Hi, sometimes I want to use Generic derivation, but don’t want expose the Generic instance outside the module. The reason, is that for some types I want to export only smart constructors / modifier lenses; yet the structure is probably simple enough to benefit from `Generic`.
If it will be possible to restrict export of the Generic instance, then I don’t see problem of auto-deriving it for everything possible though. - Oleg > On 04 Feb 2016, at 14:28, Wolfgang Jeltsch <g9ks1...@acme.softbase.org> wrote: > > > Am Donnerstag, den 04.02.2016, 14:19 +0200 schrieb Wolfgang Jeltsch: >> Hi, >> >> if you do generic programming these days, you can use DeriveAnyClass to >> write code like the following (where Serializable is a class with a >> generic default implementation): >> >>> data Tree a = Leaf | Branch (Tree a) a (Tree a) >>> deriving (Generic, Serializable) >> >> It would be great, if you could just write the following instead: >> >>> data Tree a = Leaf | Branch (Tree a) a (Tree a) deriving Serializable >> >> This would correspond exactly to what you do when using standard Haskell >> deriving. It could be made possible by letting the compiler instantiate >> the Generic class automatically every time an algebraic data type is >> declared. A potential downside of this would be that programmers would >> not be able to define non-standard instances of Generics, but I actually >> cannot see that this is very useful anyhow. > > I want to add that this would probably allow us to implement all the > other deriving mechanisms (for standard classes, for Functor, etc.) > entirely in libraries, using generic programming, without forcing users > to change their code by adding deriving of Generic. Maybe a future > standard Haskell would not even have deriving rules hardwired into the > language anymore (which always felt somehow wrong to me). Wouldn’t this > be great? ;-) > > All the best, > Wolfgang > > > _______________________________________________ > ghc-devs mailing list > ghc-devs@haskell.org <mailto:ghc-devs@haskell.org> > http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs > <http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs>
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