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HPC and Template Haskell (GHC 7.8.3, Yesod)
by David Turner 19 Dec '14

19 Dec '14

Hi, I'm having trouble making a HPC build of a Yesod application. It fails with: /usr/bin/ld: dist/build/StreamReading/Config.dyn_o: relocation R_X86_64_PC32 against undefined symbol `_hpc_tickboxes_tracszmenterprisezm0zi0zi0_Settings_hpc' can not be used when making a shared object; recompile with -fPIC I've narrowed it down to a call to ghc and posted the output in all its gory detail at http://lpaste.net/116872 if that's any help. Of note is that dist/build/Settings.dyn_o is unexpectedly missing from the list of parameters to the last call to gcc, and the missing symbol is defined in the same. There are, in fact, quite a number of missing .dyn_o files in that list. Slightly weirdly, when I run the same command line again, it seems to work. At least, there are no errors reported and the exit code is 0. Any ideas? Cheers, David

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Hackage 2 archive.tar equivalent
by Alexander Solla 19 Dec '14

19 Dec '14

On the old hackage site (running Hackage 1.*), we used to be able to download a file called archive.tar, which contained the latest version of all of the Haskell packages. Is there any way to do this with Hackage 2? I understand that my case is definitely a corner case -- I don't have a regular net connection, so I'd really like to be able to download a snapshot of Hackage at regular, convenient intervals, and serve them up at home.

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[TFP 2015] 1st call for papers
by Peter Achten 19 Dec '14

19 Dec '14

----------------------------- C A L L F O R P A P E R S ----------------------------- ======== TFP 2015 =========== 16th Symposium on Trends in Functional Programming June 3-5, 2015 Inria Sophia Antipolis, France http://tfp2015.inria.fr/ The symposium on Trends in Functional Programming (TFP) is an international forum for researchers with interests in all aspects of functional programming, taking a broad view of current and future trends in the area. It aspires to be a lively environment for presenting the latest research results, and other contributions (see below). Authors of draft papers will be invited to submit revised papers based on the feedback receive at the symposium. A post-symposium refereeing process will then select a subset of these articles for formal publication. The selected revised papers are expected to be published as a Springer Lecture Notes in Computer Science (LNCS) volume. TFP 2015 will be the main event of a pair of functional programming events. TFP 2015 will be accompanied by the International Workshop on Trends in Functional Programming in Education (TFPIE), which will take place on June 2nd. The TFP symposium is the heir of the successful series of Scottish Functional Programming Workshops. Previous TFP symposia were held in * Edinburgh (Scotland) in 2003; * Munich (Germany) in 2004; * Tallinn (Estonia) in 2005; * Nottingham (UK) in 2006; * New York (USA) in 2007; * Nijmegen (The Netherlands) in 2008; * Komarno (Slovakia) in 2009; * Oklahoma (USA) in 2010; * Madrid (Spain) in 2011; * St. Andrews (UK) in 2012; * Provo (Utah, USA) in 2013; * and in Soesterberg (The Netherlands) in 2014. For further general information about TFP please see the TFP homepage. (http://www.tifp.org/) == INVITED SPEAKERS == TFP is pleased to announce talks by the following two invited speakers: * Laurence Rideau is a researcher at INRIA and is interested in the semantics of programming languages , the formal methods, and the verification tools for programs and mathematical proofs. She participated in the beginnings of the Compcert project (certified compiler), and is part of the Component Mathematical team in the MSR-INRIA joint laboratory, who performed the formalization of the Feit-Thompson theorem successfully. Thirty years ago, computers barged in mathematics with the famous proof of the Four Color Theorem. Initially limited to simple calculation, their role is now expanding to the reasoning whose complexity is beyond the capabilities of most humans, as the proof of the classification of finite simple groups. We present our large collaborative adventure around the formalization of the Feit-Thompson theorem (http://en.wikipedia.org/wiki/Feit%E2%80%93Thompson_theorem) that is a first step to the classification of finite groups and that uses a palette of methods and techniques that range from formal logic to software (and mathematics) engineering. * Sam Aaron (?) == SCOPE == The symposium recognizes that new trends may arise through various routes. As part of the Symposium's focus on trends we therefore identify the following five article categories. High-quality articles are solicited in any of these categories: Research Articles: leading-edge, previously unpublished research work Position Articles: on what new trends should or should not be Project Articles: descriptions of recently started new projects Evaluation Articles: what lessons can be drawn from a finished project Overview Articles: summarizing work with respect to a trendy subject Articles must be original and not simultaneously submitted for publication to any other forum. They may consider any aspect of functional programming: theoretical, implementation-oriented, or experience-oriented. Applications of functional programming techniques to other languages are also within the scope of the symposium. Topics suitable for the symposium include: Functional programming and multicore/manycore computing Functional programming in the cloud High performance functional computing Extra-functional (behavioural) properties of functional programs Dependently typed functional programming Validation and verification of functional programs Debugging and profiling for functional languages Functional programming in different application areas: security, mobility, telecommunications applications, embedded systems, global computing, grids, etc. Interoperability with imperative programming languages Novel memory management techniques Program analysis and transformation techniques Empirical performance studies Abstract/virtual machines and compilers for functional languages (Embedded) domain specific languages New implementation strategies Any new emerging trend in the functional programming area If you are in doubt on whether your article is within the scope of TFP, please contact the TFP 2015 program chair, Manuel Serrano. == BEST PAPER AWARDS == To reward excellent contributions, TFP awards a prize for the best paper accepted for the formal proceedings. TFP traditionally pays special attention to research students, acknowledging that students are almost by definition part of new subject trends. A student paper is one for which the authors state that the paper is mainly the work of students, the students are listed as first authors, and a student would present the paper. A prize for the best student paper is awarded each year. In both cases, it is the PC of TFP that awards the prize. In case the best paper happens to be a student paper, that paper will then receive both prizes. == SPONSORS == TFP is financially supported by ?????????????????? == PAPER SUBMISSIONS == Acceptance of articles for presentation at the symposium is based on a lightweight peer review process of extended abstracts (4 to 10 pages in length) or full papers (20 pages). The submission must clearly indicate which category it belongs to: research, position, project, evaluation, or overview paper. It should also indicate which authors are research students, and whether the main author(s) are students. A draft paper for which ALL authors are students will receive additional feedback by one of the PC members shortly after the symposium has taken place. We use EasyChair for the refereeing process. Papers must be submitted at: https://easychair.org/conferences/?conf=tfp2015 Papers must be written in English, and written using the LNCS style. For more information about formatting please consult the Springer LNCS web site: http://www.springer.com/computer/lncs?SGWID=0-164-6-793341-0 == IMPORTANT DATES == Submission of draft papers: March 17, 2015 Notification: March 24, 2015 Registration: April 7, 2015 TFP Symposium: June 3-5, 2015 Student papers feedback: June 9, 2015 Submission for formal review: July 1, 2015 Notification of acceptance: September 8, 2015 Camera ready paper: October 8, 2015 == PROGRAM COMMITTEE == Janis Voigtländer University of Bonn, DE Scott Owens University of Kent, UK Neil Sculthorpe Swansea University, UK Colin Runciman University of York, UK Manuel Serrano Inria (PC chair), FR Rinus Plasmeijer University of Nijmegen, NL Tomas Petricek University of Cambridge, UK Marco T. Morazan Seton Hall University, USA Wolfgang De Meuter Vrije Universiteit Brussel, BE Michel Mauny Ensta ParisTech, FR Sam Lindley The University of Edinburgh, UK Daan Leijen Microsoft, USA Jurriaan Hage Utrecht University, NL Andy Gill University of Kansas, USA Thomas Gazagnaire University of Cambrige, UK Lars-Ake Fredlund Universidad Politécnica de Madrid, ES Jean-Christophe Filliatre Université Paris Sud Orsay, FR Marc Feeley Université de Montréal, CA Olaf Chitil University of Kent, UK Edwin Brady University of St Andrews, UK

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GHC Heap Profiler time axis
by Anton Dessiatov 19 Dec '14

19 Dec '14

Hello, Haskell-Cafe! For the last 2 days I’m debugging something that looks like a space leak. My program is a rather long-running network service. When I first used heap profiler I was a bit confused with its output that showed that my program was running for only about 0.3-0.4 seconds when I launched it idling for about a minute. That was confusing enough for me to dig into GHC sources trying to figure out the reason behind this and I found that values of the sample times are taken from the mut_user_time function, which returns a time that process spent in user-mode code (outside the kernel) minus time spent on garbage collection. This introduces great amount of unpredictable non-linearity of the heap profile graph x axis, which I personally consider very counterintuitive. So my question is does anybody know why is it done this way? Wouldn’t it be better if x axis would just show a time elapsed since the process started? Kind regards, Anton.

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Re: [Haskell-cafe] cabal-install on openbsd
by Ramakrishnan Muthukrishnan 19 Dec '14

19 Dec '14

On Fri, Dec 19, 2014, at 03:47 PM, Gusoi Constantin - Codrut wrote: > I have the same problem on Ubunutu 14.04, what you need to do is to > use more RAM / SWAP. I have 1 GB of swap. I still get the error. The allocation error is for 1 MegaByte (1048576 bytes). That's what make me really surprised. May be it runs out of memory and fails when it cannot allocate one more megabyte of memory? Ramakrishnan

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cabal-install on openbsd
by Ramakrishnan Muthukrishnan 19 Dec '14

19 Dec '14

Hi, I have a new OpenBSD 5.6 installation on AMD64. The OpenBSD package collection has ghc 7.6.3 and Cabal-install 1.16.0.2. After installing them, I attempted to install a new version of cabal-install using the packaged cabal-install by doing `cabal install cabal-install'. But I get a "ghc: out of memory (requested 1048576 bytes)" error while it is compiling cabal-install 1.20.0.3. I have a ticket created against ghc but I wonder if it is a bug with ghc or cabal-install or OpenBSD or something else. Anyway.. the ticket is here [1]. I can help debug the problem on my OpenBSD box. Thanks Ramakrishnan [1] <https://ghc.haskell.org/trac/ghc/ticket/9904>

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Re: [Haskell-cafe] Typed TH
by oleg＠okmij.org 19 Dec '14

19 Dec '14

Typed meta-programming has a very rich history. For a good overview of various approaches and main problems, please see the Related work section of the following paper http://okmij.org/ftp/tagless-final/TaglessStaged/beyond-journal.pdf There is a special subsection on Typed TH. (The version of that paper with minor revisions will be uploaded in two-three months). The main problems are how to ensure hygiene in the presence of effects, and how to generate polymorphic bindings (let-bindings). Both problems have been essentially solved. (The solution to the second problem has been presented at small meetings so far). The paper explains the combinator library to generate TH code that is ensured to be well-typed, *by construction*. The library permits arbitrary monadic effects. There is no Q monad since it turns out not necessary.

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gracefully invoking `less` using System.Process (and ignoring ctrl-c)
by Guillaume Hoffmann 19 Dec '14

19 Dec '14

Hi, I'm looking at a bug that we should fix for the 2.10 release of darcs. I'd like to make the invocation of the pager (most of the time `less`) as identical to git as possible. Currently darcs has a workaround for the "resource vanished (broken pipe)" problem (that happens when you leave `less` before all of the text has been read by it). The workaround involves creating a temporary file and then passing it to less [1]. This works but it's slow (for big inputs) and ugly IMO. I have a fix proposal [2] that is made of two changes: * use System.Process.createProcess (just to update the code), and * in the "ortryrunning" function (that chains attempts at calling various pagers until one works), ignoring IOError's of the kind ResourceVanished (otherwise we would invoke every pager in the chain if we quit them before they read all their input) The problem is that pressing CTRL-C in `less` now kills everything (darcs+less). Is there a way to fix this? Note that the darcs executable runs inside of the function withSignalHandled [3], which defines its behaviour with respect to various signals. Guillaume [1] http://hub.darcs.net/darcs/darcs-reviewed/browse/src/Darcs/UI/External.hs#4… [2] http://hub.darcs.net/gh/darcs-screened_1/patch/20141210002305-5ef8f [3] http://hub.darcs.net/darcs/darcs-reviewed/browse/src/Darcs/Util/SignalHandl…

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Dockerfile for Yesod
by Jonathan Paugh 18 Dec '14

18 Dec '14

Greetings, all I'm brand new to Docker, and struggled to find resources specific to Yesod. So, once I managed to piece together a Dockerfile, I decided to share it. Hope it helps someone. The Dockerfile is pasted at the bottom. It can be used by dropping it in your Yesod application directory, and replacing "app" with the name of your app. If you're new to Docker like I was, cd to your Yesod app dir, and run $ docker build --tag app-image . $ docker run -d -p 3000:3000 app-image to get started. Your web app should now be available at http://localhost:3000 NB: The approot setting can make a profound and confusing difference if it is mis-configured. I recommend temporarily setting approot to "" so that it will use absolute (site-relative) urls instead of fully specified ones. Happy Holidays, Jon Dockerfile ----------- FROM haskell:7.8 RUN cabal update RUN apt-get update && apt-get install -y libpq5 libpq-dev ADD ./app.cabal /opt/app/app.cabal WORKDIR /opt/app RUN cabal sandbox init RUN cabal install --only-dependencies --max-backjumps=-1 --reorder-goals -j ADD . /opt/app RUN cabal build RUN dist/build/db-import/db-import ENV PATH /opt/app/.cabal-sandbox/bin:$PATH EXPOSE 3000 CMD ["/opt/app/dist/build/app/app", "production", "-p", "3000"]

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Missing `$` like operators in Haskell
by Clinton Mead 18 Dec '14

18 Dec '14

Below are the `$` like operators in Haskell (view in fixed width): --------------------------------------------------------------------- | Function first | Op | Function second | Op | ------------------------------------------------------------------------------- | Plain | (a -> b) -> a -> b | $ | a -> (a -> b) -> b | | | Functor | (a -> b) -> f a -> f b | <$> | f a -> (a -> b) -> f b | | | Applicat| f (a -> b) -> f a -> f b | <*> | f a -> f (a -> b) -> f b | <**> | | Monad | (a -> m b) -> m a -> m b | =<< | m a -> (a -> m b) -> m b | >>= | ------------------------------------------------------------------------------- The "function second" forms I couldn't find for "plain" and "functor". What are the most common operators to used in these places?

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