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Name: ghc-lens | Distribution: SUSE Linux Enterprise 15 SP3 |
Version: 4.19.2 | Vendor: openSUSE |
Release: bp153.1.23 | Build date: Fri Apr 23 09:39:41 2021 |
Group: Unspecified | Build host: build72 |
Size: 5618188 | Source RPM: ghc-lens-4.19.2-bp153.1.23.src.rpm |
Packager: https://bugs.opensuse.org | |
Url: https://hackage.haskell.org/package/lens | |
Summary: Lenses, Folds and Traversals |
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 <https://github.com/ekmett/lens#lens-lenses-folds-and-traversals README>. An introductory video on the style of code used in this library by Simon Peyton Jones is available from <http://skillsmatter.com/podcast/scala/lenses-compositional-data-access-and-manipulation Skills Matter>. A video on how to use lenses and how they are constructed is available on <http://youtu.be/cefnmjtAolY?hd=1 youtube>. Slides for that second talk can be obtained from <http://comonad.com/haskell/Lenses-Folds-and-Traversals-NYC.pdf comonad.com>. More information on the care and feeding of lenses, including a brief tutorial and motivation for their types can be found on the <https://github.com/ekmett/lens/wiki lens wiki>. A small game of 'pong' and other more complex examples that manage their state using lenses can be found in the <https://github.com/ekmett/lens/blob/master/examples/ example folder>. /Lenses, Folds and Traversals/ With some signatures simplified, the core of the hierarchy of lens-like constructions looks like: <<http://i.imgur.com/ALlbPRa.png>> <images/Hierarchy.png (Local Copy)> 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).
BSD-2-Clause
* Wed May 06 2020 psimons@suse.com - Update lens to version 4.19.2. 4.19.2 [2020.04.15] - ------------------ * Remove the test suite's dependency on `test-framework-th`. * Thu Feb 27 2020 psimons@suse.com - Update lens to version 4.19.1. 4.19.1 [2020.02.13] - ------------------ * Fix a bug introduced in 4.19 where using `_TupE` to `preview` a value would always fail. * Fri Feb 07 2020 psimons@suse.com - Update lens to version 4.19. 4.19 [2020.02.03] - ---------------- * Support building with GHC 8.10. * The types of `_TupE` and `_UnboxedTupE` are now `Prism' Exp [Maybe Exp]` when built against `template-haskell-2.16` or later to reflect the new types of `TupE` and `UnboxedTupE`. * Add `_ForallVisT` and `_BytesPrimL` prisms when building against `template-haskell-2.16` or later. * Make `<>~` and `<>=` and their `<op` and `<<op` state variants require only `Semigroup`, not `Monoid`. * Add `{Functor,Foldable,Traversable}WithIndex` instances for `Control.Applicative.Const` and `Data.Functor.Constant.Constant`. * Fri Nov 08 2019 Peter Simons <psimons@suse.com> - Drop obsolete group attributes. * Sat Sep 14 2019 psimons@suse.com - Update lens to version 4.18.1. 4.18.1 [2019.09.13] - ------------------ * Remove the use of `cpp-options: -traditional`. This should be unnecessary on all versions of GHC that `lens` supports, as modern GHCs already use `-traditional` internally during preprocessing. More critically, the use of `cpp-options: -traditional` breaks profiling builds on GHC 8.8 (see https://gitlab.haskell.org/ghc/ghc/issues/17185). * Sat Sep 07 2019 psimons@suse.com - Update lens to version 4.18. Upstream has edited the change log file since the last release in a non-trivial way, i.e. they did more than just add a new entry at the top. You can review the file at: http://hackage.haskell.org/package/lens-4.18/src/CHANGELOG.markdown * Thu Aug 08 2019 Peter Simons <psimons@suse.com> - Update Cabal file to allow building with call-stack 0.2.x. * Tue Jun 11 2019 Peter Simons <psimons@suse.com> - Update Cabal file for more accurate build dependencies. * Tue Apr 30 2019 psimons@suse.com - Update lens to version 4.17.1. 4.17.1 [2019.04.26] - ------------------ * Support `th-abstraction-0.3.0.0` or later. * Only incur `semigroups` and `void` dependencies on old GHCs. * Add `holes1Of`. * Add `locally` (https://github.com/ekmett/lens/pull/829). * Add `ilocally` (https://github.com/ekmett/lens/pull/836). * Add a third `Prism` law. * Add `gplate1`. * Add `Wrapped`/`Rewrapped` instances for `Data.Monoid.Ap`. * Thu Aug 02 2018 psimons@suse.com - Add lens at version 4.17.
/usr/lib64/ghc-8.10.4/lens-4.19.2 /usr/lib64/ghc-8.10.4/lens-4.19.2/libHSlens-4.19.2-9raIaARkFNb729SEObA4SR-ghc8.10.4.so /usr/share/licenses/ghc-lens /usr/share/licenses/ghc-lens/LICENSE
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Fabrice Bellet, Tue Jul 9 14:00:23 2024