Hi Tom and Yhc, I remember that you previously mentioned that you had implemented Yhc.Typeable or something similar which provides an interface which is a superset of Data.Typeable. Is that reliable? Does it really provide a superset of the implementation? It appears that quite a few of the patches required to get Yhc compiling the base libraries are to remove Data.Typeable. These patches could be reduced if Data.Typeable could be implemented in a Yhc specific way. Thanks Neil