Data.Lens.Zoom

zoom :: forall a s r m. Optic' (Star (Focusing m r)) s a -> StateT a m r -> StateT s m r

Zooms into a substate in a StateT transformer.

type Traversal' s a = Traversal s s a a

type Traversal s t a b = forall p. Wander p => Optic p s t a b

The specialized type Traversal s a means that the type s contains zero, one, or many values of type a. They're especially useful when working with collections like arrays, maps, and any other member of the Traversable type class. They are also a more general form of lenses and prisms. Traversals which focus on at most one element (like lenses, prisms, and their composition) are called affine traversals.

newtype Tagged :: forall k. k -> Type -> Typenewtype Tagged a b

Constructors

• Tagged b

Instances

• Newtype (Tagged a b) _
• (Eq b) => Eq (Tagged a b)
• Eq1 (Tagged a)
• (Ord b) => Ord (Tagged a b)
• Ord1 (Tagged a)
• Functor (Tagged a)
• Profunctor Tagged
• Choice Tagged
• Costrong Tagged
• Closed Tagged
• Foldable (Tagged a)
• Traversable (Tagged a)

data Stall a b s t

The Stall profunctor characterizes an AffineTraversal.

Constructors

• Stall (s -> b -> t) (s -> Either t a)

Instances

• Functor (Stall a b s)
• Profunctor (Stall a b)
• Strong (Stall a b)
• Choice (Stall a b)

data Shop a b s t

The Shop profunctor characterizes a Lens.

Constructors

• Shop (s -> a) (s -> b -> t)

Instances

• Profunctor (Shop a b)
• Strong (Shop a b)

type Setter' s a = Setter s s a a

type Setter s t a b = Optic Function s t a b

type Review' s a = Review s s a a

type Review s t a b = Optic Tagged s t a b

newtype Re :: (Type -> Type -> Type) -> Type -> Type -> Type -> Type -> Typenewtype Re p s t a b

Constructors

• Re (p b a -> p t s)

Instances

• Newtype (Re p s t a b) _
• (Profunctor p) => Profunctor (Re p s t)
• (Choice p) => Cochoice (Re p s t)
• (Cochoice p) => Choice (Re p s t)
• (Strong p) => Costrong (Re p s t)
• (Costrong p) => Strong (Re p s t)

type Prism' s a = Prism s s a a

type Prism s t a b = forall p. Choice p => Optic p s t a b

Prisms are used for sum types like Maybe and Either. The specialized type Prism' s a means that the type s might contain a value of type a.

type Optic' :: (Type -> Type -> Type) -> Type -> Type -> Typetype Optic' p s a = Optic p s s a a

type Optic :: (Type -> Type -> Type) -> Type -> Type -> Type -> Type -> Typetype Optic p s t a b = p a b -> p s t

A general-purpose Data.Lens.

data Market a b s t

The Market profunctor characterizes a Prism.

Constructors

• Market (b -> t) (s -> Either t a)

Instances

• Functor (Market a b s)
• Profunctor (Market a b)
• Choice (Market a b)

type Lens' s a = Lens s s a a

Lens' is a specialization of Lens. An optic of type Lens' can change only the value of its focus, not its type. As an example, consider the Lens _2, which has this type:

_2 :: forall s t a b. Lens (Tuple s a) (Tuple t b) a b

_2 can produce a Tuple Int String from a Tuple Int Int:

set _2 "NEW" (Tuple 1 2) == (Tuple 1 "NEW")

If we specialize _2's type with Lens', the following will not type check:

set (_2 :: Lens' (Tuple Int Int) Int) "NEW" (Tuple 1 2)
           ^^^^^^^^^^^^^^^^^^^^^^^^^

See Data.Lens.Getter and Data.Lens.Setter for functions and operators frequently used with lenses.

type Lens s t a b = forall p. Strong p => Optic p s t a b

Given a type whose "focus element" always exists, a lens provides a convenient way to view, set, and transform that element.

For example, _2 is a tuple-specific Lens available from Data.Lens, so:

over _2 String.length $ Tuple "ignore" "four" == Tuple "ignore" 4

Note the result has a different type than the original tuple. That is, the four Lens type variables have been narrowed to:

• s is Tuple String String
• t is Tuple String Int
• a is String
• b is Int

See Data.Lens.Getter and Data.Lens.Setter for functions and operators frequently used with lenses.

type Iso' s a = Iso s s a a

type Iso s t a b = forall p. Profunctor p => Optic p s t a b

A generalized isomorphism. Isos are the most constrained optic, simply enabling you to transform back and forth between two types without losing information. The specialized type Iso' s a means that s and a are isomorphic – the two types represent the same information. They’re especially useful when you need to unwrap a newtype or transform an array to a list or otherwise convert between types. This optic is also useful for backward compatibility without boilerplate.

type IndexedTraversal' i s a = IndexedTraversal i s s a a

type IndexedTraversal i s t a b = forall p. Wander p => IndexedOptic p i s t a b

type IndexedSetter' i s a = IndexedSetter i s s a a

type IndexedSetter i s t a b = IndexedOptic Function i s t a b

type IndexedOptic' :: (Type -> Type -> Type) -> Type -> Type -> Type -> Typetype IndexedOptic' p i s a = IndexedOptic p i s s a a

type IndexedOptic :: (Type -> Type -> Type) -> Type -> Type -> Type -> Type -> Type -> Typetype IndexedOptic p i s t a b = Indexed p i a b -> p s t

type IndexedLens' i s a = IndexedLens i s s a a

type IndexedLens i s t a b = forall p. Strong p => IndexedOptic p i s t a b

An indexed lens.

type IndexedGetter' i s a = IndexedGetter i s s a a

type IndexedGetter i s t a b = IndexedFold a i s t a b

type IndexedFold' r i s a = IndexedFold r i s s a a

type IndexedFold r i s t a b = IndexedOptic (Forget r) i s t a b

newtype Indexed :: (Type -> Type -> Type) -> Type -> Type -> Type -> Typenewtype Indexed p i s t

Profunctor used for IndexedOptics.

Constructors

• Indexed (p (Tuple i s) t)

Instances

• Newtype (Indexed p i s t) _
• (Profunctor p) => Profunctor (Indexed p i)
• (Strong p) => Strong (Indexed p i)
• (Choice p) => Choice (Indexed p i)
• (Wander p) => Wander (Indexed p i)

newtype Grating a b s t

Instances

• Newtype (Grating a b s t) _
• Profunctor (Grating a b)
• Closed (Grating a b)

type Grate' s a = Grate s s a a

type Grate s t a b = forall p. Closed p => Optic p s t a b

A grate (http://r6research.livejournal.com/28050.html)

type Getter' s a = Getter s s a a

type Getter s t a b = forall r. Fold r s t a b

newtype Forget :: forall k. Type -> Type -> k -> Typenewtype Forget r a b

Profunctor that forgets the b value and returns (and accumulates) a value of type r.

Forget r is isomorphic to Star (Const r), but can be given a Cochoice instance.

Constructors

• Forget (a -> r)

Instances

• Newtype (Forget r a b) _
• (Semigroup r) => Semigroup (Forget r a b)
• (Monoid r) => Monoid (Forget r a b)
• Profunctor (Forget r)
• (Monoid r) => Choice (Forget r)
• Strong (Forget r)
• Cochoice (Forget r)
• (Monoid r) => Wander (Forget r)

type Fold' r s a = Fold r s s a a

type Fold r s t a b = Optic (Forget r) s t a b

data Exchange a b s t

The Exchange profunctor characterizes an Iso.

Constructors

• Exchange (s -> a) (b -> t)

Instances

• Functor (Exchange a b s)
• Profunctor (Exchange a b)

type AnIso' s a = AnIso s s a a

type AnIso s t a b = Optic (Exchange a b) s t a b

An isomorphism defined in terms of Exchange, which can be used to avoid issues with impredicativity.

type AnIndexedLens' i s a = AnIndexedLens i s s a a

type AnIndexedLens i s t a b = IndexedOptic (Shop (Tuple i a) b) i s t a b

An indexed lens defined in terms of Shop, which can be used to avoid issues with impredicativity.

type AnAffineTraversal' s a = AnAffineTraversal s s a a

type AnAffineTraversal s t a b = Optic (Stall a b) s t a b

An affine traversal defined in terms of Stall, which can be used to avoid issues with impredicativity.

type AffineTraversal' s a = AffineTraversal s s a a

type AffineTraversal s t a b = forall p. Strong p => Choice p => Optic p s t a b

An affine traversal (has at most one focus, but is not a prism).

type ATraversal' s a = ATraversal s s a a

type ATraversal s t a b = Optic (Bazaar Function a b) s t a b

A traversal defined in terms of Bazaar, which can be used to avoid issues with impredicativity.

type APrism' s a = APrism s s a a

type APrism s t a b = Optic (Market a b) s t a b

A prism defined in terms of Market to be safe from impredicativity issues in the type checker. See the docs/ folder for a more detailed explanation.

type ALens' s a = ALens s s a a

type ALens s t a b = Optic (Shop a b) s t a b

A lens defined in terms of Shop, which can be used to avoid issues with impredicativity.

type AGrate' s a = AGrate s s a a

type AGrate s t a b = Optic (Grating a b) s t a b

A grate defined in terms of Grating, which can be used to avoid issues with impredicativity.

type AGetter' s a = AGetter s s a a

type AGetter s t a b = Fold a s t a b

class Wander :: (Type -> Type -> Type) -> Constraintclass (Strong p, Choice p) <= Wander p  where

Class for profunctors that support polymorphic traversals.

Members

• wander :: forall s t a b. (forall f. Applicative f => (a -> f b) -> s -> f t) -> p a b -> p s t

Instances

• Wander Function
• (Applicative f) => Wander (Star f)