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TFP 2014 - 2nd call for papers
by Peter Achten 31 Jan '14

31 Jan '14

--------------------------------- 2ND C A L L F O R P A P E R S --------------------------------- ======== TFP 2014 =========== 15th Symposium on Trends in Functional Programming May 26-28, 2014 Utrecht University Soesterberg, The Netherlands http://www.cs.uu.nl/wiki/TFP2014/WebHome *** Submission for TFP 2014 is now open: please direct your browser to *** http://www.cs.uu.nl/wiki/TFP2014/PaperSubmission 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), described in draft papers submitted prior to the symposium. A formal post-symposium refereeing process then selects a subset of the articles presented at the symposium and submitted for formal publication. Selected revised papers will be published as a Springer Lecture Notes in Computer Science (LNCS) volume. TFP 2014 will be the main event of a pair of functional programming events. The other is the International Workshop on Trends in Functional Programming in Education (TFPIE). TFPIE will take place on May 25th. Its website is located at http://www.cs.uwyo.edu/~jlc/tfpie14/ 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, in Munich (Germany) in 2004, in Tallinn (Estonia) in 2005, in Nottingham (UK) in 2006, in New York (USA) in 2007, in Nijmegen (The Netherlands) in 2008, in Komarno (Slovakia) in 2009, in Oklahoma (USA) in 2010, in Madrid (Spain) in 2011, St. Andrews (UK) in 2012 and Provo (Utah, USA) in 2013. For further general information about TFP please see the TFP homepage. INVITED SPEAKERS TFP is pleased to announce talks by the following two invited speakers: John Hughes of Chalmers, Goteborg, Sweden, is well-known as author of Why Functional Programming Matters, and as one of the designers of QuickCheck (together with Koen Claessen); the paper on QuickCheck won the ICFP Most Influential Paper Award in 2010. Currently he divides his time between his professorship and Quviq, a company that performs property-based testing of software with a tool implemented in Erlang. Dr. Geoffrey Mainland received his PhD from Harvard University where he was advised by Greg Morrisett and Matt Welsh. After a two year postdoc with the Programming Principles and Tools group at Microsoft Research Cambridge, he is now an assistant professor at Drexel University. His research focuses on high-level programming language and runtime support for non-general purpose computation. 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 submitted for simultaneous publication to any other forum. They may consider any aspect of functional programming: theoretical, implementation-oriented, or more 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 Using functional techniques to reason about imperative/object-oriented programs Debugging 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 2014 program chair, Jurriaan Hage at J.Hage(a)uu.nl. 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 NWO (Netherlands Organisation for Scientific Research), Well-Typed and Erlang Solutions. 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 (16 pages). The submission must clearly indicate which category it belongs to: research, position, project, evaluation, or overview paper. It should also indicate whether the main author or authors are research students. In the case of a FULL STUDENT paper, the draft paper will receive additional feedback by one of the PC members shortly after the symposium has taken place. We use EasyChair for the refereeing process. IMPORTANT DATES Submission of draft papers: March 17, 2014 Notification: March 24, 2014 Registration: April 7, 2014 TFP Symposium: May 26-28, 2014 Student papers feedback: June 9th, 2014 Submission for formal review: July 1st, 2014 Notification of acceptance: September 8th, 2014 Camera ready paper: October 8th, 2014 PROGRAM COMMITTEE Peter Achten Radboud University Nijmegen Emil Axelsson Chalmers Lucilia Camarao de Figueiredo Universidade Federal de Ouro Preto Laura Castro University of A Coruna Frank Huch Christian-Albrechts-University of Kiel Matthew Fluet Rochester Institute of Technology Jurriaan Hage (chair) University of Utrecht Yukiyoshi Kameyama University of Tsukuba Andrew Kennedy Microsoft Research Tamas Kozsik Eotvos Lorand University Ben Lippmeier University of New South Wales Luc Maranget INRIA Jay McCarthy (co-chair) Brigham Young University Marco T. Morazan Seton Hall University Ricardo Pena Universidad Complutense de Madrid Alexey Rodriguez LiquidM Sven-Bodo Scholz Heriot-Watt University Manuel Serrano INRIA Sophia Antipolis Simon Thompson University of Kent Tarmo Uustalu Inst of Cybernetics David Van Horn University of Maryland Janis Voigtlaender University of Bonn

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Re: [Haskell-cafe] manage effects in a DSL
by oleg＠okmij.org 31 Jan '14

31 Jan '14

> - What do you mean by "The type Cont Int a describes an impure computation, > which may abort with an Int value, for example". > Aborting with an Int value is akin to exceptions? I see that using Cont monad wasn't a good idea. The point can be made simply, with an Error monad or applicative. Here is a simple function to multiply a list of integers: > muls :: [Integer] -> Either e Integer > muls [] = pure 1 > muls (h:t) = (h*) <$> muls t We give the signature (which the compiler accepts) with the polymorphic return type Either e Integer, fully polymorphic over e. Therefore, muls throws no exceptions. Here is a bit more optimized function, which stops all multiplications once zero is encountered. > mulse :: [Integer] -> Either Integer Integer > mulse [] = pure 1 > mulse (0:t) = Left 0 > mulse (h:t) = (h*) <$> mulse t We cannot make the return type (Either e Integer), it must be (Either Integer Integer). The function can indeed throw an exception. If we handle the exception > muls' :: [Integer] -> Either e Integer > muls' l = either pure pure $ mulse l the effect is encapsulated and the type is polymorphic again. > - for me it's not clear when to choose an "applicative" or a "monadic" DSL? > Betsides, what's the rational behind the name "let_" (never seen it before)? The first rule of thumb is to use the simplest structure that does the job. Another good rule is to distinguish the DSL from its implementation. For example, the DSL below http://okmij.org/ftp/tagless-final/index.html#call-by-any has no monads. It is a simple lambda-calculus with constants. Its implementation in Haskell, the embedding, does use monads, sometimes quite specific monads (e.g., IO, to print the trace of evaluation). But these monads are not exposed to the DSL programmer. That article also shows off let_. > data Eff = Effect | NoEffect > -- first type parameter is used to track effects > data Exp :: Eff -> * -> * where > ReadAccount :: Exp r Int --ReadAccount can be used in whatever > monad (with or without effect) > WriteAccount :: Exp NoEffect Int -> Exp Effect () --WriteAccount > takes an effect-less expression, and returns an effectfull expression This is exactly what I had in mind (and probably Jacques as well). > Other pointers where this idiom is realised?? Lots of places; ST monad comes to mind, and the Region monad. This trick is often used to track, for example, information flow security (the label then reflects the sensitivity level of data processed by the computation, Low or High). See, for example, http://www.cse.chalmers.se/~russo/seclib.htm http://www.scs.stanford.edu/~deian/pubs/stefan:2011:flexible-slides.pdf or just search for information flow control or information flow security in Haskell. Edward Yang has a lot to say on this topic.

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liboleg
by Suhail Shergill 30 Jan '14

30 Jan '14

hi, i would like to take over as maintainer of the liboleg package on hackage <http://hackage.haskell.org/package/liboleg>. i have gotten permission from the author (oleg) and the current maintainer (don) regarding the same via email. my hackage username is shergill. if there are no objections, could i be added to the maintainer group for liboleg and be granted upload rights? -- Suhail

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Deprecating bytestring version 0.10.2.0
by Christian Laustsen 30 Jan '14

30 Jan '14

Hi everyone, Following some problems I experienced with Network.HTTP.Client.TLS, I found out the problem was specific to bytestring library version 0.10.2.0 and most likely fixed with this commit https://github.com/haskell/bytestring/commit/86df1f17b2332940df69f484182c5c… . The default version shipped with GHC 7.6.3 (0.10.0.2) works fine, and the version after 0.10.2.0 (that is, version 0.10.4.0) also works. It was suggested that I mention on here that I think we should deprecate the 0.10.2.0 version of bytestring specifically, since that is the one that introduces the problem, and there can be problems with having to specify specific versions of bytestring as a dependency when compiling across GHC versions. -- Christian // Tehnix

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Builder vs Builder
by Andrew Cowie 30 Jan '14

30 Jan '14

Does anyone know whether blaze-builder is deprecated in favour of bytestring's new Builder module, or are they the same, or... I know Simon is the evil wizard cackling in his dank lair in both cases, and I do remember him saying he was trying to get his work "upstream" into bytestring, but I haven't heard anyone suggesting we should be using Data.ByteString.Lazy.Builder instead of Blaze.ByteString.Builder I can only imagine the integration with the allocation routines is much better now that it's in bytestring, but on the other hand it's hard to upgrade bytestring — it being so low in the stack — so perhaps the original blaze remains the right choice from a bugfix and stability perspective. Thoughts? AfC Sydney

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GHC iOS ARMv7/ARMv7s fat support completed
by Luke Iannini 30 Jan '14

30 Jan '14

Hi folks, Happy to report that I've finished an approach to armv7/armv7s fat compilation, just in time for 7.8's imminent release. You'll find the necessary scripts here: https://github.com/ghc-ios/ghc-ios-scripts and the latest instructions for building GHC for iOS usage here: https://ghc.haskell.org/trac/ghc/wiki/Building/CrossCompiling/iOS I've also added support for a perf-cross BuildFlavour, which will give a higher-performance and profiling-ready build that matches what we'll be putting together as the official 7.8 GHC iOS binaries: https://ghc.haskell.org/trac/ghc/ticket/8700 Cheers Luke

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Is it safe to create global variables using unsafePerformIO?
by Alexander Alexeev 30 Jan '14

30 Jan '14

Hello! Lets consider the following code: import Control.Concurrent import Control.Concurrent.STM import System.IO.Unsafe (unsafePerformIO) {-# NOINLINE counter #-} counter :: TVar Int counter = unsafePerformIO $ newTVarIO 0 incCounter :: IO Int incCounter = do r <- atomically $ do t <- readTVar counter let t' = t + 1 writeTVar counter t' return t' return r main :: IO () main = do n1 <- incCounter print n1 n2 <- incCounter print n2 n3 <- incCounter print n3 This program prints: 1 2 3 So we have a "global variable". Do I right understand that newTVarIO creates TVar and RTS memoizes it since 'counter' function is pure? If it's true, could it happen that under some circumstances memoized value will be deleted from memory? Or Haskell keeps all memoized values forever? Another issue which I'm afraid of --- would the given code be safe in multithread application? For example, is it possible to encounter a race condition if two threads will try to create a new counter in the same time? Is there any other problems which should be taken in account? -- Best regards, Alexander Alexeev http://eax.me/

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Lazy MWC Random?
by Sacha Sokoloski 29 Jan '14

29 Jan '14

Dear Haskellers, I'm in a situation where I'd like to generate an infinite list of random elements (basically, I'm simulating stochastic systems). I feel like MWC Random is the fastest RNG available, but when I try to pull the infinite list out of RandST, it obviously doesn't halt, because ST is strict. Someone posted a way around this in this stack overflow thread: https://stackoverflow.com/questions/16248600/parallel-computations-with-fas… Which would fix my problem. My question is though, why isn't ST.Lazy included as a PrimMonad instance anyway? The best answer I can come up with is that, since evaluating the Generator is time dependent, it's best to make it strict to make sure that one's program isn't tapping into /dev/random at arbitrary times. In this way the best stackoverflow solution is quite good. It requires one to strictly generate a Seed (since that's the only way to do it), but then converts the ST Monad to the Lazy version to Lazify everything else. However, my understanding of PrimMonad is simply that it's a class of low level monads i.e. IO and ST, so if there's some deeper reason to this, it's beyond me. Another question that I'm puzzling over: In the stack overflow solution, they also make an effort to only have to generate the seed a single time. Is this important performance wise? What I suppose this must hinge upon, is whether in saving an ST s Gen to a Seed, the conversion from an immutable to mutable array requires a copy or not. Is that the full extent of the complexity of this? Is the stackoverflow solution ultimately the most efficient? Is using MWC Random to generate infinite lists and efficient solution anyway? Thanks for any insight, - Sacha Sokoloski

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New Functional Programming Job Opportunities
by Functional Jobs 29 Jan '14

29 Jan '14

Here are some functional programming job opportunities that were posted recently: Haskell Developer at Zalora http://functionaljobs.com/jobs/8678-haskell-developer-at-zalora Cheers, Sean Murphy FunctionalJobs.com

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ANNOUNCE: GLUT 2.5.1.0
by Sven Panne 29 Jan '14

29 Jan '14

A new version of the GLUT package is available on Hackage, with the following new features: * Added support for left/right SHIFT/CTRL/ALT special keys. * Added skipStaleMotionEvents state flag, making it possible to skip all but the last motion event. * Added leaveFullScreen call. * Added support for position, application life cycle and multi-touch window callbacks. * Various object drawing improvements: * Added teacup and teaspoon objects, so we support the full Newell tea set now. * Added geometryVisualizeNormals state flag. * Added support for drawing objects via VBOs: vertexAttribCoord3, vertexAttribNormal, and vertexAttribTexCoord2. * Added support for menu fonts via new constructor MenuWithFont. Apart from glutInitErrorFunc and glutInitWarningFunc, which are not extremely useful IMHO, all freeglut features are now exposed on the Haskell side. Cheers, S.

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