar functionality for adapters, grates, traversals, setters, resetters, getters, and folds respectively. Unfortunately, it is not yet known how to clone prisms and grids.

Note: Cloning is only need if you use a functional reference multiple times with different instances.

21 types
2 classes
8 values

Packagelens-family-core-2.1.3
Exports31
LanguageHaskell2010
LicenceBSD-3-Clause
SourceClone.hs

valuecloneAdapter

:: (Functor f, Functor g)
=> AnAdapter s t a b
-> AdapterLike f g s t a b

Converts a universal adapter instance back into a polymorphic adapter.

valuecloneLens :: Functor f => ALens s t a b -> LensLike f s t a b

Converts a universal lens instance back into a polymorphic lens.

valuecloneGrate :: Functor g => AGrate s t a b -> GrateLike g s t a b

Converts a universal grate instance back into a polymorphic grater.

valuecloneTraversal :: Applicative f => ATraversal s t a b -> LensLike f s t a b

Converts a universal traversal instance back into a polymorphic traversal.

valuecloneSetter :: Identical f => ASetter s t a b -> LensLike f s t a b

Converts a universal setter instance back into a polymorphic setter.

valuecloneResetter :: Identical f => AResetter s t a b -> GrateLike f s t a b

Converts a universal resetter instance back into a polymorphic resetter.

valuecloneGetter :: Phantom f => AGetter s t a b -> LensLike f s t a b

Converts a universal getter instance back into a polymorphic getter.

valuecloneFold

:: (Phantom f, Applicative f)
=> AFold s t a b
-> LensLike f s t a b

Converts a universal fold instance back into a polymorphic fold.

Types

12 declarations

typetype AnAdapter s t a b = AdapterLike (PStore (s -> a) b) ((->) s) s t a b

AnAdapter s t a b is a universal Adapter s t a b instance

typetype AnAdapter' s a = AdapterLike' (PStore (s -> a) a) ((->) s) s a

AnAdapter' s a is a universal Adapter' s a instance

typetype ALens s t a b = LensLike (PStore a b) s t a b

ALens s t a b is a universal Lens s t a b instance

typetype ALens' s a = LensLike' (PStore a a) s a

ALens' s a is a universal Lens' s a instance

typetype ATraversal s t a b = LensLike (PKleeneStore a b) s t a b

ATraversal s t a b is a universal Traversal s t a b instance

typetype ATraversal' s a = LensLike' (PKleeneStore a a) s a

ATraversal' a b is a universal Traversal' a b instance

typetype AGetter s t a b = FoldLike a s t a b

AGetter s t a b is a universal Getter s t a b instance

typetype AGetter' s a = FoldLike' a s a

AGetter' s a is a universal Getter' s a instance

typetype AFold s t a b = FoldLike [a] s t a b

AFold s t a b is a universal Fold s t a b instance

typetype AFold' s a = FoldLike' [a] s a

AFold' s a is a universal Fold' s a instance

datadata PStore i j a

Instances1Functor

Functor (PStore i j)Defined in lens-family-core-2.1.3 · Lens.Family.Clone

datadata PKleeneStore i j a

Instances2Functor, Applicative

Functor (PKleeneStore i j)Defined in lens-family-core-2.1.3 · Lens.Family.Clone
Applicative (PKleeneStore i j)Defined in lens-family-core-2.1.3 · Lens.Family.Clone

Re-exports

11 declarations

typetype LensLike (f :: Type -> Type) s t a b = (a -> f b) -> s -> f t

typetype LensLike' (f :: Type -> Type) s a = (a -> f a) -> s -> f s

typetype GrateLike (g :: Type -> Type) s t a b = (g a -> b) -> g s -> t

typetype GrateLike' (g :: Type -> Type) s a = (g a -> a) -> g s -> s

typetype FoldLike r s t a b = LensLike (Constant r) s t a b

typetype FoldLike' r s a = LensLike' (Constant r) s a

typetype AGrate s t a b = GrateLike (PCont b a) s t a b

typetype ASetter s t a b = LensLike Identity s t a b

typetype AResetter s t a b = GrateLike Identity s t a b

classclass Functor f => Phantom (f :: Type -> Type) where

Instances8Phantom, …

Phantom (Const a)Defined in lens-family-core-2.1.3 · Lens.Family.Phantom
Phantom (Constant a)Defined in lens-family-core-2.1.3 · Lens.Family.Phantom
Phantom f => Phantom (AlongsideLeft f a)Defined in lens-family-core-2.1.3 · Lens.Family.Stock
Phantom f => Phantom (AlongsideRight f a)Defined in lens-family-core-2.1.3 · Lens.Family.Stock
Phantom f => Phantom (Backwards f)Defined in lens-family-core-2.1.3 · Lens.Family.Phantom
Phantom g => Phantom (FromG e g)Defined in lens-family-core-2.1.3 · Lens.Family.Stock
Phantom g => Phantom (FromF i j g)Defined in lens-family-core-2.1.3 · Lens.Family.Stock
(Phantom f, Functor g) => Phantom (Compose f g)Defined in lens-family-core-2.1.3 · Lens.Family.Phantom

classclass (Traversable f, Applicative f) => Identical (f :: Type -> Type) where

Instances3Identical

Identical IdentityDefined in lens-family-core-2.1.3 · Lens.Family.Identical
Identical f => Identical (Backwards f)Defined in lens-family-core-2.1.3 · Lens.Family.Identical
(Identical f, Identical g) => Identical (Compose f g)Defined in lens-family-core-2.1.3 · Lens.Family.Identical