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