August 2010 - Haskell-Cafe

Preview the new haddock look and take a short survey
by Mark Lentczner 09 Aug '10

09 Aug '10

The Haddock team has spent the last few months revamping the look of the generated output. We're pretty close to done, but we'd like to get the community's input before we put it in the main release. Please take a look, and then give us your feedback through a short survey Sample pages: http://www.ozonehouse.com/mark/snap-xhtml/index.html Frame version: http://www.ozonehouse.com/mark/snap-xhtml/frames.html Survey: http://spreadsheets.google.com/viewform?formkey=dHcwYzdMNkl5WER1aVBXdV9HX1l… Short link to same survey: http://bit.ly/9Zvs9B Thanks! - Mark Mark Lentczner http://www.ozonehouse.com/mark/ irc: MtnViewMark

22 32

Re: [Haskell-cafe] cairo rendered to screen examples
by Herng Yi Cheng 08 Aug '10

08 Aug '10

<original> Date: Sun, 8 Aug 2010 11:13:33 -0700 From: <briand(a)aracnet.com> Subject: [Haskell-cafe] cairo rendered to screen examples To: haskell-cafe(a)haskell.org Message-ID: <20100808111333.44b5f14a(a)windy.deldotd.com> Content-Type: text/plain; charset=US-ASCII I've been running around the gtk2hs web site and can't seem to find the actual code (I did find the cairo blog, with examples but no code). Can some kind soul post a link ? Thanks <\original> If you've installed gtk2hs on your computer, go to gtk2hs/0.10.1/share/demo/cairo or some similar folder (using your own gtk2hs version). There are some cairo examples there with source code. regards, Herng Yi

1 0

Spivak's "Databases are Categories" video/slides at www.galois.com
by Vasili I. Galchin 08 Aug '10

08 Aug '10

Hello, I'm sorry if this has already been posted. http://www.galois.com/blog/2010/05/27/tech-talk-categories-are-databases/ Vasili

1 0

Re: [Haskell-cafe] Is there any experience using Software Transactional Memory in substantial applications?
by Johnny Morrice 08 Aug '10

08 Aug '10

> My opponent gave me that link: http://logicaloptimizer.blogspot.com/2010/06/so-microsofts-experiments-with… I enjoy the article you linked but I sort of skimmed it because it was a little boring, however its main point seem to be: 1. Ghostbusters. 2. Artificial intelligence is useless [1] 3. Listen to Anders! [2] An interesting sample: "Anders Hejlsberg: Well, the best Software Transactional Memory implementations are still sitting at around 200% to 400% and that's even in best cases actually and still with Software Transactional Memory it's still, in a sense, it's still a problem of synchronization and shared state which... Carl Franklin: It's just under the lower level. Anders Hejlsberg: Some would argue it's t h e wrong way to look at the problem in the beginning. We shouldn't have the shared state to begin with. Richard Campbell: Right. Hat guy from xkcd (Enter stage left): But don't you see that Haskell has no shared state. That's exactly why STM is so great for doing concurrency in Haskell!" (I maybe edited that a little there.) Ta ta, Johnny [1] Artificial intelligence is pointless http://www.youtube.com/watch?v=nvZBtJ-ncEM [2] The internet audio talkshow http://www.dotnetrocks.com/default.aspx?showNum=541 I found this transcript on google. Server seems to give of fake 404 pages, so have to hotlink :( http://perseus.franklins.net/dotnetrocks_0541_anders_hejlsberg.pdf

3 2

cairo rendered to screen examples
by briand＠aracnet.com 08 Aug '10

08 Aug '10

I've been running around the gtk2hs web site and can't seem to find the actual code (I did find the cairo blog, with examples but no code). Can some kind soul post a link ? Thanks

1 1

Fwd: [Haskell-cafe] Is there any experience using Software Transactional Memory in substantial applications?
by Alberto G. Corona 08 Aug '10

08 Aug '10

---------- Forwarded message ---------- From: Alberto G. Corona <agocorona(a)gmail.com> Date: 2010/8/8 Subject: Re: [Haskell-cafe] Is there any experience using Software Transactional Memory in substantial applications? To: Serguey Zefirov <sergueyz(a)gmail.com> This first papers is the first that describes the preliminary haskell implementation and the performance data says that STM scales well with the number of CPU cores Blocking does not scale, as expected. http://research.microsoft.com/en-us/um/people/simonpj/papers/stm/lock-free-… In this other study, also for microsoft: <http://research.microsoft.com/en-us/um/people/simonpj/papers/stm/lock-free-…> Dissecting Transactional Executions in Haskell<http://www.cs.rochester.edu/meetings/TRANSACT07/papers/perfumo.pdf> . The worst performance in the study is from an extreme case example form my package TCache described here<http://haskell-web.blogspot.com/2006/11/transactional-cache-for-haskell.html>. In that example, a set of treads update the same two objects all the time. Since STM is non blocking, all threads tries to perform the task and rollback at the very end if things have been changed by other thread in the meantime. Just like databases. The bad thing is that the more CPU cores are executing the example, the more work being rolled back is done. That is more or less the history. I heard (The Monad Reader -mplementing STM in pure Haskell<http://themonadreader.files.wordpress.com/2010/01/issue15.pdf>) about other tentative implementation that do not wait for the end of the atomic task to test the atomicity of the transaction, but instead, any update of a TVar inmediately invalidates (and kill) all atomic transactions that uses that TVar. This could potentially improve the performance a lot. However I don´t know the strategy of the current haskell implementation nor the strasategy of the Microsoft runtime(s) either. Anyway, it is waranteed 100% that 1) the slowest in memory transaction is way faster than the transaction delegated to the fastest external database. 2) in memory transactions with blocking is a nightmare. For me these are enough arguments for STM usage in many ordinary (I mean Web) applications. 2010/8/8 Serguey Zefirov <sergueyz(a)gmail.com> Recently we discussed Haskell and especially types in Russian part of > LiveJournal and of course we talk about STM. > > My opponent gave me that link: > > http://logicaloptimizer.blogspot.com/2010/06/so-microsofts-experiments-with… > > It says that performance with STM in Microsoft Research was more than > horrible. > > I failed to find convincing counter-evidence on the web. Not for > Haskell, even for Java/C#/C++. > > So I asking Haskell-cafe for clarification. Do anyone here have an > experience with STM in computing-intensive tasks? Did it help there? > What are the possible reasons for STM failure in MR? > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >

2 1

using shared libs on the windows version
by Axel Huizinga 08 Aug '10

08 Aug '10

Hi to all from a haskell newbie! I run into problems using shared libs on windows. The error messages I get looks like: Could not find module `Data.List': Perhaps you haven't installed the "dyn" libraries for package `base'? Any ideas how to enable shared libs system-wide? Cordially, Axel

2 1

hdbc-mysql broken on snow-leopard?
by Carter Schonwald 08 Aug '10

08 Aug '10

Hey All, when i build hdbc-mysql and then try to run some example code, i get the following error message: Loading package HDBC-mysql-0.6.3 ... can't load .so/.DLL for: mysqlclient (dlopen(libmysqlclient.dylib, 9): no suitable image found. Did find: /usr/local/lib/libmysqlclient.dylib: mach-o, but wrong architecture) does this mean that it won't build on OS X snow leopard? (and yes, I am aware of hdbc-odbc, but i was curious if I could use hdbc-mysql thanks -Carter

3 2

Re: [Haskell-cafe] What is <-
by michael rice 08 Aug '10

08 Aug '10

That was my suspicion. So, you can't change horses (monads) in mid-stream. A parallel question: main = do ... -- in the IO monad I know I can have other *do*s in main, if foo then do . . else do . . but must all these other *do*s also be in the same IO monad? What determines what monad a *do* is "in"? The first line after the *do*? Thanks for your patience. Michael --- On Sun, 8/8/10, Henning Thielemann <lemming(a)henning-thielemann.de> wrote: From: Henning Thielemann <lemming(a)henning-thielemann.de> Subject: Re: [Haskell-cafe] What is <- To: "michael rice" <nowgate(a)yahoo.com> Date: Sunday, August 8, 2010, 11:01 AM On Sun, 8 Aug 2010, michael rice wrote: > How would I print each of these integers, one per line? > > [1,2,3,4,5] >>= \x -> ? You can't do this from inside the List monad, but you can easily do it from outside, since the result of a 'do' block in List monad is just a list. mapM_ print [1..5] or mapM_ print $ do x <- [1..] ... return (x+y+z)

3 2

setting gcc during the ghc-build phase
by Günther Schmidt 08 Aug '10

08 Aug '10

Hi all, for build ghc from source, how can I set which c-compiler to use? ./configure --with-gcc= .... does not seem to work for ghc-6.12.3 nor does setting the CC-environment variable. Günther

1 0