- Haskell-Cafe - Haskell.org

Haskell-based iPhone development
by Conal Elliott 18 Jun '09

18 Jun '09

If you are working with Haskell and making iPhone apps, or if you intend to soon, please say so at http://haskell.org/haskellwiki/IPhone. By helping each other out, I hope we can work more productively and have more fun in the process. At this point, I'd like to find out what you'd like to share, what help you'd like from others, and generally what kind of apps you want to make. We'll see what evolves from there. - Conal

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Which windowing toolkit to use?
by Patai Gergely 17 Jun '09

17 Jun '09

Hi all, I intend to start coding the UI of the heap profiling toolkit I'm working on [1] soon. I'd be happy to get some advice on choosing the right windowing toolkit for this task. The main requirements are: - portability and native look & feel if possible - easy to distribute executables under Windows - relatively slow code rot - sane interface that doesn't need wild workarounds even if what I'm doing is not trivial or elementary - trouble-free source installation in case someone wants to contribute As I see, at the moment there's no serious alternative besides GTK and wx, so my question is which do you think is better suited to this task? I have absolutely no development experience with GTK, and while I used a bit of wx in the past (in C++), I'm not really familiar with it either, especially not the Haskell bindings. I noticed that installing the wx binding with user rights doesn't seem to work directly from hackage (doesn't pass --user to ghc-pkg?), but it looks like a problem that can be solved with some hand editing. I'm a bit more afraid of setting up a development environment under Windows; is there any major pain involved with either of these libraries if I use MinGW? And how about their interface? Is there any significant difference? I'd especially like to hear the opinion of someone who's reasonably familiar with both. Thanks, Gergely [1] http://code.google.com/p/hp2any/ -- http://www.fastmail.fm - Or how I learned to stop worrying and love email again

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Fwd: Boston Haskell June 23rd meeting: openings for Lightning Talks
by Ravi Nanavati 17 Jun '09

17 Jun '09

---------- Forwarded message ---------- From: Ravi Nanavati <ravi(a)bluespec.com> Date: Wed, Jun 17, 2009 at 3:55 PM Subject: June 23rd meeting: openings for Lightning Talks To: bostonhaskell(a)googlegroups.com Both speakers for the June 23rd meeting have let me know that they expect their presentations to be on the shorter side of the 30-45 minutes alloted, so that means we have some space in the schedule. We could just use that as additional free-form discussion and mingling time, but since I saw them be successful at ILC'2009 and at the Boston Lisp Meeting after that, I'd like to offer that space to anyone who wants to give a "Lightning Talk". I think we should use the same formula as the Lisp Meeting: strictly-timed 5-minute talks followed by 2-minutes for questions and answers from the audience. Lightning talks don't have to be Haskell-specific, as long as the topic is appropriate for the audience. If you're interested in giving a Lightning Talk at the June 23rd meeting, please contact me ( ravi(a)bluespec.com ) and let me know what you'd like to talk about. Thank you, - Ravi Nanavati

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measuring time differences between functions
by Nico Rolle 17 Jun '09

17 Jun '09

Hi everyone. I made parallel versions of my functions projection selection and sort and i wanted to test the difference in runtime. But he only printed 0.00 twice. Maybe hes just too fast? Or is it because of lazy evaluation? or is there a better way to mesure performance in execution time? regards main = do xs <- readCSV "dataconvert/lineitem.tbl" '|' start <- getCurrentTime let pnp = projection [5] xs let snp = selection (\x -> (x!!0) > (Int 17000)) pnp let sortnp = sort [0] [ASC] snp end <- getCurrentTime putStrLn $ show (end `diffUTCTime` start) start2 <- getCurrentTime let pp = pProjection [5] xs let sp = pSelection (\x -> (x!!0) > (Int 17000)) pp let sortp = pSort [0] [ASC] sp end2 <- getCurrentTime putStrLn $ show (end2 `diffUTCTime` start2) return snp

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Wiki user accounts
by Philippa Cowderoy 17 Jun '09

17 Jun '09

I'm hearing reports of people having difficulty obtaining accounts on the Haskell wiki, without which it is impossible to make edits. Currently, account creation is disabled as an anti-spam measure, and the idea is for people to mail the admin and request an account. If this is to work, accounts need to be granted reasonably quickly - so far, I'm aware of a case where after 4 days there has been no response. This is particularly problematic for Anglohaskell, as signups and the like are via the wiki page - as a temporary workaround, I'll (and anyone else willing to lend a hand who already has an account) have to make edits on others' behalf, which is a serious inconvenience for both myself and attendees, as well as something of a barrier to entry. What's going on, and how can we speed things up? -- Philippa Cowderoy <flippa(a)flippac.org>

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Start to Finish C2HS guide
by Yaakov Nemoy 17 Jun '09

17 Jun '09

Hey List, I was experimenting a bit with binding RPM in Haskell and i figured i would document the process a bit. The link below sums up from start to finish in tutorial fashion how to write bindings. http://loupgaroublond.blogspot.com/2009/06/haskell-bindings-to-c-from-start… Perhaps would it be possible to include some of this kind of information with C2HS documentation in the future? -Yaakov Nemoy

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ghc does not link after compiling
by Nico Rolle 17 Jun '09

17 Jun '09

hi I wanted to compile my little test programm so it can take advantage of a multicore system. But when i call the compiler with ghc -O2 --make Benchmark.hs -threaded it just produces a acouple of .hi and .o files but no executable. But in the documantation was written that i just need to call ghc like that and it will produce my desired executable. My version of ghc is 6.10.3 regards

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ANNOUNCE: clock 0.1 released
by Cetin Sert 17 Jun '09

17 Jun '09

clock <http://hackage.haskell.org/package/clock> is a library published under a BSD3 license that provides bindings to clock_gettime and clock_getres for monotonic, realtime, processtime and threadtime clocks from time.h <http://www.opengroup.org/onlinepubs/007908799/xsh/time.h.html>. It was implemented in response to a haskell-cafe discussion: http://www.mail-archive.com/haskell-cafe@haskell.org/msg51244.html Any suggestions for improvement, bug-fixes, joint-development offers are most welcome *^o^*!! Cetin Sert

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Android and Haskell
by Vasili I. Galchin 17 Jun '09

17 Jun '09

Hello, I was just reading a Linux Mag article on Android and scripting. The underlying OS is Linux? Python is one of the scripting languages. http://code.google.com/p/android-scripting/ ... Is Python one of the supported languages simply because it (I think) has JVM bindings? My bottom line question is what is preventing Haskell98 from running on "Android" if Python can? Regards, Vasili

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slow code
by brian 17 Jun '09

17 Jun '09

Haskell Gurus, I have tried to use profiling to tell me what's going on here, but it hasn't helped much, probably because I'm not interpreting the results correctly. Empirically I have determined that the show's are pretty slow, so an alternative to them would be helpful. I replaced the show's with "", and compiled with -O2 and not much improvement. I need to write _a lot_ of code in this style. A few words about how best to do this would be helpful. Laziness, infinite lists, uvector ?? Help... Thanks, Brian import Complex import System.IO genData :: Double -> Int -> (Double -> Complex Double) -> ([Double], [Complex Double]) genData tstop n f = let deltat = tstop / (fromIntegral n) t = [ fromIntegral(i) * deltat | i <- [0..n-1]] in (t, map f t) main = do let (t, y) = genData 100.0E-6 (2 ^ 15) (\x -> x :+ 0.0) h <- openFile "data.txt" WriteMode mapM_ (\(x, y) -> do hPutStr h (show t) hPutStr h " " hPutStrLn h (show (realPart y))) (zip t y) hClose h

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