commit: 4e200d25d801924de0fccbe8e0994d8482e7b291 Author: Sergei Trofimovich <slyfox <AT> gentoo <DOT> org> AuthorDate: Sun Sep 11 09:47:10 2016 +0000 Commit: Sergei Trofimovich <slyfox <AT> gentoo <DOT> org> CommitDate: Sun Sep 11 10:01:31 2016 +0000 URL: https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=4e200d25
dev-haskell/data-accessor: access library to record fields, a depend of dev-haskell/idiii Package-Manager: portage-2.3.0 dev-haskell/data-accessor/Manifest | 1 + .../data-accessor/data-accessor-0.2.2.7.ebuild | 26 ++++++++ dev-haskell/data-accessor/metadata.xml | 70 ++++++++++++++++++++++ 3 files changed, 97 insertions(+) diff --git a/dev-haskell/data-accessor/Manifest b/dev-haskell/data-accessor/Manifest new file mode 100644 index 00000000..b9ef247 --- /dev/null +++ b/dev-haskell/data-accessor/Manifest @@ -0,0 +1 @@ +DIST data-accessor-0.2.2.7.tar.gz 9670 SHA256 3465227ad5f81059a885d354e2f3c108d550287580e6939e18350fa65e78c2ed SHA512 42f78d5be738e83e2bc64a2f38bc70748ecb741433916c4e527355f5e808a844e43b14607cfff149a5951f557c73a947469c878340738244e3778f475ccd021d WHIRLPOOL 5d9cb0eeda4d89b6e5b5e22820431b20faa9736cf539705afdd3bdc9accadec1138ff8acd33d00389755f1b803b79cfd240b13037cafdb27576478084e813ec1 diff --git a/dev-haskell/data-accessor/data-accessor-0.2.2.7.ebuild b/dev-haskell/data-accessor/data-accessor-0.2.2.7.ebuild new file mode 100644 index 00000000..cf00a33 --- /dev/null +++ b/dev-haskell/data-accessor/data-accessor-0.2.2.7.ebuild @@ -0,0 +1,26 @@ +# Copyright 1999-2016 Gentoo Foundation +# Distributed under the terms of the GNU General Public License v2 +# $Id$ + +EAPI=5 + +# ebuild generated by hackport 0.4.6.9999 + +CABAL_FEATURES="lib profile haddock hoogle hscolour" +inherit haskell-cabal + +DESCRIPTION="Utilities for accessing and manipulating fields of records" +HOMEPAGE="http://www.haskell.org/haskellwiki/Record_access"; +SRC_URI="mirror://hackage/packages/archive/${PN}/${PV}/${P}.tar.gz" + +LICENSE="BSD" +SLOT="0/${PV}" +KEYWORDS="~amd64 ~x86" +IUSE="" + +RDEPEND=">=dev-haskell/transformers-0.2:=[profile?] <dev-haskell/transformers-0.6:=[profile?] + >=dev-lang/ghc-7.4.1:= +" +DEPEND="${RDEPEND} + >=dev-haskell/cabal-1.6 +" diff --git a/dev-haskell/data-accessor/metadata.xml b/dev-haskell/data-accessor/metadata.xml new file mode 100644 index 00000000..1962ea1 --- /dev/null +++ b/dev-haskell/data-accessor/metadata.xml @@ -0,0 +1,70 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd";> +<pkgmetadata> + <maintainer type="project"> + <email>[email protected]</email> + <name>Gentoo Haskell</name> + </maintainer> + <longdescription> + In Haskell 98 the name of a record field + is automatically also the name of a function which gets the value + of the according field. + E.g. if we have + + data Pair a b = Pair + first :: a, second :: b + + then + + > first :: Pair a b -> a + > second :: Pair a b -> b + + However for setting or modifying a field value + we need to use some syntactic sugar, which is often clumsy. + + modifyFirst :: (a -> a) -> (Pair a b -> Pair a b) + modifyFirst f r\@(Pair + first=a + ) = r + first = f a + + With this package you can define record field accessors + which allow setting, getting and modifying values easily. + The package clearly demonstrates the power of the functional approach: + You can combine accessors of a record and sub-records, + to make the access look like the fields of the sub-record belong to the main record. + + Example: + + > *Data.Accessor.Example> (first^:second^=10) (('b',7),"hallo") + > (('b',10),"hallo") + + You can easily manipulate record fields in a 'Control.Monad.State.State' monad, + you can easily code 'Show' instances that use the Accessor syntax + and you can parse binary streams into records. + See @Data.Accessor.Example@ for demonstration of all features. + + It would be great if in revised Haskell versions the names of record fields + are automatically 'Data.Accessor.Accessor's + rather than plain @get@ functions. + For now, the package @data-accessor-template@ provides Template Haskell functions + for automated generation of 'Data.Acesssor.Accessor's. + See also the other @data-accessor@ packages + that provide an Accessor interface to other data types. + The package @enumset@ provides accessors to bit-packed records. + + For similar packages see @lenses@ and @fclabel@. + A related concept are editors + <http://conal.net/blog/posts/semantic-editor-combinators/>. + Editors only consist of a modify method + (and @modify@ applied to a 'const' function is a @set@ function). + This way, they can modify all function values of a function at once, + whereas an accessor can only change a single function value, + say, it can change @f 0 = 1@ to @f 0 = 2@. + This way, editors can even change the type of a record or a function. + An Arrow instance can be defined for editors, + but for accessors only a Category instance is possible ('(.)' method). + The reason is the @arr@ method of the @Arrow@ class, + that conflicts with the two-way nature (set and get) of accessors. + </longdescription> +</pkgmetadata>
