> I was wondering about this:
> -- My goal with this instance was to make it work just enough to do what
> -- I want when used with the HStringTemplate library.
> instance Data UUID where
> toConstr uu = mkConstr uuidType (show uu)  (error "fixity")
> gunfold _ _ = error "gunfold"
> dataTypeOf _ = uuidType
> Is there any reason not to just say "deriving Data" in the type declaration?
I didn't want my 'Data' instance to leak the details of the
constructor. Also I don't know much about how 'Data' works.
I think a similar conversation is going on about the Data declarations
in the 'containers' library.