On 2003-11-13T13:19:28-0000, Simon Peyton-Jones wrote:
| From: haskell-cafe-bounces@haskell.org | | Has anyone thought about adding hereditary Harrop formulas, in other | words hypothetical reasoning and universal quantification, to the | instance contexts in the Hsakell type class system?
Yes, absolutely. See http://research.microsoft.com/~simonpj/Papers/derive.htm Section 7, and Trifanov's paper at the Haskell Workshop 2003
Thanks for the pointers! I am now thinking about encoding SML-style module systems into Haskell using type classes with functional dependencies. For this purpose, I seem to need hereditary Harrop formulas in instance contexts. I wonder if such encodings have been proposed previously in the literature? The closest I was able to find is Kahl and Scheffczyk's paper at the 2001 Haskell Workshop. Thanks again, Ken -- Edit this signature at http://www.digitas.harvard.edu/cgi-bin/ken/sig Anytime I see something screech across a room and latch onto someones neck, and the guy screams and tries to get it off, I have to laugh, because what is that thing. [http://philip.greenspun.com/humor/deep-thoughts]