Summary
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 @README@: <https://github.com/ekmett/lens#lens-lenses-folds-and-traversals> A video on how to use lenses and how they are constructed is available from youtube: <http://youtu.be/cefnmjtAolY?hd=1> Slides can be obtained here: <http://comonad.com/haskell/Lenses-Folds-and-Traversals-NYC.pdf> More information on the care and feeding of lenses, including a brief tutorial and motivation for their types can be found on the lens wiki: <https://github.com/ekmett/lens/wiki> A small game of @pong@ and other more complex examples that manage their state using lenses can be found in the example folder: <https://github.com/ekmett/lens/blob/master/examples/> /Lenses, Folds and Traversals/ The core of the hierarchy of lens-like constructions looks like: <<http://i.imgur.com/4fHw3Fd.png>> Local copy (<Hierarchy.png>) 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) > -- baz :: 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).
Versions
v4.19.1 :: 0/4.19.1 :: gentoo
- Modified
- License
- BSD-2
- Keywords
- ~amd64 ~x86
- USE flags
- benchmark-uniplate doc dump-splices hscolour inlining j old-inline-pragmas profile safe test test-doctests test-templates trustworthy
USE flags
General
- benchmark-uniplate
- Enable benchmarking against Neil Mitchell's uniplate library for comparative performance analysis. Defaults to being turned off to avoid the extra dependency.
- doc
- Add extra documentation (API, Javadoc, etc). It is recommended to enable per package instead of globally
- dump-splices
- Build and run the doctests test-suite.
- hscolour
- Include coloured haskell sources to generated documentation (dev-haskell/hscolour)
- inlining
- Generate inline pragmas when using template-haskell. This defaults to enabled, but you can to shut it off to benchmark the relative performance impact, or as last ditch effort to address compile errors resulting from the myriad versions of template-haskell that all purport to be 2.8.
- j
- Attempt a parallel build with GHC 7.8.
- old-inline-pragmas
- Some 7.6.1-rc1 users report their TH still uses old style inline pragmas. This lets them turn on inlining.
- profile
- Add support for software performance analysis (will likely vary from ebuild to ebuild)
- safe
- Disallow unsafeCoerce
- test
- Enable dependencies and/or preparations necessary to run tests (usually controlled by FEATURES=test but can be toggled independently)
- test-doctests
- Build and run the doctests test-suite.
- test-templates
- Build the test templates if we're building tests
- trustworthy
- Assert that we are trustworthy when we can
Dependencies
dev-haskell / base-orphans : Backwards-compatible orphan instances for base
dev-haskell / bifunctors : Haskell98 bifunctors package
dev-haskell / cabal : A framework for packaging Haskell software
dev-haskell / cabal-doctest : A Setup.hs helper for doctests running
dev-haskell / call-stack : Use GHC call-stacks in a backward compatible way
dev-haskell / comonad : Haskell 98 compatible comonads
dev-haskell / contravariant : Contravariant functors
dev-haskell / distributive : Distributive functors -- Dual to Traversable
dev-haskell / doctest : Test interactive Haskell examples
dev-haskell / exceptions : Extensible optionally-pure exceptions
dev-haskell / free : Monads for free
dev-haskell / generic-deriving : Generic programming library for generalised deriving
dev-haskell / haddock : A documentation-generation tool for Haskell libraries
dev-haskell / hashable : A class for types that can be converted to a hash value
dev-haskell / hscolour : Colourise Haskell code
dev-haskell / hunit : A unit testing framework for Haskell
dev-haskell / kan-extensions : Kan extensions, lifts, forms of the Yoneda lemma, and (co)density (co)monads
dev-haskell / mtl : Monad classes, using functional dependencies
dev-haskell / nats : Natural numbers
dev-haskell / parallel : Parallel programming library
dev-haskell / profunctors : Haskell98 profunctors package
dev-haskell / quickcheck : Automatic testing of Haskell programs
dev-haskell / reflection : Reifies arbitrary terms into types that can be reflected back into terms
dev-haskell / semigroupoids : Semigroupoids: Category sans id
dev-haskell / semigroups : Anything that associates
dev-haskell / simple-reflect : Simple reflection of expressions containing variables
dev-haskell / tagged : Haskell 98 phantom types to avoid unsafely passing dummy arguments
dev-haskell / test-framework : Framework for running and organising tests, with HUnit and QuickCheck support
dev-haskell / test-framework-hunit : HUnit support for the test-framework package
dev-haskell / test-framework-quickcheck2 : QuickCheck2 support for the test-framework package
dev-haskell / test-framework-th : Automagically generate the HUnit and Quickcheck code using Template Haskell
dev-haskell / text : An efficient packed Unicode text type
dev-haskell / th-abstraction : Nicer interface for reified information about data types
dev-haskell / transformers-compat : A small compatibility shim for dev-haskell/transformers
dev-haskell / unordered-containers : Efficient hashing-based container types
dev-haskell / vector : Efficient Arrays
dev-haskell / void : A Haskell 98 logically uninhabited data type
Runtime Dependencies
dev-haskell / base-orphans : Backwards-compatible orphan instances for base
dev-haskell / bifunctors : Haskell98 bifunctors package
dev-haskell / call-stack : Use GHC call-stacks in a backward compatible way
dev-haskell / comonad : Haskell 98 compatible comonads
dev-haskell / contravariant : Contravariant functors
dev-haskell / distributive : Distributive functors -- Dual to Traversable
dev-haskell / exceptions : Extensible optionally-pure exceptions
dev-haskell / free : Monads for free
dev-haskell / generic-deriving : Generic programming library for generalised deriving
dev-haskell / hashable : A class for types that can be converted to a hash value
dev-haskell / kan-extensions : Kan extensions, lifts, forms of the Yoneda lemma, and (co)density (co)monads
dev-haskell / mtl : Monad classes, using functional dependencies
dev-haskell / nats : Natural numbers
dev-haskell / parallel : Parallel programming library
dev-haskell / profunctors : Haskell98 profunctors package
dev-haskell / reflection : Reifies arbitrary terms into types that can be reflected back into terms
dev-haskell / semigroupoids : Semigroupoids: Category sans id
dev-haskell / semigroups : Anything that associates
dev-haskell / tagged : Haskell 98 phantom types to avoid unsafely passing dummy arguments
dev-haskell / text : An efficient packed Unicode text type
dev-haskell / th-abstraction : Nicer interface for reified information about data types
dev-haskell / transformers-compat : A small compatibility shim for dev-haskell/transformers
dev-haskell / unordered-containers : Efficient hashing-based container types
dev-haskell / vector : Efficient Arrays
dev-haskell / void : A Haskell 98 logically uninhabited data type
Depending packages
app-forensics / quickfuzz : An experimental grammar fuzzer in Haskell using QuickCheck
dev-haskell / dav : RFC 4918 WebDAV support
dev-haskell / dbus : A client library for the D-Bus IPC system
dev-haskell / lens-aeson : Law-abiding lenses for aeson
dev-haskell / linear : Linear Algebra
dev-haskell / mustache : A mustache template parser library
dev-haskell / thyme : A faster time library
dev-haskell / trifecta : A modern parser combinator library with convenient diagnostics
dev-haskell / wreq : An easy-to-use HTTP client library
Bugs
- 657408
- dev-haskell/lens-4.14 : src/.../FieldTH.hs:619:28: error:
Change logs
- Repository mirror & CI · gentoo
Merge updates from master - Sergei Trofimovich · gentoo
dev-haskell/lens: drop old
Package-Manager: Portage-3.0.4, Repoman-3.0.1 Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org> - Repository mirror & CI · gentoo
Merge updates from master - Jack Todaro · gentoo
dev-haskell/lens: bump up to 4.19.1
Package-Manager: Portage-3.0.1, Repoman-2.3.23 Signed-off-by: Jack Todaro <solpeth@posteo.org> Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org> - Repository mirror & CI · gentoo
Merge updates from master - Sergei Trofimovich · gentoo
*/*: destabilize dev-lang/ghc for all arches
dev-lang/ghc is a fast-moving target without much of stable API across major GHC releases. This makes stabilization process a fragile process. The change moves all haskell revdeps to pure ~arch. There are not many outside dev-haskell/*: - app-emulation/ganeti - app-text/pandoc - dev-util/bustle - dev-util/shellcheck - dev-vcs/darcs - x11-wm/xmonad/xmonad Existing stable haskell users are recommended to keyword used packages and all of dev-haskell/* to ease upgrades. Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org> - Repository mirror & CI · gentoo
Merge updates from master - Michał Górny · gentoo
*/*: [QA] Fix trivial cases of MissingTestRestrict
The result was achieved via the following pipeline: pkgcheck scan -c RestrictTestCheck -R FormatReporter \ --format '{category}/{package}/{package}-{version}.ebuild' | xargs -n32 grep -L RESTRICT | xargs -n32 sed -i -e '/^IUSE=.*test/aRESTRICT="!test? ( test )"' The resulting metadata was compared before and after the change. Few Go ebuilds had to be fixed manually due to implicit RESTRICT=strip added by the eclass. Two ebuilds have to be fixed because of multiline IUSE. Suggested-by: Robin H. Johnson <robbat2@gentoo.org> Closes: https://github.com/gentoo/gentoo/pull/13942 Signed-off-by: Michał Górny <mgorny@gentoo.org> - Repository mirror & CI · gentoo
Merge updates from master - Michał Górny · gentoo
*/*: Inline mirror://hackage and update URIs
This change inlines mirror://hackage in all ebuilds, and updates URIs to the modern form (old URIs redirect to that). The change has been made using the following command: find -name '*.ebuild' -exec sed -r -i \ -e 's@mirror://hackage/@https://hackage.haskell.org/@g' \ -e 's@https://hackage.haskell.org/packages/archive/([^/]*)/([^/]*)/@https://hackage.haskell.org/package/\1-\2/@g' \ -e '/hackage\.haskell\.org/s@\$\{PN}-\$\{PV}@${P}@g' \ -e '/hackage\.haskell\.org/s@\$\{MY_PN}-\$\{PV}@${MY_P}@g' \ -e '/hackage\.haskell\.org/s@\$\{PN}-\$\{MY_PV}@${MY_P}@g' \ {} + Signed-off-by: Michał Górny <mgorny@gentoo.org> - Sergei Trofimovich · gentoo
dev-haskell/lens: stable 4.14 for x86/amd64, bug #631138
Package-Manager: Portage-2.3.10, Repoman-2.3.3 RepoMan-Options: --include-arches="amd64 x86" - Robin H. Johnson · gentoo
Drop $Id$ per council decision in bug #611234.
Signed-off-by: Robin H. Johnson <robbat2@gentoo.org> - Sergei Trofimovich · gentoo
dev-haskell/lens: bump up to 4.14
Package-Manager: Portage-2.3.3, Repoman-2.3.1 - Sergei Trofimovich · gentoo
dev-haskell/lens: amd64/x86 stable, bug #563090
Package-Manager: portage-2.2.28 - Sergei Trofimovich · gentoo
dev-haskell/lens: stable for x86, amd64
Package-Manager: portage-2.2.27 - Justin Lecher · gentoo
Use https by default
Signed-off-by: Justin Lecher <jlec@gentoo.org> - Robin H. Johnson · gentoo
proj/gentoo: Initial commit
This commit represents a new era for Gentoo: Storing the gentoo-x86 tree in Git, as converted from CVS. This commit is the start of the NEW history. Any historical data is intended to be grafted onto this point. Creation process: 1. Take final CVS checkout snapshot 2. Remove ALL ChangeLog* files 3. Transform all Manifests to thin 4. Remove empty Manifests 5. Convert all stale $Header$/$Id$ CVS keywords to non-expanded Git $Id$ 5.1. Do not touch files with -kb/-ko keyword flags. Signed-off-by: Robin H. Johnson <robbat2@gentoo.org> X-Thanks: Alec Warner <antarus@gentoo.org> - did the GSoC 2006 migration tests X-Thanks: Robin H. Johnson <robbat2@gentoo.org> - infra guy, herding this project X-Thanks: Nguyen Thai Ngoc Duy <pclouds@gentoo.org> - Former Gentoo developer, wrote Git features for the migration X-Thanks: Brian Harring <ferringb@gentoo.org> - wrote much python to improve cvs2svn X-Thanks: Rich Freeman <rich0@gentoo.org> - validation scripts X-Thanks: Patrick Lauer <patrick@gentoo.org> - Gentoo dev, running new 2014 work in migration X-Thanks: Michał Górny <mgorny@gentoo.org> - scripts, QA, nagging X-Thanks: All of other Gentoo developers - many ideas and lots of paint on the bikeshed