@unpublished{Gibbons&Paterson2008:Parametric,
  abstract = "Datatype-generic programs are programs that are parametrized by a datatype or type functor: whereas polymorphic programs abstract from the "integers" in "lists of integers", datatype-generic programs abstract from the "lists of". There are two main styles of datatype-generic programming: the Algebra of Programming approach, characterized by structured recursion operators arising from initial algebras and final coalgebras, and the Generic Haskell approach, characterized by case analysis over the structure of a datatype. We show that the former enjoys a kind of higher-order naturality, relating the behaviours of generic functions at different types; in contrast, the latter is more ad hoc, with no coherence required or provided between the various clauses of a definition. Moreover, the naturality properties arise "for free", simply from the parametrized types of the generic functions: we present a higher-order parametricity theorem for datatype-generic operators.",
  author = "Jeremy Gibbons and Ross Paterson",
  note = "Submitted for publication",
  title = "Parametric Datatype-Genericity",
  url = "http://www.comlab.ox.ac.uk/jeremy.gibbons/publications/parametric.pdf",
  year = "2008",
}