Re: [Haskell-cafe] Making MVar and Chan Instances of Typeable

On Fri, Nov 05, 2004 at 01:57:53PM +0100, Benjamin Franksen wrote:

Hello Experts,

I need MVar and Chan to be instances of Typeable. Any hint on how this is most easily done would be greatly appreciated. I could change the libraries and add 'deriving Typeable' but I hesitate to do so.

Cheers, Ben

It can be done in Haskell 98 the same way `asTypeOf' is defined in the Report: instance Typeable a => Typeable (MVar a) where typeOf v = mkAppTy (mkTyCon "Control.Concurrent.MVar.MVar") [typeOf (t v)] where t :: a b -> b t = undefined Groetjes, Remi -- Nobody can be exactly like me. Even I have trouble doing it.