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The optics family of Haskell packages make it possible to define and use Lenses, Traversals, Prisms and other optics, using an abstract interface. They are roughly comparable in functionality with the lens package, but explore a different part of the design space. For a detailed introduction, see the Haddocks for the main Optics module.

Authors and contributors

The authors of the optics family of packages are:

  • Adam Gundry
  • Andres Löh
  • Andrzej Rybczak
  • Oleg Grenrus

Our thanks go to those who have (involuntarily) contributed code and ideas to optics. In particular, we have liberally reused parts of the lens package by Edward Kmett and contributors.

Package structure

Officially supported packages

  • optics is a "batteries-included" package with many dependencies. It incorporates:

    • optics-core: core definitions with a minimal dependency footprint.

    • optics-extra: extra definitions and instances that extend optics-core, incurring dependencies on various boot library packages.

    • optics-th: machinery to construct optics using TemplateHaskell.

    • indexed-profunctors: internal definitions of indexed profunctor representation.

  • optics-vl: utilities for compatibility with van Laarhoven isomorphisms and prisms, as defined in the lens library. This package is not included in optics as it imposes a dependency on profunctors. Note that optics-core already supports conversion for van Laarhoven lenses and various other optics.

  • template-haskell-optics: optics for working with types in the template-haskell package (see optics-th for using TemplateHaskell to construct optics).

Work in progress packages

These packages have not (yet) been officially released. If you find them useful, we would welcome offers to maintain these packages.

  • optics-sop: generic construction of optics using the generics-sop package, and optics for generics-sop types.

Internal packages

These packages are for internal use only, and are not intended to be released:

  • metametapost: generates diagrams used in the documentation, and an example of using optics.

  • optics-codegen: code generator for the Is class and Join type family used internally by optics.