lens-family-core

Haskell 98 Lens Families

Version on this page:	1.2.3
LTS Haskell 24.28:	2.1.3
Stackage Nightly 2026-01-14:	2.1.3
Latest on Hackage:	2.1.3

See all snapshots lens-family-core appears in

BSD-3-Clause licensed by Russell O'Connor

Maintained by Russell O'Connor

This version can be pinned in stack with:lens-family-core-1.2.3@sha256:447c296620a861b5a9bb4d3caf0ebe37933a3eb901eb8bf553da8eac82ea19e4,2008

Module documentation for 1.2.3

Lens
- Lens.Family
  - Lens.Family.Clone
  - Lens.Family.State
    - Lens.Family.State.Lazy
    - Lens.Family.State.Strict
  - Lens.Family.Stock
  - Lens.Family.Unchecked

Depends on 3 packages(full list with versions):

base, containers, transformers

Used by 3 packages in nightly-2019-06-03(full list with versions):

dhall, lens-family, lens-simple

This package provides first class(†) functional references. In addition to the usual operations of getting, setting and composition, plus integration with the state monad, lens families provide some unique features:

Polymorphic updating
Traversals
Cast projection functions to read-only lenses
Cast "toList" functions to read-only traversals
Cast semantic editor combinators to modify-only traversals.

(†) For optimal first-class support use the lens-family package with rank 2 / rank N polymorphism. Lens.Family.Clone allows for first-class support of lenses and traversals for those who require Haskell 98.