Just to clarify, I really liked the SYB solution to my previous issue with stripping token locations. It looked like this: strip :: (Data a) => a -> a strip = everywhere (mkT f) where f (TokenPos a _) = a f x = x In the general AST transformation case, my constructor name is the same and so is the number of arguments. So, yes, it's a different type but it's a derivative of Data and Typeable just like the original type. Conceptually, I want to "lookup" the new type from a given module, using the same constructor name as the original type. Then I want to apply morph to every argument of the source constructor and give the resulting values to the new constructor. Lastly, I would like to write pattern matches for special cases (see TokenPos above) and write out the transformation by hand. My ASTs are quite large and there aren't that many special cases. Thanks, Joel On Apr 19, 2007, at 5:11 PM, Joel Reymont wrote:
instance Morpher Type C.Type where ... morph (TyList ty) = liftM C.TyList (morph ty) morph (TyArray ty) = liftM C.TyArray (morph ty) morph (TySeries ty) = liftM C.TySeries (morph ty) morph (TyInput ty) = liftM C.TyProp (morph ty) morph (TyRef ty) = liftM C.TyRef (morph ty) morph TyUnit = return C.TyUnit morph TyPrintDest = return C.TyPrintDest