Greg Meredith
Thanks for the references! Have two-level types been applied to parser generation?
Hrm, I'm not sure what kind of application you have in mind, so I suppose the answer is that I'm not aware of any application. (: I suppose that the parser for the type-level fixpoint of a type constructor is the term-level fixpoint of a parser constructor. Unfortunately "data Fix f = Fix (f (Fix f)) deriving Read" doesn't work in Haskell, because there's no way to express the constraint that the type "f a" is an instance of Read whenever the type "a" is. However, see Valery Trifonov. 2003. Simulating quantified class constraints. In Haskell workshop, 98-102. http://flint.cs.yale.edu/trifonov/papers/sqcc.pdf http://flint.cs.yale.edu/trifonov/papers/sqcc.ps.gz This discussion also reminds me of Ralf Hinze. 2000. A new approach to generic functional programming. In POPL, 119-132. http://www.informatik.uni-bonn.de/~ralf/publications.html Cheers, Ken -- Edit this signature at http://www.digitas.harvard.edu/cgi-bin/ken/sig Nevertheless, most cosmologists, including Dr. Guth and Dr. Linde, agree that the universe ultimately must come from somewhere, and that nothing is the leading candidate. Dennis Overbye, New York Times, May 22, 2001.