lens package:optics-core

Build a lens from a getter and a setter, which must respect the well-formedness laws. If you want to build a Lens from the van Laarhoven representation, use lensVL.

A Lens is a generalised or first-class field. If we have a value s :: S, and a l :: Lens' S A, we can get the "field value" of type A using view l s. We can also update (or put or set) the value using over (or set). For example, given the following definitions:

>>> data Human = Human { _name :: String, _location :: String } deriving Show

>>> let human = Human "Bob" "London"

we can make a Lens for _name field:

>>> let name = lens _name $ \s x -> s { _name = x }

which we can use as a Getter:

>>> view name human
"Bob"

or a Setter:

>>> set name "Robert" human
Human {_name = "Robert", _location = "London"}

Type synonym for a type-modifying lens.

Build a lens from the van Laarhoven representation.

Type synonym for a type-preserving lens.

Type synonym for a type-modifying van Laarhoven lens.

Type synonym for a type-preserving van Laarhoven lens.

Tag for a lens.

Tag for a reversed lens.

An IxLens is an indexed version of a Lens. See the "Indexed optics" section of the overview documentation in the Optics module of the main optics package for more details on indexed optics.

Type synonym for a type-modifying indexed lens.

Type synonym for a type-preserving indexed lens.

Type synonym for a type-modifying van Laarhoven indexed lens.

Type synonym for a type-preserving van Laarhoven indexed lens.

Build an indexed lens from a getter and a setter. If you want to build an IxLens from the van Laarhoven representation, use ilensVL.

Build an indexed lens from the van Laarhoven representation.

Convert an indexed lens to its van Laarhoven representation.

Work with an indexed lens in the van Laarhoven representation.

Convert a lens to the van Laarhoven representation.

Work with a lens as a getter and a setter.

withLens (lens f g) k ≡ k f g

Work with a lens in the van Laarhoven representation.

A ReversedLens is a backwards Lens, i.e. a ReversedLens s t a b is equivalent to a Lens b a t s. These are typically produced by calling re on a Lens. They are distinguished from a Review so that re . re on a Lens returns a Lens.

Type synonym for a type-modifying reversed lens.

Type synonym for a type-preserving reversed lens.