name: lens version: 4.17 id: lens-4.17-5R1nkIDzovdC6jcuCd3LNE key: lens-4.17-5R1nkIDzovdC6jcuCd3LNE license: BSD-2-Clause copyright: Copyright (C) 2012-2016 Edward A. Kmett maintainer: Edward A. Kmett author: Edward A. Kmett stability: provisional homepage: http://github.com/ekmett/lens/ synopsis: Lenses, Folds and Traversals description: This package comes \"Batteries Included\" with many useful lenses for the types commonly used from the Haskell Platform, and with tools for automatically generating lenses and isomorphisms for user-supplied data types. . The combinators in @Control.Lens@ provide a highly generic toolbox for composing families of getters, folds, isomorphisms, traversals, setters and lenses and their indexed variants. . An overview, with a large number of examples can be found in the . . An introductory video on the style of code used in this library by Simon Peyton Jones is available from . . A video on how to use lenses and how they are constructed is available on . . Slides for that second talk can be obtained from . . More information on the care and feeding of lenses, including a brief tutorial and motivation for their types can be found on the . . A small game of @pong@ and other more complex examples that manage their state using lenses can be found in the . . /Lenses, Folds and Traversals/ . With some signatures simplified, the core of the hierarchy of lens-like constructions looks like: . . <> . . You can compose any two elements of the hierarchy above using @(.)@ from the @Prelude@, and you can use any element of the hierarchy as any type it linked to above it. . The result is their lowest upper bound in the hierarchy (or an error if that bound doesn't exist). . For instance: . * You can use any 'Traversal' as a 'Fold' or as a 'Setter'. . * The composition of a 'Traversal' and a 'Getter' yields a 'Fold'. . /Minimizing Dependencies/ . If you want to provide lenses and traversals for your own types in your own libraries, then you can do so without incurring a dependency on this (or any other) lens package at all. . /e.g./ for a data type: . > data Foo a = Foo Int Int a . You can define lenses such as . > -- bar :: Lens' (Foo a) Int > bar :: Functor f => (Int -> f Int) -> Foo a -> f (Foo a) > bar f (Foo a b c) = fmap (\a' -> Foo a' b c) (f a) . > -- quux :: Lens (Foo a) (Foo b) a b > quux :: Functor f => (a -> f b) -> Foo a -> f (Foo b) > quux f (Foo a b c) = fmap (Foo a b) (f c) . without the need to use any type that isn't already defined in the @Prelude@. . And you can define a traversal of multiple fields with 'Control.Applicative.Applicative': . > -- traverseBarAndBaz :: Traversal' (Foo a) Int > traverseBarAndBaz :: Applicative f => (Int -> f Int) -> Foo a -> f (Foo a) > traverseBarAndBaz f (Foo a b c) = Foo <$> f a <*> f b <*> pure c . What is provided in this library is a number of stock lenses and traversals for common haskell types, a wide array of combinators for working them, and more exotic functionality, (/e.g./ getters, setters, indexed folds, isomorphisms). category: Data, Lenses, Generics abi: ad2acce2286b1f67303b54df750eba27 exposed: True exposed-modules: Control.Exception.Lens Control.Lens Control.Lens.At Control.Lens.Combinators Control.Lens.Cons Control.Lens.Each Control.Lens.Empty Control.Lens.Equality Control.Lens.Extras Control.Lens.Fold Control.Lens.Getter Control.Lens.Indexed Control.Lens.Internal Control.Lens.Internal.Bazaar Control.Lens.Internal.ByteString Control.Lens.Internal.CTypes Control.Lens.Internal.Coerce Control.Lens.Internal.Context Control.Lens.Internal.Deque Control.Lens.Internal.Exception Control.Lens.Internal.FieldTH Control.Lens.Internal.Fold Control.Lens.Internal.Getter Control.Lens.Internal.Indexed Control.Lens.Internal.Instances Control.Lens.Internal.Iso Control.Lens.Internal.Level Control.Lens.Internal.List Control.Lens.Internal.Magma Control.Lens.Internal.Prism Control.Lens.Internal.PrismTH Control.Lens.Internal.Review Control.Lens.Internal.Setter Control.Lens.Internal.TH Control.Lens.Internal.Zoom Control.Lens.Iso Control.Lens.Lens Control.Lens.Level Control.Lens.Operators Control.Lens.Plated Control.Lens.Prism Control.Lens.Reified Control.Lens.Review Control.Lens.Setter Control.Lens.TH Control.Lens.Traversal Control.Lens.Tuple Control.Lens.Type Control.Lens.Unsound Control.Lens.Wrapped Control.Lens.Zoom Control.Monad.Error.Lens Control.Parallel.Strategies.Lens Control.Seq.Lens Data.Array.Lens Data.Bits.Lens Data.ByteString.Lazy.Lens Data.ByteString.Lens Data.ByteString.Strict.Lens Data.Complex.Lens Data.Data.Lens Data.Dynamic.Lens Data.HashSet.Lens Data.IntSet.Lens Data.List.Lens Data.Map.Lens Data.Sequence.Lens Data.Set.Lens Data.Text.Lazy.Lens Data.Text.Lens Data.Text.Strict.Lens Data.Tree.Lens Data.Typeable.Lens Data.Vector.Generic.Lens Data.Vector.Lens GHC.Generics.Lens Language.Haskell.TH.Lens Numeric.Lens Numeric.Natural.Lens System.Exit.Lens System.FilePath.Lens System.IO.Error.Lens hidden-modules: Paths_lens import-dirs: /var/lib/jenkins/workspace/JHCR/.cabal-sandbox/lib/x86_64-linux-ghc-8.6.3/lens-4.17-5R1nkIDzovdC6jcuCd3LNE library-dirs: /var/lib/jenkins/workspace/JHCR/.cabal-sandbox/lib/x86_64-linux-ghc-8.6.3/lens-4.17-5R1nkIDzovdC6jcuCd3LNE dynamic-library-dirs: /var/lib/jenkins/workspace/JHCR/.cabal-sandbox/lib/x86_64-linux-ghc-8.6.3 data-dir: /var/lib/jenkins/workspace/JHCR/.cabal-sandbox/share/x86_64-linux-ghc-8.6.3/lens-4.17 hs-libraries: HSlens-4.17-5R1nkIDzovdC6jcuCd3LNE depends: array-0.5.3.0 base-4.12.0.0 base-orphans-0.8.1-HeyTAcy4PKhDcGhjvJwDzq bifunctors-5.5.3-7j0mgi7D0yS2oNiXe9r7ql bytestring-0.10.8.2 call-stack-0.1.0-J1eWgTNOnM4IGVyeW0v2YZ comonad-5.0.4-2EQIiLfvxxtIIllz8gbEQo containers-0.6.0.1 contravariant-1.5-4tjvhiNPMk29NhGPKE1GIF distributive-0.6-8EpfN2RsUZm8inygL04Eq7 exceptions-0.10.1-DdWfqA1lutT4wybeL2xRnx filepath-1.4.2.1 free-5.1-DoPMLe6y3QF1n3oFXCkA0Z ghc-prim-0.5.3 hashable-1.2.7.0-2SI038axTEd7AEZJ275kpi kan-extensions-5.2-AzwJTlWu0B6WzRYHmeQOO mtl-2.2.2 parallel-3.2.2.0-EGl5SOk48TWHAD161C93aQ profunctors-5.3-HontJ8S7sNw4ZYeZaPLNNK reflection-2.1.4-D3IaixAKGmk6dzEKDGsgtn semigroupoids-5.3.2-7SYmTspzpbUFHQFapWvcfu semigroups-0.18.5-8pPnWqWrcWhEagTFf5Pnk2 tagged-0.8.6-FABECvKnqYbBCttH1EeJvB template-haskell-2.14.0.0 text-1.2.3.1 th-abstraction-0.2.11.0-DAhuCgi08HTBWsDjm9nrOq transformers-0.5.5.0 transformers-compat-0.6.4-K8aXsnheDmiIf9wwPX2j5s unordered-containers-0.2.10.0-LgoTL3wbBEY5bZIDJiyxW4 vector-0.12.0.2-H1Eu1OCXL0L9y980iV8EwU void-0.7.2-1ijpCmwDTXMGDRdU43YY14 haddock-interfaces: /var/lib/jenkins/workspace/JHCR/.cabal-sandbox/share/doc/x86_64-linux-ghc-8.6.3/lens-4.17/html/lens.haddock haddock-html: /var/lib/jenkins/workspace/JHCR/.cabal-sandbox/share/doc/x86_64-linux-ghc-8.6.3/lens-4.17/html