- Haskell-Cafe - Haskell.org

Arkadasa yardimci olalim
by Dr. Ahmet Yalcin 27 Apr '03

27 Apr '03

Arkadaslar, lütfen dikkate alin, yardimci olalim: Merhaba, cok zor durumda ve baska caresi kalmamis biri olarak hosgörünüze ve insan sevginize siginarak sizden bana cok kisada olsa kulak vermenizi rica edecegim. Ben, 34 yasinda evli ve 4 yasinda olan bir cocuk babasiyim. Aile hayatimizin sorunsuz ve mutlu sekilde devam ederken biricik oglumuz aniden rahatsizlandi. Uzun süren arastirmalar sonucu oglumuz Ali Can'in kalbinde hayati bir fonksiyon bozuklugunun bulundugu doktorlar tarafindan tespit edildi. Oglumuz cok acil sekilde ameliyat olmazsa maalesef hayata gözlerini yumacak. Ancak ne varki ameliyat icin gerekli olan parayi ödememiz bizim icin mümkün gözükmüyor. Bu nedenle uzun ugraslar sonucu iki önemli Internet sirketi ile yaptigimiz görüsme sonucu, bize her mailde gönderecegimiz link'in tiklanmasi durumunda cocugumuzun ameliyat masraflarina 10 Cent (= 0,10 Euro) katkida bulunacaklari yönünde anlasmaya varabildik. Bu dogrultuda sizden rica edecegimiz, sizi sözkonusu sirketlerin sayfalarina yönelten bu linki tiklamaniz. Bu linki tiklayarak sizinde ameliyat masraflarini karsilamamizda katkiniz olabilir. Sizden bu zor durumumuzda istedigimiz sadece bir tik. >> TIKLAYINIZ --> http://partners.webmasterplan.com/click.asp?ref=160073&site=2514&type=text&… Bunun yaninda bu emaili tüm tanidiklariniza gönderirseniz bize son derece yardimci olursunuz. Ne kadar kisi linki tiklarsa, gerekli olan ameliyat masrafini yakalayabilmemiz o kadar olasi olur. Hos görünüz icin tesekkür eder, saygilarimi sunarim. Mehmet Can Yakupoglu.

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Sell:Industrial Permanent Magnets
by L.Z.Mou 26 Apr '03

26 Apr '03

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Re: Is this a bug in multithreading code?
by Nick Name 25 Apr '03

25 Apr '03

Il 22:54, mercoledì 23 aprile 2003, hai scritto: > I conjecture that the problem would go away if you added appropriate > uses of seq or $! to your program so that the value stored in the MVar > was always fully evaluated You are right, the following code works well strictIncM x = return $! x + 1 ... forkIO (loopM (modifyMVar_ v strictIncM)) ... Thanks for your help Vincenzo

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RE: Super Haddock (was Re: Literate Programming)
by Simon Marlow 25 Apr '03

25 Apr '03

Ketil Z. Malde writes: > > "Simon Marlow" <simonmar(a)microsoft.com> writes: > > > Somebody else¹ wrote: > > >> This seems like a good way of transitioning from .lhs to > >> haddock'd .hs. In the long run, I think we (meaning Simon :-) > >> should to extend haddock to take the place of the .lhs style of > >> documenting code. > > > That's an interesting idea. It's not at all what Haddock > was intended > > for, but that's not to say it couldn't be done! > > I'm not sure I would like this. I guess I'm one of (the apparently > very few?) who are using LaTeX lhs style (using \begin/\end{code}). > Would a Haddock replacement give me the same kind of functionality in > producing a nice printable copy? I definitely have grown attached to > having math, footnotes, page headings, sections, and so on. Haddock isn't (intended to be) a literate programming system, so I don't imagine it will replace full LaTeX literate source any time soon. The suggestion is just that it could produce nicely-formatted source code complete with lightly marked-up comments - which I think is a fine idea, and not too difficult to implement using the existing framework. > ¹) As Exchange doesn't leave useful thread information, I'm not quite > sure who. Simon and others, if you must use Exchange, could you take > care to leave an attribution, prefereably including the message-id? I can get proper In-Reply-To headers by avoiding Exchange altogether, but it requires me to select an option each time I send a message, so I often forget (sorry!). I've reported it as a bug in Exchange, but it might be a generation or two before it gets fixed. Cheers, Simon

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Slow program
by Mark Carroll 25 Apr '03

25 Apr '03

One of my GHC programs is running much more slowly than I'd expect, and I wonder if laziness is getting in the way or if it's getting into an infinite loop. How should I diagnose the problem? Tonight I've started with Hat - it seems to install okay, but doesn't seem to have a Control/Monad/Identity.hx file that I need. ): -- Mark

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Haskell Help
by Gyslain Giguère 25 Apr '03

25 Apr '03

Hi! I'm a computer science student whose last assignment (due next wednesday) of the semester is to present and explain a Haskell 98 program I found on the internet. Unfortunately, I can't find anything written in Haskell 98 that can be explained in about 20 minutes, and doesn't use any graphic libraries (since we haven't studied them). So if you have any examples (course exercises, handouts), I would be very grateful! Thanks to all! Gyslain Giguère, Student, Cognitive Computer Science, Université du Québec à Montréal giguere.gyslain(a)courrier.uqam.ca

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Re: Extracting values from several data constructors
by Dean Herington 23 Apr '03

23 Apr '03

[redirected to haskell-cafe] On 24 Apr 2003, Steffen Mazanek wrote: > Hello. > I am sure this question is not new. Even so, please > give me the solution or point me to an old thread. > > How can I implement something like: > > data Test = T1 Int | T2 Int > test::Test->Int > test (_ x) = x > > Or is this impossible? In case of yes, why? > This would save a lot of case differentiations in > my application. Or is there an appropriate compiler option? It can be done, but only for labeled fields. For example: data Test = T1 { test :: Int } | T2 { test :: Int } See section 3.15 of the Haskell report. Dean

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Re: Writing for both State and StateT
by Jon Cast 23 Apr '03

23 Apr '03

Derek Elkins <ddarius(a)hotpop.com> wrote : <snip> > Yes, I've tried it. I didn't mean GHCi doesn't EVER validate the > constraints on input, just that it doesn't when you use :t. So do you mean to use :t & cut & paste the definition? Interesting. A fair bit of work (more than just adding a parameter () to the definition), but I guess it'd work. <snip> Jon Cast

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Is this a bug in multithreading code?
by Nick Name 23 Apr '03

23 Apr '03

Hi all, does someone know why this program works ------------------------ import Concurrent loopM = sequence_ . repeat main = do v <- newMVar 0 forkIO (loopM (modifyMVar_ v (return . (1+)))) -- forkIO (loopM (modifyMVar_ v (return . (1+)))) loopM (readMVar v >>= print) ------------------------- but uncommenting the commented line makes the program fail with "stack overflow" ? Thanks for help Vincenzo

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Re: Writing for both State and StateT
by Jon Cast 23 Apr '03

23 Apr '03

Mark Carroll <mark(a)chaos.x-philes.com> wrote: > On Tue, 22 Apr 2003, Jon Cast wrote: > > When you have two identical methods like this, you can try removing > > the type from one and seeing what hugs or ghci thinks the type is. > > Then, you can specialize that if you want. > Unfortunately, in this case, with that function in isolation I get, > Ambiguous type variable(s) `s', `m' > in the constraint `MonadState s m' > arising from use of `get' .... Ah, yes the good old monomorphism restriction. Should have thought about that. The way around this is to make the declaration a function: > next_random_probability () = > do old_rng <- get > let (random_probability, new_rng) = randomR (0, 1) old_rng > put new_rng > return random_probability This will typecheck, giving most general type (MonadState s m, Num a, Random a, RandomGen s) => () -> m a, according to ghci. Then, you can take off the argument type to get the resulting type. <snip> Jon Cast

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