December 2011 - Haskell-Cafe

GHC 7.4: Expected behavior or bug?
by Michael Snoyman 27 Dec '11

27 Dec '11

Thanks to Mark Wright for pointing this out[1]. We have the equivalent of the following code in persistent: {-# LANGUAGE MultiParamTypeClasses #-} data Key backend entity = Key class Monad (b m) => Foo b m where func :: b m (Key b m) This code works fine with GHC 7.0, but I get the following message from GHC 7.4: Expecting two more arguments to `b' In the type `b m (Key b m)' In the class declaration for `Foo' Is this expected behavior, or a bug? If the former, what would be a possible workaround? Thanks, Michael [1] https://github.com/yesodweb/persistent/issues/31

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Haskell Platform and Windows - where's 2011.4?
by Steve Horne 27 Dec '11

27 Dec '11

On haskell.org, the 2011.4.0.0 version is shown as the current stable release - but the most recent download link is for the 2011.2.0.0 version. This is bugging me a little because the documentation in the 2011.2 Haskell Platform download for Windows is broken - there's at least one bug report about this already. There's online documentation, but it's (1) online, where I need something I can read on an old no-internet laptop, and (2) I assume for the most recent version, and therefore it potentially misleading. I already fixed the "online" side - sorry, I know slurping a whole site is evil but I had little choice. The fact that the docs relate to a version of the platform that I can't access remains. I just have to hope that the changes are few and won't affect me. Extra annoying - there's no mention of why 2011.4 is missing from the Windows download page - no "temporarily delayed" or "skipped due to an awkward technical issue" or "not enough Windows developers volunteering". For all I know, it could just be an oversight updating haskell.org itself, but I think that's unlikely. So... what's the situation with the Haskell Platform on Windows? - both WRT my specific bit of whinging and whining, and in general? Is Windows a low priority niche from the Haskell POV? If I intend to take Haskell more seriously, do I need to make Linux or some other *nix my primary OS? Please say no - I've been an on-and-off Linux user for around 10 years, with the most recent 2 years on ending around May this year. For all the pros, the cons of endless graphics card driver issues, awkward configuration hassles and so on have defeated me yet again.

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[ANNOUNCEMENT] github 0.1.1
by Mike Burns 27 Dec '11

27 Dec '11

The Github API now has a fancy Haskell library for accessing it, and this library is named: github. http://hackage.haskell.org/package/github https://github.com/mike-burns/github The module structure reflects the Github API v3 documentation. It currently only supports the non-authenticated parts of the API. It does not support a few API endpoints which are documented by Github but which don't work under a command-line curl. I love pull requests, so send 'em!

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ANNOUNCE: hxournal-0.5.0.0 - A pen notetaking
by Greg Weber 27 Dec '11

27 Dec '11

I got the program installed after creating the libstdc++.so symlink. No ink shows up from my drawing though. I am on a Thinkpad X201 Tablet and xournal works. I am glad you are experimenting with window splits. I think the worst part of xournal is it constrains you to a notebook-width piece of paper.

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ANNOUNCE: xournal-convert-0.1
by Ian-Woo Kim 27 Dec '11

27 Dec '11

Hi, all, I have uploaded a utility program xournal-convert which is a command-line utility for changing xournal file format to various other formats. Currently, converting xournal file format (xoj) to several SVG files for each page and index.html for navigating all those pages are implemented. I will support more output formats as I implement. I think that SVG/html support must be useful to some people as it is now. This program depends on xournal-types, xournal-render and xournal-parser libraries which are also used for hxournal program ( a notetaking program written in haskell. similar to xournal) Installation should be simple. Just type > cabal update > cabal install xournal-convert In command line, you can run the program like > xournal-convert makesvg --dest=[destination folder] xojfilename Currently, this program only accepts gunzipped xoj file. For xoj file you generated from xournal program, you need to rename the file as xxx.xoj.gz (xxx is some filename) and gunzip xxx.xoj.gz to make gunzipped xoj format file. For files from hxournal, you can just use the file directly. By this program, you can simply generate static webpages for each xournal file. I personally found this useful for reading my notes on the web. Note: As for hxournal, the current version is 0.6.1.0. It currently supports pdf background and has undo/redo and smoother scrolling (not completed yet though). If you are interested, please try the latest version. Thank you for your interest. Happy holidays. best regards, Ian-Woo Kim

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Re: [Haskell-cafe] If you'd design a Haskell-like language, what would you do different?
by Hans Aberg 26 Dec '11

26 Dec '11

On 26 Dec 2011, at 16:11, AUGER Cédric wrote: >> There is >> http://www.stixfonts.org/ >> For typesetting with Xe[La]TeX or Lua[La]TeX, use XITS (in the >> TeXLive package). >> >>> (And then we'll have to deal with folks trying to use the letter, >>> because everyone knows the Roman alphabet is the only one that >>> matters and of *course* Greek letters are symbol characters.... >>> Pfeh.) >> >> This is the big problem right now: how to enter these symbols >> efficiently. > > Under Xorg, "XCompose" might be your friend! I have a whole bunch of > them for Coq programing. > > Having something like: > > ---------8<--------------------------------------------------------- > # ~/.XCompose contents: > > # the Compose file of the xorg distribution to have a lot > # of useful symbols such as "☭" ^^ > include "/usr/local/lib/X11/locale/en_US.UTF-8/Compose" > # the Compose file that could be included in Haskell distributions > include "/usr/local/share/haskell/Compose" > # other personnal notations > ------->8----------------------------------------------------------- > # /usr/local/share/haskell/Compose contents: > > # maybe to be downloaded via a Hackage cabal package? > # of course "<Multi_key> <H>" should be replaced by a > # user specified combo > <Multi_key> <H> <colon> <colon> : "∷" > <Multi_key> <H> <greater> <greater> <greater> : "⋙" > <Multi_key> <H> <less> <less> <less> : "⋘" > <Multi_key> <H> <less> <minus> <less> : "↢" U2919 > <Multi_key> <H> <greater> <minus> <greater> : "↣" U291A > <Multi_key> <H> <minus> <less> <less> : U291B > <Multi_key> <H> <greater> <greater> <minus> : U291C > <Multi_key> <H> <a> <l> <l> : "∀" > <Multi_key> <H> <e> <x> : "∃" > <Multi_key> <H> <a> <n> <d> : "∧" > <Multi_key> <H> <o> <r> : "∨" > <Multi_key> <H> <a> <b> <s> <t> : "λ" > <Multi_key> <H> <c> <o> <m> <p> : "∘" > <Multi_key> <H> <minus> <greater> : "→" > --------8<---------------------------------------------------------- > > But if you are under Windows, or Mac OS, I cannot tell (as well as I > cannot tell if you are under a POSIX system not running xorg, such as > the tty1..ttyn consoles) On OS X one can make ones owns key maps, like with the program on the link below, but it is very time consuming. Hans http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=ukelele

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Non-exhaustive pattern match warning (incorrect?)
by Michael Orlitzky 26 Dec '11

26 Dec '11

I'm cleaning up some old projects, and hit this: src/Octet.hs:47:27: Warning: Pattern match(es) are non-exhaustive In a record-update construct: Patterns not matched: Octet.None But in the source, I've checked for that case: class Maskable a where apply_mask :: a -> Maskbits -> Bit -> a instance Maskable Octet where apply_mask _ Maskbits.None _ = Octet.None apply_mask Octet.None _ _ = Octet.None apply_mask oct mask bit | mask == Eight = oct | mask == Seven = oct { b8 = bit } -- Line 47 ... | otherwise = Octet.None Am I overlooking something, or did I already match Octet.None?

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[ANNOUNCE] HaskellNet has a new maintainer
by Jonathan Daugherty 26 Dec '11

26 Dec '11

Hi all, I recently took over maintenance duties for the HaskellNet library from its previous maintainer, Robert Wills: http://hackage.haskell.org/package/HaskellNet The codebase has been moved to GitHub: https://github.com/jtdaugherty/HaskellNet So far my focus on HaskellNet has been code cleanup and pruning. Once I'm confident I didn't introduce any silly bugs, I'll do a new release on Hackage. After that, I plan to: - Write protocol tests against scripted installations of popular implementations, such as Dovecot - Split up HaskellNet into SMTP, IMAP, and POP packages So, if you are a HaskellNet user and have an interest in these changes, speak up! In addition, if you are interested in maintaining one or more of the resulting smaller packages (especially POP), let me know! Thanks, -- Jonathan Daugherty

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Re: [Haskell-cafe] If you'd design a Haskell-like language, what would you do different?
by Hans Aberg 26 Dec '11

26 Dec '11

On 26 Dec 2011, at 19:29, AUGER Cédric wrote: > Le Mon, 26 Dec 2011 18:20:55 +0100, > Hans Aberg <haberg-1(a)telia.com> a écrit : > >> On 26 Dec 2011, at 16:11, AUGER Cédric wrote: >> >>> Under Xorg, "XCompose" might be your friend! I have a whole bunch of >>> them for Coq programing. >>> >>> Having something like: >>> >>> ---------8<--------------------------------------------------------- >>> # ~/.XCompose contents: >>> >>> # the Compose file of the xorg distribution to have a lot >>> # of useful symbols such as "☭" ^^ >>> include "/usr/local/lib/X11/locale/en_US.UTF-8/Compose" >>> # the Compose file that could be included in Haskell distributions >>> include "/usr/local/share/haskell/Compose" >>> # other personnal notations >>> ------->8----------------------------------------------------------- >>> # /usr/local/share/haskell/Compose contents: >>> >>> # maybe to be downloaded via a Hackage cabal package? >>> # of course "<Multi_key> <H>" should be replaced by a >>> # user specified combo >>> <Multi_key> <H> <colon> <colon> : "∷" >>> <Multi_key> <H> <greater> <greater> <greater> : "⋙" >>> <Multi_key> <H> <less> <less> <less> : "⋘" >>> <Multi_key> <H> <less> <minus> <less> : "↢" U2919 >>> <Multi_key> <H> <greater> <minus> <greater> : "↣" U291A >>> <Multi_key> <H> <minus> <less> <less> : U291B >>> <Multi_key> <H> <greater> <greater> <minus> : U291C >>> <Multi_key> <H> <a> <l> <l> : "∀" >>> <Multi_key> <H> <e> <x> : "∃" >>> <Multi_key> <H> <a> <n> <d> : "∧" >>> <Multi_key> <H> <o> <r> : "∨" >>> <Multi_key> <H> <a> <b> <s> <t> : "λ" >>> <Multi_key> <H> <c> <o> <m> <p> : "∘" >>> <Multi_key> <H> <minus> <greater> : "→" >>> --------8<---------------------------------------------------------- >>> >>> But if you are under Windows, or Mac OS, I cannot tell (as well as I >>> cannot tell if you are under a POSIX system not running xorg, such >>> as the tty1..ttyn consoles) >> >> On OS X one can make ones owns key maps, like with the program on the >> link below, but it is very time consuming. >> http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=ukelele >> > I have heard of ukelele (but I didn't remembered the name as I am not > a Mac OS user); I have heard it was a rather dirty solution, but that > should work. I think so, too. > I guess that having a Haskell (or any script language by > the way) patching the xml file (and able to "unpatch" if we want to > uninstall) and make possible to get that patch via Hackage could be a > solution (it would be time consuming for the patch writer, but then > any Mac OS user would benefit it). > > Of course it would only work for the basic Haskell notations, for > custom ones, I guess it would be interesting to have a program which > reads a "XCompose like" file (which is quite easy to edit) and generate > the xml file for ukelele. > > Note that the rest of the Haskell cafe mailing list won't be able to > read my response since it seems that I cannot post on the list (I > subscribed 2 years ago and never posted; waiting to learn and Haskell > and then read the mailing list, but I learnt Haskell only about one > month ago). If one had a way to replace ASCII multicharacter symbols, that might be easier. Hans

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parListChunk problem
by Burak Ekici 26 Dec '11

26 Dec '11

Hi there, I was not able to parallelize the below code by "parListChunk" strategy. Actually, code works fine without ant mistake in the result but no improvement in the performance handled. Threadscope demonstrates that parallelization happens after the sequential run of the program which is meaningless. In short, parListChunk is not working as intended. As far as I know, it should divide an arbitrarily given list into its chunks and then apply the given function to each sub-list (chunk) in parallel with reducing the evaluation of each element of each chunk into head normal form, if you use "rdeepseq" as the input strategy. In the below code, I want to divide the given list into 2000 chunks and then apply "ersa" function to each chunk in parallel with evaluating each element into its head normal form in serial internally. However, as I wrote, it first runs in serial after than the parallel scenario I admire to happen at the beginning happens. How can I solve this problem? Thanks in advance, Burak. ersa :: RSAPublicKey -> [Integer] -> [Integer] ersa (PUB n e) (x:xs) = ersa (PUB n e) (xs) ++ [expm n x e] ersa (PUB n e) [] = [] splitToEnc :: RSAPublicKey -> [Integer] -> [Integer] splitToEnc (PUB n e) [] = [] splitToEnc (PUB n e) (x:xs) = (ersa (PUB n e) (x:xs)) `using` parListChunk 2000 rdeepseq

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