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Munich Haskell Meeting, 2017-09-25 @ 19:30
by Christian Neukirchen 22 Sep '17

22 Sep '17

Dear all, Next week, our monthly Munich Haskell Meeting will take place again on Monday, September 25 at Max Emanuel Brauerei at 19h30. For details see here: http://muenchen.haskell.bayern/dates.html If you plan to join, please add yourself to this dudle so we can reserve enough seats! It is OK to add yourself to the dudle anonymously or pseudonymously. https://dudle.inf.tu-dresden.de/haskell-munich-sep-2017/ Everybody is welcome! cu, -- Christian Neukirchen <chneukirchen(a)gmail.com> http://chneukirchen.org

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Curious why there's no ioe_description accessor in System.IO.Error?
by Viktor Dukhovni 21 Sep '17

21 Sep '17

The IOError type re-exported from GHC.IO.Exception by System.IO.Error has accessors for some of the error elements fields, but is notably missing an accessor for ioe_description, which is only available as "ioeGetErrorString" for UserError, for all other errors you just get the string form of the error type: ioeGetErrorType :: IOError -> IOErrorType ioeGetErrorString :: IOError -> String ioeGetLocation :: IOError -> String ioeGetHandle :: IOError -> Maybe Handle ioeGetFileName :: IOError -> Maybe FilePath ioeGetErrorString ioe | isUserErrorType (ioe_type ioe) = ioe_description ioe | otherwise = show (ioe_type ioe) the real ioe_description for other error types can only be brought into scope by importing GHC.IO.Exception instead, or alternatively via the System.IO.Error.Lens: -- | Error type specific information. description :: Lens' IOException String description f s = f (ioe_description s) <&> \e -> s { ioe_description = e } {-# INLINE description #-} I am curious why ioeGetDescription was left out of System.IO.Error, and/or why it should not be added? Somehow it feels "wrong" to import GHC.IO.Exception instead of System.IO.Error just to get at the specific error text... Is it the case that, given all the other language extensions my code depends on, I should not have any qualms about importing GHC.* modules? Or perhaps is it the case that one should just start using lens, and so adding "missing" record accessors just delays migration to the right way and is no longer a priority? -- Viktor.

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Traversable instance for ((->) a)?
by David Banas 20 Sep '17

20 Sep '17

Is there a Traversable instance for ((->) a)? -db

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Re: [Haskell-cafe] Why is Haskell so slow (comparing to Java/Scala)?
by Saurabh Nanda 20 Sep '17

20 Sep '17

Intresting. Wont using "void" or "_ <- forM blah" have the same effect? Why not? On 20-Sep-2017 9:37 PM, "Nick Smallbone" <nick(a)smallbone.se> wrote: Hi Stanislav, Станислав Черничкин <schernichkin(a)gmail.com> writes: > I've wrote simple Haskell benchmark program, which populated primitive vector > from vector package: > > ... > void $ for [0..1000000 - 1] $ flip (P.unsafeWrite v) (1 :: Int) 'for' is a variant of 'map' - it returns a list of results (in this case a list of a million () values). Instead you should use 'forM_' (note the underscore) from Control.Monad, which discards the result - that cuts the runtime by a huge amount when I try it. (And make sure to compile with -O too.) Nick _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.

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Call for Contributions: BOB 2018 - Berlin, Feb 23, 2018
by Matthias Fischmann 20 Sep '17

20 Sep '17

BOB Conference 2018 "What happens when we use what's best for a change?" http://bobkonf.de/2018/en/cfp.html Berlin, February 23 Call for Contributions Deadline: October 29, 2017 You are actively engaged in advanced software engineering methods, implement ambitious architectures and are open to cutting-edge innovation? Attend this conference, meet people that share your goals, and get to know the best software tools and technologies available today. We strive to offer a day full of new experiences and impressions that you can use to immediately improve your daily life as a software developer. If you share our vision and want to contribute, submit a proposal for a talk or tutorial! Topics ------ We are looking for talks about best-of-breed software technology, e.g.: - functional programming - persistent data structures and databases - types - formal methods for correctness and robustness - abstractions for concurrency and parallelism - metaprogramming - probabilistic programming - math and programming - controlled side effects - beyond REST and SOAP - effective abstractions for data analytics - ... everything really that isn’t mainstream, but you think should be. Presenters should provide the audience with information that is practically useful for software developers. We’re especially interested in experience reports. But this could also take other forms, e.g.: - introductory talks on technical background - overviews of a given field - demos and how-tos Requirements ------------ We accept proposals for presentations of 45 minutes (40 minutes talk + 5 minutes questions), as well as 90 minute tutorials for beginners. The language of presentation should be either English or German. Your proposal should include (in your presentation language of choice): - an abstract of max. 1500 characters. - a short bio/cv - contact information (including at least email address) - a list of 3-5 concrete ideas of how your work can be applied in a developer’s daily life - additional material (websites, blogs, slides, videos of past presentations, ...) Submit here: https://docs.google.com/forms/d/e/1FAIpQLSdjgwulSMpaITJ6q6cK_ndrfR1FlEs_HQl… Organisation - direct questions to contact at bobkonf dot de - proposal deadline: October 29, 2017 - notification: November 13, 2017 - program: December 1, 2017 NOTE: The conference fee will be waived for presenters, but travel expenses will not be covered. Speaker Grants -------------- BOB has Speaker Grants available to support speakers from groups under-represented in technology. We specifically seek women speakers and speakers who are not be able to attend the conference for financial reasons. Details are here: http://bobkonf.de/2018/en/speaker-grants.html Shepherding ----------- The program committee offers shepherding to all speakers. Shepherding provides speakers assistance with preparing their sessions, as well as a review of the talk slides. Program Committee ----------------- (more information here: http://bobkonf.de/2018/en/programmkomitee.html) - Matthias Fischmann, zerobuzz UG - Matthias Neubauer, SICK AG - Nicole Rauch, Softwareentwicklung und Entwicklungscoaching - Michael Sperber, Active Group - Stefan Wehr, factis research Scientific Advisory Board - Annette Bieniusa, TU Kaiserslautern - Torsten Grust, Uni Tübingen - Peter Thiemann, Uni Freiburg

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Haskell job opportunity at RELEX Solutions in Helsinki, Finland
by samuli.thomasson＠paivola.fi 19 Sep '17

19 Sep '17

Would you like to get paid for writing Haskell? And do you live in Helsinki, Finland area (or could re-locate)? If yes, please read on. RELEX Solutions is Europe’s fastest growing provider of integrated retail and supply chain planning solutions. We are now hiring one or two Haskell programmers in Helsinki, Finland to join our small but impactful group of Haskellers to develop our internal tools. You would be working pretty much exclusively in Haskell and Elm. Exact role is somewhat flexible, depending on what other skills you might bring to the table. Read more and apply now here: https://www.relexsolutions.com/open-positions/#op-209192-haskell-and-elm-en… A good working knowledge of general Haskell programming is preferred, although eager learners can and should apply as well - if it's a good match, you just pick up the skills on the job. Unfortunately, we can't accept full remote for this position, so you should be able to be be present at the Helsinki office at least some days every week. Other details are largely negotiable. Note that the deadline for applications is quite soon, by October 2nd. Regards, Samuli Thomasson

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Eindhoven Haskell Meetup session - Oct 3, 2017
by Damian Nadales 19 Sep '17

19 Sep '17

Dear All, A new edition of our Haskell meetup will be held in Eindhoven: https://www.meetup.com/preview/Eindhoven-Haskell-Meetup/events/243342181 I would like to invite all the people that might be around this area. Also if you don't live close by, but you're visiting and want to give a talk please let me know, as we can always use a speaker. And at the same time I want to thank to the speakers that came (and will come) from far away to support his meetup (the Haskell community is -in my experience- great!). Kind regards, Damian.

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Haskell Programmers Wanted
by Brian Hurt 19 Sep '17

19 Sep '17

Code Haskell. Build great things. We’re Wrinkl, a well-funded startup working closely with Obsidian Systems to build a powerful new communications platform. We use Haskell on both the backend and the frontend (using GHCJS and Reflex). And we’re looking to hire Haskell developers, preferably in the Philly area or willing to relocate to Philly. If this sounds interesting, visit https://www.wrinkl.com/jobs/ for more info. Women and minorities strongly encouraged to apply. Brian

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ghc-devs@haskell.org
by Robin Palotai 19 Sep '17

19 Sep '17

Hello GHC devs, Before inventing the wheel, want to check if there is a GHC API way to look up the (fully) resolved instance method from a class method. For example, given a code data Foo Int deriving Show bar = show (Foo 3) when inspecting the Typechecked AST for bar's show call, I would like to get to the Name / Id of 'show' of the 'Show' typeclass. I believe I could use splitHsSigmaTy on the HsType of the function call to get the context, and then evaluate the HsWrapper somehow to find out what instance dictionary is applied to the class restriction in the context, and then look up the instance method from the dictionary.. Two questions: 1) Is there maybe functionality for this? 2) If not, is there any guarantee about the constraint order in the context, at the method call? So I could more easily determine which constraint's application to look for.. Any hints welcome && Thank you! Robin

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Haskell in Leipzig 2017: 1st call for participation
by Wolfgang Jeltsch 18 Sep '17

18 Sep '17

Event: Haskell in Leipzig 2017 Time: October 26–28, 2017 Place: HTWK Leipzig, Germany Homepage: https://hal2017.softbase.org/ About ===== Haskell is a modern functional programming language that allows rapid development of robust and correct software. It is renowned for its expressive type system, its unique approaches to concurrency and parallelism, and its excellent refactoring capabilities. Haskell is both the playing field of cutting-edge programming language research and a reliable base for commercial software development. The workshop series Haskell in Leipzig (HaL), now in its 12th year, brings together Haskell developers, Haskell researchers, Haskell enthusiasts, and Haskell beginners to listen to talks, take part in tutorials, join in interesting conversations, and hack together. To support the latter, HaL will include a one-day hackathon this year. The workshop will have a focus on functional reactive programming (FRP) this time, while continuing to be open to all aspects of Haskell. As in the previous year, the workshop will be in English. Invited Speaker =============== * Ivan Perez, University of Nottingham, UK Invited Performer ================= * Lennart Melzer, Robert-Schumann-Hochschule Düsseldorf, Germany Registration ============ Registration information is available on the web page of the local organizers at http://nfa.imn.htwk-leipzig.de/HAL2017/. Program Committee ================= * Edward Amsden, Plow Technologies, USA * Heinrich Apfelmus, Germany * Jurriaan Hage, Utrecht University, The Netherlands * Petra Hofstedt, BTU Cottbus-Senftenberg, Germany * Wolfgang Jeltsch, Tallinn University of Technology, Estonia (chair) * Andres Löh, Well-Typed LLP, Germany * Keiko Nakata, SAP SE, Germany * Henrik Nilsson, University of Nottingham, UK * Ertuğrul Söylemez, Intelego GmbH, Germany * Henning Thielemann, Germany * Niki Vazou, University of Maryland, USA * Johannes Waldmann, HTWK Leipzig, Germany Questions ========= If you have any questions, please do not hesitate to contact Wolfgang Jeltsch at wolfgang-it(a)jeltsch.info.

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