[Haskell-cafe] Re: re: generics and grammars

[Chung-chieh Shan]

Greg Meredith <lgreg.meredith at biosimilarity.com> wrote in article <5de3f5ca0712120917h7864fe39m2c6a2c6c379437e7 at mail.gmail.com> in gmane.comp.lang.haskell.cafe:
> 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.