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Building/installing OS X application bundles for GUIs - cabal-macosx
by Andy Gimblett 24 Feb '10

24 Feb '10

Hi all, Last week I quietly released v0.1.0 of cabal-macosx, providing support for building OSX application bundles (e.g. and in particular for GUIs created using wxHaskell and gtk2hs - hence all the cross-posting): http://hackage.haskell.org/package/cabal-macosx I'm now soliciting input on how to handle the install stage, leading (I hope) to a loudly-announcable release soon. :-) The current package provides a post-build hook which creates an application bundle at dist/build/foo.app (for example). It seems to work well. See the source repository for examples. However, running "runghc Setup install" copies the bare executable at dist/build/foo/foo (rather than the foo.app bundle) to the install location, which is no good. So I need to put in some install infrastructure to copy the .app, not the bare executable, to the right place. That raises the question: what is the right place? It seems to me that the defaults are not the right defaults for this case. --global should probably go to /Applications, and --user should perhaps go to ~/ Applications (though I'm less sure about that). Of course, end-users can explicitly set this on a per-install basis, but it seems that for bundles we'd want to override the default. Thus I'm currently asking: * What do people think about the default installation question? * Can anyone advise me on the right way to handle this (installing the .app, and overriding the default locations) with Cabal? I'm hoping I can just tweak part of the LocalBuildInfo and let the default machinery then handle the work, but at present it's not clear to me how to do that, and rather than spend ages trying to figure it out, perhaps someone who knows can help me out? I'm hoping I'm not going to have to completely override the install machinery - that would feel somewhat self-defeating. Many thanks, -Andy -- Andy Gimblett http://gimbo.org.uk/

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Linux ghci vs Windows ghci
by Donghee Nah 24 Feb '10

24 Feb '10

I'm using Windows 7 32bit Host OS(ghc 6.8.3) and Virtualbox Archlinux Guest OS(ghc 6.8.4) I feel that ghci code executing speed in guest os is 1.5~2x faster than host os The code: let t n = do {if n `mod` 100000 == 0 then print n else return ()} >> t (n+1) t 1 any clue?

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Profiling OpenGL applications
by Sönke Hahn 23 Feb '10

23 Feb '10

On Sunday, Andrew Coppin asked: > Is Thread Scope any use for profiling single-threaded programs? I used threadscope to look at eventlogs from a program that uses OpenGL to render multiple frames per second (compiled without "-threaded"). That means, there is CPU activity regularly (multiple times per second), and this can be observed via threadscope and i found it somewhat useful. There are some problems, though: 1. I can't definitely tell, which time span corresponds to CPU activity for the calculations for one frame. Is it possible to generate threadscope bookmarks from within the profiled program? (Or other events that can be shown in threadscope?) 2. The GPU activity cannot be observed. This is not a problem specific to Haskell, though. Is it even possible (with end user hardware) to get something similar to threadscope, not for CPU, but GPU activity? Any other ideas, that might help gathering information, about what's going on on the CPU(s) and the GPU? Many thanks, Sönke

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Parsing of bytestrings with non-String errors?
by Magnus Therning 23 Feb '10

23 Feb '10

I've looked at polyparse and attoparsec and they seem to have in common that the error always is a String. My current ideas for a project would be a lot easier if I could just return some other type, something that I can pattern match on. Is there a parser combinator library out there that works on bytestrings and allows using a custom error type? Or maybe there's some very basic reason why String is so commonly used? /M -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus＠therning．org http://therning.org/magnus identi.ca|twitter: magthe

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Alex Lexer: Trying to get rid of "Alex"
by Amit Deshwar 23 Feb '10

23 Feb '10

Hi Haskell-cafe My problem: I'm trying to obtain the current position of the lexer once it reaches the end of the file (line and row number). I'm trying to do this in a function: getEndPosition = do (a,b,c) <- alexGetInput return a Unfortunately, the type of a is 'Alex AlexPosn' instead of just 'AlexPosn' How do I strip the Alex so I'm left with just a AlexPosn object? Thanks, Amit Deshwar University of Calgary

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grapefruit on windows or osX
by gladstein＠gladstein.com 23 Feb '10

23 Feb '10

I'm unable to get grapefruit going on osx or windows because (I think) I can't get the underlying GTK installed. Most recently I can't install gtk2hs over 6.10.4 because the installer tells me my haskell install isn't working and I should reinstall 6.10.1. It invites me to continue anyway and fix the DLL path myself. I continued and it doesn't work; cabal install grapefruit-ui-gtk still fails because it can't find a version of 'gtk'. The gtk demo program does work. Is the situation impossible, or do I just have to somehow tell something about some path? Hope that's all clear, and thanks in advance.

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Scarry parallel garbage collection behavior (6.12.1, Mac OSX)
by Pavel Perikov 22 Feb '10

22 Feb '10

Hi, list. This is a long post, sorry. The bottom line: specifying +RTS -Nn where n > number of cores slows the program compiled with 6.12.1 by orders of magnitude under Mac OSX. Turning off parallel garbage collections with -qg resolves the problem. Independent verification is appreciated. I have a very simple program: import Control.Parallel main=do let s = s1 `par` ( s2 `pseq` s1 + s2) s1 = sum [1..10000000] s2 = sum [1..10000005] print s compiled with ghc -O -threaded running it with without any options time ./clocktime produces the following times: real 0m3.779s user 0m3.644s sys 0m0.053s Giving -N option to RTS (or -N2, I have two core macbook) shows decent speedup: 100000060000015 real 0m2.678s user 0m4.762s sys 0m0.043s though increase in processor time by 30% seems suspicious. Things become weird if I increase the number of threads. I couldn't expect any further speedup for this task but what I get is absolutely unexpected: time ./clocktime +RTS -N3 100000060000015 real 0m57.071s user 1m40.910s sys 0m0.921s Almost a minute!! Adding more threads does not help either :) time ./clocktime +RTS -N4 100000060000015 real 1m48.281s user 3m10.832s sys 0m1.590s A bit of playing with Instruments/DTrace shows that runaway garbage collection puts the program on its knees. I the case of -N1 the top time consumers look like this: Self % Total % Self Run % Running % # Self # Samples ms Self Run ms Running Parent % Library Source Path Symbol Name 12.8 12.8 408 clocktime __gmpz_add 10.7 10.7 341 clocktime integer_cmm_plusIntegerzh 10 10 321 clocktime allocateLocal etc. This looks absolutely reasonable. Going to -N2 changes the picture to: Self % Total % Self Run % Running % # Self # Samples ms Self Run ms Running Parent % Library Source Path Symbol Name 15.6 15.6 989 clocktime gcWorkerThread 11.6 11.6 736 clocktime waitForGcThreads 9.5 9.5 603 clocktime scavenge_until_all_done 7.4 7.4 471 clocktime setContextSwitches 6.2 6.2 396 clocktime __gmpz_add -N3 Is awful: Self % Total % Self Run % Running % # Self # Samples ms Self Run ms Running Parent % Library Source Path Symbol Name 51.7 51.7 29514 clocktime gcWorkerThread 25.5 25.5 14591 clocktime scavenge_until_all_done 7.2 7.2 4114 clocktime waitForGcThreads 5.5 5.5 3180 clocktime GarbageCollect 5.2 5.2 2998 clocktime setContextSwitches 0.4 0.4 240 clocktime integer_cmm_plusIntegerzh Pavel

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A small oversight
by Andrew Coppin 22 Feb '10

22 Feb '10

I just discovered the highly useful function Data.Function.on. I vaguely recall a few people muttering a couple of years back that this would be a useful thing to have, but I had no idea it was in the standard libraries now. Anyway, while using it, I discovered a small omission from the Haskell libraries: We have min, max, minimum and maximum. We also have minimumBy and maximumBy. But there's no sign of minBy or maxBy. You can do, for example, (min `on` postcode) customer1 customer2 but that gives you the lowest postcode, not the customer to which this postcode belongs. By contrast, minimumBy (compare `on` postcode) [customer1, customer2] gives you the corresponding customer. But it seems silly to have to actually construct a list just for this. So... is there any danger of getting minBy and maxBy added? (I don't actually know off the top of my head where min and max are defined - the Prelude?) Also, constructions like sortBy (compare `on` foo) must surely be very common. Perhaps it would be an idea to define a family of functions like sortOn :: (Ord y) => (x -> y) -> [x] -> [x] sortOn foo = sortBy (compare `on` foo) Just an idea. Finally, take a look at this: newtype SwapOrd x = SwapOrd (unswap_ord :: x) deriving Eq instance Ord x => Ord (SwapOrd x) where compare x y = swap_ord $ compare x y swap_ord :: Ordering -> Ordering swap_ord o = case o of EQ -> EQ GT -> LT LT -> GT Just in case you wanted to sort things in reverse order. I think having swap_ord would be nice if nothing else...

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Pointfree composition for higher arity
by Sean Leather 22 Feb '10

22 Feb '10

I find myself often writing this pattern: someFun x y z = ... fun y z = runFun $ someFun someDefault y z > or, alternatively: fun y = runFun . someFun someDefault y > The second option approaches the ideal pointfreeness (or pointlessness if you prefer), but I'd like to go farther: (...) :: (c -> d) -> (a -> b -> c) -> a -> b -> d > (...) f g x y = f (g x y) > infixr 9 ... > > fun = runFun ... someFun someDefault > There, that's better. More points for fewer points (which means I should really change the name from fun to pun). Does anybody else care about this? What are some alternative solutions? I'd love to have something like this available in the Prelude or a library. (I have no strong feelings about the particular operator.) Regards, Sean

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Re: [Haskell] Functional Programming User Group Ghent
by minh thu 22 Feb '10

22 Feb '10

[moving to café from haskell] 2010/2/21 Jeroen Janssen <jejansse(a)gmail.com>: > Dear all, > We are in the progress of starting up a Functional Programming User Group in > Ghent. The basic idea of the group is to have occasional informal meetings > where people can give talks, where we have invited speakers, where we go to > a bar to chat about all things Functional Programming, to organize Haskell > Hacking events etc. > To see if enough people would be interested in such a group, and to make the > organizing process of the first meeting easier, we would like to ask anyone > interested to tick off the dates he/she is available on the Doodle-page > provided below. Note that the indicated time is only a rough guideline; if > you would prefer another time of day, you can indicate this in the Comments > section of the Doodle. > http://www.doodle.com/xq2i5hsueidwkh2f > If enough people are interested, and a date is decided upon, we will e-mail > the Haskell list once more to confirm the date and give anyone who was > interested, but could not fill in the doodle, a chance to be present. Also, > this ensures that you do not have to leave your e-mail address on Doodle. > If you have any questions, do not hecessitate to contact one of us at either > Bart.Coppens(a)UGent.be > jejansse(a)gmail.com > Kind Regards, > Bart Coppens > Jeroen Janssen Hi Jeroen, Great, a fp user group in Belgium! Alas my dutch is too rusty too even understand the Doodle poll description. Is the group planned only for dutch-speaking programmers ? Cheers, Thu

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