Hey that's a great idea! On Tue, Oct 29, 2013 at 7:18 PM, Tom Ellis < tom-lists-haskell-cafe-2013@jaguarpaw.co.uk> wrote:
On Tue, Oct 29, 2013 at 04:31:49AM +0000, AntC wrote:
Lyndon Maydwell
writes: I was wondering if it's possible to have automatic deriving for some classes for the Void type. ...
Hi Lyndon, I'm struggling to see any use case for that.
You'd 'achieve' `show (undefined :: Nada)` crashing your program at run- time; rather than failing to compile (if you didn't have the instance).
Just bite the bullet and give your Void type a constructor.
It was considered a worthwhile enough idea to add a Show instance to the "void" package
http://hackage.haskell.org/package/void-0.6.1/docs/Data-Void.html
(where the instance was written by hand, of course, not derived).
Lyndon: perhaps
import Data.Void
newtype Nada = Nada Void deriving (Show)
will suit you use case.
Tom _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe