Optics.Re · optics-core-0.4.1.1

Optics.Re

Some optics can be reversed with re. This is mainly useful to invert Isos:

Example2 expressions

>>> let _Identity = iso runIdentity Identity>>> view (_1 % re _Identity) ('x', "yz")Identity 'x'

Yet we can use a Lens as a Review too:

Example1 expression

>>> review (re _1) ('x', "yz")'x'

In the following diagram, red arrows illustrate how re transforms optics. The ReversedLens and ReversedPrism optic kinds are backwards versions of Lens and Prism respectively, and are present so that re . re does not change the optic kind.

Reversed Optics

1 class

classclass ReversibleOptic (k :: OpticKind) where

Class for optics that can be reversed.

Associated types

type family ReversedOptic (k :: OpticKind)

Injective type family that maps an optic kind to the optic kind produced by reversing it.

ReversedOptic An_Iso            = An_Iso
ReversedOptic A_Prism           = A_ReversedPrism
ReversedOptic A_ReversedPrism   = A_Prism
ReversedOptic A_Lens            = A_ReversedLens
ReversedOptic A_ReversedLens    = A_Lens
ReversedOptic A_Getter          = A_Review
ReversedOptic A_Review          = A_Getter

Methods

re :: AcceptsEmptyIndices "re" is => Optic k is s t a b -> Optic (ReversedOptic k) is b a t s
Reverses optics, turning around Iso into Iso, Prism into ReversedPrism (and back), Lens into ReversedLens (and back) and Getter into Review (and back).

Instances7ReversibleOptic, …

ReversibleOptic A_GetterDefined in optics-core-0.4.1.1 · Optics.Re
ReversibleOptic A_LensDefined in optics-core-0.4.1.1 · Optics.Re
ReversibleOptic A_PrismDefined in optics-core-0.4.1.1 · Optics.Re
ReversibleOptic A_ReversedLensDefined in optics-core-0.4.1.1 · Optics.Re
ReversibleOptic A_ReversedPrismDefined in optics-core-0.4.1.1 · Optics.Re
ReversibleOptic A_ReviewDefined in optics-core-0.4.1.1 · Optics.Re
ReversibleOptic An_IsoDefined in optics-core-0.4.1.1 · Optics.Re