These questions are exactly what Control.Lens answers. On 04/09/2013 12:50 PM, "Mario Blažević" <blama...@acanac.net> wrote:
> On 09/02/13 06:53, Nicolas Trangez wrote: > >> # Redirected to haskell-cafe >> >> On Sun, 2013-09-01 at 14:58 +0400, Artyom Kazak wrote: >> >>> Would this be an appropriate place to propose adding mapM_ (and then >>> possibly mapM) to bytestring library? >>> >>> Was it suggested before? If yes, why was it rejected? >>> >> >> This got me wondering: there are several type-classes useful for >> polymorphic container types, e.g. Functor, Foldable & Traversable which >> all apply to some type of kind (* -> *). >> >> Are there related things for monomorphic containers, like ByteString, >> Text or some newtype'd Vector with fixed element type, e.g. >> >> class MFunctor f a where >> mfmap :: (a -> a) -> f -> f >> >> instance MFunctor ByteString Word8 where >> mfmap = ByteString.map >> > > > I'm not aware of this particular class, but I have considered it. > In the end I've chosen to generalize the class to FactorialMonoid instead: > > class Monoid m => FactorialMonoid m where > ... > foldMap :: Monoid n => (m → n) → m → n > > ByteString and Text are instances of the class, and so are lists, > maps, and other containers, and Sum and Product as well. > > > http://hackage.haskell.org/**packages/archive/monoid-** > subclasses/0.3.2/doc/html/**Data-Monoid-Factorial.html<http://hackage.haskell.org/packages/archive/monoid-subclasses/0.3.2/doc/html/Data-Monoid-Factorial.html> > > > > >> or (maybe even better) >> >> class MFunctor f where >> type Elem >> mfmap :: (Elem -> Elem) -> f -> f >> >> instance MFunctor ByteString where >> type Elem = Word8 >> mfmap = ByteString.map >> >> and similar for other classes. >> >> Nicolas >> >> >> ______________________________**_________________ >> Haskell-Cafe mailing list >> Haskell-Cafe@haskell.org >> http://www.haskell.org/**mailman/listinfo/haskell-cafe<http://www.haskell.org/mailman/listinfo/haskell-cafe> >> >> > > ______________________________**_________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/**mailman/listinfo/haskell-cafe<http://www.haskell.org/mailman/listinfo/haskell-cafe> >
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