March 2007 - Haskell-Cafe

Haskell and AI
by Adam Wyner 19 Mar '07

19 Mar '07

I agree with Andrew Wagner re: Haskell and AI. There are some relevant resources on Haskell, Maths, and Logic: *The Haskell Road To Logic, Maths And Programming (Paperback) * by Kees Doets <http://www.amazon.com/exec/obidos/search-handle-url/103-5196905-1677457?%5F…> (Author), Jan van Eijck <http://www.amazon.com/exec/obidos/search-handle-url/103-5196905-1677457?%5F…> (Author) http://www.amazon.com/Haskell-Road-Logic-Maths-Programming/dp/0954300696/re… van Eijck has another book on Computational Semantics. Elsewhere, there is work on learning algorithms in Haskell. Broadly, we might start by gathering known resources, projects, and people. We could consider one of the standard AI books as a guide for chapters, sections, and problems to fill in with Haskell approaches. I'd be very interested to contribute to this. Cheers, Adam Wyner Message: 7 Date: Mon, 19 Mar 2007 12:51:19 -0400 From: "Andrew Wagner" <wagner.andrew(a)gmail.com> Subject: Re: [Haskell-cafe] Haskell Chess To: haskell-cafe(a)haskell.org Message-ID: <b8a8636e0703190951y21c7cb01qcb4f5b58089b169d(a)mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Here's my take on this: I've thought for a while now that Haskell needs a general toolkit for AI. After all, functional programming has long been recognized for being good at AI, yet you rarely hear about it being done in Haskell. Anyway, my suggestion would be to concentrate on methods of AI. For example, if we implement alpha-beta polymorphically enough, it should be trivial to use it for any game that it makes sense to use it on. This kind of thing is what I was thinking of when I talked about some "fundamental design" ideas I had. Things like writing a Board type-class, so that you can implement any board representation you want to for chess. Or writing alpha-beta in terms of positions and moves, regardless of what kind of game you're talking about (I also think you simply must use unfoldTree, as this is a beautiful instance of it). Things like learning, and other general strategies, should be developed independently of any particular game, IMHO.

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Re: [Haskell] Haskell Chess
by dons＠cse.unsw.edu.au 19 Mar '07

19 Mar '07

smazanek: > Hello again, > > I got a lot of interesting and useful comments on my posting > about Haskell Chess. Somebody suggested using the program > for benchmarks. Several people asked me to open the program > for contributions. And others were just interested in the exercises. > > It is probably the best to branch the development, so that we > have a teachers' and a hackers' version (ease of understanding > and learning paradigms vs. efficiency and implementation of > full ruleset). I will do the necessary steps next week (svn, etc). > Somebody already offered help for cabalizing hsChess. hsChess has been cabalised, and is available now via darcs; darcs get http://www.cse.unsw.edu.au/~dons/code/contrib/hsChess/ You can also browse the source directly: http://www.cse.unsw.edu.au/~dons/code/contrib/hsChess/ > Several people asked me for the exercises so I started the wiki > page > http://haskell.org/haskellwiki/Learning_Haskell_With_Chess > on this topic. I will add more content when I am back to office. > > Every contribution and discussion is welcome. I am happy to host the code at the above url, unless Steffen, you have a better place to host the repository? -- Don

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Re: [Haskell-cafe] N and R are categories, no?
by Dominic Steinitz 19 Mar '07

19 Mar '07

> I haven't formally checked it, but I would bet that this endofunctor > over N, called Sign, is a monad: Just to be picky a functor isn't a monad. A monad is a triple consisting of a functor and 2 natural transformations which make certain diagrams commute. If you are looking for examples, I always think that a partially ordered set is a good because the objects don't have any elements. A functor is then an order preserving map between 2 ordered sets and monad is then a closure (http://en.wikipedia.org/wiki/Closure_operator) - I didn't know this latter fact until I just looked it up. Dominic.

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N and R are categories, no?
by Steve Downey 19 Mar '07

19 Mar '07

EOk, i'm trying to write down, not another monad tutorial, because I don't know that much yet, but an explication of my current understanding of monads. But before I write down something that is just flat worng, I thought I'd get a cross check. (and I can't get to #haskell) Monads are Functors. Functors are projections from one category to another such that structure is preserved. One example I have in mind is the embedding of the natural numbers into the real numbers. The mapping is so good, that we don't flinch at saying 1 == 1.0. The functor that takes us from N to R is probably a Monad, that is, if N and R are categories. The real hard part is tying together how unit, join and bind produce a spacesuit that can protect apples from nuclear waste. I'm still getting that clear in my head, although my recent blinding flash of obviousness that M a is a type, and that of course types can do interesting things, I think gets me further along.

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Algorithms
by P. R. Stanley 19 Mar '07

19 Mar '07

Hi "When you write a general solution for a class of problems, as opposed to a specific solution to a single problem, you have written an algorithm." Discuss! Regards, Paul

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Haskell and AI
by Andrew Wagner 19 Mar '07

19 Mar '07

> I agree with Andrew Wagner re: Haskell and AI. > > There are some relevant resources on Haskell, Maths, and Logic: > > The Haskell Road To Logic, Maths And Programming (Paperback) > by Kees Doets (Author), Jan van Eijck (Author) > > http://www.amazon.com/Haskell-Road-Logic-Maths-Programming/dp/0954300696/re… > I liked this book. What parts did you have in mind specifically as being relevant to AI? > van Eijck has another book on Computational Semantics. Elsewhere, there is > work on learning algorithms in Haskell. > > Broadly, we might start by gathering known resources, projects, and people. > We could consider one of the standard AI books as a guide for chapters, > sections, and problems to fill in with Haskell approaches. I like this idea. On the other thread [1] Ricardo Herrmann suggested following the structure of "AI: A Modern Approach", the classical text [2] by Russell and Norvig. Do others agree? I think we should carve out a section of the wiki, in the Applications and Libraries section [3] for AI, which should then be split into (at least) a section each for relevant papers, code, interesting AI problems with their solutions, and a table-of-contents type page, structured according to a text like this. Comments? > > I'd be very interested to contribute to this. > Maybe we should assemble an AI strike force? :) > Cheers, > Adam Wyner > [1] http://www.haskell.org/pipermail/haskell-cafe/2007-March/023646.html [2] http://aima.cs.berkeley.edu/ [3] http://www.haskell.org/haskellwiki/Libraries_and_tools

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System.Random StdGen read fails on some strings?
by Fritz Ruehr 19 Mar '07

19 Mar '07

According to the documentation for System.Random (see <http:// haskell.org/ghc/docs/latest/html/libraries/base/System-Random.html>): > In addition, read may be used to map an arbitrary string (not > necessarily one produced by show) onto a value of type StdGen. In > general, the read instance of StdGen has the following properties: > > * It guarantees to succeed on any string. > * ... On the other hand, I get the following on the (admittedly stupid, spur-of-the-moment) String argument "whateva": > Hugs> :l System.Random > System.Random> read "whateva" :: StdGen > > Program error: Prelude.read: no parse > > System.Random> map read $ words "this is a test of the System dot > Random StdGen read, which seems to fail only on ... whateva" :: > [StdGen] > [4580 1,440 1,101 1,4584 1,445 1,1485 1,35261 1,1377 1,32825 > 1,34047 1,13422 1,14037 1,13637 1,469 1,4132 1,4514 1,453 1,626 1, > Program error: Prelude.read: no parse Am I missing something here? Or am I just being punished for the stupidity of my particular choice of String? :) -- Fritz PS: this happens with both Hugs Version: September 2006 and GHC Interactive, version 6.6, running on Mac/Tiger, for what that's worth.

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Type synonym application
by C Rodrigues 19 Mar '07

19 Mar '07

Type synonyms aren't applied as I would expect during kind checking. What's going on here? type WithList a b = b [a] type FooPair a b = (b, a -> b) -- error: `WithList' is applied to too many type arguments ints1 :: WithList Int FooPair [Int] ints1 = ([1], id) -- error: `FooPair' is not applied to enough type arguments ints2 :: (WithList Int FooPair) [Int] ints2 = ([1], id) -- after manually applying the first type synonym ints3 :: FooPair [Int] [Int] ints3 = ([1], id) _________________________________________________________________ Live Search Maps find all the local information you need, right when you need it. http://maps.live.com/?icid=hmtag2&FORM=MGAC01

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Re: [Haskell] Haskell Chess
by Andrew Wagner 19 Mar '07

19 Mar '07

Andrzej, I'd love to hear some of your thoughts on these things. I agree with you about brute-force not being the best approach in haskell (or maybe at all). I think we should switch to haskell-cafe, since that's where much of this discussion has gone, and that's more for extended discussions anyway. On 3/18/07, Andrzej Jaworski <himself(a)poczta.nom.pl> wrote: > Didactic it may be but brute force on search trees means in Haskell problem > with garbage collection. So students may build a punch but loose a street > fight. > > Instead of using Haskell as a hammer I would rather explore what monadic > programming can offer in terms of encapsulating constraints, heuristics, > modal logic or agents. Chess is a human game so why not use computing along > this line and employ Haskell on humane terms? The force is with us! > > Cheers, > -Andrzej > > _______________________________________________ > Haskell mailing list > Haskell(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell >

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Re: [Haskell] Summer of Code project proposal
by Neil Mitchell 19 Mar '07

19 Mar '07

Hi Nikhil, haskell-case is probably a better choice of list for this - haskell is more for announcements. > > I am Nikhil N, a third year Computer Science student from India. I am > looking at building a good > IDE for people learning Haskell(as part of SoC).This IDE will be modeled > on Dr Scheme or blueJ. Have you looked at something based on HIDE or GuiHaskell? The latter is certainly in the SoC database (I added it), the former was an active project a while ago. How much work do you think is involved in writing an IDE? I suspect its a massive amount - much more than one summers worth.... Thanks Neil

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