September 2007 - Haskell-Cafe

non POSIX/Win32 API support
by Galchin Vasili 24 Sep '07

24 Sep '07

Hello, I want to provide support for another OS. How are the POISIX modules implemented? E.g. in terms of Green Card? Kind regards, Bill Halchin

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Re:[Haskell] Math behind Haskell
by Tomas Caithaml 24 Sep '07

24 Sep '07

Hi and thanks for that many replies! > The haskell-cafe@ mailing list is more appropriate for messages such > as this. haskell@ is just for announcements (it should be called > haskell-annouce@ !) Sorry for misposting. > I'd add: > * Discrete Maths - booleans, relations, functions etc. > * Type theory > * Logic programming (Prolog) > * Semantics > Most of these are computer science courses, rather than maths ones. My formulation was somewhat unfortunate on this point. I wasn't strictly looking for math courses, so Type Theory a Semantics seems to be a very good suggestions. Alas, I do not recall any course named "Type Theory" being taught here. But thanks for these hints. I should have probably also noted that I am not new to university (4th year), so I have already taken some courses. Notably: several semesters of real analysis Linear algebra, Algebra Discrete mathematics and graph theory few algorithm and datastructure courses, Logic Programming introduction courses into: Propositional and Predicate logic Computability theory Computational complexity theory Set Theory And I think I have enough of basic mathematical fluency to be able to follow (at least to some degree) any math course if it is not extra hard or if it does not heavily depend on other courses. >Just take the computer science courses that the fewest of your fellow > students see any point to. Well, there are too many of those :-) Thanks, Tom.

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Re: [Haskell-cafe] PROPOSAL: Rename haskell@ to haskell-announce@
by Simon Michael 24 Sep '07

24 Sep '07

The gmane newsgroups corresponding to haskell mail lists can be found eg at: http://gmane.org/find.php?list=haskell

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Complexity question
by Andrew Coppin 24 Sep '07

24 Sep '07

Greetings. Anybody happen to know what the time complexity of "transpose" is?

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Re: [Haskell] Math behind Haskell
by Neil Mitchell 24 Sep '07

24 Sep '07

Hi The haskell-cafe@ mailing list is more appropriate for messages such as this. haskell@ is just for announcements (it should be called haskell-annouce@ !) > * Lambda calculus - the basis of functional languages > > * Category theory - where all these mysterious things like monads, > arrows, and functors come from. I'd add: * Discrete Maths - booleans, relations, functions etc. * Type theory * Logic programming (Prolog) * Semantics Most of these are computer science courses, rather than maths ones. Thanks Neil

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PROPOSAL: Rename haskell@ to haskell-announce@
by Andrzej Jaworski 24 Sep '07

24 Sep '07

Sorry guys for joining the thread of sinners on haskell@ today. Forgot to check if guests had not moved to cafe;-) It is a good example though how insufficient this verbal principles are, since I have myself raised the need to revise names of the lists here. On second thought, with rising traffic the problem should be approached by introducing AI automation - sort of scunning, learning, summerising and sending tagged abstracts onto haskel@. In other words the only possible input onto haskell list should be robotic:-) Be brave guys, you are ment to make history:-) Cheers, -Andrzej Jaworski

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Noob question and sequence of operations (print then do something else)
by John Wicket 24 Sep '07

24 Sep '07

I am still in an imperative way of thinking. In this example here; how would I call "putStrLn" and then set the function with a value. Eg: aa :: String -> IO () aa instr = do putStrLn "abc" putStrLn "abc" return "123" --- The error I am getting. Couldn't match expected type `()' against inferred type `[Char]' In the first argument of `return', namely `"123"' In the expression: return "123" In the expression: do putStrLn "abc" putStrLn "abc" return "123"

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Re: [Haskell] Re: [Haskell-cafe] PROPOSAL: Rename haskell@ to haskell-announce@
by Neil Mitchell 24 Sep '07

24 Sep '07

Hi > Forgive me, but I would much prefer a newsgroup to a mailing list. > > True, I could unsubscribe now and just browse the mailman archives - > but for posting, I'd have to temporarily re-subscribe, which is awkward. > (Indeed that's the only reason I'm not doing it.) I believe you can post from the gmane archives, and that they also offer a newsgroup feed of this list. I think the general consensus (and my personal view) is that a mailing list is the preferred mechanism for most people. Thanks Neil > > We already have comp.lang.haskell. - Best regards, > -- > -- Johannes Waldmann -- Tel/Fax (0341) 3076 6479/80 -- > ---- http://www.imn.htwk-leipzig.de/~waldmann/ ------- > > _______________________________________________ > Haskell mailing list > Haskell(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell >

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Re: [Haskell] Math behind Haskell
by Andrzej Jaworski 24 Sep '07

24 Sep '07

Tomas Caithaml wrote: > Hi all. > > When I was playing with Haskell and reading stuff about it, I noticed > that there is a lot of information in a form of research papers and a > lot of mathematics involved. I must confess that I quite like this > academic approach. > > Well, I thought that while I am still at university I could take some > math classes to help me better understand these things and > broaden my horizon. > > Any suggestion what could be relevant? > > I came up with: > > * Lambda calculus - the basis of functional languages > > * Category theory - where all these mysterious things like monads, > arrows, and functors come from. > > * Topology (?) - don't know; I thought it is important rather in > mathematical analysis (which I don't like much) but I have seen > somewhere some references to it in context of CS. > > Any other suggestions? All the advice you got was good but I will add: never go after one thing in mathematics before you really know what you are doing. Topology is probably best intellectually but must be combined with functional analysis or algebra to have something to experiment with. Similarly category theory alone will never teach you to think mathematically - to build models. For CS inclined entering into logic study is today a very rewording experiance but you must feel confident with CT for reading modern proof theory and additionally operator algebra entering into linear logic. The reward: you get closer to functional programming or quantum mechanics without even knowing that:-) Digging in Haskell can make you fluent in writing some computational stuff to experiment with, but it will most certainly follow thought experiment not vice versa. Relying on such hybrid thinking too much can be harmful though. A mathematician follows intuition, ideally he should not even plan what he will do before he spots something that will drive his attention. Programming is the opposite - planning lies at the heart of it. Even languages that fancy mathematical concepts belong still to technology and thechnology is to eliminate problems and not to investigate them. Mathematics and logic will definitelly influence CS more with each decade untill it becomes a science like phisics. However how shellow this science still is in CS today demonstrate the havoc with multicore, where linguistics, model theory, tamplet programming, object programming, Haskell(?) compete head in head to cover the bare ass... Cheers, -Andrzej Jaworski Moving to Haskell Cafe <haskell-cafe(a)haskell.org>

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Library Process (was Building "production stable" software in Haskell)
by Dominic Steinitz 24 Sep '07

24 Sep '07

This discussion has sparked a question in my mind: What is the process for the inclusion of modules / packages in ghc, hugs and other compilers & interpreters? I thought the master plan was that less would come with the compiler / interpreter and the user would install packages using cabal. I was thus mildly surprised earlier this year to find e.g. data.bytestring was included with ghc. Now that I look at the haddock, it says this is a base package but doesn't say anything about its status. On the other hand, there are lots of modules that are base packages that are experimental. Should something experimental be a base package? And shouldn't all modules that are base packages declare their status? Perhaps these are questions for the libraries mailing list but I thought I'd start here. Yours confused of Kingston.

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