May 2010 - Haskell-Cafe

IORef memory leak
by Jim Snow 15 Oct '10

15 Oct '10

I'm having some trouble with excessive memory use in a program that uses a lot of IORefs. I was able to write a much simpler program which exhibits the same sort of behavior. It appears that "modifyIORef" and "writeIORef" leak memory; perhaps they keep a reference to the old value. I tried both ghc-6.8.3 and ghc-6.10.1. Is this a known limitation, or is this a ghc bug, or am I using IORefs in the wrong way? -jim module Main where import Data.IORef import Control.Monad -- Leaks memory leakcheck1 ior = do go 1000000000 where go 0 = return () go n = do modifyIORef ior (+1) go (n-1) -- Leaks memory leakcheck2 ior = do go 1000000000 where go 0 = return () go n = do x <- readIORef ior writeIORef ior (x+1) go (n-1) -- Runs in constant memory leakcheck3 ior = do go 1000000000 where go 0 = return () go n = do x <- readIORef ior go (n-1) main :: IO () main = do ior <- newIORef 0 leakcheck2 ior compiled with: ghc -O2 --make Leak.hs -o Leak

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cabal problem on OS X
by Bill Atkins 20 Sep '10

20 Sep '10

When I run "cabal update" on my Mac (Snow Leopard, Intel), I get: % cabal update Downloading the latest package list from hackage.haskell.org cabal: Codec.Compression.Zlib: incompatible zlib version Anyone else seeing this? Reinstalling the Haskell Platform hasn't helped. Thanks!

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Re: [Haskell-cafe] iPhone/Android and Haskell [Was: Embedded funcional programming?]
by Liam O'Connor 10 Aug '10

10 Aug '10

Our best bet is to compile to ARM native code and then use the NDK to talk to the Java APIs. Cheers. ~Liam

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ANN: scan-0.1.0.3, a Haskell style scanner
by Christian Maeder 03 Aug '10

03 Aug '10

Dear Haskell friends, I like to announce a Haskell style scanner at http://hackage.haskell.org/package/scan documented under http://projects.haskell.org/style-scanner/ It's best used in conjunction with hlint http://community.haskell.org/~ndm/hlint/ and gives many suggestions regarding the file format. Feedback is welcome. Thanks Christian (Discussions should only be posted to either haskell-cafe@ or beginners@)

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Fwd: [Haskell-cafe] Bytestrings and [Char]
by Alberto G. Corona 18 Jul '10

18 Jul '10

The question can be generalized via type classes: Is there any common set of primitives encapsulated into a single type class that has instances for Strings (Data.List) ByteStrings, Data.Text, Lazy bytestrings, Arrays, vectors and wathever container that can store an boxed, unboxed, packed unpacked sequence of wathever including chars? All of them have folds, heads, tails and a lot of common functions with the same name, but since there is not a single type class, the library programmer can not abstract his code when it is possible, so the library user can chose the particular instance for his particular problem. 2010/3/23 Johann Höchtl <johann.hoechtl(a)gmail.com> On 22.03.2010 14:15, Ivan Miljenovic wrote: > >> On 23 March 2010 00:10, Johan Tibell<johan.tibell(a)gmail.com> wrote: >> >> >>> A sequence of bytes is not the same thing as a sequence of Unicode >>> code points. If you want to replace String by something more efficient >>> have a look at Data.Text. >>> >>> >> Though Data.Text still has the disadvantage of not being as nice to >> deal with as String, since you can't pattern match on it, etc. >> >> Whilst it may degrade performance, treating String as a list of >> characters rather than an array provides you with greater flexibility >> of how to deal with it. >> >> >> > But doesn't this basically mean sacrifice performance / applicability for > algorithmic beauty? Sure, pattern match comes in handy, but in the case of > strings at a high price > > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >

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haskell platform questions
by Warren Harris 12 Jul '10

12 Jul '10

I installed haskell platform some time ago, and now I'm wondering what version I have. How do I find out? Also, when the new one comes along on the 21st, is there a way to upgrade? Or if I must first uninstall the one I have now, how do I uninstall it? Is it recommended to periodically upgrade packages that came with the platform (cabal upgrade), or is it recommended that they be left alone to avoid dependency incompatibilities. Similar question for ghc itself -- can/should it be upgraded in the context of haskell platform? (I was hoping to try Leksah, but it dies without ghc 6.12.1. I seem to have 6.10.4.) Apologies in advance if this is all documented somewhere, but I couldn't find it on the haskell platform site/trac. BTW, I'm on Mac/ Leopard -- love the fact that it didn't take hours to build everything! Warren

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haskell on suse?
by gladstein＠gladstein.com 12 Jul '10

12 Jul '10

I've been spoiled by package managers that download and install everything for you, and I've forgotten how RPM works. In particular, I want to install Haskell on suse, and I read that "RPMs are available from openSUSE. " I followed the link, and found a bunch of folders of folders of RPM files. What exactly should I do to install Haskell? Sorry about the newbicity of this request, but I'm totally stumped. If suse isn't a well-supported platform, I'll switch. Thanks in advance.

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ANN: ForSyDe DSL v3.1
by Seyed Hosein Attarzadeh Niaki 25 Jun '10

25 Jun '10

Dear All, A new version of the ForSyDe DSL is uploaded to the Hackage database. "The ForSyDe (Formal System Design) methodology has been developed with the objective to move system design to a higher level of abstraction and to bridge the abstraction gap by transformational design refinement. This library provides ForSyDe's implementation as a Haskell-embedded Domain Specific Language (DSL). For more information, please see ForSyDe's website: http://www.ict.kth.se/forsyde/." In addition to compatibility with base 4 and GHC 6.10.x, the new version provides more freedom for declaration of process functions (e.g., support for when and let blocks). BR/ Hosein Attarzadeh

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ANN: parameterized-data library v0.1.4
by Seyed Hosein Attarzadeh Niaki 25 Jun '10

25 Jun '10

Dear Haskell developers, A new version of the parameterized-data library providing fixed-sized vectors (based on the type-level library) is pushed into the repository and uploaded to the Hackage database. This is only a minor update to fix the compatibility issues with base 4, GHC>=6.10 and cabal-install (not backward compatible). Bests, Hosein Attarzadeh

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Haskell Weekly News?
by aditya siram 23 Jun '10

23 Jun '10

Hi all, I haven't seen a "Haskell Weekly News" in a while. Is there anything I can do to help? -deech

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