[Haskell-cafe] Typeable and Dynamic

Hi, Given a TypeRep and a Dynamic value with type corresponding to the TypeRep, I'd like to be able to use fromDyn *without* specifying a type (given as an additional 'default' argument) (since it is somewhat known from the TypeRep). That is, I'd like an undefinedOf that can be used in extract :: Typeable a => TypeRep -> Dynamic -> a extract typerep dyn = fromDyn (undefinedOf typerep) dyn For instance, if TypeRep is Int, extract Int dyn = fromDyn (undefined::Int) dyn Is it possible to write "extract" ? Thanks, Thu