- Haskell-Cafe - Haskell.org

xmonad install problem
by Никитин Лев 31 Oct '13

31 Oct '13

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Call for Contributions - Haskell Communities and Activities Report, November 2013 edition
by Janis Voigtlaender 31 Oct '13

31 Oct '13

[Transition in editorship of HCAR in progress!] Dear all, We would like to collect contributions for the 25th edition of the ================================================================ Haskell Communities & Activities Report http://www.haskell.org/haskellwiki/Haskell_Communities_and_Activities_Report Submission deadline: 1 Nov 2013 (please send your contributions to hcar at haskell.org, in plain text or LaTeX format) ================================================================ This is the short story: * If you are working on any project that is in some way related to Haskell, please write a short entry and submit it. Even if the project is very small or unfinished or you think it is not important enough --- please reconsider and submit an entry anyway! * If you are interested in an existing project related to Haskell that has not previously been mentioned in the HCAR, please tell us, so that we can contact the project leaders and ask them to submit an entry. * Feel free to pass on this call for contributions to others that might be interested. More detailed information: The Haskell Communities & Activities Report is a bi-annual overview of the state of Haskell as well as Haskell-related projects over the last, and possibly the upcoming six months. If you have only recently been exposed to Haskell, it might be a good idea to browse the previous edition --- you will find interesting projects described as well as several starting points and links that may provide answers to many questions. Contributions will be collected until the submission deadline. They will then be compiled into a coherent report that is published online as soon as it is ready. As always, this is a great opportunity to update your webpages, make new releases, announce or even start new projects, or to talk about developments you want every Haskeller to know about! Looking forward to your contributions, Mihai Maruseac and Janis Voigtlaender (for this edition) FAQ: Q: What format should I write in? A: The required format is a LaTeX source file, adhering to the template that is available at: http://haskell.org/communities/11-2013/template.tex There is also a LaTeX style file at http://haskell.org/communities/11-2013/hcar.sty that you can use to preview your entry. If you do not know LaTeX, then use plain text. If you modify an old entry that you have written for an earlier edition of the report, you should soon receive your old entry as a template (provided we have your valid email address). Please modify that template, rather than using your own version of the old entry as a template. Q: Can I include Haskell code? A: Yes. Please use lhs2tex syntax (http://www.andres-loeh.de/lhs2tex/) The report is compiled in mode polycode.fmt. Q: Can I include images? A: Yes, you are even encouraged to do so. Please use .jpg format, then. Q: Should I send files in .zip archives or similar? A: No, plain file attachements are the way. Q: How much should I write? A: Authors are asked to limit entries to about one column of text. A general introduction is helpful. Apart from that, you should focus on recent or upcoming developments. Pointers to online content can be given for more comprehensive or "historic" overviews of a project. Images do not count towards the length limit, so you may want to use this opportunity to pep up entries. There is no minimum length of an entry! The report aims for being as complete as possible, so please consider writing an entry, even if it is only a few lines long. Q: Which topics are relevant? A: All topics which are related to Haskell in some way are relevant. We usually had reports from users of Haskell (private, academic, or commercial), from authors or contributors to projects related to Haskell, from people working on the Haskell language, libraries, on language extensions or variants. We also like reports about distributions of Haskell software, Haskell infrastructure, books and tutorials on Haskell. Reports on past and upcoming events related to Haskell are also relevant. Finally, there might be new topics we do not even think about. As a rule of thumb: if in doubt, then it probably is relevant and has a place in the HCAR. You can also simply ask us. Q: Is unfinished work relevant? Are ideas for projects relevant? A: Yes! You can use the HCAR to talk about projects you are currently working on. You can use it to look for other developers that might help you. Q: If I do not update my entry, but want to keep it in the report, what should I do? A: Tell us that there are no changes. The old entry will typically be reused in this case, but it might be dropped if it is older than a year, to give more room and more attention to projects that change a lot. Do not resend complete entries if you have not changed them. Q: Will I get confirmation if I send an entry? How do I know whether my email has even reached its destination, and not ended up in a spam folder? A: Prior to publication of the final report, we will send a draft to all contributors, for possible corrections. So if you do not hear from us within two weeks after the deadline, it is safer to send another mail and check whether your first one was received.

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ANNOUNCE: urembed-0.5.0.1 urxml-0.2.0.0
by Sergey Mironov 31 Oct '13

31 Oct '13

Hello. I'm glad to announce the release of Ur/Web[1] helper applications: urembed-0.5.0.1 and urxml-0.2.0.0 Ur is a programming language in the tradition of ML and Haskell, but featuring a significantly richer type system. Ur is functional, pure, statically-typed, and strict. Ur supports a powerful kind of metaprogramming based on row types. Ur/Web is Ur plus a special standard library and associated rules for parsing and optimization. Ur/Web supports construction of dynamic web applications backed by SQL databases. Uermbed and urxml are aimed at making Ur/Web development more pleasant. * Urembed https://github.com/grwlf/urembed Urembed embeds file or files into the Ur/Web project by generating the module which provides the programmer with functions serving the specified file as a binary. This way Ur/Web application no longer requires standalone webserver for serving static content. Also, Urembed supports generating JavaScript FFI signatures for *js files. https://github.com/grwlf/uru project uses urembed and may illustrate it's abilities. * UrXML https://github.com/grwlf/urxml UrXML is yet another XML parser/pretty-printer application. This time, it supports ur/web syntax extensions of XML. One can integrate this tool with VIM editor to indent XML parts of non-XML files like Ur/Web sources. Please, read README.md for the details. Regards, Sergey [1] - http://www.impredicative.com/ur/

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ICFP 2014: Call for Workshop & Co-located Event Proposals
by David Van Horn 30 Oct '13

30 Oct '13

CALL FOR WORKSHOP AND CO-LOCATED EVENT PROPOSALS ICFP 2014 19th ACM SIGPLAN International Conference on Functional Programming August 31 – September 6, 2014 Gothenburg, Sweden http://icfpconference.org/icfp2014/ The 19th ACM SIGPLAN International Conference on Functional Programming will be held in Gothenburg, Sweden on August 31-September 6, 2014. ICFP provides a forum for researchers and developers to hear about the latest work on the design, implementations, principles, and uses of functional programming. Proposals are invited for workshops (and other co-located events, such as tutorials) to be affiliated with ICFP 2014 and sponsored by SIGPLAN. These events should be less formal and more focused than ICFP itself, include sessions that enable interaction among the attendees, and foster the exchange of new ideas. The preference is for one-day events, but other schedules can also be considered. The workshops are scheduled to occur on August 31 (the day before ICFP) and September 4-6 (the three days after ICFP). ---------------------------------------------------------------------- Submission details Deadline for submission: November 15, 2013 Notification of acceptance: December 15, 2013 Prospective organizers of workshops or other co-located events are invited to submit a completed workshop proposal form in plain text format to the ICFP 2014 workshop co-chairs (Sam Tobin-Hochstadt and Tom Schrijvers), via email to icfp2014-workshops(a)ugent.be by November 15, 2013. (For proposals of co-located events other than workshops, please fill in the workshop proposal form and just leave blank any sections that do not apply.) Please note that this is a firm deadline. Organizers will be notified if their event proposal is accepted by December 15, 2013, and if successful, depending on the event, they will be asked to produce a final report after the event has taken place that is suitable for publication in SIGPLAN Notices. The proposal form is available at: http://www.icfpconference.org/icfp2014/icfp14-workshops-form.txt Further information about SIGPLAN sponsorship is available at: http://acm.org/sigplan/sigplan_workshop_proposal.htm ---------------------------------------------------------------------- Selection committee The proposals will be evaluated by a committee comprising the following members of the ICFP 2014 organizing committee, together with the members of the SIGPLAN executive committee. Workshop Co-Chair: Sam Tobin-Hochstadt (Indiana University) Workshop Co-Chair: Tom Schrijvers (Ghent University) General Chair : Johan Jeuring (Utrecht University) Program Chair: Manuel Chakravarty (University of New South Wales) ---------------------------------------------------------------------- Further information Any queries should be addressed to the workshop co-chairs (Sam Tobin-Hochstadt and Tom Schrijvers), via email to icfp2014-workshops(a)ugent.be.

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Re: [Haskell-cafe] interfacing TradeKing API
by Donn Cave 30 Oct '13

30 Oct '13

I worked up a little application for Etrade's API, which is at least the same basic idea. This was some time ago and memory is pretty fuzzy, but ... I see that for some reason I modified hoauth Consumer.hs, replacing showURL with a path-to-text function I wrote myself, and I use my own version of the signRq function from that module that returns an unpacked request value. I'm sure it would be much more helpful to say what problems I was to solving there, sorry! Authentication was the hard part, naturally. Donn

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liftN
by Wvv 30 Oct '13

30 Oct '13

I try to write a function "liftN", but I'm not satisfied with result. lift :: (MonadTrans t) => Monad m => m a -> t m a liftN n | n < 1 = error "liftN: n<1" | n == 1 = lift | otherwise = lift . (liftN (n-1)) 1) I know(?), that it is impossible to write liftN now: typechecker can't decide which signature it is. 2) Main reason is finite recursive constraint 3) Let's think, it is possible to write Main candidates: promoted data and data-kinds For example, lift . lift . lift :: (Monad (t1 (t2 m)), Monad (t2 m), Monad m, MonadTrans t, MonadTrans t1, MonadTrans t2) => m a -> t (t1 (t2 m)) a My best solution looks like: data MT = M | T Int MT liftN :: forall tm. ( forall x n. Monad 'M, Monad (x :: MT), MonadTrans ('T n), ) => Int -> 'M a -> ('T 0) (tm :: MT) a liftN n | n < 1 = error "liftN: n < 1" | n == 1 = lift | otherwise = lift . (liftN (n-1)) Am I miss something? I think this function could look much prettier. But I don't know how. -- View this message in context: http://haskell.1045720.n5.nabble.com/liftN-tp5738612.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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interfacing TradeKing API
by Miro Karpis 30 Oct '13

30 Oct '13

Hi, did anybody tried to interface TradeKing API? (couldn't find anything on web) Cheers, m.

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fcntl locks, executeFile and threaded runtime
by diego souza 30 Oct '13

30 Oct '13

Hi, I'm having problems with executeFile as it seems to clear the advisory locks using the threaded runtime. Consider the following snippet (a simplification of what I'm doing): import System.IO import Control.Monad import System.Posix.IO import Control.Concurrent import System.Posix.Files import System.Posix.Process main = do let lock = (WriteLock, AbsoluteSeek, 0, 0) fd <- openFd "/tmp/foobar" ReadWrite (Just stdFileMode) defaultFileFlags {trunc=True} pid <- forkProcess $ do setLock fd lock >> putStrLn "child: ok" executeFile "/usr/bin/sleep" False ["5"] Nothing threadDelay $ 1 * 1000 * 1000 setLock fd lock >> putStrLn "parent: fail!" void $ getProcessStatus True False pid Then I consistentlty get these results: $ ghc -threaded --make test.hs; ./test child: ok parent: fail! $ ghc -rtsopts --make test.hs; ./test child: ok test: setLock: resource exhausted (Resource temporarily unavailable) Any pointers? At first I though it might be an issue with the unix package but that doesn't seem to be the case. $ ghc-pkg list | grep unix unix-2.6.0.1 $ ./test +RTS --info [("GHC RTS", "YES") ,("GHC version", "7.6.3") ,("RTS way", "rts_thr") ,("Build platform", "x86_64-unknown-linux") ,("Build architecture", "x86_64") ,("Build OS", "linux") ,("Build vendor", "unknown") ,("Host platform", "x86_64-unknown-linux") ,("Host architecture", "x86_64") ,("Host OS", "linux") ,("Host vendor", "unknown") ,("Target platform", "x86_64-unknown-linux") ,("Target architecture", "x86_64") ,("Target OS", "linux") ,("Target vendor", "unknown") ,("Word size", "64") ,("Compiler unregisterised", "NO") ,("Tables next to code", "YES") ] Thanks! ~dsouza

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ANNOUNCE: lens-family 1.0.0
by roconnor＠theorem.ca 30 Oct '13

30 Oct '13

Before there was lens there was lens-family.... I'm pleased to announce the second major release of the lens-family pacakges: lens-family-core-1.0.0 and lens-family-1.0.0. They can be found at * <http://hackage.haskell.org/package/lens-family-core> * <http://hackage.haskell.org/package/lens-family> I consider these packages to be kiddie-pool sized lens libraries for those people who are, for whatever reason, too intimidated by the lens library. I think this is a good way to get one's feet wet with lenses. The type for lenses and traversals are completely compatible with the lens library. This release brings two major developments to lens-family: * Support for traversals and folds. * The names have been all renamed to be mostly compatible with the lexicon developed by lens. With a common lexicon, I hope that users will find it easy to transition from lens-family to lens when they outgrow the kiddie pool. The lens-family-core package is a completely Haskell 98 package for those who need the compatibility. The lens-family package is a wrapper around lens-family-core that provides a few useful Rank 2 type synonyms to make using functional references a little easier. P.S. If edwardk is reading, I've used Ryan Ingram's definition from <http://twanvl.nl/blog/haskell/cps-functional-references#comment-comment0> to implement alongside so that it works for both lenses and getters. You probably want to do the same. -- Russell O'Connor <http://r6.ca/> ``All talk about `theft,''' the general counsel of the American Graphophone Company wrote, ``is the merest claptrap, for there exists no property in ideas musical, literary or artistic, except as defined by statute.''

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Unwanted http-conduit buffering of chunked request body?
by Manuel Gómez 30 Oct '13

30 Oct '13

Hi list, I’ve been playing with http-conduit in an attempt to do some manual testing on a HTTP service, and I ran into something I had not expected. I was trying to set up a POST request with a chunked request body from a conduit. The following code does work: > {-# LANGUAGE OverloadedStrings #-} > > import Blaze.ByteString.Builder.ByteString (fromByteString) > import Control.Concurrent (threadDelay) > import Control.Monad.IO.Class (liftIO) > import Control.Monad.Trans.Resource (runResourceT) > import Data.ByteString (getLine) > import Data.Conduit (yield) > import Network.HTTP.Conduit (RequestBody(RequestBodySourceChunked), http, method, parseUrl, rawBody, requestBody, withManager) > > source = do say "a"; wait; say "b"; wait; say "c" > > wait = liftIO $ threadDelay 1000000 > say = yield . fromByteString > > main = runResourceT $ do > req <- parseUrl "http://localhost:12345/" > withManager $ http req > { method = "POST" > , requestBody = RequestBodySourceChunked source > } The important part is the `source` conduit: it yields a string, waits for a bit, yields another, waits for a bit, and yields again. I expected this to send chunks as soon as the source yielded them. However, it seems to be sending all the chunks together at the end, when the source finishes. Doing the same thing without `wait`, and with `forever` as opposed to just sending three bits of string, seems to work closer to my expectations: it seems to buffer for a bit, then it sends what was buffered, then it buffers some more, and so on. Is this http-conduit or Blaze doing undesired buffering? A quick run on `strace` seems to indicate it’s only doing the `send` system call every once in a while, so the buffering seems to be happening inside Haskell. I’m not even sure this is how the HTTP chunked transfer encoding is meant to be used — my actual use case has to do with sending potentially large files and hopefully using constant memory at the other end, but I’m also curious about using this to send asynchronous events and such. Is this how it’s supposed to work?

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