- Haskell-Cafe - Haskell.org

GHC 6.10 and scoped variables
by Hugo Pacheco 15 Nov '08

15 Nov '08

Hi, When migrating some code with type families to GHC 6.10, I frequently get the same error. The deal is. If I define some type family and instance: *type family Rep (f :: * -> *) x :: * data (g :+: h) x = Inl (g x) | Inr (h x) type instance Rep (g :+: h) x = Rep g x `Either` Rep h x* and then define a function that has a scoped argument: *test :: Rep (g :+: h) x -> y test (Left x :: Rep (g :+: h) x) = undefined* I get the error: * Pattern signature must exactly match: Rep (g :+: h) x In the pattern: Left x :: Rep (g :+: h) x In the definition of `test': test (Left x :: Rep (g :+: h) x) = undefined* Is this error expected? At least the error message is not clear... Interestingly, when experimenting with a different functor, I get the impossible: * newtype Const t x = Const {unConst :: t} type instance Rep (Const t) x = t** **test2 :: Rep (Const t) x -> y test2 x = undefined* *ghc: panic! (the 'impossible' happened) (GHC version 6.10.1 for i386-unknown-linux): readFilledBox x{tv aoB} [box] Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug > * Sorry for the extensiveness. Thanks, hugo -- www.di.uminho.pt/~hpacheco

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HSDL 0.5.4 on GHC 6.10.1
by Korcan Hussein 15 Nov '08

15 Nov '08

Hi the package at hackage fails to build on GHC 6.10.1 (on windows mingw) this is due to 2 reasons: 1. I believe the order of libraries to be linked needs to change from "-lmingw32 -lSDLmain -lSDL" to "-lSDLmain -lSDL -lmingw32" otherwise you get linker errors which multiple definitions of main. I think the build system should output `sdl-config --cflags --libs` instead of explicitly stating which libraries besides. 2. For some reason the the library & include paths plus the list of which libraries to be linked gets appened to the output twice and thus causing linker errors. I'm a casual user of haskell so I don't much about cabal packages so I manged to figure out a hackish workaround by deleting the entry in the SDL.buildinfo file (the entry for the ld-options). _________________________________________________________________ Win £1000 John Lewis shopping sprees with BigSnapSearch.com http://clk.atdmt.com/UKM/go/117442309/direct/01/

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Re: Haskell-Cafe Digest, Vol 63, Issue 23
by John Lato 15 Nov '08

15 Nov '08

You could use HSoundFile, but I wouldn't recommend it for this specific case. I'm not extremely familiar with the Haskell OpenAL bindings, but IIRC they take buffers (pointers). Since HSoundFile marshals data to [Double], you'd then have to convert it back to CWord16 array. Seems wasteful and slow to me. Here are 3 possible approaches: 1. Look through HSoundFile (or similar) to learn how they work and write your own code. 2. Look at the Codecs or Wave packages, which might be coerced into doing what you want (there is also hsndfile, a binding to libsndfile, however I think that normalizes data like HSoundFile does, although you could likely avoid the marshaling problem. 3. I have a revised HSoundFile, which I think could be much more suitable for this sort of work. If you'd like the code for that, let me know and I'd be happy to pass it along. I'm hoping to do a release next week, but there's a lot of tidying to be done in the current state. How many people care about reading/writing audio files? I've been re-working the HSoundFile API, experimenting with different designs, comparing packages, etc., and I could do a write-up if anyone is interested. John Lato > > Message: 19 > Date: Fri, 14 Nov 2008 08:11:59 +0100 > From: Marc Weber <marco-oweber(a)gmx.de> > Subject: Re: [Haskell-cafe] openal & alut troubles > To: haskell-cafe(a)haskell.org > Message-ID: <20081114071159.GB18112(a)gmx.de> > Content-Type: text/plain; charset=utf-8 > > On Fri, Nov 14, 2008 at 02:33:05AM +0000, Stephen wrote: >> ah, damn I feel stupid. I hadn't it installed. I just tried to, and, >> after verifying with the internet, it seems that ALUT isn't supported on >> macs anymore anyway. Which leads me to the following question: does >> anyone have any example code for saving/loading wav files, say, using >> openal (minus alut) with haskell? I'm not too sure how to go about >> doing it myself (though the people on this thread >> [1]http://groups.google.com/group/fa.haskell/browse_thread/thread/33b57c9452… >> seem to indicate that it would be a relatively easy task). > > Wave files are realitively easy to write .. However you can also try the > encoder from hackage (catergory sound) called HSoundFile.. (I've never > used it before) Also using the haskell wiki search from haskell.org > reveals: http://haskell.org/haskellwiki/Sound_data_structures > > good luck > > Marc

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Calling Haskell from other languages?
by Colin Paul Adams 14 Nov '08

14 Nov '08

Is there a way to call Haskell code from other languages? I have looked on the wiki, and as far as I can see, it only talks about the other way round (when Haskell is the main program). -- Colin Adams Preston Lancashire

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ANN: bustle-0.1, a D-Bus activity charting tool
by Will Thompson 14 Nov '08

14 Nov '08

Hi, For the (probably small) set of people who are interested both in D-Bus and in Haskell, I'm pleased to announce the first release of Bustle, a tool to show diagrams of D-Bus traffic for profiling purposes. It consists of a small C executable to log traffic, and a Gtk+ application which draws diagrams using Cairo. There's no single web page for it yet. http://resiak.livejournal.com/59590.html has slightly more information and context, the release is at http://people.collabora.co.uk/~wjt/bustle/releases/bustle-0.1.tar.gz and the source at git://git.collabora.co.uk/git/user/wjt/bustle.git . Unfortunately, it's not on Hackage, as I haven't written the necessary glue to get Cabal to compile the C executable, but I hope to have time to work on getting Cabal to invoke make appropriately for the next release. Thanks, -- Will

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TimeDiff to Int?
by Lyle Kopnicky 14 Nov '08

14 Nov '08

Hi folks, I had some code using the oldtime package, and want to convert it to use the time package. One of the things I need to do is calculate the number of seconds since midnight. The easy part is getting a TimeDiff result: utc <- getCurrentTime tz <- getCurrentTimeZone let td = timeOfDayToTime $ localTimeOfDay $ utcToLocalTime tz utc Now td is a TimeDiff representation of the number of seconds since midnight. It prints nicely, but I'm having a heck of a time figuring out how to truncate it to an Int. The floor function is only supported by the RealFrac class. Although TimeDiff has an instance of RealFrac and Fractional, it doesn't have an instance of RealFrac. I looked up the various to* and from* functions and have come up short. fromEnum yields an Int but it's the wrong value. I know I could use show and then use readS to get an Integer, or use formatTime (and reparse that), but that's a hack. I can convert it to a TimeOfDay which gives me hours, minutes, and seconds, but then I have to do arithmetic on it, and the seconds are of type Pico, which I can't call floor on either. I can convert it to a Rational via timeOfDayToDayFraction, but a TimeDiff is already a Rational those don't have floor. What am I missing? There has got to be an easy way to count seconds! Thanks, Lyle

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[magnus@galois.com: Re: [Haskell-cafe] Monads for Incremental computing]
by Don Stewart 14 Nov '08

14 Nov '08

Magnus writes: Thanks to Peter Jonsson, the source is now on hackage: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Adaptive Cheers, Magnus Donnie Jones wrote: > Hello sanzhiyan, > > I believe this is the same paper, the pdf is available here: > http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.8.3014 > > Cheers. > __ > Donnie > > On Thu, Nov 13, 2008 at 9:02 PM, Don Stewart <dons(a)galois.com > <mailto:dons@galois.com>> wrote: > > I sit next to the author, CC'd. > > -- Don > > sanzhiyan: > > I'm looking for the source code of the library for adaptive > computations > > exposed in Magnus Carlsson's "Monads for Incremental > Computing"[1], but > > the link in the paper is broken. > > So, does anyone have the sources or knows how to contact the > author? > > > > [1] http://portal.acm.org/citation.cfm?id=581482 > > > _______________________________________________ > > Haskell-Cafe mailing list > > Haskell-Cafe(a)haskell.org <mailto:Haskell-Cafe@haskell.org> > > http://www.haskell.org/mailman/listinfo/haskell-cafe > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org <mailto:Haskell-Cafe@haskell.org> > http://www.haskell.org/mailman/listinfo/haskell-cafe > > ----- End forwarded message -----

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ghci start-up banner
by Cetin Sert 14 Nov '08

14 Nov '08

Hi all, after reading this announcement on the Galois blog: http://www.galois.com/blog/2008/11/13/tech-talk-mechanically-verified-lisp-… I installed Hol4 to play around with it a little bit. I made 2 obvious observations ^_^: 1) It looks like the Hol4 system is just a ML module that gets loaded into the Moscow ML interpreter with the help of a script 2) it prints a custom banner after loading And now I have the following questions: == about proof assistants in general == 1) how many other proof assistants are built the same way as Hol4: as a module loaded into some interpreter? 2) is there a paper or even better a funny but detailed comparison of proof assistants? == about custom banners at module load time == 1) is there a way to do it in ghci? Regards, CS

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openal & alut troubles
by Stephen 14 Nov '08

14 Nov '08

The link to the OpenAL documentation [ http://haskell.org/ghc/docs/latest/html/libraries/OpenAL/Sound-OpenAL.html ] from here [ http://www.haskell.org/haskellwiki/OpenAL ] seems to be down. Also, I tried to use cabal to install ALUT and got the following checking for unistd.h... yes checking AL/alut.h usability... no checking AL/alut.h presence... no checking for AL/alut.h... no checking OpenAL/alut.h usability... no checking OpenAL/alut.h presence... no checking for OpenAL/alut.h... no configure: error: no ALUT header found, so this package cannot be built See `config.log' for more details. cabal: Error: some packages failed to install: ALUT-2.1.0.0 failed during the configure step. The exception was: exit: ExitFailure 1 :/

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Monads for Incremental computing
by sanzhiyan＠gmail.com 14 Nov '08

14 Nov '08

I'm looking for the source code of the library for adaptive computations exposed in Magnus Carlsson's "Monads for Incremental Computing"[1], but the link in the paper is broken. So, does anyone have the sources or knows how to contact the author? [1] http://portal.acm.org/citation.cfm?id=581482

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