It could, yes. Actually, using DefaultSignatures you can probably use SYB for defining classes with generic default methods, by adding Data and Typeable constraints instead of Generic.
Cheers, Pedro 2012/3/12 Yves Parès <yves.pa...@gmail.com> > Thanks for the clarification. > But could not class Data have been used for generic Deriving of classes? I > imagine it would have been harder, but I fail to see if would have been > possible... > > Le 12 mars 2012 16:58, José Pedro Magalhães <j...@cs.uu.nl> a écrit : > > Hi Yves, >> >> GHC.Generics [1] and SYB [2] are two rather different approaches to >> generic programming. There are things that can be done in one but not in >> the other, and there are things that are easier on one rather than the >> other. For instance, SYB tends to be very useful for large AST >> transformations, with functions that have a general behaviour but a couple >> of particular cases for a few constructors. GHC.Generics, on the other >> hand, can encode functions such as generic fmap and traverse. It lends >> itself better to optimisation since it doesn't use runtime casts, and as >> such tends to be faster than SYB. It isn't planned to replace SYB. >> >> >> Cheers, >> Pedro >> >> [1] http://www.haskell.org/haskellwiki/Generics >> [2] http://www.cs.uu.nl/wiki/bin/view/GenericProgramming/SYB >> >> >> On Mon, Mar 12, 2012 at 16:35, Yves Parès <yves.pa...@gmail.com> wrote: >> >>> I'd have a question concerning GHC.Generics: how does it relate to SYB's >>> Data.Generics? >>> Is it intended to replace it or complete it? >>> In other words: does class Data.Generics.Data class do things that class >>> GHC.Generics.Generic can't do? >>> >>> >>> Le 12 mars 2012 04:27, Reiner Pope <reiner.p...@gmail.com> a écrit : >>> >>>> Hi all, >>>> >>>> I've been playing with GHC's new generics features (see >>>> http://www.haskell.org/ghc/docs/latest/html/users_guide/generic-programming.html). >>>> All the documentation I've seen suggests creating a "helper class" -- for >>>> instance, the GSerialize class in the above link -- on which one defines >>>> generic instances. >>>> >>>> It seems to me that this isn't necessary. For example, here's the the >>>> example from the GHC docs, but without a helper class: >>>> >>>> > -- set the phantom type of Rep to (), to avoid ambiguity >>>> > from0 :: Generic a => a -> Rep a () >>>> > from0 = from >>>> > >>>> > data Bit = O | I >>>> > >>>> > class Serialize a where >>>> > put :: a -> [Bit] >>>> > >>>> > default put :: (Generic a, Serialize (Rep a ())) => a -> [Bit] >>>> > put = put . from0 >>>> > >>>> > instance Serialize (U1 x) where >>>> > put U1 = [] >>>> > >>>> > instance (Serialize (a x), Serialize (b x)) => Serialize ((a :*: b) >>>> x) where >>>> > put (x :*: y) = put x ++ put y >>>> > >>>> > instance (Serialize (a x), Serialize (b x)) => Serialize ((a :+: b) >>>> x) where >>>> > put (L1 x) = O : put x >>>> > put (R1 x) = I : put x >>>> > >>>> > instance (Serialize (a x)) => Serialize (M1 i c a x) where >>>> > put (M1 x) = put x >>>> > >>>> > instance (Serialize a) => Serialize (K1 i a x) where >>>> > put (K1 x) = put x >>>> >>>> Is there a reason to prefer using helper classes? Or perhaps we should >>>> update the wiki page (http://www.haskell.org/haskellwiki/Generics) to >>>> avoid using helper classes? >>>> >>>> Regards, >>>> Reiner >>>> >>>> _______________________________________________ >>>> Haskell-Cafe mailing list >>>> Haskell-Cafe@haskell.org >>>> http://www.haskell.org/mailman/listinfo/haskell-cafe >>>> >>>> >>> >>> _______________________________________________ >>> Haskell-Cafe mailing list >>> Haskell-Cafe@haskell.org >>> http://www.haskell.org/mailman/listinfo/haskell-cafe >>> >>> >> >
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