"Scrap your boilerplate" --- Generic programming in Haskell See
http://www.cs.uu.nl/wiki/GenericProgramming/SYB. The present
module contains thirteen
Data instances which are considered
dubious (either because the types are abstract or just not meant to be
traversed). Instances in this module might change or disappear in
future releases of this package.
(This module does not export anything. It really just defines
instances.)