Re: [Haskell-cafe] Type-Level Programming

Jason Dagit wrote:

On Fri, Jun 25, 2010 at 2:26 PM, Walt Rorie-Baety wrote:

...

I've noticed over the - okay, over the months - that some folks enjoy the puzzle-like qualities of programming in the type system (poor Oleg, he's become #haskell's answer to the "Chuck Norris" meme commonly encountered in MMORPGs).

Anyway,... are there any languages out there whose term-level programming resembles Haskell type-level programming, and if so, would a deliberate effort to appeal to that resemblance be an advantage (leaving out for now the hair-pulling effort that such a change would entail)?

I'm not a prolog programmer, but I've heard that using type classes to do your computations leads to code that resembles prolog.

Indeed. If you like the look of Haskell's type-level programming, you should look at logic programming languages based on Prolog. Datalog gives a well understood fragment of Prolog. ECLiPSe[1] extends Prolog with constraint programming. Mercury[2], lambda-Prolog[3], and Dyna give a more modern take on the paradigm. If you're just a fan of logic variables and want something more Haskell-like, there is Curry[4]. In a similar vein there's also AliceML[5] which gives a nice futures/concurrency story to ML. AliceML started out on the same VM as Mozart/Oz[6], which has similar futures, though a different overall programming style. And, as Jason said, if you're just interested in having the same programming style at both term and type levels, then you should look into dependently typed languages. Agda is the most Haskell-like, Epigram draws heavily from the Haskell community, and Coq comes more from the ML tradition. There's a menagerie of others too, once you start looking. [1] http://eclipse-clp.org/ is currently down, but can be accessed at http://87.230.22.228/ [2] http://www.mercury.csse.unimelb.edu.au/ [3] http://www.lix.polytechnique.fr/~dale/lProlog/ [4] http://www-ps.informatik.uni-kiel.de/currywiki/ [5] http://www.ps.uni-saarland.de/alice/ [6] http://www.mozart-oz.org/ -- Live well, ~wren