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Diffstat (limited to 'dev-haskell/lens/metadata.xml')
| -rw-r--r-- | dev-haskell/lens/metadata.xml | 74 |
1 files changed, 0 insertions, 74 deletions
diff --git a/dev-haskell/lens/metadata.xml b/dev-haskell/lens/metadata.xml index 480622bff29c..b1e5405daf62 100644 --- a/dev-haskell/lens/metadata.xml +++ b/dev-haskell/lens/metadata.xml @@ -5,77 +5,6 @@ <email>haskell@gentoo.org</email> <name>Gentoo Haskell</name> </maintainer> - <longdescription> - 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). - </longdescription> <use> <flag name="benchmark-uniplate"> Enable benchmarking against Neil Mitchell's @@ -89,12 +18,9 @@ or as last ditch effort to address compile errors resulting from the myriad versions of template-haskell that all purport to be 2.8. </flag> - <flag name="old-inline-pragmas">Some 7.6.1-rc1 users report their TH still uses old style inline pragmas. This lets them turn on inlining.</flag> <flag name="safe">Disallow unsafeCoerce</flag> <flag name="dump-splices">Build and run the doctests test-suite.</flag> <flag name="j">Attempt a parallel build with GHC 7.8.</flag> - <flag name="test-doctests">Build and run the doctests test-suite.</flag> - <flag name="test-templates">Build the test templates if we're building tests</flag> <flag name="trustworthy">Assert that we are trustworthy when we can</flag> </use> <upstream> |