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diff --git a/dev-haskell/lens-simple/metadata.xml b/dev-haskell/lens-simple/metadata.xml new file mode 100644 index 000000000000..17f85a4e3a88 --- /dev/null +++ b/dev-haskell/lens-simple/metadata.xml @@ -0,0 +1,73 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd"> +<pkgmetadata> + <maintainer type="project"> + <email>haskell@gentoo.org</email> + <name>Gentoo Haskell</name> + </maintainer> + <longdescription> + This module, <http://hackage.haskell.org/package/lens-simple/docs/Lens-Simple.html Lens.Simple>, + just re-exports the main modules from Russell O\'Connor's + <http://hackage.haskell.org/package/lens-family lens-family> package, the + original van Laarhoven-O'Connor lens library. + @lens-family@ is particularly remarkable for its minute number of dependencies: + (apart from <http://hackage.haskell.org/package/mtl mtl> + they are all ghc \'boot\' libraries); but more importantly for its + extreme conceptual simplicity and theoretical soundness. Much of + the material it contains is well-explained, from a tutorial point of view, by + <http://hackage.haskell.org/package/lens-tutorial lens-tutorial> It is independent, + self-standing and readily intelligible apart from any darker + more general system of combinators that might attempt to extend it. Much + of it ought to be in the Prelude. + + Convenient import of the elementary combinators from @lens-family@, + however, a little complicated. The idea of this trivial module, then, is just to make a sort of + low-powered, minimal-dependency, @lens-family@ equivalent of + the 800 lb gorilla of lens library imports: + + > import Control.Lens + + namely, the light-weight and elegant: + + > import Lens.Simple + + Check it out, it's even one character shorter! + + The material in <http://hackage.haskell.org/package/lens-tutorial lens-tutorial> + will work fine if you make this substitution in the underlying + <http://hackage.haskell.org/package/lens-tutorial-1.0.0/docs/src/Control-Lens-Tutorial.html source> + and follow along as prompted. + + As another illustration of the simplicity of the + fundamental van Laarhoven-O'Connor lens combinators - and their homogeneity with + @Control.Lens@ - note that the gloss + <https://github.com/michaelt/lens-family-simple/blob/master/examples/Pong.hs pong example> + from the @lens@ library examples directory - which continues to be + among the best introductory lens tutorials precisely by saying nothing - + requires only this abbreviating change of imports. + + If you make that program more complicated, + you might of course end up needing + the more sophisticated material in @Control.Lens@ and + its immense mass of dependencies. On the other hand, + you might just need some of the additional material + present in the similarly demystifying + <http://hackage.haskell.org/package/microlens microlens> + or <http://hackage.haskell.org/package/microlens-th microlens-th> and + the associated modules. + + This module was originally intended to simplify the use of packages that + follow the original promise of the van Laarhoven-O'Connor lenses. + /Correct practice is to export lenses without depending on a lens-library, where possible./ + In basic cases these just use familiar @Prelude@ types, after all. + Examples of best practices in this respect are e.g. <http://hackage.haskell.org/package/lens-family-th lens-family-th> which + doesn't depend on @lens-family@ despite its name and pipes-related packages like + <http://hackage.haskell.org/package/pipes-bytestring pipes-bytestring> + and <http://hackage.haskell.org/package/pipes-group pipes-group>. + + @Lens.Simple@ also re-exports @makeLenses@ and + other convenient TH incantations from Dan Burton's associated + <http://hackage.haskell.org/package/lens-family-th lens-family-th>. + + </longdescription> +</pkgmetadata> |