instance Typeable

Christian Maeder
Tue, 22 Jul 2003 17:51:16 +0200

Simon Peyton-Jones wrote:
> GHC 6.0 supports deriving( Typeable ), but for some strange reason it's
> not in the manual.  It will be.

Yes, I tried it before and gave up after a message:

     Can't make a derived instance of `Typeable BasicSpec'
     (`Typeable' is not a derivable class)
     When deriving instances for type `BasicSpec'

But with "-fglasgow-exts" it works! (and Data.Dynamic needs to be imported.)