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2nd Call for Papers: OCL and Textual Modeling Tools and Textual Model Transformations (OCL 2016) - Submit Your Paper Until July 17, 2016
by Achim D. Brucker 14 Jun '16

14 Jun '16

(Apologies for duplicates) Only four weeks until the deadline! -- Dr. Achim D. Brucker | Senior Lecturer | University of Sheffield https://www.brucker.ch/

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Package takeover (also: the future of Netwire)
by esz＠posteo.de 14 Jun '16

14 Jun '16

Hi everybody, I'd like to take over the following Hackage packages with my account named [esz]: * acme-schoenfinkel, * cascading, * continue, * contstuff-monads-tf, * contstuff-transformers, * contstuff, * dnscache, * fastirc, * ihttp, * instinct, * ismtp, * netlines, * netwire, * quickset, * web-page, * webwire, * yesod-tableview. These are actually already mine, but because my old account has become practically inaccessible, I'm now following the official [takeover procedure], asking myself whether I'm okay with that. =) After the takeover, I'm going to deprecate the following packages, unless someone would like to take over maintenance: * cascading: Clay is more comprehensive and easier to use. * contstuff*: Childhood experiments, because after writing a monad tutorial of course you must write an mtl replacement. * dnscache: Useful library, but needs maintenance. * fastirc: irc is reasonably efficient now (it used to be a String parser). * ihttp: use http-client. * ismtp: Useful library, but needs maintenance and should be rewritten using a modern streaming library. * netlines: use a modern streaming library. * netwire: Useful library, but needs maintenance and has high maintenance cost due to its design. I'll likely replace it by a new abstraction at some point, using a different package name. Currently I recommend using one of the following libraries for FRP: * reactive-banana: My former favourite when it comes to push/pull FRP. Well designed, clean semantics, reasonably efficient. * reflex: My current favourite when it comes to push/pull FRP. Well designed, clean semantics, reasonably efficient. * Yampa: AFRP for games, simulations and other real-time applications (for when a high and predictable framerate is more important than pushed events, same target domain as Netwire). * webwire: Experiment with FRP for handling server-side sessions in web applications. Works with some caveats, not that useful in practice. * yesod-tableview: needs maintenance, not that useful in modern web applications. That leaves the following packages for active maintenance by me, which includes making sure they compile, keeping them free of bugs and verifying/applying contributions. Most of these need maintenance right now: * acme-schoenfinkel: Surprisingly useful joke package. Needs a few adjustments to compile with modern GHC. * continue: Monad transformer for named reentry points, isomorphic to CofreeT. Ideally this should be just an interface to CofreeT from 'free', but unfortunately that one's instances are more restrictive than necessary (Alternative instead of Plus), making it useless. You couldn't use reasonable data structures like HashMap or Map. * instinct: Efficient feed-forward neural networks with backprop learning. To be replaced by a more general machine learning framework at some point, but still useful on its own. Needs maintenance. * quickset: Compact query-only binary search arrays. Needs a more comprehensive API. * web-page: Component system for web pages. Needs a more general API, because currently it makes too many assumptions on which packages you use (blaze-html, clay and jmacro). Note: do not confuse with Athan Clark's 'webpage' library. [esz]: https://hackage.haskell.org/user/esz [takeover procedure]: https://wiki.haskell.org/Taking_over_a_package Greets, Ertugrul

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Reminder: 10 days to submit talks to CUFP 2016
by Alex Lang 14 Jun '16

14 Jun '16

This CFP and the form for submitting presentation proposals can be found at: http://cufp.org/2016/call-for-presentations.html ---------------------------------------------------------------------- 2016 Call for Presentations Workshop for Commercial Users of Functional Programming 2016 Sponsored by SIGPLAN CUFP 2016 Co-located with ICFP 2016 Nara, Japan September 22-24 Talk Proposal Submission Deadline: 24 June 2016 The annual CUFP event is a place where people can see how others are using functional programming to solve real world problems; where practitioners meet and collaborate; where language designers and users can share ideas about the future of their favorite language; and where one can learn practical techniques and approaches for putting functional programming to work. ---------------------------------------------------------------------- Giving a CUFP Talk If you have experience using functional languages in a practical setting, we invite you to submit a proposal to give a talk at the event. We're looking for two kinds of talks: Retrospective talks are typically 25 minutes long. Now that CUFP has run for more than a decade, we intend to invite past speakers to share what they’ve learned after a decade spent as commercial users of functional programming. We will favour experience reports that include technical content. Technical talks are also 25 minutes long, and should focus on teaching the audience something about a particular technique or methodology, from the point of view of someone who has seen it play out in practice. These talks could cover anything from techniques for building functional concurrent applications, to managing dynamic reconfigurations, to design recipes for using types effectively in large-scale applications. While these talks will often be based on a particular language, they should be accessible to a broad range of programmers. We strongly encourage submissions from people in communities that are underrepresented in functional programming, including but not limited to women; people of color; people in gender, sexual and romantic minorities; people with disabilities; people residing in Asia, Africa, or Latin America; and people who have never presented at a conference before. We recognize that inclusion is an important part of our mission to promote functional programming. So that CUFP can be a safe environment in which participants openly exchange ideas, we abide by the SIGPLAN Conference Anti-Harassment Policy. If you are interested in offering a talk, or nominating someone to do so, please submit your presentation before 24 June 2016 via the CUFP 2016 Presentation Submission Form You do not need to submit a paper, just a short proposal for your talk. There will be a short scribe's report of the presentations and discussions but not of the details of individual talks, as the meeting is intended to be more of a discussion forum than a technical interchange. Nevertheless, presentations will be recorded and presenters will be expected to sign an ACM copyright release form. Note that we will need all presenters to register for the CUFP workshop and travel to Japan at their own expense. There are some funds available to would-be presenters who require assistance in this respect. ---------------------------------------------------------------------- Program Committee Katie Ots (Facebook), co-chair Alex Lang (Tsuru Capital), co-chair Rúnar Óli Bjarnason (Verizon Labs) Mark Hibberd (Ambiata) Mirai Ikebuchi (Nagoya University) Paul Khuong (AppNexus) Carin Meier (Cognitect) Kenji Rikitake (Kenji Rikitake Professional Engineer's Office) ---------------------------------------------------------------------- More information For more information on CUFP, including videos of presentations from previous years, take a look at the CUFP website at http://cufp.org. Note that presenters, like other attendees, will need to register for the event. Acceptance and rejection letters will be sent out by July 15th. ---------------------------------------------------------------------- Guidance on giving a great CUFP talk Focus on the interesting bits: Think about what will distinguish your talk, and what will engage the audience, and focus there. There are a number of places to look for those interesting bits. Setting: FP is pretty well-established in some areas, including formal verification, financial processing, and server-side web services. An unusual setting can be a source of interest. If you're deploying FP-based mobile UIs or building servers on oil rigs, then the challenges of that scenario are worth focusing on. Did FP help or hinder in adapting to the setting? Technology: The CUFP audience is hungry to learn about how FP techniques work in practice. What design patterns have you applied, and to what areas? Did you use functional reactive programming for user interfaces, or DSLs for playing chess, or fault-tolerant actors for large-scale geological data processing? Teach us something about the techniques you used, and why we should consider using them ourselves. Getting things done: How did you deal with large-scale software development in the absence of pre-existing support tools that are often expected in larger commercial environments (IDEs, coverage tools, debuggers, profilers) and without larger, proven bodies of libraries? Did you hit any brick walls that required support from the community? Don't just be a cheerleader: It's easy to write a rah-rah talk about how well FP worked for you, but CUFP is more interesting when the talks also cover what doesn't work. Even when the results were all great, you should spend more time on the challenges along the way than on the parts that went smoothly. ----------------------------------------------------------------------

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CUFP 2016 Call For Tutorials
by Román González 14 Jun '16

14 Jun '16

Hi all, The Commercial Users of Functional Programming (CUFP) 2016 has its Call for Tutorials open for submission. CUFP 2016 is being held in the historic city of Nara, Japan. The conference is devoted to showcase the state of the art of Functional Programming on industrial settings. This conference is co-located with the International Conference of Functional Programming (ICFP). We're looking for tutors that would like to host workshops on on the following themes: - Introductions to functional programming languages. In the past we have had sessions of Clojure, Erlang, F#, F*, Haskell, ML, OCaml, Scala, Scheme and others. - Advanced programming languages, concepts and applications (e.g. Lens, Liquid-Haskell, Agda, Idris, etc.) - Applying functional programming in particular areas, including Web, high-performance computing, finance. - Tools and techniques supporting state of the art functional programming. In the past we have had tutorials on QuickCheck, Elm and others. - Theory. Type theory, category theory, abstract algebra, ongoing or new research, and anything useful or interesting to functional programmers. If you'd like to submit a proposal, just fill this form http://goo.gl/forms/qoyK9qYPZhiDPSzO2. More info can be found at http://cufp.org/2016/call-for-tutorials.html Regards, Roman Gonzalez.

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[ANN] aivika-lattice-0.1
by David Sorokin 12 Jun '16

12 Jun '16

Hi Cafe, I’m glad to introduce a complete new module aivika-lattice [1] for the Aivika simulation library. It allows running nested discrete event simulations within lattice. If the naive approach implies that traversing the nested simulation nodes has an exponential complexity, then the lattice approach gives us a quadratical growth. This is a key feature, which makes the traversing a computationally feasible task even for a large size lattice. It can be useful for financial modeling, for instance. The model can be divided into two different parts. The first part is a discrete event simulation that branches in the lattice nodes. Within this simulation, we can update a mutable reference that can be observed in another part of the model. For example, such a reference can store a value of the modeled interest rate, or stock price, or exchange rate. It is important that the first part is forward traversing, when the time increases from the past to the future. The first part can even include discontinuous processes, resources, queues, streams of transacts if required. This is a general purpose simulation library. The second part is quite opposite. This is an estimating part. It is backward-traversing, where we estimate the past based on estimations of the future. When estimating, we can observe the mutable reference values. This is a bridge for connecting two different parts of the model. For example, we can estimate the price of the contract by the model of interest and exchange rates specified in the first part of the model. The package is quite experimental. It is mainly a proof of concept. There was no goal to achieve the highest possible speed of simulation, which is important for such tasks. Best regards, David Sorokin [1] http://hackage.haskell.org/package/aivika-lattice

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left to right pipeline of functions
by Christopher Howard 12 Jun '16

12 Jun '16

Hi, I am learning about monads, and this question came to mind: is there a way to have a sequence of functions left to right like so: g = return 2 >>= \n -> return (n + 1) >>= \n -> return (n + 3) Either: some kind of generic monad that makes this legal, or some way to do this without monad (i.e., without the "returns"). -- http://justonemoremathproblem.com To protect my privacy, please use PGP encryption. It's free and easy to use! My public key ID is 0x340EA95A (pgp.mit.edu)

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All-fail case in asum
by Юрий Сыровецкий (Yuriy Syrovetskiy) 11 Jun '16

11 Jun '16

Hello I want to define some parser such way: myParser = tryA <|> tryB <|> fail "input must be either A or B" It works. But then I want to rewrite it with asum: myParser = asum [tryA, tryB, fail "must be A or B"] It works, but the wrong way. Instead of my error it writes "empty". Just "empty". It is so because in base library asum = foldr (<|>) empty What if it was defined asum [] = empty asum [x:xs] = x <|> asum xs It would help me with my parser. But what can this break? Why isn't this done yet? -- Yuriy Syrovetskiy, http://cblp.su

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Call pattern specialization limit messages
by David Feuer 11 Jun '16

11 Jun '16

When I compile Data.Sequence with -dppr-debug, I get several messages about constructor specialization exceeding the call pattern limit. Things like SpecConstr Function ‘$j_ssfy{v} [lid]’ has four call patterns, but the limit is 3 Use -fspec-constr-count=n to set the bound Specialisations: [([sc_sAZr{v} [lid]], [sc_sAZr{v} [lid], lvl_sdmH{v} [lid]]), ([sc_sAZs{v} [lid]], [sc_sAZs{v} [lid], lvl_sw9X{v} [lid]]), ([sc_sAZt{v} [lid]], [sc_sAZt{v} [lid], lvl_swa0{v} [lid]]), ([sc_sAZu{v} [lid]], [sc_sAZu{v} [lid], lvl_swat{v} [lid]])] How can I figure out what function this sort of thing is actually talking about? I'd love to see what benchmarks say about whether tweaking -fspec-constr-count is a good idea, but I don't know what to benchmark. Thanks, David

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Re: [Haskell-cafe] All-fail case in asum
by David Feuer 10 Jun '16

10 Jun '16

Or, to keep it a fold, asum xs = foldr go (fromMaybe empty) xs Nothing where go x r Nothing = r (Just x) go x r (Just prev) = prev <|> r (Just x) On Jun 10, 2016 11:09 AM, "Dan Burton" <danburton.email(a)gmail.com> wrote: Add a pattern match for the single-element list to stop it from hitting the empty list base case. asum [] = empty asum [x] = x asum (x:xs) = x <|> asum xs On Friday, June 10, 2016, Tom Ellis < tom-lists-haskell-cafe-2013(a)jaguarpaw.co.uk> wrote: > On Fri, Jun 10, 2016 at 05:37:41PM +0300, Юрий Сыровецкий (Yuriy > Syrovetskiy) wrote: > > It is so because in base library > > > > asum = foldr (<|>) empty > > > > What if it was defined > > > > asum [] = empty > > asum [x:xs] = x <|> asum xs > > Those are the same (assuming you mean (x:xs) instead of [x:xs]). > > Tom > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe > -- -- Dan Burton _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe(a)haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe

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GHC 8 + ImpredictiveTypes + $
by Brendan Hay 10 Jun '16

10 Jun '16

Hi, I have had a number of trivial compilation failures in many of my projects that contain instances for MonadBaseControl (from monad-control) since upgrading to GHC 8. Now, I say 'trivial' since the actual fix is incredibly minor - a change of compose (.) to apply ($). What was less trivial was the (additional) hair loss arriving at the fix. I've put together a minimal example that demonstrates both the failing (pre-GHC8) and the fixed (GHC8) instances here: https://gist.github.com/brendanhay/e6f2501c15ac5160ca7dbb6ada6777f0 Since I found the error message somewhat directionless, I'd like some help actually understanding the root cause and why the 'fix' works: * I assume previously GHC did not fully check type aliases that were impredictive prior to GHC 8? * What does this imply for a type alias such as for the alias RunInBase used in monad-control that contains RankNTypes: http://hackage.haskell.org/package/monad-control-1.0.1.0/docs/Control-Monad… - Is such an alias not safe in some sense? (Was it never safe?) * How does the use of ($) vs (.) fix this particular issue? (I'd naively assume the usage here would be equivalent.) I recall reading about ($)'s magical type alias somewhere - is this related? Cheers, Brendan

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couldn't match expected type ByteString with actual type IO ByteString
by Carl Petersen 09 Jun '16

09 Jun '16

Hello All, I'm getting the following error: /apps/workspace/hade/src/Step/ReadExcel.hs:39:23: Couldn't match expected type ‘L.ByteString’ with actual type ‘IO L.ByteString’ In the first argument of ‘IBuf’, namely ‘j’ In the second argument of ‘sendChan’, namely ‘(IBuf j)’ when I compile the following code: data Buf = IChan (SendPort Buf) | IBuf (L.ByteString) deriving (Show,Generic,Typeable) instance Binary Buf readExcel :: Process() readExcel = do sendChan chan (IBuf j) where IChan chan = expect j = do r <- toTableRowsFromFile 8 "final-project.xlsx" let b = A.encode r return b remotable ['readExcel] Any ideas as to what I'm doing wrong? Carl

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FHPC'16 - deadline extension to 14th June
by David Duke 09 Jun '16

09 Jun '16

Dear colleagues, Following several requests for an extension, the submission deadline for FHPC'16 has been extended by 5 days to 15th June. ====================================================================== CALL FOR PAPERS FHPC 2016 The 5th ACM SIGPLAN Workshop on Functional High-Performance Computing Nara, Japan September 22, 2016 https://sites.google.com/site/fhpcworkshops/ Co-located with the International Conference on Functional Programming (ICFP 2016) Submission Deadline: Wednesday, 15 June, 2016 (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. Experience reports are also welcome. Proceedings: ============ FHPC 2016 seeks to encourage a range of submissions, focussing on work in progress and facilitating early exchange of ideas and open discussion on innovative and/or emerging results. To this end submissions should take the form of short (maximum 6 page) papers. Accepted papers will be published by the ACM and will appear in the ACM Digital Library. * Submissions due: Wednesday 15 June, 2016 (anywhere on earth) * Author notification: Friday, 8 July, 2016 * Final copy due: Sunday, 31 July, 2016 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. Papers should be no longer than 6 pages. Contributions to FHPC 2016 should be submitted via Easychair, at the following URL: * https://www.easychair.org/conferences/?conf=fhpc16 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: ==================== David Duke (co-chair) University of Leeds, UK Yukiyoshi Kameyama (co-chair) University of Tsukuba, Japan Baris Aktemur Özyeğin University, Turkey Marco Aldinucci University of Torino, Italy Jost Berthold Commonwealth Bank, Australia Kei Davis Los Alamos National Laboratory, USA Kento Emoto Kyushu Institute of Technology, Japan Zhenjiang Hu National Institute of Informatics, Japan Ben Lippmeier University of New South Wales, Australia Rita Loogen University of Marburg, Germany Geoffrey Mainland Drexel University, USA Mike Rainey INRIA, France Mary Sheeran Chalmers University of Technology, Sweden Satnam Singh Facebook, UK --- David Duke T: +44 113 3436800 Professor of Computer Science E: D.J.Duke(a)leeds.ac.uk Head, School of Computing W: www.comp.leeds.ac.uk/scsdjd/ PA: Gaynor Butterwick, E: G.Butterwick(a)leeds.ac.uk T: +44 113 3435767

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Haskell in Leipzig 2016: Second Call for Papers
by Joachim Breitner 09 Jun '16

09 Jun '16

Haskell in Leipzig September 14-15, 2016 HTKW Leipzig, Germany http://hal2016.haskell.org/ Allow me to remind everyone of the opportunity to talk about your research, projects or ideas at this year’s Haskell in Leipzig. The deadline is three weeks from now. == News == Unsure about whether HaL is interesting to you? No need to worry: Alejandro Russo (from Chalmers) is our keynote speaker and will talk about his work on information-flow control (i.e. SecLib, LIO, MAC, HLIO) – a great topic that is of interest to researchers, practitioners and beginners alike. == About HaL == The workshop series “Haskell in Leipzig”, now in its 11th year, brings together Haskell developers, Haskell researchers, Haskell enthusiasts and Haskell beginners to listen to talks, take part in tutorials, and join in interesting conversations. Everything related to Haskell is on topic, whether it is about current research, practical applications, interesting ideas off the beaten track, education, or art, and topics may extend to functional programming in general and its connections to other programming paradigms as well. This year, HaL is colocated with two related conferences, * the Workshop on Functional and (Constraint) Logic Programming (WFLP) and * the Workshop on (Constraint) Logic Programming (WLP), to form the Leipzig Week of Declarative Programming (L-DEC): http://nfa.imn.htwk-leipzig.de/LDEC2016/ In order to accommodate and welcome a more international audience, this year’s HaL will be held in English. == Submissions == Contributions can take the form of * talks (about 30 minutes), * tutorials (about 90 minutes), * demonstrations, artistic performances, or other extraordinary things. Please submit an abstract that describes the content and form of your presentation, the intended audience, and required previous knowledge. We recommend a length of 2 pages, so that the PC and the audience get a good idea of your submission, but this is not a hard requirement. You can submit your abstract, as an PDF document, at https://easychair.org/conferences/?conf=hal2016 until Friday, July 1, 2016. You will be notified by July 15, 2016. == Program committee == * Andreas Abel, Chalmers and Gothenburg University, Sweden * Heinrich Apfelmus, Leipzig, Germany * Joachim Breitner, Karlsruhe Institute of Technology, Germany (Chair) * Matthias Fischmann, Zerobuzz, Germany * Petra Hofstedt, BTU Cottbus-Senftenberg, Germany * Wolfgang Jeltsch, Institute of Cybernetics at Tallinn University of Technology, Estonia * Andres Löh, Well-Typed LLP, Germany * Alejandro Serrano Mena, Universiteit Utrecht, Netherlands * Neil Mitchell, Standard Chartered Bank, UK * Katie Ots, Facebook, UK * Peter Stadler, University of Leipzig, Germany * Henning Thielemann, Freelancer, Germany * Niki Vazou, University of California, San Diego, USA If you have any questions, please do not hesitate to contact Joachim Breitner <breitner(a)kit.edu>. -- Dr. rer. nat. Joachim Breitner Wissenschaftlicher Mitarbeiter http://pp.ipd.kit.edu/~breitner

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Call for talks: Haskell Implementors Workshop 2016, Sep 24 (FIXED), Nara
by Edward Z. Yang 09 Jun '16

09 Jun '16

(...and now with the right date in the subject line!) Call for Contributions ACM SIGPLAN Haskell Implementors' Workshop http://haskell.org/haskellwiki/HaskellImplementorsWorkshop/2016 Nara, Japan, 24 September, 2016 Co-located with ICFP 2016 http://www.icfpconference.org/icfp2016/ Important dates --------------- Proposal Deadline: Monday, 8 August, 2016 Notification: Monday, 22 August, 2016 Workshop: Saturday, 24 September, 2016 The 8th Haskell Implementors' Workshop is to be held alongside ICFP 2016 this year in Nara. It is a forum for people involved in the design and development of Haskell implementations, tools, libraries, and supporting infrastructure, to share their work and discuss future directions and collaborations with others. Talks and/or demos are proposed by submitting an abstract, and selected by a small program committee. There will be no published proceedings; the workshop will be informal and interactive, with a flexible timetable and plenty of room for ad-hoc discussion, demos, and impromptu short talks. Scope and target audience ------------------------- It is important to distinguish the Haskell Implementors' Workshop from the Haskell Symposium which is also co-located with ICFP 2016. The Haskell Symposium is for the publication of Haskell-related research. In contrast, the Haskell Implementors' Workshop will have no proceedings -- although we will aim to make talk videos, slides and presented data available with the consent of the speakers. In the Haskell Implementors' Workshop, we hope to study the underlying technology. We want to bring together anyone interested in the nitty-gritty details behind turning plain-text source code into a deployed product. Having said that, members of the wider Haskell community are more than welcome to attend the workshop -- we need your feedback to keep the Haskell ecosystem thriving. The scope covers any of the following topics. There may be some topics that people feel we've missed, so by all means submit a proposal even if it doesn't fit exactly into one of these buckets: * Compilation techniques * Language features and extensions * Type system implementation * Concurrency and parallelism: language design and implementation * Performance, optimisation and benchmarking * Virtual machines and run-time systems * Libraries and tools for development or deployment Talks ----- At this stage we would like to invite proposals from potential speakers for talks and demonstrations. We are aiming for 20 minute talks with 10 minutes for questions and changeovers. We want to hear from people writing compilers, tools, or libraries, people with cool ideas for directions in which we should take the platform, proposals for new features to be implemented, and half-baked crazy ideas. Please submit a talk title and abstract of no more than 300 words. Submissions should be made via HotCRP. The website is: https://icfp-hiw16.hotcrp.com/ We will also have a lightning talks session which will be organised on the day. These talks will be 5-10 minutes, depending on available time. Suggested topics for lightning talks are to present a single idea, a work-in-progress project, a problem to intrigue and perplex Haskell implementors, or simply to ask for feedback and collaborators. Organisers ---------- * Joachim Breitner (Karlsruhe Institut für Technologie) * Duncan Coutts (Well Typed) * Michael Snoyman (FP Complete) * Luite Stegeman (ghcjs) * Niki Vazou (UCSD) * Stephanie Weirich (University of Pennsylvania) * Edward Z. Yang - chair (Stanford University)

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Call for talks: Haskell Implementors Workshop 2016, Aug 24, Nara
by Edward Z. Yang 09 Jun '16

09 Jun '16

Call for Contributions ACM SIGPLAN Haskell Implementors' Workshop http://haskell.org/haskellwiki/HaskellImplementorsWorkshop/2016 Nara, Japan, 24 September, 2016 Co-located with ICFP 2016 http://www.icfpconference.org/icfp2016/ Important dates --------------- Proposal Deadline: Monday, 8 August, 2016 Notification: Monday, 22 August, 2016 Workshop: Saturday, 24 September, 2016 The 8th Haskell Implementors' Workshop is to be held alongside ICFP 2016 this year in Nara. It is a forum for people involved in the design and development of Haskell implementations, tools, libraries, and supporting infrastructure, to share their work and discuss future directions and collaborations with others. Talks and/or demos are proposed by submitting an abstract, and selected by a small program committee. There will be no published proceedings; the workshop will be informal and interactive, with a flexible timetable and plenty of room for ad-hoc discussion, demos, and impromptu short talks. Scope and target audience ------------------------- It is important to distinguish the Haskell Implementors' Workshop from the Haskell Symposium which is also co-located with ICFP 2016. The Haskell Symposium is for the publication of Haskell-related research. In contrast, the Haskell Implementors' Workshop will have no proceedings -- although we will aim to make talk videos, slides and presented data available with the consent of the speakers. In the Haskell Implementors' Workshop, we hope to study the underlying technology. We want to bring together anyone interested in the nitty-gritty details behind turning plain-text source code into a deployed product. Having said that, members of the wider Haskell community are more than welcome to attend the workshop -- we need your feedback to keep the Haskell ecosystem thriving. The scope covers any of the following topics. There may be some topics that people feel we've missed, so by all means submit a proposal even if it doesn't fit exactly into one of these buckets: * Compilation techniques * Language features and extensions * Type system implementation * Concurrency and parallelism: language design and implementation * Performance, optimisation and benchmarking * Virtual machines and run-time systems * Libraries and tools for development or deployment Talks ----- At this stage we would like to invite proposals from potential speakers for talks and demonstrations. We are aiming for 20 minute talks with 10 minutes for questions and changeovers. We want to hear from people writing compilers, tools, or libraries, people with cool ideas for directions in which we should take the platform, proposals for new features to be implemented, and half-baked crazy ideas. Please submit a talk title and abstract of no more than 300 words. Submissions should be made via HotCRP. The website is: https://icfp-hiw16.hotcrp.com/ We will also have a lightning talks session which will be organised on the day. These talks will be 5-10 minutes, depending on available time. Suggested topics for lightning talks are to present a single idea, a work-in-progress project, a problem to intrigue and perplex Haskell implementors, or simply to ask for feedback and collaborators. Organisers ---------- * Joachim Breitner (Karlsruhe Institut für Technologie) * Duncan Coutts (Well Typed) * Michael Snoyman (FP Complete) * Luite Stegeman (ghcjs) * Niki Vazou (UCSD) * Stephanie Weirich (University of Pennsylvania) * Edward Z. Yang - chair (Stanford University)

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ANN: Intero for Emacs
by Christopher Done 08 Jun '16

08 Jun '16

Here is a new Emacs package providing *very basic* Haskell programmer needs: - Type checking - Autocompletion - Go to definition - Type of selection - A basic REPL support It’s very simple, tries to *just work*, is based on Stack (required), the Emacs package auto-installs the correct version of its backend within your Stack working directory, supports the recently released GHC 8 all the way back to GHC 7.8.3. Having to configure anything to get basic functionality is considered a bug. The home page is here with details and demonstrations: http://commercialhaskell.github.io/intero/ The GitHub project where you can submit feature requests or bug reports: https://github.com/commercialhaskell/intero Thanks for reading!

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so strange but interesting
by dek5＠yandex.ru 08 Jun '16

08 Jun '16

Hi, I know it might be something strange, but still so interesting, you have to see it here <http://spalogoxe.njtec.com/aebez> Warmest, dek5(a)yandex.ru

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[ANN] New docs for the Aivika simulation platform
by David Sorokin 08 Jun '16

08 Jun '16

Hi Cafe, I wrote a new article "Aivika - A Constructor of General-Purpose Simulation Libraries" [1]. It uncovers key ideas of that how I implemented nested simulation and parallel distributed simulation in the Aivika platform [2]. Monads, immutable data structures, managed side effects, continuations, streams, recursive computations are all those things that are widely used in Aivika. The article can be useful for those who will have a willingness to use my simulation libraries for nested simulation, or distributed simulation, or some other field I cannot still imagine. Finally, I wrote a small tutorial for beginners [3]. It takes a simple discrete event simulation model and shows how we can add a Monte-Carlo experiment, save the results in the CSV files, plot histograms and charts, for the example, the deviation chart with a trend and confidence interval using rule 3-sigma. This tutorial can be used for quick diving into Aivika. All the programming code is written in Haskell. Best regards, David Sorokin Yoshkar-Ola, Russia [1] http://www.aivikasoft.com/en/tutorials/constructor/aivika-constructor.html [2] http://www.aivikasoft.com/en/products/aivika.html [3] http://www.aivikasoft.com/en/tutorials/beginners/aivika-tutorial-for-beginn…

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ANN: SciFlow-0.5.0
by Kai Zhang 07 Jun '16

07 Jun '16

Hi Cafe, I've been working on a package to manage data analysis pipelines, mainly for personal use. But I feel there may be others who are interested in this as well, so I just published an up-to-date version to hackage. Briefly, this package help you design and manage data analysis pipelines written in Haskell, with computation steps being just Haskell functions with type: a -> IO b. I use template Haskell to construct the dependency graph, and computation steps are assembled according to the graph and type checked at compile time. Each step can be configured to run either locally or on a remote machine. Concurrency is also supported. Independent steps will run simultaneously. Take a look at https://github.com/kaizhang/SciFlow for breif introduction and some examples. This package is still under heavy development, but it is quite stable otherwise as I've been using it on our cluster for some time. I hope you would find it useful and any feedback is welcome!

1 0

How to capture the output of GHCi :show command
by Alex 07 Jun '16

07 Jun '16

I would like to be able to bind the output of GHCi's :show to a variable, but I don't see a nice way to do so. Is it possible to do this directly in GHCi? My specific use for this is appending to the current prompt.

2 1

Vacancy: Professor Software technology at Utrecht University
by Johan Jeuring 07 Jun '16

07 Jun '16

The Faculty of Science at Utrecht University is seeking to appoint a Full Professor in Software Technology to lead, alongside the other two chairs, the division of Software Systems within the Faculty. The full Professor directs and supervises research in the field of software technology, specifically in the design and development of formalisms and methodologies for effective program construction and program analysis. She/he develops new initiatives, aiming at research programs in software technology. This includes the acquisition of external research funds, both at the national and international levels, and the dissemination of research results and its applications to the relevant research communities. The full professor has a leading role in teaching and supervision. She or he contributes to the department’s curriculum development at BSc, MSc and PhD levels. The full professor plays an active role in the leadership and administrative duties of the Department and/or Faculty. For more information about this vacancy, go to http://goo.gl/1vLeVc ——————— Johan Jeuring Department of Information and Computing Sciences Utrecht University The Netherlands http://www.jeuring.net/

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On-site GHC-related Haskell/C opportunity at Positive Technologies (Moscow)
by Kosyrev Serge 07 Jun '16

07 Jun '16

Good day! The Moscow office of Positive Technologies (https://www.ptsecurity.com) is looking for an experienced Haskell developer with a strong C background. You will be working in a team that develops a next generation security platform: think widely available, easy to use, dramatically enhanced security. In particular, we want you to help rewrite our core application in Haskell, which in turn requires porting GHC runtime to run on bare metal. Details can be seen in our Reddit posting: https://www.reddit.com/r/haskell/comments/4msraq/onsite_ghcrelated_haskellc… To apply, send you resume or questions to career(a)ptsecurity.com and CC skosyrev(a)ptsecurity.com. -- respectfully, Kosyrev Serge http://www.ptsecurity.com/ Habr: http://habr.ru/company/pt Twitter: @ptsecurity https://twitter.com/ptsecurity

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Re: [Haskell-cafe] New Haddock
by Johannes Waldmann 07 Jun '16

07 Jun '16

.. is hyperlinked source active on hackage when ghc-8 is used? here it is not: http://hackage.haskell.org/package/obdd-0.3.3/reports/1 - J.

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Re: [Haskell-cafe] New Haddock
by Johannes Waldmann 07 Jun '16

07 Jun '16

> You can now document your libraries even more beautifully Yes. Formulas are nice. But the main selling point is hyperlinked source? But it's really not applicable for me at the moment, because when I build with 7.10.3, I get (conflict: haddock-api => ghc>=8.0 && <8.2) I want to use it for documenting source that's not 8-ified. Well, perhaps my source is, but it depends on other packages that currently are not. - J.

1 0

uninstalling ghc-8.0.1-x86_64 installed through "install-haskell-platform.sh"
by Patrice 06 Jun '16

06 Jun '16

Hi all, How can I uninstall cleanly ghc-8.0.1-x86_64 that I installed using the script install-haskell-platform.sh (found on haskell.org website under Generic Linux). I'm on ubuntu Trusty. Thanks, Pat

2 2

Having issue in running Haskell code in Atom
by Balraj Singh 06 Jun '16

06 Jun '16

Hello All, I have started learning Haskell couple of days ago. I was looking for an IDE and found Atom as one of them. When I started using it I installed multiple packages and tried running creating Haskell files and saving it. This IDE always gives me following error. Please help to debug this: [Enter steps to reproduce below:] 1. ... 2. ... **Atom Version**: 1.7.4 **System**: Microsoft Windows 10 Pro **Thrown From**: [haskell-ghc-mod]( https://github.com/atom-haskell/haskell-ghc-mod) package, v1.14.5 ### Stack Trace Haskell-ghc-mod: ghc-mod failed to launch. It is probably missing or misconfigured. ENOENT ``` At Error: spawn ghc-mod ENOENT PATH: undefined path: undefined Path: C:\Program Files (x86)\Intel\iCLS Client\;C:\Program Files\Intel\iCLS Client\;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;C:\Program Files\Intel\Intel(R) Management Engine Components\DAL;C:\Program Files (x86)\Intel\Intel(R) Management Engine Components\DAL;C:\Program Files\Intel\Intel(R) Management Engine Components\IPT;C:\Program Files (x86)\Intel\Intel(R) Management Engine Components\IPT;C:\Program Files (x86)\ATI Technologies\ATI.ACE\Core-Static;C:\Users\Balraj Singh\.dnx\bin;C:\Program Files\Microsoft DNX\Dnvm\;C:\Program Files\Microsoft SQL Server\120\Tools\Binn\;C:\Program Files (x86)\Windows Kits\10\Windows Performance Toolkit\;C:\Program Files\Microsoft SQL Server\130\Tools\Binn\;C:\Program Files (x86)\Java\jdk1.7.0_71\lib;C:\Program Files (x86)\Java\jre7\lib;C:\Program Files (x86)\Java\jdk1.7.0_71\bin;C:\Program Files (x86)\Java\jre7\bin;C:\Program Files\Git\cmd;C:\Program Files (x86)\WinMerge;C:\ghc-8.0.1\bin;C:\Users\Balraj Singh\AppData\Local\atom\bin Error at file:///C:/Users/Balraj Singh/.atom/packages/haskell-ghc-mod/lib/util.coffee:60:26 at exithandler (child_process.js:232:5) at ChildProcess.errorhandler (child_process.js:244:5) at emitOne (events.js:77:13) at ChildProcess.emit (events.js:169:7) at Process.ChildProcess._handle.onexit (internal/child_process.js:198:12) at onErrorNT (internal/child_process.js:344:16) at doNTCallback2 (node.js:465:9) at process._tickCallback (node.js:379:17) ``` ### Commands ``` -8:25.4.0 core:backspace (atom-text-editor.editor.is-focused) 3x -8:22 core:save (atom-text-editor.editor.is-focused) -8:00.7.0 tabs:open-in-new-window (li.texteditor.tab.sortable.active.right-clicked) -7:50.5.0 tree-view:show-in-file-manager (span.name.icon.icon-file-text) -3:30.1.0 core:save (atom-text-editor.editor.is-focused) -3:22.2.0 haskell-ghc-mod:go-to-declaration (atom-text-editor.editor.is-focused) 2x -2:53 ide-haskell:prettify-file (atom-text-editor.editor.is-focused) -2:39.2.0 ide-haskell:toggle-output (atom-text-editor.editor.is-focused) -2:34.6.0 ide-haskell-cabal:build (atom-text-editor.editor.is-focused) -2:24.8.0 ide-haskell-cabal:test (atom-text-editor.editor.is-focused) -2:18.5.0 haskell-ghc-mod:check-file (atom-text-editor.editor.is-focused) -2:14.6.0 haskell-ghc-mod:lint-file (atom-text-editor.editor.is-focused) -2:03.4.0 ide-haskell:prettify-file (atom-text-editor.editor.is-focused) -1:53.1.0 haskell-ghc-mod:lint-file (atom-text-editor.editor.is-focused) 2x -0:59.2.0 haskell-ghc-mod:check-file (atom-text-editor.editor.is-focused) -0:03.8.0 haskell-ghc-mod:shutdown-backend (atom-text-editor.editor.is-focused) ``` ### Config ```json {} ``` ### Installed Packages ```coffee # User haskell-ghc-mod, v1.14.5 ide-haskell, v1.6.5 ide-haskell-cabal, v1.4.0 ide-haskell-repl, v0.0.23 language-haskell, v1.7.16 # Dev No dev packages ``` Regards, Balraj Singh

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New Haddock
by Dominic Steinitz 06 Jun '16

06 Jun '16

I couldn’t find an announcement of the new version of Haddock. You can now document your libraries even more beautifully. For example, > -- \[ > -- f(k;n,p) = \Pr(X = k) = \binom n k p^k(1-p)^{n-k} > -- \] will render as https://hackage.haskell.org/package/random-fu-0.2.7.0/docs/Data-Random-Dist… <https://hackage.haskell.org/package/random-fu-0.2.7.0/docs/Data-Random-Dist…> Also don’t forget you can put really nice diagrams in your documentation e.g. http://hackage.haskell.org/package/diagrams-contrib-1.3.0.7/docs/Diagrams-E… <http://hackage.haskell.org/package/diagrams-contrib-1.3.0.7/docs/Diagrams-E…> and http://hackage.haskell.org/package/diagrams-contrib-1.3.0.7/docs/Diagrams-T… <http://hackage.haskell.org/package/diagrams-contrib-1.3.0.7/docs/Diagrams-T…>. Dominic Steinitz dominic(a)steinitz.org http://idontgetoutmuch.wordpress.com

1 0

New version of itself
by martin 06 Jun '16

06 Jun '16

Hello all, I find myself frequentlly writing types like this data Logger a l = Lgr { runLogger :: a -> Log l -> (Log l, Logger a l) } The purpose is to give a logger a chance to carry an internal state. It could e.g. choose to log only every n invocations. To do this it must keep track of how many times it has been called. I want to leave such things private to the Logger. (1) I know that this is not an unusal thing to do, but it has an OO feel to it. Is there a more functional alternative to it. Should I just not worry? (2) I can write a combinator which creates a Logger from a list of Loggers. Since each Logger potentially returns a new version of itself, I must always re-assemble the combined logger from all the returned new versions. I am worried that this is a costly operation, particularly when most Loggers just return themselves unaltered. I don't have any hard numbers about the performance penalty though. These Loggers are used in a discrete-event-simulation and they will get called many times (once for each event), but only occastionally actually write to the Log.

6 9

haskell-ide-engine versus hsdev (and Debuggers)
by Leonard Janke 05 Jun '16

05 Jun '16

Hello, I am new to Haskell and thinking of contributing to the IDE efforts. I've noticed two projects which aim to provide a "service" that editors and IDEs can call to help present useful information to programmers. I am wondering how these projects differ and why they are separate efforts since they seem to have very similar end goals? Another thing that I am wondering is if either of these two projects aims to provide debugger support and what the general state of debuggers for Haskell is? I've seen a project for a Haskell remote debugger which looks it was ghci/interpreter based and was being used by Eclipse and IntelliJ. It didn't work when I tried it, however, and I am not sure that the project is still active. It also looks like ghc only recently began adding support for debugging compiled Haskell and that initial efforts may be to get things working with gdb or lldb. Am I correctly understanding the current landscape as far as Haskell debuggers go? Thanks! Leonard

2 1

Final CFP: 4th ACM SIGPLAN International Workshop on Functional Art, Music, Modelling and Design
by Michael Sperber 05 Jun '16

05 Jun '16

4th ACM SIGPLAN International Workshop on Functional Art, Music, Modelling and Design http://functional-art.org/2016/ Co-located with ICFP Nara, Japan, 24 September, 2016 Key Dates: Submission deadline - June 24 Author Notification - 15 July Camera Ready - 31 July Workshop - September 24, 2016 We welcome submissions from academic, professional, and independent programmers and artists. Final Call for Papers, Demos, *and* Performances The ACM SIGPLAN International Workshop on Functional Art, Music, Modelling and Design (FARM) gathers together people who are harnessing functional techniques in the pursuit of creativity and expression. Functional Programming has emerged as a mainstream software development paradigm, and its artistic and creative use is booming. A growing number of software toolkits, frameworks and environments for art, music and design now employ functional programming languages and techniques. FARM is a forum for exploration and critical evaluation of these developments, for example to consider potential benefits of greater consistency, tersity, and closer mapping to a problem domain. FARM encourages submissions from across art, craft and design, including textiles, visual art, music, 3D sculpture, animation, GUIs, video games, 3D printing and architectural models, choreography, poetry, and even VLSI layouts, GPU configurations, or mechanical engineering designs. Theoretical foundations, language design, implementation issues, and applications in industry or the arts are all within the scope of the workshop. The language used need not be purely functional ("mostly functional" is fine), and may be manifested as a domain specific language or tool. Moreover, submissions focusing on questions or issues about the use of functional programming are within the scope. Submit at : https://easychair.org/conferences/?conf=farm2016

1 0

Strange type error with -XTypeApplications
by Mitchell Rosen 04 Jun '16

04 Jun '16

This program: * {-# LANGUAGE TypeApplications #-}* * main = print (fromDynamic @Int undefined)* produces this error message: * foo.hs:3:15: error:* * • Cannot apply expression of type ‘t0’* * to a visible type argument ‘Int’* * • In the first argument of ‘print’, namely* * ‘(fromDynamic @Int undefined)’* * In the expression: print (fromDynamic @Int undefined)* * In an equation for ‘main’:* * main = print (fromDynamic @Int undefined)* However, I'd expect it to be "Not in scope: fromDynamic"

1 0

Accumulating and threading output of functions
by martin 04 Jun '16

04 Jun '16

Hello all, I have a number of functions, whose type is something like this: f:: a -> b -> (b, c) i.e. it returns a modified b and an additional c. Now I want to write a combinator, which assembles a list of such functions into a single one. This combinator will have to thread the bs from one function to the next and accumulate the cs into a single c. While I was able to write this using a fold, I am not happy with it (my first attempt had a bad error in it, which is always a bad sign). Are you aware of any idioms, how to do such things on the beaten track?

4 3

announce: arithmoi 0.4.2.0
by Carter Schonwald 04 Jun '16

04 Jun '16

It is with great pleasure that the arithmoi maintainers (andrew lelechenko and myself) would like to share the 0.4.2.0 release with the haskell community. This release https://hackage.haskell.org/package/arithmoi-0.4.2.0 includes a multiplicatively infinite (but addititively finite) increase in test coverage and correspondingly every known bug in arithmoi has been fixed (so theres no known crashing/faulting bugs, and all tested code gives mathematically correct answers) I would especially like to thank Andrew Lelechenko for becoming a fellow maintainer, his incredibly meticulous, clean, thorough engineering is really what made this release possible and excellent. this should treated as a stable library version release.

1 0

Month in Haskell Mode May 2016
by Gracjan Polak 04 Jun '16

04 Jun '16

Hi, Month in Haskell Mode May 2016 progress report is available: https://github.com/haskell/haskell-mode/wiki/Month-in-Haskell-Mode-May-2016 -- Gracjan

1 0

10 open roles in expanding team at Standard Chartered
by Don Stewart 03 Jun '16

03 Jun '16

I have another ten open roles in the growing Strats team at Standard Chartered. https://donsbot.wordpress.com/2016/06/03/multiple-haskell-developer-roles-i… These are full time or contract Haskell developer positions in London or Singapore. Details in the post .

1 0

how to reify an API?
by Johannes Waldmann 02 Jun '16

02 Jun '16

Dear Cafe, I wanted to benchmark (part of) an API of a package, by enumerating all possible (nested) calls by size of their AST, much as smallcheck does it for data. So I made this straightforward AST representation and (generically) got its Serial instances. That last part has been in smallcheck for a long time, and works nicely. But I do wonder if there is a way to get the AST (and corresponding interpreter) with less boilerplate code (than this: https://github.com/jwaldmann/pretty-test/blob/master/src/Lib.hs#L29 ) If you read the code: it also has a type for "AST contexts" because I wanted to iterate them (to produce larger trees). Again - easy to write down, but boring. - J.

1 0

Re: [Haskell-cafe] Is there any way to use somethig like global backtrack with parsec
by Erik Rantapaa 01 Jun '16

01 Jun '16

If don't have to use Parsec, you can use a parser library like ReadP / ReadS. For example: import Text.ParserCombinators.ReadP abc = (choice [ string "a", string "ab" ] ) >> char 'c' >> eof run p s = case (readP_to_S p) s of [] -> Left "no parse" ((a,_):_) -> Right a test1 = run abc "ac" test2 = run abc "abc" test3 = run abc "ab" -- should fail On Monday, May 30, 2016 at 1:15:25 PM UTC-5, Petr Sokolov wrote: > > For example this parser doesn't parse "abc" > > test :: Parser String > test = ((try $ string "a") <|> (string "ab")) *> (string "c") > > I can rewrite it so it would parse "abc", but is there any general > approach to force parser to return and try other branches? > > (try a <|> b) *> c > > Something like > > (tryOtherBranchesIfFail (try a <|> b)) *> c > > So if it cannot parse "abc" with (try a *> c) it could return and try (b > *> c) > Or it isn't possible? > >

2 1

SIGPLAN Programming Languages Mentoring Workshop @ ICFP
by Lindsey Kuper 31 May '16

31 May '16

SIGPLAN Programming Languages Mentoring Workshop @ ICFP Nara, Japan (co-located with ICFP 2016) Sunday, September 18th, 2016 http://conf.researchr.org/track/icfp-2016/PLMW-ICFP-2016/ We are pleased to invite students interested in functional programming research to the programming languages mentoring workshop at ICFP. The goal of this workshop is to introduce senior undergraduate and early graduate students to research topics in functional programming as well as provide career mentoring advice. We have recruited leaders from the functional programming community to provide overviews of current research topics and give students valuable advice about how to thrive in graduate school, search for a job, and cultivate habits and skills that will help them in research careers. This workshop is part of the activities surrounding ICFP, the International Conference on Functional Programming, and takes place the day before the main conference. One goal of the workshop is to make the ICFP conference more accessible to newcomers and we hope participants will stay through the entire conference. Through the generous donation of our sponsors, we are able to provide travel scholarships to fund student participation. These travel scholarships will cover reasonable travel expenses (airfare and hotel) for attendance at both the workshop and the main three days of the ICFP conference. The workshop is open to all. Students with alternative sources of funding for their travel and registration fees are welcome. In particular, many student attendance programs provide full or partial travel funding for students to attend ICFP 2016, including the ACM Student Research Competition. More information about student attendance programs at ICFP is available: http://conf.researchr.org/home/icfp-2016 Application for Travel Support: The travel funding application is available from the PLMW webpage. The deadline for full consideration of funding is July 1st, 2016. Selected participants will be notified by July 15th. Organizers: Amal Ahmed, Northeastern University Robby Findler, Northwestern University Atsushi Igarashi, Kyoto University

1 0

Does the GHC GC handle const application?
by David Feuer 31 May '16

31 May '16

If I create a thunk representing const x y will the garbage collector be sure to replace this with x? I'm just wondering if I have to be concerned about the fact that Data.Sequence defines update in terms of adjust, with update x = adjust (const x)

2 2

JSON parser that returns the rest of the string that was not used
by Ryan Newton 31 May '16

31 May '16

As someone who spent many years putting data in S-expression format, it seems natural to me to write multiple S-expressions (or JSON objects) to a file, and expect a reader to be able to read them back one at a time. This seems comparatively uncommon in the JSON world. Accordingly, it looks like the most popular JSON parsing lib, Aeson, doesn't directly provide this functionality. Functions like decode just return a "Maybe a", not the left-over input, meaning that you would need to somehow split up your multi-object file before attempting to parse, which is annoying and error prone. It looks like maybe you can get Aeson to do what I want by dropping down to the attoparsec layer and messing with IResult. But is there a better way to do this? Would this be a good convenience routine to add to aeson in a PR? I.e. would anyone else use this? Thanks, -Ryan

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Quantum Programming EDSLs other than Quipper
by Nicola Gigante 30 May '16

30 May '16

Hi all, Quipper [1] is a well-known library that provides an EDSL for writing and simulating quantum algorithms in Haskell. I was wondering if there was any other attempt to design an EDSL in Haskell to express quantum algorithms. In particular, Quipper is not able to statically ensure that the algorithm written is physically meaningful, as one could violate the "non-cloning property", for example (a qubit cannot be copied, for those who do not speak quantumly). Violations like this are detected at runtime when simulating the algorithm or when producing the corresponding circuit as output. Authors of Quipper already said that some of those properties could be possible to check “if Haskell had linear types”. The point is that Haskell's support for dependently typed programming has grown quite a lot in the last years, and I think that, at least theoretically, something better can now be achieved. So do anyone know any more recent attempt to express quantum computations in an Haskell EDSL that leverages cutting-edge type-level features to statically check for physically meaningful programs? Greetings, Nicola [1]: http://www.mathstat.dal.ca/~selinger/quipper/

2 4

configurable mapping between data declarations and given XML schema?
by Johannes Waldmann 30 May '16

30 May '16

Dear Cafe, I have a legacy XML schema, and some Haskell data declarations. I want to map bidirectionally between XML documents and data. I absolutely cannot change the schema. I could change the data declarations, but it would not help much, since I don't think there is any form of declaring data that would allow me to derive the transformations generically. So, I have a mess of ad-hoc transformations. What could be done about this? I think I need "generic with customization". More detail: https://github.com/jwaldmann/haskell-tpdb/issues/16 Comments appreciated. - J.W.

3 2

Mobile Development
by Justin Wood 29 May '16

29 May '16

I'm wondering if anyone has any experience they can share, know of any blog posts or anything else documenting the use of Haskell when developing a mobile application. Ideally, I would like something along the lines of having a native UI, a language bridge, and use Haskell for the core logic. My main focus would be getting this to work on Android and iOS. If this would also work on Blackberry and Windows Phone it would be a plus. I have successfully done this using C++ in place of Haskell in the past, but would really be interested in getting something working using Haskell. Thanks, Justin

4 3

Testing for different dependency versions?
by Christopher Howard 29 May '16

29 May '16

Hi, I was wondering: what is the most practical way to go about testing or otherwise determining if your packaged library works with other dependency versions? E.g., cabal init specified base 4.6 because that is what happens to be installed on my Debian Jessie system, but that wouldn't even build on hackage. -- http://justonemoremathproblem.com To protect my privacy, please use PGP encryption. It's free and easy to use! My public key ID is 0x340EA95A (pgp.mit.edu)

2 1

Re: [Haskell-cafe] Testing for different dependency versions?
by Simon Jakobi 29 May '16

29 May '16

(I'm sending this again because I had subscribed to the mailing list with a different email address) Hi! I'm not sure if there's a better tool out there but I think stack (http://haskellstack.org/) is pretty convenient for testing a package with different versions of base and other packages on the same system. To test your package with base-4.7 you'd simply run stack test --resolver ghc-7.8 --install-ghc To test your package with base-4.8.2.0 and pkg-x-1.2.3 you'd save the following in a stack.yaml in the same directory as your cabal file: resolver: ghc-7.10.3 extra-deps: - pkg-x-1.2.3 Then run stack solver --update-config to add the remaining dependencies and stack test to build the package and run the tests. If you have your package on Github you can also use Travis CI to test your package with different configurations: http://docs.haskellstack.org/en/stable/travis_ci/ Hope that helps! Simon

1 1

Higher order type functions
by Matt 28 May '16

28 May '16

Hi folks! I'm playing with GHC 8 and have the following type family definend: type family InsertSorted (gt :: k -> k -> Bool) (a :: k) (xs :: [k]) :: [k] where InsertSorted f a '[] = '[a] InsertSorted f a (x ': xs) = If (f a x) (x ': InsertSorted f a xs) (a ': x ': xs) With appropriate type functions, I can evaluate this in GHCi with `:kind!` and it does what I want: λ> :kind! InsertSorted GreaterThan One '[Two, Four] InsertSorted GreaterThan One '[Two, Four] :: [Face] = '['One, 'Two, 'Four] λ> :kind! InsertSorted GreaterThan Queen '[Two, Four] InsertSorted GreaterThan Queen '[Two, Four] :: [Face] = '['Two, 'Four, 'Queen] However, I get an error if I try to use this in a type signature. This code: data Deck (b :: [k]) where Empty :: Deck '[] (:::) :: CardT s f -> Deck xs -> Deck (InsertSorted GreaterThan '(s, f) xs) gives me this error: • The type family ‘GreaterThan’ should have 2 arguments, but has been given none • In the definition of data constructor ‘:::’ In the data type declaration for ‘Deck’ What's the best way to use higher order type families? Thanks! Matt Parsons Here's the definitions I'm using for the above code: data Face = One | Two | Three | Four | Five | Six | Seven | Eight | Nine | Jack | Queen | King deriving (Eq, Ord, Bounded, Enum) type family FaceOrd (a :: Face) (b :: Face) :: Ordering where FaceOrd a a = 'EQ FaceOrd a 'One = 'GT FaceOrd 'One a = 'LT FaceOrd a b = FaceOrd (PredFace a) (PredFace b) type family FaceGT (a :: Face) (b :: Face) :: Bool where FaceGT a b = CompK a b == GT class GtK (a :: k) where type GreaterThan (a :: k) (b :: k) :: Bool instance GtK (a :: Face) where type GreaterThan a b = CompK a b == GT

3 3

read "2" in a "void" context?
by Erik Rantapaa 28 May '16

28 May '16

Hi fellow Haskellers! If I bring up ghci and evaluate `read 2` I get the error "Prelude.read: no parse" GHCi, version 7.10.2: http://www.haskell.org/ghc/ :? for help Prelude> read "2" *** Exception: Prelude.read: no parse Exactly how is this message coming about? I understand that `read` needs a return type in order to determine which type class instance to run. So, in this case, which type is `read` being asked to return? Thanks, Erik

4 4

Reminder: Functional High-Performance Computing 2016
by David Duke 28 May '16

28 May '16

Dear colleagues, A reminder of the approaching paper deadline (10th June) for FHPC 2016 ... ====================================================================== CALL FOR PAPERS FHPC 2016 The 5th ACM SIGPLAN Workshop on Functional High-Performance Computing Nara, Japan September 22, 2016 https://sites.google.com/site/fhpcworkshops/ Co-located with the International Conference on Functional Programming (ICFP 2016) Submission Deadline: Friday, 10 June, 2016 (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. Experience reports are also welcome. Proceedings: ============ FHPC 2016 seeks to encourage a range of submissions, focussing on work in progress and facilitating early exchange of ideas and open discussion on innovative and/or emerging results. To this end submissions should take the form of short (maximum 6 page) papers. Accepted papers will be published by the ACM and will appear in the ACM Digital Library. * Submissions due: Friday, 10 June, 2016 (anywhere on earth) * Author notification: Friday, 8 July, 2016 * Final copy due: Sunday, 31 July, 2016 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. Papers should be no longer than 6 pages. Contributions to FHPC 2016 should be submitted via Easychair, at the following URL: * https://www.easychair.org/conferences/?conf=fhpc16 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: ==================== David Duke (co-chair) University of Leeds, UK Yukiyoshi Kameyama (co-chair) University of Tsukuba, Japan Baris Aktemur Özyeğin University, Turkey Marco Aldinucci University of Torino, Italy Jost Berthold Commonwealth Bank, Australia Kei Davis Los Alamos National Laboratory, USA Kento Emoto Kyushu Institute of Technology, Japan Zhenjiang Hu National Institute of Informatics, Japan Ben Lippmeier University of New South Wales, Australia Rita Loogen University of Marburg, Germany Geoffrey Mainland Drexel University, USA Mike Rainey INRIA, France Mary Sheeran Chalmers University of Technology, Sweden Satnam Singh Facebook, UK

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Re: [Haskell-cafe] Fwd: representing institutions in haskell
by Till Mossakowski 28 May '16

28 May '16

Dear Rick, actually, in the Hets system [1], which is one of the largest Haskell programs, we have represented logics as institutions since 2002. Hets comprises of about 25 logics represented as institutions, including propositional logic, first-order logic, higher-oder logic, modal logic, OWL, and even some functional programming language. Hets provides parsing, static analysis, and proof management for logical theories formulated within these institutions (and also heterogeneous theories spanning several institutions). Interfaces to various theorem provers, SAT solvers and model finders are included. Hets' input language is the Distributed Ontology, Model and Specification language (DOL) [2], which has been standardized by the Object Management Group (OMG). More specifically, Hets employs a type class "Category" for representing categories, with functions for identities, domain, codomain and composition. On top of this, institutions form a multi-parameter type class "Logic", with a representation of signatures and signature morphisms as a category. The set of sentences is represented as one parameter type. This is a pragmatic decision, since in most institutions, sentences are uniform over signatures, and making this dependent on signature would be much more complicated. But many functions on sentences depend on a signature. Sentence translation along a signature morphism is represented by a function of the type class as well. Models and satisfaction are generally not represented due to their (in general) infinitary nature. But in some case, we represent models as certain theories, e.g. when processing the output of some model finder. Such models can even be translated using institution comorphisms. That said, we are interested in improving the representations of institutions in Hets, e.g. by making more using some libraries for category theory that have not been available in 2002 when we started Hets. However, I must admit that I did not understand your representation, Rick. Could you explain its general principles? What is the purpose of having "data Sign a = Sign a"? Why do conjunction and disjunction play such a role, given that there are institutions like equational logic that neither have conjunction nor disjunction? I could I execute your code, neither with ghc 7.6.3, nor ghc 8.0.2. I suggest that you choose some simple logic, like propositional logic, and represent it as an institution in Haskell with your approach. Then we will have a better basis for discussion. Best, Till [1] http://hets.eu [2] http://dol-omg.org Am 17.05.2016 um 14:55 schrieb rick: > Hello Christian: > > I thought I should send this to you separately in case you are not on > the Haskell list any more. > > You may enjoy the samples below which use some standard Haskell > libraries that may not have been available when you and Till started > work on HETS. > > -- > Rick > > -------- Forwarded Message -------- > Subject: [Haskell-cafe] representing institutions in haskell > Date: Mon, 16 May 2016 15:13:34 -0400 > From: rick <rick(a)rickmurphy.org> > To: haskell-cafe(a)haskell.org > > Has anyone here taken an interest in representing institutions [1] in > Haskell? > > Institutions originated in work on CLEAR [2] which was the first > algebraic specification language with rigorous semantics. > > Institutions take some time to explain, or unravel if you follow the > reference, but they come with a convenient slogan : "Truth is invariant > under change of notation." > > The stretch goal of institutions is transforming logics while preserving > satisfaction. > > They are conceived in terms of categorical abstractions, so it's natural > to represent them in categories. I hope some folks here find > institutions a useful domain to apply their work on categories. > > I've attached two samples in Haskell that uses some standard libraries : > Arrow, Monad, Category and Dual. > > The first sample, ri-0, outlines the essentials. The category of > signatures, constructions in the categories, signature morphisms, > sentences, models and the satisfaction condition. > > Using plain old Nat reduces the complexity of the exposition. > > I provide a constructive witness for satisfaction of the morphism from > conjunction to disjunction. > > You may recognize that I borrow some Bird/Hinze notation on Functors > like mapSign. And you find some experiments with Quickcheck and Yampa. > > Ri-0 runs from main, but just computes the witness to the satisfaction > condition. > > The second sample, ri-1, builds on ri-0. Rather than Nat, I use Either > to inject disjunction into the exposition. The exposition becomes more > complex, but the increased complexity is justified because maintaining > satisfaction under change on notation is central to institutions. > > The functions prodSum takes conjunction to disjunction and sumProd takes > disjunction to conjunction. I owe a citation to @BartoszMilewski and his > work on categories for programmers where I first saw these functions. > > The satisfaction condition and witness appear more complex in ri-1, but > its really just the substitution of the signature morphism on product > and sum rather than plain old Nat as in ri-0. > > I also plan a better write up, but before I do I expect to learn much > from an email exchange with interested folks here. > > Thanks for taking a look at this material. > > 1. https://cseweb.ucsd.edu/~goguen/pps/ins.ps > > 2. http://hopl.info/showlanguage.prx?exp=945 >

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Announce: Haskell Platform 8.0.1
by Gershom B 28 May '16

28 May '16

On behalf of the Haskell Platform team, I'm happy to announce the release of Haskell Platform 8.0.1 Now available at https://www.haskell.org/platform/ This platform includes features initially planned in the "Improving the 'Get Haskell Experience'" proposal of June 2015. [1] * Minimal as well as Full distributions. The minimal distribution only includes GHC core libraries as well as additional tools. This is now the recommended distribution. The Full distribution remains an option for those who want a one-step installer with the broader set of platform libraries preinstalled. * Inclusion of the Stack tool for developing Haskell projects [2] Other highlights of this release include the following * The new cabal 1.24 including the great "new-build" tech preview of nix-like build dependency management [3] * On windows, a cabal/msys setup that allows packages such as "network" to build "out of the box". (almost*) * At long last, prebuilt Linux 32 bit platform installers Changes to Contents: * Some packages have been removed from the installed packages set (both minimal and full) including old-locale, old-time, cgi, and the transitive cgi dependencies: transformers-compat, multipart, and exceptions. * fixed has been added to the platform as a transitive dependency of GLUT. A full list of contents is available at https://www.haskell.org/platform/contents.html Thanks to all the contributors to this release, thanks to all the package and tool maintainers and authors, and a big thanks to the GHC team for putting together such an exciting new compiler release! A fuller list of new GHC changes is available at: https://mail.haskell.org/pipermail/ghc-devs/2016-May/012098.html A fuller list of new cabal changes is available at: http://coldwa.st/e/blog/2016-05-04-Cabal-1-24.html Happy Haskell Hacking all, Gershom [1] http://projects.haskell.org/pipermail/haskell-platform/2015-July/003129.html [2] http://haskellstack.org [3] http://blog.ezyang.com/2016/05/announcing-cabal-new-build-nix-style-local-b… * To build "network" and other msys-dependent packages on windows, you will need to augment your cabal config file with the following lines: extra-prog-path: C:\Program Files\Haskell Platform\8.0.1\msys\usr\bin extra-lib-dirs: C:\Program Files\Haskell Platform\8.0.1\mingw\lib extra-include-dirs: C:\Program Files\Haskell Platform\8.0.1\mingw\include

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