Optics.View

EXPERIMENTAL

Documentation

class ViewableOptic k r where

Generalized view (even more powerful than view from the lens library).

View the value(s) pointed to by an optic.

The type of the result depends on the optic. You get:

• Exactly one result a with Iso, Lens, ReversedPrism and Getter.
• At most one result Maybe a with Prism, AffineTraversal and AffineFold.
• Monoidal summary of all results Monoid a => a with Traversal and Fold.

When in doubt, use specific, flavour restricted versions. This function is mostly useful for things such as passthrough.

Associated Types

type ViewResult k r :: Type

Methods

gview :: MonadReader s m => Optic' k is s r -> m (ViewResult k r)

gviews :: MonadReader s m => Optic' k is s a -> (a -> r) -> m (ViewResult k r)

Instances

ViewableOptic An_Iso r

Defined in Optics.View

Associated Types

type ViewResult An_Iso r :: Type

Methods

gview :: MonadReader s m => Optic' An_Iso is s r -> m (ViewResult An_Iso r)

gviews :: MonadReader s m => Optic' An_Iso is s a -> (a -> r) -> m (ViewResult An_Iso r)

ViewableOptic A_Lens r

Defined in Optics.View

Associated Types

type ViewResult A_Lens r :: Type

Methods

gview :: MonadReader s m => Optic' A_Lens is s r -> m (ViewResult A_Lens r)

gviews :: MonadReader s m => Optic' A_Lens is s a -> (a -> r) -> m (ViewResult A_Lens r)

ViewableOptic A_Prism r

Defined in Optics.View

Associated Types

type ViewResult A_Prism r :: Type

Methods

gview :: MonadReader s m => Optic' A_Prism is s r -> m (ViewResult A_Prism r)

gviews :: MonadReader s m => Optic' A_Prism is s a -> (a -> r) -> m (ViewResult A_Prism r)

ViewableOptic An_AffineTraversal r

Defined in Optics.View

Associated Types

type ViewResult An_AffineTraversal r :: Type

Methods

gview :: MonadReader s m => Optic' An_AffineTraversal is s r -> m (ViewResult An_AffineTraversal r)

gviews :: MonadReader s m => Optic' An_AffineTraversal is s a -> (a -> r) -> m (ViewResult An_AffineTraversal r)

Monoid r => ViewableOptic A_Traversal r

Defined in Optics.View

Associated Types

type ViewResult A_Traversal r :: Type

Methods

gview :: MonadReader s m => Optic' A_Traversal is s r -> m (ViewResult A_Traversal r)

gviews :: MonadReader s m => Optic' A_Traversal is s a -> (a -> r) -> m (ViewResult A_Traversal r)

ViewableOptic A_ReversedPrism r

Defined in Optics.View

Associated Types

type ViewResult A_ReversedPrism r :: Type

Methods

gview :: MonadReader s m => Optic' A_ReversedPrism is s r -> m (ViewResult A_ReversedPrism r)

gviews :: MonadReader s m => Optic' A_ReversedPrism is s a -> (a -> r) -> m (ViewResult A_ReversedPrism r)

ViewableOptic A_Getter r

Defined in Optics.View

Associated Types

type ViewResult A_Getter r :: Type

Methods

gview :: MonadReader s m => Optic' A_Getter is s r -> m (ViewResult A_Getter r)

gviews :: MonadReader s m => Optic' A_Getter is s a -> (a -> r) -> m (ViewResult A_Getter r)

ViewableOptic An_AffineFold r

Defined in Optics.View

Associated Types

type ViewResult An_AffineFold r :: Type

Methods

gview :: MonadReader s m => Optic' An_AffineFold is s r -> m (ViewResult An_AffineFold r)

gviews :: MonadReader s m => Optic' An_AffineFold is s a -> (a -> r) -> m (ViewResult An_AffineFold r)

Monoid r => ViewableOptic A_Fold r

Defined in Optics.View

Associated Types

type ViewResult A_Fold r :: Type

Methods

gview :: MonadReader s m => Optic' A_Fold is s r -> m (ViewResult A_Fold r)

gviews :: MonadReader s m => Optic' A_Fold is s a -> (a -> r) -> m (ViewResult A_Fold r)

guse :: (ViewableOptic k a, MonadState s m) => Optic' k is s a -> m (ViewResult k a)

Use the target of a Lens, Iso, or Getter in the current state, or use a summary of a Fold or Traversal that points to a monoidal value.

>>> evalState (guse _1) ('a','b')
'a'

>>> evalState (guse _2) ("hello","world")
"world"

Since: 0.2

guses :: (ViewableOptic k r, MonadState s m) => Optic' k is s a -> (a -> r) -> m (ViewResult k r)

Use the target of a Lens, Iso or Getter in the current state, or use a summary of a Fold or Traversal that points to a monoidal value.

>>> evalState (guses _1 length) ("hello","world")
5

Since: 0.2

glistening :: (ViewableOptic k r, MonadWriter s m) => Optic' k is s r -> m a -> m (a, ViewResult k r)

This is a generalized form of listen that only extracts the portion of the log that is focused on by a Getter. If given a Fold or a Traversal then a monoidal summary of the parts of the log that are visited will be returned.

Since: 0.2

glistenings :: (ViewableOptic k r, MonadWriter s m) => Optic' k is s a -> (a -> r) -> m b -> m (b, ViewResult k r)

This is a generalized form of listen that only extracts the portion of the log that is focused on by a Getter. If given a Fold or a Traversal then a monoidal summary of the parts of the log that are visited will be returned.

Since: 0.2