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[TFP2014] Final Call For Papers
by Peter Achten 11 Mar '14

11 Mar '14

--------------------------------- F I N A L 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. FINANCIAL SUPPORT TFP is financially supported by the Department of Information and Computing Sciences of Utrecht University, 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. For the preproceedings, papers can be in any format (inclduing LNCS, IEEE and ACM style), but papers submitted to the postrefereeing process must be in LNCS style, and are bound by the limitations on paper length. 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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Haskell Hackathon in NYC, April 4-6 (last reminder)
by MightyByte 11 Mar '14

11 Mar '14

Greetings, We're just under a month out from the first Hac NYC, so I wanted to send out one more reminder to the community. For the full details see the previous announcement. http://www.haskell.org/pipermail/haskell-cafe/2014-January/112362.html Once again, if you plan on coming, you must officially register by filling out our registration form [1]. Other details for travel, lodging, etc can be found on the Hac NYC wiki [2]. And if you would like to give a talk, please let us know [3] so we can schedule them. We're looking forward to seeing you here. -The Hac NYC Team [1] https://docs.google.com/forms/d/1taZtjgYozFNebLt1TR2VnKv-ovD2Yv5sOdSZzmi_xF… [2] http://www.haskell.org/haskellwiki/Hac_NYC [3] http://www.haskell.org/haskellwiki/Hac_NYC/Talks

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ANNOUNCE: San Diego Haskell User Group.
by Cesar Lopez 11 Mar '14

11 Mar '14

Hello everyone: I would like to announce the creation and meeting of the *San Diego Haskell User Group*, the first meeting will be held on Wednesday March 19th. 2014 at 60:30PM at MindTouch, Inc's office in downtown San Diego. Please join us! *Information about the group:* The San Diego Haskell User Group aims to bring together academics, hobbyists, and software developers to discuss real world usage of the Haskell programming language. You can follow us on twitter @loshaskelleros<https://twitter.com/loshaskelleros> Information about the first meeting. *Unconference style Haskell meeting #1:* http://www.meetup.com/SanDiegoHUG/events/168606962/ Cheers cesar

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Fwd: On Haskell IDEs
by Michal Antkiewicz 11 Mar '14

11 Mar '14

Vagif, it's all about separation of concerns and low coupling. There's no point adding all possible functionality into GHCi because it'll become too big and most users won't use most of it (ever used MSoft Word?). The ecosystem can be architected in some service-oriented way, in which some tools will be data providers and others will provide some added layers of functionality. That does not imply that all tools will need to maintain their own independent copies of information about the project. There largest overlap, as far as I can see, is between ghc-mod and hdevtools. Both are proofs of concept. Maybe parts could actually be incorporated into GHCi. hsdev seems to be specialized to source file editing and should remain separate but it can use the other ones as data sources (incl. Cabal and GHCi). Re: wasted effort. I don't agree. hdevtools was made to make a point that running a process in the background which maintains data and answers queries is much more responsive to the user than otherwise. And it has proven that point. Now, GHCi can learn that lesson and provide something similar, if that indeed belongs to GHCi's scope. Finally, all this is just speculation since I don't know exactly what the actual overlap among the tools is. It might be smaller than we think. Cheers, Michal On Mon, Mar 10, 2014 at 3:44 PM, Vagif Verdi <vagif.verdi(a)gmail.com> wrote: > Sorry, i meant ghci not cabal. > > As for hsdev, in order to provide its features it will have to load and > keep track of entire project information which is already done by ghc-mod > and hdevtools separately. So you ushould see how much effort is wasted on > doing the same thing again and again in each of 4 different tools (ghci, > ghc-mod, hdevtools and hsdev) > > > On Monday, March 10, 2014 12:32:25 PM UTC-7, Niklas Hambüchen wrote: > >> On 10/03/14 18:41, Vagif Verdi wrote: >> > This is an excellent illustration of how fragmentation in this specific >> > area hurts community. Not only you are forced to use 3 different tools >> > (ghc-mod, hdevtools, cabal) each of which basically provides the same >> > service but in an incompatible and incomplete way. But you decided to >> > create yet another one instead of contributing to the ones you already >> > use (they are all open source) >> >> I'm not sure what you mean to say; ghc-mod and cabal certainly do not do >> the same. Hsdev doesn't either, and claiming that we don't contribute to >> these projects is strange. >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskel...(a)haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe >> > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > > <mantkiew(a)gsd.uwaterloo.ca> -- Michal Antkiewicz, M.Sc., Ph.D Research Engineer Network for the Engineering of Complex Software-Intensive Systems (NECSIS) University of Waterloo http://gsd.uwaterloo.ca/mantkiew mantkiew(a)gsd.uwaterloo.ca

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[GSOC] haskell-type-exts?
by Andy Morris 10 Mar '14

10 Mar '14

On the GSOC ideas page for haskell.org is haskell-type-exts[1], which—as the name may suggest :)—is a proposal for a typechecker for haskell-src-exts. It doesn't seem to have got much attention, having only a single comment from two years ago, and I haven't seen anyone talking about it here or elsewhere. I guess this is still something that would be useful, so unless anyone has a reason why not, I'd like to apply to do it. I'll probably start working on the application later today unless some objections surface :) (Is Niklas Broberg subscribed to this list? If so: would you still be willing to mentor this project?) [1] https://ghc.haskell.org/trac/summer-of-code/ticket/1620

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Extensible Binary-Meta-Language libraries
by Mateusz Kowalczyk 10 Mar '14

10 Mar '14

Greetings, Does anyone know if there are any libraries to work with Extensible Binary Meta-Language (used by Matroska)? I find mentions of such a thing in IRC logs from years ago by a person going by ‘ksf’ but he/she has disappeared from IRC about 5 weeks ago and I can not find their e-mail address. Is anyone interested in such a library? I am planning to implement it anyway but it'd be nice to know if there's any interest. Thanks -- Mateusz K.

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New Functional Programming Job Opportunities
by Functional Jobs 10 Mar '14

10 Mar '14

Here are some functional programming job opportunities that were posted recently: Developer at Northwestern University http://functionaljobs.com/jobs/8690-developer-at-northwestern-university Cheers, Sean Murphy FunctionalJobs.com

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Fwd: facebook exception
by Corentin Dupont 09 Mar '14

09 Mar '14

Hi, I am posting here in case one of you got this error. It's an old bug in my game that I was never able to solve. I use happstack-authenticate, but when I select facebook to login with, I get: FacebookException {fbeType = " ()", fbeMessage = ""} However, it seems well configured. I put: facebookAuth = Credentials {appName = "Nomyx", appId = "161007670738608", appSecret = <my secret>} On the facebook website, I have the application configured: application Id: 161007670738608 secret key: <my secret> Display Name: Nomyx NameSpace: nomyx-app App Domains: www.nomyx.net URL: http://www.nomyx.net:8000/ Do you have any hints? Thanks a lot!! Corentin <http://www.nomyx.net:8000>

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Re: [Haskell-cafe] Overcome type restrictions?
by Dušan Kolář 07 Mar '14

07 Mar '14

Well, for the case, we even do not need RankNTypes, as the type of the list is known, so newtype Wrap = Wrap { unwrap :: [Wrap] -> Wrap } wself (h:t) = unwr $ unwr h t will work, which is not too far from encoding function into data :-) This solution saves space, of course. Best regards, Dušan On 03/07/2014 10:35 AM, Tobias Brandt wrote: > The problem is, that the type parameter 'a' of the functions in the > list is fixed. You can work around that with RankNTypes: > > newtype Wrap = Wrap { unwrap :: forall a. [a] -> a } > > unwrap $ (\(h:t) -> (unwrap h) t) [Wrap head, Wrap last] > > This specializes the type of the functions at every point of use > separately. > > > On 7 March 2014 09:14, Kolář Dušan <kolar(a)fit.vutbr.cz > <mailto:kolar@fit.vutbr.cz>> wrote: > > Well my fault, the example should have been like this: > > We have and error of infinite type for > Prelude> :t ((\(h:t) -> h t) [head, last, head, last, head, last]) > > Of course, head and tail are incompatible on type level... > > Dušan > > > > On Fri, 07 Mar 2014 07:57:09 +0100, Kolář Dušan > <kolar(a)fit.vutbr.cz <mailto:kolar@fit.vutbr.cz>> wrote: > > : > : > > But we have an error of infinite type construction for > > Prelude> :t ((\(h:t) -> h t) [head,tail, head, tail, head, > tail]) > > Well I can overcome this by encoding functions into data > types and then performing "conversion" back and forth, > nevertheless, is there any way how to overcome this? > > > It seems like you need heterogenous collections[0] > > Regards, > Henk-Jan van Tuyl > > > [0] http://www.haskell.org/haskellwiki/Heterogenous_collections > > > -- > Folding@home > What if you could share your unused computer power to help > find a cure? In just 5 minutes you can join the world's > biggest networked computer and get us closer sooner. Watch the > video. > http://folding.stanford.edu/ > > > http://Van.Tuyl.eu/ > http://members.chello.nl/hjgtuyl/tourdemonad.html > Haskell programming > -- > > > > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org <mailto:Haskell-Cafe@haskell.org> > http://www.haskell.org/mailman/listinfo/haskell-cafe > >

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SystemF, universal quantification, and rigid type variables
by David Rush 07 Mar '14

07 Mar '14

In short, I'm trying to decide if there is a real difference between the types: (forall a.a) -> b a -> b and frankly, I'm not seeing a difference. But ghc apparently does *SystemF.Tests> :t ((\u (x::forall a. a) y -> u x y) (\x y -> y)) True <interactive>:1:49: Couldn't match type `a' with `Bool' `a' is a rigid type variable bound by a type expected by the context: a at <interactive>:1:1 In the second argument of `\ u (x :: forall a. a) y -> u x y', namely `True' In the expression: ((\ u (x :: forall a. a) y -> u x y) (\ x y -> y)) True *SystemF.Tests> Since this is a 'rigid type variable' complaint, I am inclined to think that this is a limitation of ghc, rather than a particular issue with the logic of System F. I'd actually love to be wrong. Is there an actual difference between the types? - david rush

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Overcome type restrictions?
by Kolář Dušan 07 Mar '14

07 Mar '14

Hello Café, Is there any way to overcome this other way then by introducing some helper data types etc. etc.? We have: Prelude> :t ([head, last, head, last, head, last]) ([head, last, head, last, head, last]) :: [[a] -> a] Prelude> :t (\(h:t) -> head t) (\(h:t) -> head t) :: [a] -> a Prelude> :t ((\(h:t) -> head t) [head, last, head, last, head, last]) ((\(h:t) -> head t) [head, last, head, last, head, last]) :: [a] -> a But we have an error of infinite type construction for Prelude> :t ((\(h:t) -> h t) [head,tail, head, tail, head, tail]) Well I can overcome this by encoding functions into data types and then performing "conversion" back and forth, nevertheless, is there any way how to overcome this? My real problem is not about head/tail, but head/tail is the simplest way how to explain. Thanks for any references, Dušan

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gloss-raster: Couldn't figure out LLVM version! (osx 10.8.5)
by Miro Karpis 06 Mar '14

06 Mar '14

Hi, please can you help me with following: I'm unable to install gloss-raster. Output is: dev$ cabal install gloss-raster Resolving dependencies... Configuring gloss-raster-1.8.1.2... Building gloss-raster-1.8.1.2... Preprocessing library gloss-raster-1.8.1.2... [1 of 2] Compiling Graphics.Gloss.Raster.Array ( Graphics/Gloss/Raster/Array.hs, dist/build/Graphics/Gloss/Raster/Array.o ) <no location info>: Warning: Couldn't figure out LLVM version! Make sure you have installed LLVM ghc: could not execute: opt Failed to install gloss-raster-1.8.1.2 cabal: Error: some packages failed to install: gloss-raster-1.8.1.2 failed during the building phase. The exception was: ExitFailure 1 llvm seems to be installed: $ brew install llvm Warning: llvm-3.3 already installed cheers, m.

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Short survey re: use of haskell.org funds to drive development -- please help!
by Brent Yorgey 06 Mar '14

06 Mar '14

The haskell.org committee is trying to figure out how to use some of its newfound power (the Power of Collecting Money) to best benefit the open-source Haskell community. You can help us by filling out a very short survey (it should only take you about 5 minutes): https://docs.google.com/forms/d/1rEobhHwFpjzPnra9L1TmrozWNFFyAVNPmdUMCcT--3… Please do fill it out, especially if you have opinions about what parts of the Haskell open-source world need more work, and could benefit by having some people paid to work on them. Thanks! -Brent, for the haskell.org committee

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question about show
by k＠ioctl.it 06 Mar '14

06 Mar '14

Hello! I'm sure this has been answered many times before, but I can't find an explanation for this behavior anywhere. The question I have is a general one regarding 'show'. Why does main = do putStrLn "ü" ➜ ~ runhaskell test.hs ü and: main = do putStrLn $ show "ü" ➜ ~ runhaskell test.hs "\252" Thank you all for an enlightening answer already! Best, k

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In Windows, it is better to install development environments outside of the Programs Files folder ...
by KC 06 Mar '14

06 Mar '14

In Windows, it is better to install development environments outside of the Programs Files folder because Windows has protections on that folder plus some other folders. I suppose another alternative is to use the Wubi installer for Ubuntu or is there a better Linux one should be using. :) Oooops! The Wubi installer is not recommended for a computer sporting the Windows 8 logo or using UEFI firmware. -- -- Sent from an expensive device which will be obsolete in a few months! :D Casey

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2013.2 on Win8.1 64 bit
by james 05 Mar '14

05 Mar '14

Hi, Does the current latest Haskell Platform install on Win8.1? I don't seem to have luck. I have it installed on my portable, which runs Win7. On my desktop I have 8.1, and the installers asks me whether I want to stop and restart with elevated permissions. It does this however I start it, including from a command prompt running as administrator, or from the 'right click' run as administrator. Continuing then fails to write to Program Files (x86). Any ideas? James

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question re: FFI and ensuring unwrapped values are present on stack
by Charles Strahan 04 Mar '14

04 Mar '14

Hello all, This is probably going to be a pretty niche question, but I'm hoping someone here can lend a hand. I'm working on a binding for the YARV Ruby VM, and I'm struggling to come up a with a good interop story with respect to its GC implementation. I have two options to prevent premature GC of Ruby object pointers: 1) Guarantee that the pointers reside on the stack or in registers, 2) or copy the pointer itself to another static area of memory and register that address with the GC. So, the big question is: is there a way to make #1 a reality, while operating in the IO monad? I can picture something like the following: newtype RValue = RValue (Ptr RValue) deriving (Storable) withObject :: IO RValue -- e.g. result of some ccall, or some further transformation thereof -> (RValue -> IO a) -- the RValue is now on the stack (or in a register), available for use without worry of premature GC -> IO a -- the result of computation With Haskell being a non-strict language, I understand that there are a lot of instances where a value could end up on the heap, with a thunk being passed via stack/registers. For my needs, I'd need some way to guarantee that the RValues being passed to and from withObject are at all times kept unwrapped and off the heap, and likewise within the second argument. Given my rather limited knowledge of Haskell (I've been programming in Haskell for about a month now), I think the best I can come up with is the second option suggested above: withObject :: (Ptr RValue -> IO ()) -- e.g. void some_fun(VALUE* out) {...} -> (RValue -> IO a) -- e.g. do something with `out` derefed -> IO a withObject f g = alloca $ \ptr -> do rb_gc_register_address ptr -- prevent GC f ptr -- call wrapped native function val <- peek ptr -- deref the VALUE* res <- g val -- pass to function rb_gc_unregister_address ptr -- clean up res So, while the above would work, it's really, really ugly (IMO). That, and I'd have to wrap all the native functions so that instead of returning VALUE, they'd write to some out ptr and return void. And there's the otherwise unnecessary alloca. I hope that was clear enough - any advice would be super duper appreciated! I'm assuming that there isn't a way I can get away with using the typical monadic bind syntax while keeping the RValues off the heap; if I'm wrong, and I can skip the whole withObject/HOF approach, I'd love to know it! I'm not (yet) familiar enough with the compiler / language spec to know about such guarantees, should they exist... - Charles

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CFP: FHPC 2014: 3rd workshop on Functional High-Performance Computing [w/ICFP]
by Ryan Newton 04 Mar '14

04 Mar '14

===================================================================== CALL FOR PAPERS FHPC 2014 The 2nd ACM SIGPLAN Workshop on Functional High-Performance Computing Gothenburg, Sweden September 4, 2014 https://sites.google.com/site/fhpcworkshops/ Co-located with the International Conference on Functional Programming (ICFP 2014) Submission Deadline: Sunday, 15 May, 2014 (anywhere on earth) ===================================================================== The FHPC workshop aims at bringing together researchers exploring uses of functional (or more generally, declarative or high-level) programming technology in application domains where high performance is essential. The aim of the meeting is to enable sharing of results, experiences, and novel ideas about how high-level, declarative specifications of computationally challenging problems can serve as maintainable and portable code that approaches (or even exceeds) the performance of machine-oriented imperative implementations. All aspects of performance critical programming and parallel programming are in-scope for the workshop, irrespective of hardware target. This includes both traditional large-scale scientific computing (HPC), as well as work targeting single node systems with SMPs, GPUs, FPGAs, or embedded processors. It is becoming apparent that radically new and well founded methodologies for programming such systems are required to address their inherent complexity and to reconcile execution performance with programming productivity. Every year, the FHPC workshop has an application area as a theme. Papers touching on this topic are especially encouraged, though all in-scope papers are welcomed. For FHPC 2014, the theme is "Heterogeneous computing". In the systems and parallelism communities, there has been a lot of work on programming systems with CPUs and GPUs (or other mixed parallel architectures), but in the programming languages community this idea has not received as much attention. At their best, high-level languages can have the degrees of flexibility necessary to abstract over platform differences. Proceedings: ============ Accepted papers will be published by the ACM and will appear in the ACM Digital Library. * Submissions due: Sunday, 15 May, 2014 (anywhere on earth) * Author notification: Friday, 15 June, 2014 * Final copy due: Sunday, 22 June, 2014 Submitted papers must be in portable document format (PDF), formatted according to the ACM SIGPLAN style guidelines (2 column, 9pt format). See http://www.sigplan.org/authorInformation.htm for more information and style files. Typical papers are expected to be 8 pages (but up to four additional pages are permitted). Contributions to FHPC 2014 should be submitted via Easychair, at the following URL: * https://www.easychair.org/conferences/?conf=fhpc14 The submission site is now open. The FHPC workshops adhere to the ACM SIGPLAN policies regarding programme committee contributions and republication. Any paper submitted must adhere to ACM SIGPLAN's republication policy. PC member submissions are welcome, but will be reviewed to a higher standard. http://www.sigplan.org/Resources/Policies/Review http://www.sigplan.org/Resources/Policies/Republication Travel Support: =============== Student attendees with accepted papers can apply for a SIGPLAN PAC grant to help cover travel expenses. PAC also offers other support, such as for child-care expenses during the meeting or for travel costs for companions of SIGPLAN members with physical disabilities, as well as for travel from locations outside of North America and Europe. For details on the PAC programme, see its web page (http://www.sigplan.org/PAC.htm) Programme Committee: ==================== Mary Sheeran (co-chair), Chalmers University of Technology, SE Ryan Newton (co-chair), Indiana University, USA Lennart Augustsson, Standard Chartered Bank, UK Jost Berthold, University of Copenhagen, Denmark Guy Blelloch, Carnegie Mellon University, USA Marius Eriksen, Twitter, USA Clemens Grelck, University of Amsterdam, Netherlands Vinod Grover, Nvidia, USA Kevin Hammond, University of St. Andrews, UK Ben Lippmeier, University of New South Wales, Australia Liu (Paul) Hai, Intel, USA Rita Loogen, University of Marburg, Germany Greg Michaelson, Heriot-Watt University, UK Marc Pouzet, ENS Paris, France John Reppy, Univesity of Chicago, USA Tiark Rompf, Oracle Labs and EPFL, Switzerland Satnam Singh, Google, USA Dimitrios Vytiniotis, Microsoft Research, UK General Chairs: ==================== Jost Berthold University of Copenhagen

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Type checking string literal in Haskell?
by KwangYul Seo 04 Mar '14

04 Mar '14

In Java, the Checker Framework ( http://types.cs.washington.edu/checker-framework/) provides a way to type check string literals. For example, Java signatures type system differentiates strings literals in different forms: 1. Unqualified strings : "Hello, world!" -> @Unqualified String 2. Fully qualified names: "package.Outer.Inner" -> @FullyQualifiedString String 3. Binary names: "package.Outer$Inner" -> @BinaryName String 4. Field descriptors: "Lpackage/Outer$Inner;" -> @FieldDescriptor String It can do the similar checks with regular expressions or SQL statements. Is it possible to type check string literals in Haskell? I think it would be nice if we can check if a given string literal is a valid URL or an email address at compile time. Regards, Kwang Yul Seo

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Journal of Functional Programming - Call for PhD Abstracts
by Graham Hutton 03 Mar '14

03 Mar '14

============================================================ CALL FOR PHD ABSTRACTS Journal of Functional Programming Deadline: 30th April 2014 http://tinyurl.com/jfp-phd-abstracts ============================================================ PREAMBLE: Many students complete PhDs in functional programming each year, but there is currently no common location in which to promote and advertise the resulting work. The Journal of Functional Programming would like to change that! As a service to the community, JFP is launching a new feature, in the form of a yearly publication of abstracts from PhD dissertations that were completed during the previous year. To start this new feature off, we would like to reach back three years for the first round of abstracts. The abstracts will be freely available on the JFP website, i.e. not behind any paywall, and will not require any transfer for copyright, merely a license from the author. Please submit dissertation abstracts according to the instructions below. A dissertation is eligible if parts of it have or could appear in JFP, that is, if it is in the general area of functional programming. JFP will not have these abstracts reviewed. We welcome submissions from both the PhD student and PhD advisor/supervisor although we encourage them to coordinate. ============================================================ SUBMISSION: Please submit the following information to Graham Hutton <graham.hutton(a)nottingham.ac.uk> by 30th April 2014. o Student: (full name) o Advisor/supervisor: (full names) o Dissertation title: (including any subtitle) o Dissertation abstract: (plain text, maximum 1000 words; you may use \emph{...} for emphasis, but we prefer no other markup or formatting in the abstract, but do get in touch if this causes significant problems) o Dissertation URL: (please provide a permanently accessible link to the dissertation if you have one, such as to an institutional repository or other public archive; links to personal web pages should be considered a last resort) o Awarding institution: (full name and location) o Date of PhD award: (depending on the institution, this may be the date of the viva, date when corrections were approved, date of graduation ceremony, or otherwise) Please do not submit a copy of the dissertation itself, as this is not required. JFP reserves the right to decline to publish abstracts that are not deemed appropriate. ============================================================ PHD ABSTRACT EDITOR: Graham Hutton School of Computer Science University of Nottingham Nottingham NG8 1BB United Kindgdom ============================================================ This message and any attachment are intended solely for the addressee and may contain confidential information. If you have received this message in error, please send it back to me, and immediately delete it. Please do not use, copy or disclose the information contained in this message or in any attachment. Any views or opinions expressed by the author of this email do not necessarily reflect the views of the University of Nottingham. This message has been checked for viruses but the contents of an attachment may still contain software viruses which could damage your computer system, you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation.

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Re: [Haskell-cafe] [TYPES] OutsideIn(X) question
by Dimitrios Vytiniotis 03 Mar '14

03 Mar '14

Dear Alejandro, thanks for your notice! You are right, the entailment relation in the JFP paper is too weak for type classes. As we formulated it, the simplifier can take a type class reduction step but there is no way to show that the new set of constraints is equivalent to the original class constraint. There is nothing very deep going on, it's an oversight in the definition of entailment. The fix -- at least in the case of non-overlapping instances and vanilla multi-parameter type classes -- is to ensure that all axioms for type class instances form bi-implications. In fact in the constraint handling rules formulation of type classes, class instances always gave rise to such bi-implications. I will post the correction to the article on my web page in the next couple of weeks and let you know, but I thought I should send an update. Best regards, Dimitrios -----Original Message----- From: Types-list [mailto:types-list-bounces@lists.seas.upenn.edu] On Behalf Of Alejandro Serrano Mena Sent: Thursday, February 27, 2014 10:18 AM To: types-list(a)lists.seas.upenn.edu Subject: [TYPES] OutsideIn(X) question [ The Types Forum, http://lists.seas.upenn.edu/mailman/listinfo/types-list ] Dear Types List, I have a small question related to the "OutsideIn(X): Modular type inference with local assumptions" and was hoping that you could help me a bit. My question related about the proof of soundness and principality, specifically Lemma 7.2 (to be found in page 67). In that lemma, it's stated that QQ and \phi' Q_q ||- \phi Q_w <-> \phi' Q_w'. I'm trying to recover the proof (which is omitted in the text), but I stumble upon a wall when trying to work out what happens in the case an axiom is applied. In particular, I'm playing with an example where QQ (the set of axioms) = { forall. C a => D a } (where C and D are one-parameter type classes) Q_q = { } Q_w = { D Int } Thus, if I apply the rule DINSTW (to be found in page 65), I get a new Q_w' = { C Int } Now, if the lemma 7.2 is true, it should be the case that (1) QQ ||- C Int <-> D Int which in particular means that I have the two implications (2) { forall. C a => D a, C Int } ||- D Int (3) { forall. C a => D a, D Int } ||- C Int (2) follows easily by applying the AXIOM rule of ||- (as shown in page 54). However, I don't see how to make (3) work :( I think that understanding this example will be key for my understanding of the whole system. Anybody could point to the error in my reasoning or to places where I could find more information? Thanks in advance.

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I'm trying to design a GUI library -- a design question
by Ömer Sinan Ağacan 03 Mar '14

03 Mar '14

Hi all, I'm designing a ncurses based GUI library. I'm calling smallest GUI elements "widgets". A widget can have internal state of any type. Let's call this type `s`. I want to be able to have something like this: > data Widget s = Widget > { handleKey :: Key -> s -> s > , draw :: Int -> Int -> Int -> Int -> IO () > , getFocus :: s -> s > , loseFocus :: s -> s > -- more methods may be added in the future > } I also want to be able to have container types like this: > data Container = Container [Widget s] but obviously this does not work because widgets may have different types of states. So problem I'm trying to solve here is that I should somehow abstract internal state used in a Widget but still be able to keep track of that state so that I can pass it to methods in sequential invocations of that methods. Also, once I have a container like this, updating widget states would become a problem. I'd have to somehow keep all those states like: > data Container = Container [Widget] [WidgetState] or > data Container = Container [(Widget, WidgetState)] and then manually pass state to widgets when calling methods, and update the list using return values of methods. In a sense I'm like trying to emulate something like closures with mutable closed-over data in impure languages. I think one way to have a similar effect is to use closures with closed-over IORefs. Then I could modify that state but then I'd need to have methods with types `IO ()`. I want to have more "precise" types. i.e. IO is a lot more general than what I'd like to have as my widget methods. (side effect of a widget should be limited with changes in it's internal state) Sorry for badly organized post, I'm a bit tired right now and I hope my points are clear. I'm trying to figure out Haskell way of doing something like this, without going into IO world. Ideas/suggestions would be appreciated. Thanks, --- Ömer Sinan Ağacan http://osa1.net

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New Functional Programming Job Opportunities
by Functional Jobs 03 Mar '14

03 Mar '14

Here are some functional programming job opportunities that were posted recently: NixOS/Haskell DevOps Engineer at Zalora http://functionaljobs.com/jobs/8687-nixos-haskell-devops-engineer-at-zalora functional software developer at OpinionLab http://functionaljobs.com/jobs/8685-functional-software-developer-at-opinio… Platform Engineer at Signal Vine LLC http://functionaljobs.com/jobs/8684-platform-engineer-at-signal-vine-llc Cheers, Sean Murphy FunctionalJobs.com

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ANN: tasty-0.8
by Roman Cheplyaka 03 Mar '14

03 Mar '14

I'm glad to announce the 0.8 release of tasty, a modern Haskell testing framework. http://hackage.haskell.org/package/tasty-0.8 Among the important user-visible changes are: - New running modes `--hide-successes` and `--quiet` - Short flags for some existing options (`-p` for `--pattern`, `-j` for `--num-threads`) - Timeout support - Possibility to pass options via environment variables - Fix of a resources-related bug For details, see the CHANGELOG and README: https://github.com/feuerbach/tasty/blob/master/CHANGES.md http://documentup.com/feuerbach/tasty tasty now has a mailing list[ml] and an IRC channel #tasty at FreeNode. The IRC channel is logged at ircbrowse.net[logs] (thanks to Chris Done). [ml]: https://groups.google.com/forum/#!forum/haskell-tasty [logs]: http://ircbrowse.net/tasty Read more: http://ro-che.info/articles/2014-03-03-tasty-0.8.html Roman

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ANN: poppler-0.12.3 is released.
by Ian-Woo Kim 03 Mar '14

03 Mar '14

Hi, Haskellers! A new version of haskell poppler library is now released. Poppler is a pdf rendering library, based on xpdf code base. It's being developed and has quite complete features. Haskell poppler library is a binding to the native poppler library. Recently, gtk2hs-0.12.5 was released and we now have support to gtk3. We also have a great advance of Cabal-1.18, but the previous version of poppler was not buildable with the new Cabal. So this version (0.12.3) of poppler is to support gtk2hs-0.12.5 and Cabal-1.18. By default, poppler is compiled against gtk version 2, but with -fgtk3 option, one can build poppler with gtk3. The new version of poppler is available on hackage. Enjoy! Ian-Woo Kim

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Scaling Haskell/Yesod on OpenShift
by Joey Eremondi 02 Mar '14

02 Mar '14

I was wondering, does anyone have experience with using Haskell/Yesod on the OpenShift PaaS? I've seen the Haskell and Yesod cartridges, but I'm wondering if there's any way to get Haskell playing nice with their load-balancing and automatic scaling capabilities? Would CloudHaskell be useful at all in this? I'm reasonably experienced with Haskell but very new to Cloud computing and Web stuff, so any advice, even if basic, is helpful. Thanks!

2 1

ICFP 2014 deadline discrepancy: UTC -11 /= anywhere in the world
by Philip Dexter 02 Mar '14

02 Mar '14

ICFP 2014's website [1] (and all notices) list the deadline as Saturday, 1 March 2014, 23:59 UTC-11 (anywhere in the world) Anywhere in the world time, also known as Anywhere on Earth (AoE), is UTC-12, not UTC-11. Is there anybody that can confirm that this is intentional? EasyChair does not list a deadline. -- [1] http://www.icfpconference.org/icfp2014/index.html

2 2

questions about ghc-clang-wrapper
by Richard Cobbe 02 Mar '14

02 Mar '14

I've just run the ghc-clang-wrapper script (from https://gist.github.com/tibbe/8448715) to try to get GHC 7.6.3 (part of Haskell Platform 2013-2.0.0) working with XCode 5.0.2 on a MacOS 10.8.5 machine. Things look good, but I have two questions: Question 1: How do I know this worked? I tested it by modifying a package that I'm writing so that it requires CPP to build correctly, and successfully built it with "cabal clean; cabal configure; cabal build". (More details available on request.) Does that mean I'm in good shape? (I'm asking because I was never entirely clear on what the incompatibility was; all I know is that it has something to do with cpp.) Question 2: Is there any harm in adding -Wno-return-type to extraClangArgs in ghc-clang-wrapper? This silences an annoying but apparently harmless warning I get from "cabal configure". Thanks, Richard

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parsec problem: infinite loop (possibly connected to try(lookahead ...)) but how?)
by keydana＠gmx.de 01 Mar '14

01 Mar '14

Hi, I want to parse a rather unstructured log file, skipping blocks I'm not interested in but keeping others. For that purpose, I define "markers" that flag the beginning of interesting chunks. The "skip parser" reads anything until such a marker (using manyTill parseAny (try (lookAhead parseMarker)) and then the relative content parser starts by really consuming this marker string. I have a test case demonstrating this principle which works fine, but when I execute the (seemingly!) equivalent "real" code on a piece of a (seemingly!) equivalent "real log file", ghci enters an infinite loop - and I have no idea why... I'd be very grateful for any help, as I'm completely stuck here ;-) Following are: - the test input file - the piece of "real logfile" - the complete code in one piece (Main.hs), with the test case code in the bottom These are the results when I run 1) the test case: *Main> readFile "testfile.txt" >>= parseTest parseAll ["aaa\naaa\n","aaa\naaa\n","aaa\naaa\n"] 2) the main code (endless loop interrupted, with output from debug.trace): parseUntilChunkWFG: "" parseMaybeChunk: Nothing parseWFGMarker: Global Wait-For-Graph(WFG) at ddTS[0.3] : parseUntilChunkWFG: "" parseMaybeChunk: Nothing ^CparseWFGMarker: Global Wait-For-Graph(WFG) at ddTS[0.3] : parseUntilChunkWFG: "" parseMaybeChunk: Nothing Interrupted. This is the test input file, with vi newline symbols: ########################################################################## this is just some stuff$ I wanna skip$ $ this is, too$ 12[] $ $ BEGIN_MARKER$ aaa$ aaa$ $ this here again I can skip$ $ BEGIN_MARKER$ aaa$ aaa$ $ and then it goes on till the end of the file$ ########################################################################## ... and this is the real piece (part of, what is important I have 2 chunks of "interesting content"): ########################################################################## client details:$ O/S info: user: oracle, term: pts/2, ospid: 5820$ machine: node1.skyrac.com program: sqlplus(a)node1.skyrac.com (TNS V1-V3)$ application name: sqlplus(a)node1.skyrac.com (TNS V1-V3), hash value=10026263$ current SQL:$ insert into test values(2)$ DUMP LOCAL BLOCKER: initiate state dump for DEADLOCK$ possible owner[39.5827] on resource TX-00080011-00000545$ $ *** 2014-02-22 08:43:55.554$ Submitting asynchronized dump request [28]. summary=[ges process stack dump (kjdglblkrdm1)].$ Global blockers dump end:-----------------------------------$ Global Wait-For-Graph(WFG) at ddTS[0.3] :$ BLOCKED 0x83437238 3 wq 2 cvtops x1 TX 0xc0006.0x1c5(ext 0x4,0x0)[27000-0001-00000001] inst 1 $ BLOCKER 0x83b196a8 3 wq 1 cvtops x28 TX 0xc0006.0x1c5(ext 0x4,0x0)[36000-0002-00000005] inst 2 $ BLOCKED 0x83437238 3 wq 2 cvtops x1 TX 0x80011.0x545(ext 0x2,0x0)[36000-0002-00000005] inst 2 $ BLOCKER 0x83b35b10 3 wq 1 cvtops x28 TX 0x80011.0x545(ext 0x2,0x0)[27000-0001-00000001] inst 1 $ $ *** 2014-02-22 08:43:56.292$ * Cancel deadlock victim lockp 0x83437238 $ DUMP LOCAL BLOCKER: initiate state dump for DEADLOCK$ possible owner[39.5827] on resource TX-00080011-00000545$ $ *** 2014-02-22 08:43:55.554$ Submitting asynchronized dump request [28]. summary=[ges process stack dump (kjdglblkrdm1)].$ Global blockers dump end:-----------------------------------$ Global Wait-For-Graph(WFG) at ddTS[0.3] :$ BLOCKED 0x83437238 3 wq 2 cvtops x1 TX 0xc0006.0x1c5(ext 0x4,0x0)[27000-0001-00000001] inst 1$ BLOCKER 0x83b196a8 3 wq 1 cvtops x28 TX 0xc0006.0x1c5(ext 0x4,0x0)[36000-0002-00000005] inst 2$ BLOCKED 0x83437238 3 wq 2 cvtops x1 TX 0x80011.0x545(ext 0x2,0x0)[36000-0002-00000005] inst 2$ BLOCKER 0x83b35b10 3 wq 1 cvtops x28 TX 0x80011.0x545(ext 0x2,0x0)[27000-0001-00000001] inst 1$ $ *** 2014-02-22 08:43:56.292$ ########################################################################## ... and this is the code: ########################################################################## module Main ( main ) where import System.Environment import System.Directory import Text.ParserCombinators.Parsec import Debug.Trace import Numeric import Data.Maybe import Data.Char main = do --files <- getArgs currDir <- getCurrentDirectory --let filepaths = map ((currDir ++ "/") ++) ["munip1_lmd0_5702.trc", "munip2_lmd0_5966.trc"] let filepaths = map ((currDir ++ "/") ++) ["munip1_lmd0_5702.trc"] wfgs <- mapM (\p -> parseFromFile parseChunks p) filepaths print wfgs parseChunks :: Parser [Chunk] parseChunks = do chunks <- many1 parseMaybeChunk -- trace ("parseChunks: " ++ (show chunks)) return (catMaybes chunks) return (catMaybes chunks) parseMaybeChunk :: Parser (Maybe Chunk) parseMaybeChunk = do chunk <- try (parseChunkWFG >>= return . Just) <|> try (parseUntilChunkWFG >> return Nothing) <|> (parseTillEOF >> return Nothing) trace ("parseMaybeChunk: " ++ show chunk) return chunk --return chunk parseUntilChunkWFG :: Parser [Char] parseUntilChunkWFG = do skip <- manyTill parseAny (try (lookAhead parseWFGMarker) ) trace ("parseUntilChunkWFG: " ++ show skip) return skip --return skip parseAny :: Parser Char parseAny = do anyC <- oneOf (['a'..'z'] ++ ['A'..'Z'] ++ ['0'..'9'] ++ "()[]* -:.,/_?@='\n\\") --trace ("parseAny: " ++ (show anyC)) return anyC return anyC parseWFGMarker :: Parser [Char] parseWFGMarker = do marker <- string "Global Wait-For-Graph(WFG) at ddTS[0.3] :\n" trace ("parseWFGMarker: " ++ marker) return marker --return marker parseTillEOF :: Parser [Char] parseTillEOF = do anyCs <- many1 anyChar eof --trace ("parseTillEOF: " ++ anyCs) return anyCs return anyCs parseChunkWFG :: Parser Chunk parseChunkWFG = do marker <- string "Global Wait-For-Graph(WFG) at ddTS[0.3] :\n" wfg <- manyTill parseWFGEntry newline --trace ("parseChunkWFG: " ++ (show wfg)) return $ ChunkWFG wfg return $ ChunkWFG wfg parseWFGEntry :: Parser WFGEntry parseWFGEntry = do role <- try (string "BLOCKER") <|> string "BLOCKED" skipMany1 (space >> string "0x") lockaddr <- many1 hexDigit skipMany1 (space >> (many1 digit) >> space >> string "wq" >> space >> (many1 digit) >> space >> string "cvtops" >> space >> char 'x' >> (many1 digit) >> space) restype <- manyTill upper space skipMany1 (string "0x") id1 <- manyTill hexDigit (string ".0x") id2 <- manyTill hexDigit (string "(ext ") manyTill (digit <|> oneOf ")[]x,-") (string " inst ") instid <- manyTill digit (space >> newline) let wfgEntry = WFGEntry (read role :: Role) lockaddr (ResourceId id1 id2 restype) (read instid) --trace ("parseWFGEntry: " ++ show wfgEntry) return $ wfgEntry {- trace ("parseWFGEntry: " ++ role ++ " " ++ lockaddr ++ " " ++ restype ++ " " ++ id1 ++ " " ++ id2 ++ " " ++ instid) return $ wfgEntry -} return $ wfgEntry data Chunk = ChunkWFG WFG deriving (Show, Read) data ResourceId = ResourceId { id1 :: String, id2 :: String, restype :: String } deriving (Show, Read) data WFGEntry = WFGEntry { role :: Role, lockaddr :: String, resource :: ResourceId, instid :: Int } deriving (Show, Read) type WFG = [WFGEntry] data Role = BLOCKED | BLOCKER deriving (Show, Read) ------------------- testcase code --------------------------- parseAll :: Parser [String] parseAll = do chunks <- many1 parseChunk return (catMaybes chunks) parseChunk :: Parser (Maybe [Char]) parseChunk = do chunk <- try (parseContent >>= return . Just) <|> try (parseUntilMarker >> return Nothing) <|> (parseTillEOF >> return Nothing) --trace ("parseChunk: " ++ show chunk) return chunk return chunk parseUntilMarker :: Parser [Char] parseUntilMarker = do skip <- manyTill parseAny (try (lookAhead parseMarker) ) --trace ("parseUntilMarker: " ++ show skip) return skip return skip parseMarker :: Parser [Char] parseMarker = do marker <- string "BEGIN_MARKER\n" --trace ("parseWFGMarker: " ++ marker) return marker return marker parseContent :: Parser [Char] parseContent = do marker <- string "BEGIN_MARKER\n" items <- manyTill parseItem newline --trace ("parseContent: " ++ (show items)) return $ concat items return $ concat items parseItem :: Parser [Char] parseItem = string "aaa\n" ########################################################################## Many thanks in advance for any hints what might be going on :-)! Sigrid

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Safe Haskell design question - package trust
by Omari Norman 01 Mar '14

01 Mar '14

Safe Haskell has three levels of safety: Safe - pure functions won't launch missiles. Well, sort of. They might launch missiles if they apply functions from other Trustworthy modules that do launch missiles, though one can use -fpackage-trust to mitigate this issue. Unsafe - pure functions might launch missiles, watch out. Trustworthy - module author raises her hand and says "My pure functions won't launch missiles, I promise." I can use the package trust feature to say "only trust a Trustworthy package if I say so." My issue is this: why is there no easy way to trust *any* package, not just packages that are Trustworthy? I should be able to say "I trust this package." It is immaterial whether the package author has raised her hand and said "my pure functions don't launch missiles" when I can examine the code for myself and determine whether the code launches missiles. Indeed, if I use package trust, I need to either examine the code or trust the author--the author's pledge isn't determinative. I see what "Trustworthy" adds when you're not using package trust, but it's just an informational flag if you are using package trust. Despite this Safe Haskell will not recognize the trustworthiness of packages that I have deliberately marked as trusted--merely because the author has not made a pledge. I ask because Safe Haskell has been around for over two years now yet the time package, which ships with GHC, has modules that are unsafe. I have examined them; they don't launch missiles. Yet the only easy way to get them working with Safe Haskell is to get the modules marked Trustworthy. I have emailed the maintainer and the libraries mailing list and so far have heard nothing. I have seen at least one package author get annoyed because people asked him to mark his modules Trustworthy, and I think he's right. He shouldn't need to say they're Trustworthy; rather, the Safe Haskell user should be able to do this himself. (True, the Safe Haskell user can do this by recompiling--come on, it shouldn't be that hard, and I don't want to recompile a package like time, that ships with GHC.)

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Re: [Haskell-cafe] [Haskell] Can Haskell use short floats; i.e. 16 bit floats to save space?
by Henning Thielemann 01 Mar '14

01 Mar '14

moving to Haskell-Cafe ... Am 01.03.2014 07:09, schrieb KC: > Can Haskell use short floats; i.e. 16 bit floats to save space? You could wrap an Int16 in a newtype and implement your own floating point arithmetic with some bit manipulation and make that instances of Num, Fractional or numeric-prelude or yap classes.

3 2

GHC 7.6.3 and Plugins 1.5.4.0
by Fabian Bergmark 28 Feb '14

28 Feb '14

Im using the plugins library and am unable get it to work with user defined types. I.e. evaluating the string "id :: Int -> Int" works, but "id :: Test -> Test" yield the runtime-error. test: /tmp/MXXXXX27601.o: unknown symbol `testdzm0zi0zi0_DataziTestD_zdfTypeableTestD_closure' I have created a small compiling example of the bug here https://github.com/fabianbergmark/plugins-bug I have tried to move the data-type to a separate library without success. Curiously, loading the library exposing the data-type in GHCi, and running eval "id :: Test -> Test" works and yields the correct result.

2 1

SBLP 2014 - Call for Papers
by Simon Thompson 28 Feb '14

28 Feb '14

CALL FOR PAPERS 18th Brazilian Symposium on Programming Languages (SBLP 2014) A member of CBSoft joint conference http://www.ic.ufal.br/evento/cbsoft2014/ to be held in Maceio, Brazil. SBLP happens on Thursday, Oct 2nd, and Friday, Oct 3rd. CBSoft dates are September 28, 2014 to October 3, 2014 This CFP is also available at the webpage of the event: http://www.ic.ufal.br/evento/cbsoft2014/en/call-for-papers-sblp.html IMPORTANT DATES Paper abstract submission: May 2nd, 2014 Full paper submission: May 9th, 2014 Notification of acceptance: June 13th, 2014 Final papers due: July 4th, 2014 INTRODUCTION The 18th Brazilian Symposium on Programming Languages, SBLP 2014, will be held in Maceio, a beautiful city in the Northeastern part of Brazil. The conference will happen on October 2nd, and October 3rd, 2014. SBLP provides a venue for researchers and practitioners interested in the fundamental principles and innovations in the design and implementation of programming languages and systems. SBLP 2014 invites authors to contribute with technical papers related (but not limited) to: * Program generation and transformation, including domain-specific languages and model-driven development in the context of programming languages. * Programming paradigms and styles, including functional, object-oriented, aspect-oriented, scripting languages, real-time, service-oriented, multithreaded, parallel, and distributed programming. * Formal semantics and theoretical foundations, including denotational, operational, algebraic and categorical. * Program analysis and verification, including type systems, static analysis and abstract interpretation. * Programming language design and implementation, including new programming models, programming language environments, compilation and interpretation techniques. SUBMISSIONS Contributions should be written in Portuguese or English. Papers should fall into one of two different categories: full papers, with at most 15 pages, or short papers, with at most 5 pages. Accepted papers written in English will be published in a volume of Lecture Notes in Computer Science (LNCS), by Springer. For this reason, all papers must be prepared using the LNCS template, available at http://www.springer.com/computer/lncs?SGWID=0-164-6-793341-0. We encourage the submission of short papers reporting partial results of on-going master dissertations or doctoral theses. Submissions should be done through the SBLP 2014 page at EasyChair, which is available at http://www.easychair.org/conferences/?conf=sblp2014. As in previous editions, a journal's special issue, with selected papers from accepted contributions, is anticipated. Selected papers from the 2003 to the 2008 editions of SBLP were published in special issues of the Journal of Universal Computer Science, by Springer. The post-proceedings of SBLP from 2009 to 2012, also with selected papers from the conference, have been published as special issues of Science of Computer Programming, by Elsevier. KEYNOTE SPEAKERS Louis-Noel Pouchet, University of California Los Angeles Fabrice Rastello, INRIA PROGRAMME CHAIR Fernando Magno Quintao Pereira, UFMG PROGRAMME COMMITTEE Alberto Pardo, Universidad de la República Alex Garcia, IME Alvaro Moreira, Federal University of Rio Grande do Sul Andre Rauber Du Bois, Federal University of Pelotas Carlos Camarão, Federal University of Minas Gerais Christiano Braga, Fluminense Federal University Fabio Mascarenhas, Federal University of Rio de Janeiro Fabrice Rastello, INRIA Fernando Pereira, Federal University of Minas Gerais Fernando Castor, Federal University of Pernambuco Francisco Carvalho-Junior, Federal University of Ceara Hans-Wolfgang Loidl, Heriot-Watt University Jeremy Singer University of Glasgow João Saraiva, University of Minho Joao F. Ferreira, Teesside University Louis-Noel Pouchet, University of California, Los Angeles Lucilia Figueiredo, Federal University of Ouro Preto Luis Barbosa, University of Minho Manuel A. Martins, University of Aveiro Marcello Bonsangue, Leiden University Marcelo Maia, Federal University of Uberlândia Marcelo D'Amorim, Federal University of Pernambuco Mariza Bigonha, Federal University of Minas Gerais Martin Musicante, Federal University of Rio Grande do Norte Noemi Rodriguez, PUC-Rio Peter Mosses, Swansea University Rafael Lins, Federal University of Pernambuco Renato Cerqueira, PUC-Rio Roberto Bigonha, Federal University of Minas Gerais Roberto Ierusalimschy PUC-Rio Rodrigo Geraldo, Federal University of Ouro Preto Sandro Rigo, State University of Campinas Sérgio Medeiros, Federal University of Rio Grande do Norte Simon Thompson, University of Kent Varmo Vene, University of Tartu Zongyan Qiu Peking University Simon Thompson | Professor of Logic and Computation School of Computing | University of Kent | Canterbury, CT2 7NF, UK s.j.thompson(a)kent.ac.uk | M +44 7986 085754 | W www.cs.kent.ac.uk/~sjt Simon Thompson | Professor of Logic and Computation School of Computing | University of Kent | Canterbury, CT2 7NF, UK s.j.thompson(a)kent.ac.uk | M +44 7986 085754 | W www.cs.kent.ac.uk/~sjt

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export DataKinds
by Corentin Dupont 28 Feb '14

28 Feb '14

Hi Cafe, I create kinds using the DataKinds extension: {-# LANGUAGE DataKinds #-} module MyModule where data Foo = Bar | Baz The problem is that the generated Bar and Baz type constructors are not exported! I am obliged to put the pragma DataKinds in every package that uses MyModule (a lot). Is there a way to avoid that? Thanks! Corentin

2 2

Haskell spec vs FlexibleInstances
by Doug McIlroy 28 Feb '14

28 Feb '14

What potential evil motivates the prohibition of repeated type parameters in an instance declaration? (Restriction removed by FlexibleInstances) Doug McIlroy

6 6

[ANN] Rasterific & FontyFruity
by Vincent Berthoux 28 Feb '14

28 Feb '14

Hello Haskellers, I'm pleased to announce two new packages, whom work hand in hand: FontyFruity, a truetype file parser, and Rasterific a vector drawing engine. This two libraries enable us to generate pictures without the need of an external C library, and saving them to a file or directly send them over the network. FontyFruity: * hackage : http://hackage.haskell.org/package/FontyFruity * Github : https://github.com/Twinside/FontyFruity Rasterific: * hackage : http://hackage.haskell.org/package/Rasterific * Github : https://github.com/Twinside/Rasterific Regards Vincent

2 2

OutsideIn(X) question
by Alejandro Serrano Mena 27 Feb '14

27 Feb '14

Dear Haskell-café, I don't know if this is the best forum to ask questions about the OutsideIn(X) paper that lies below type inference in GHC. But given that this is the place where I know many GHC devs look at, I'll just try :) My question related about the proof of soundness and principality, specifically Lemma 7.2 (to be found in page 67). In that lemma, it's stated that QQ and \phi' Q_q ||- \phi Q_w <-> \phi' Q_w'. I'm trying to recover the proof (which is omitted in the text), but I stumble upon a wall when trying to work out what happens in the case an axiom is applied. In particular, I'm playing with an example where QQ (the set of axioms) = { forall. C a => D a } (where C and D are one-parameter type classes) Q_q = { } Q_w = { D Int } Thus, if I apply the rule DINSTW (to be found in page 65), I get a new Q_w' = { C Int } Now, if the lemma 7.2 is true, it should be the case that (1) QQ ||- C Int <-> D Int which in particular means that I have the two implications (2) { forall. C a => D a, C Int } ||- D Int (3) { forall. C a => D a, D Int } ||- C Int (2) follows easily by applying the AXIOM rule of ||- (as shown in page 54). However, I don't see how to make (3) work :( I think that understanding this example will be key for my understanding of the whole system. Anybody could point to the error in my reasoning or to places where I could find more information? Thanks in advance.

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Portfolio Analytics group at S&P CapitalIQ Hiring Summer Interns for 2014
by Gershom B 27 Feb '14

27 Feb '14

Our team is full of people with strong functional programming interests, and we even have an in-house Haskell-like DSL. To get a sense of the work we do, you can watch Edward Kmett's CUFP presentation (http://www.youtube.com/watch?v=o3m2NkusI9k) and browse his slides (http://cufp.org/sites/all/files/slides/2013/kmett.pdf) We have work that directly requires FP knowledge, and other work involving Scala, or even C# and SQL. If you are a college junior who wants to get paid to spend a summer in New York working in this environment, then apply by March 15 and see where it goes. You'll need to apply at the below web link, and _also_ email us directly so we can route your resume to our team. More than any particular experience or skills, we're interested in people who love computer science and like building new things. Application site: http://careers.mhfi.com/ShowJob/Id/131214/Software-Engineer-Summer-Intern-%… Additional contacts to email: smcfarland at spcapitaliq.com and gbazerman at spcapitaliq.com

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Berlin HUG meeting at Tuesday, March 4th
by Simon Hengel 26 Feb '14

26 Feb '14

Hi, we have regular Haskell meetings in Berlin, but I think it was never officially announced on this list. There is a meetup page [1] and the next meeting is at Tuesday, March 4th Big thanks to Adam for organizing things! One important thing, please join on meetup if you want to come! Cheers, Simon [1] http://www.meetup.com/berlinhug/

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[ANN] profiteur: a tool to visualise GHC .prof files
by Jasper Van der Jeugt 26 Feb '14

26 Feb '14

Hey all, I just released the tool profiteur [1]. You can use it to visualise GHC `.prof` files in a tree map -- I think this makes looking at huge `.prof` files a lot less unwieldy. More information can be found in this blogpost [2]. [1]: http://hackage.haskell.org/package/profiteur [2]: http://jaspervdj.be/posts/2014-02-25-profiteur-ghc-prof-visualiser.html Peace, Jasper

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Q: haskell type inference algorithm paper
by Di Xu 25 Feb '14

25 Feb '14

Hi, all I'm new to haskell, I'm learning haskell for its type system, and I found haskell type inference is excellent, I'm interested in its type inference algorithm, could you give me some paper or material reference that describe the haskell type inference algorithm? I want to port it to typed clojure.

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Haskell minimal (portable) development environment
by dabd 25 Feb '14

25 Feb '14

Hi, I am currently reading through Packer documentation http://www.packer.io/ and vagrant http://www.vagrantup.com/. I would like to set up a minimal reproducible Haskell development environment on Manjaro Linux (64-bit) running on VirtualBox. Does anyone have a Packer template for this distro or a Vagrant box for Haskell development on any other distro? Thanks.

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Fwd: manage effects in a DSL
by Corentin Dupont 25 Feb '14

25 Feb '14

Oleg: Very interresting, thanks. I have some questions: - 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? - 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)? Linsey, Jacques: Thanks for the pointer! I learned about data kinds. I tried to apply your suggestions to add a phantom type parameter to Exp. I came up to (I dropped the Free monad idea, which seems unrelated to the problem): > 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 > SetVictory :: Exp NoEffect Bool -> Exp Effect () -- same for SetVictory > OnTimer :: Exp Effect () -> Exp Effect () --OnTime can program whatever expression to be triggered every minutes, in particular effectful ones > Return :: a -> Exp r a > Bind :: Exp r a -> (a -> Exp r b) -> Exp r b This is the (simplified) game state: > data Game = Game { bankAccount :: Int, > victory :: Exp NoEffect Bool, > timerEvent :: Exp Effect ()} > -- victory when account > 100 > victoryRule' :: Exp Effect () > victoryRule' = SetVictory $ do > m <- readAccount > --WriteAccount (return $ m + 1) --won't compile (good) > return (m > 100) > --increase my bank account by 1 every minute > myTimer :: Exp Effect () > myTimer = OnTimer $ do > m <- readAccount > writeAccount (return $ m + 1) Do you have a better name suggestion for Eff? Other pointers where this idiom is realised?? Thanks!! Corentin

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segfault on fromIntegral (floor $ sqrt (-123.123)) == -123.123
by Erik Rantapaa 24 Feb '14

24 Feb '14

I'm getting a segfault on this expression entered into ghci: GHCi, version 7.6.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Prelude> fromIntegral (floor $ sqrt (-123.123)) == -123.123 Segmentation fault: 11 I'm running the 32-bit version of the Haskell Platform on OSX. Is this a bug? a problem with my setup? "Just don't take square roots of negative numbers - you should know better!"???

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Munich Haskell Meeting
by Heinrich Hördegen 24 Feb '14

24 Feb '14

Dear all, Wednesday, the 26th of February, our Monthly Haskell Meeting is taking place once again in Munich, Cafe Puck. We start at 19h30. If you plan to join, please go to http://www.haskell-munich.de/dates and hit the button. This time, we will have a guest from India, Raman, who will bring along some boards and shows us how to run PicoLisp [1] on bare metal. There is also work in progress for running Hugs [2] on bare metal. If you are interested in embedded systems, this will be surely an enlightening meeting. Raman is looking also for people from the Haskell community who are willing to help him embed Hugs or some other Haskell programming system on bare metal. If you are interested, I can make the contact. With hope to see many of you on Wednesday, Heinrich [1] http://picolisp.com/wiki/?home [2] http://www.haskell.org/hugs/

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#haddock lives
by Mateusz Kowalczyk 24 Feb '14

24 Feb '14

Hi all, This is just a small heads up that the IRC channel, #haddock (on Freenode) is now revived. Previously any Haddock chatter would have taken place across #ghc, #hackage, #hspec and #haskell which made it difficult to track. Please use this channel if you have questions. Thanks -- Mateusz K.

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Re: [Haskell-cafe] Is the wiki really this out of date?
by Dominic Steinitz 24 Feb '14

24 Feb '14

Daniil Frumin <difrumin <at> gmail.com> writes: > > There are also some interesting charts on ircbrowse: > http://ircbrowse.net/haskell > Very cool! Unless someone objects, I will update the 2009 data on the wiki with these more up-to- date presentations of the data.

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Want to create your first Haskell project?
by Roman Cheplyaka 24 Feb '14

24 Feb '14

Hi, I'd like to see an html test reporter for the tasty testing framework (http://documentup.com/feuerbach/tasty) I could do that myself, but I thought it would be a nice little project for someone who's about to write their first useful piece of Haskell. To participate you need to know Haskell on LYAH level and be good at html/css/js. If you're interested, get in touch. I'll provide help, review your code etc. Roman

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Data.Foldable UArray
by Marcus D. Gabriel 24 Feb '14

24 Feb '14

Hello, I wanted to make a simple Data.Foldable UArray, and I naively modelled it on > instance Ix i => Foldable (Array i) where > foldr f z = Prelude.foldr f z . elems with, of course, > instance Ix i => Foldable (UArray i) where > foldr f z = Prelude.foldr f z . elems which did not work yielding the following type message Could not deduce (IArray UArray a) arising from a use of `elems' from the context (Ix i) bound by the instance declaration at ... Possible fix: add an instance declaration for (IArray UArray a) In the second argument of `(.)', namely `elems' In the expression: Data.List.foldr f z . elems In an equation for `foldr': foldr f z = Data.List.foldr f z . elems I clearly do not understand something because I cannot make this work, and I am not sure why. With the Haskell type system or even with ghc extensions, can one even make a Data.Foldable UArray? If so, how? Thanks in advance, - Marcus

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[ANN] cabal-bounds: A command line program for managing the bounds/versions of the dependencies in a cabal file.
by Daniel Trstenjak 23 Feb '14

23 Feb '14

Hi all, If you have several cabalized projects, then it can be quite time consuming to keep the bounds of your dependencies up to date. Especially if you're following the package versioning policy, then you want to raise your upper bounds from time to time, to allow the building with newer versions of the dependencies. `cabal-bounds` tries to automate this update process to some degree. So a typical update process might look like: $> # update the version infos of all libraries $> cabal update $> # drops the upper bound of all dependencies in 'myproject.cabal', most likely you want to ignore 'base' $> cabal-bounds drop --upper --ignore=base myproject.cabal $> # create a cabal sandbox for building of 'myproject' $> cabal sandbox init $> # build 'myproject' $> cabal install $> # update the upper bound of all dependencies in 'myproject.cabal' by the cabal build information $> cabal-bounds update --upper --ignore=base myproject.cabal dist/dist-sandbox-*/setup-config Perhaps the currently most annoying thing is, that you have to live with the reformating of your `cabal` file done by the pretty printer of the `Cabal` library. https://github.com/dan-t/cabal-bounds Greetings, Daniel

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