December 2008 - Haskell-Cafe

Re: Haskell-Cafe Digest, Vol 64, Issue 17
by Artyom Shalkhakov 11 Dec '08

11 Dec '08

Hello, 2008/12/10 Ben <midfield(a)gmail.com>: > do you have any plans for iteratee based IO? I would like to use it in XHB (X Haskell Bindings). We use ByteStrings ATM, but I find the code hard to read. > have you seen takusen? Actually, I only took a glance or two. Regards, Artyom Shalkhakov.

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Source code
by Andrew Coppin 10 Dec '08

10 Dec '08

The library documentation pages on Haskell.org used to have helpful links to the library source code. But they don't seem to be there any more. Anybody know why?

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ANNOUNCE: haskell-src-exts 0.4.4
by Niklas Broberg 10 Dec '08

10 Dec '08

Fellow Haskelleers, it is my pleasure to announce the new release of the haskell-src-exts package, version 0.4.4: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/haskell-src-exts… darcs get http://code.haskell.org/HSP/haskell-src-exts The new feature in this release is support for pragmas. haskell-src-exts-0.4.4 supports all pragmas supported by GHC, with the exception of option-level pragmas (LANGUAGE, OPTIONS_GHC etc) that appear before the module header. The reason these are not yet supported is simply time, there's no real difficulty involved in supporting them too and I will surely get there eventually. 0.4.4 is backwards incompatible with 0.4.3 for two constructors: * The Module constructor (:: Module) now has an extra argument of type 'Maybe WarningText', used for deprecated modules. * The ImportDecl constructor (:: ImportDecl) now has an extra argument of type Bool, stating whether the SOURCE pragma has been used for the import. The full list of pragmas supported by 0.4.4 is: SOURCE, RULES, DEPRECATED, WARNING, INLINE, NOINLINE, SPECIALISE, CORE, SCC, GENERATED and UNPACK. Cheers and Happy Haskelling, /Niklas

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Re: Iteratee-based IO and lightweight monadic
by John Lato 10 Dec '08

10 Dec '08

> From: "Artyom Shalkhakov" <artyom.shalkhakov(a)gmail.com> > > Hello, > > Is anybody planning to use these shiny new ways for doing IO? > > I'm also interested in a fair comparison of ByteString/Binary > with iteratee-based IO. Has anybody done this? > I would like to use Iteratee-based IO, and have been doing some experiments with it recently for my problem domain (reading sound files). There has been a discussion recently on the haskell-art list about this specific topic. I posted some timing/memory data, and links to my test code, which you should be able to find in the archives if you're interested. I have found that, with my specific implementations and test case, Iteratee-based IO is slightly slower than the most performant ByteString/Binary code I used, however it uses significantly less memory and has nice composability. Also note that my ByteString-based reader actually reads strict ByteStrings and outputs a stream of UArr Doubles (from the uvector package) using unsafeInterleaveIO rather than using lazy ByteStrings directly. Other implementations made different choices, which I covered in some detail in the mentioned thread. Oleg has recently (after I did my tests) published a small library for reading TIFF files using Iteratees. This new code offers some significant advantages over what I was doing with Iteratees, and may offer performance benefits. More work for me... Unfortunately, neither approach (Iteratee nor ByteString) is yet competitive with hsndfile/libsndfile. However, an Iteratee layer that uses hsndfile to read could be implemented, giving the benefits of the Iteratee approach with high performance. I believe the hsndfile authors are interested in this. It should be very easy to implement.

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Re: [Haskell-cafe] File name encodings
by Don Stewart 10 Dec '08

10 Dec '08

Oh, perhaps you want to 'decode' the string that dirOpenDialog returns. redcom: > Hi Don, > > must be doing something wrong. > > The messed up string originates from calling Graphics.UI.WX.dirOpenDialog > and selecting a directory with Umlauts. > > The encode function doesn't seem to help here as it's too far at the end > of the chain. > > Günther > > Am 10.12.2008, 02:45 Uhr, schrieb Don Stewart <dons(a)galois.com>: > > >redcom: > >>Hi, > >> > >>how can I convert a file name with for example umlauts (ü, ä ... ) into > >>UTF8, or some other format that I can actually use it? > >> > >>Günther > >> > > > >Using the utf8-string package to encode the file name string. > > > > e.g. > > > > x <- readFile (encode "ኃይሌ ገብረሥላሴ") > > > > http://hackage.haskell.org/cgi-bin/hackage-scripts/package/utf8-string > >

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Associated data types
by Eyal Lotem 10 Dec '08

10 Dec '08

If we have associated type synonyms, is there still reason to have associated data types? For example, we can replace: class C b where data D b ... instance C Int where data D Int = D | E with: class C b where type D b ... data DInt = D | E instance C Int where type D Int = DInt Or perhaps allow, for convenience, this form (which would desugar to the above): class C b where type D b ... instance C Int where data D Int = D | E

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Translating RWH into other languages
by Bulat Ziganshin 10 Dec '08

10 Dec '08

Hello Don, There is a team of people which want to translate RWH book into Russian. is it ok? can you help us by establishing "subversion" of RWH book on your site. if it will contain copy of the English book for the beginning and allow team members to further edit it - it will be great! -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com

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Does ghc use Language.Haskell.*?
by Maurício 10 Dec '08

10 Dec '08

Hi, I've just coded a small utility to prettyprint my code, based on Language.Haskell.Parser and friends. Much to my surprise it wasn't able to parse itself, complaining about a non-ASC character (í). Why can ghc read the program, but not the standard library parser? Does ghc use something else? Is it possible to use whatever ghc uses to build a prettyprinter? Thanks, Maurício

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a haskell_proposals subreddit
by Jason Dusek 10 Dec '08

10 Dec '08

There is a subreddit for people to propose libraries: http://www.reddit.com/r/haskell_proposals/ The idea being, that Web 2.0 will help us to allocate our collective talents more efficiently when it comes to extensions (and perhaps clue us in when our pet project is something people really want). -- _jsn

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File name encodings
by Günther Schmidt 09 Dec '08

09 Dec '08

Hi, how can I convert a file name with for example umlauts (ü, ä ... ) into UTF8, or some other format that I can actually use it? Günther -- On a German Win XP

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