- Haskell-Cafe - Haskell.org

[ANN] wai-middleware-metrics package
by Sebastian 20 Jun '15

20 Jun '15

Hello everyone, I'm announcing the release of the wai-middleware-metrics package. http://hackage.haskell.org/package/wai-middleware-metrics https://github.com/Helkafen/wai-middleware-metrics Full example here with scotty: https://hackage.haskell.org/package/wai-middleware-metrics-0.2.1/docs/Netwo… It registers some ekg metrics in WAI web servers (scotty, servant, yesod...) using a middleware. Right now the metrics are: - wai.request_count - wai.server_error_count - wai.latency_distribution Time distributions will benefit from future developments <http://blog.johantibell.com/2014/05/ekg-04-released.html> in ekg and become more descriptive. Other metrics could be added. Ideas, contributions and comments are welcome! Cheers -- Sebastian de Bellefon

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OCL 2015: Second Call for Papers - Only Four Weeks Left
by Achim D. Brucker 19 Jun '15

19 Jun '15

(Apologies for duplicates) CALL FOR PAPERS 15th International Workshop on OCL and Textual Modeling Tools and Textual Model Transformations Co-located with ACM/IEEE 18th International Conference on Model Driven Engineering Languages and Systems (MODELS 2015) September 28th, 2015, Ottawa, Canada http://ocl2015.lri.fr Modeling started out with UML and its precursors as a graphical notation. Such visual representations enable direct intuitive capturing of reality, but some of their features are difficult to formalize and lack the level of precision required to create complete and unambiguous specifications. Limitations of the graphical notations encouraged the development of text-based modeling languages that either integrate with or replace graphical notations for modeling. Typical examples of such languages are OCL, textual MOF, Epsilon, and Alloy. Textual modeling languages have their roots in formal language paradigms like logic, programming and databases. The goal of this workshop is to create a forum where researchers and practitioners interested in building models using OCL or other kinds of textual languages can directly interact, report advances, share results, identify tools for language development, and discuss appropriate standards. In particular, the workshop will encourage discussions for achieving synergy from different modeling language concepts and modeling language use. The close interaction will enable researchers and practitioners to identify common interests and options for potential cooperation. Topics of interest include (but are not limited to) =================================================== - Mappings between textual modeling languages and other languages/formalisms - Algorithms, evaluation strategies and optimizations in the context of textual modeling languages for -- validation, verification, and testing, -- model transformation and code generation, -- meta-modeling and DSLs, and -- query and constraint specifications - Alternative graphical/textual notations for textual modeling languages - Evolution, transformation and simplification of textual modeling expressions - Libraries, templates and patterns for textual modeling languages - Tools that support textual modeling languages (e.g., verification of OCL formulae, runtime monitoring of invariants) - Complexity results for textual modeling languages - Quality models and benchmarks for comparing and evaluating textual modeling tools and algorithms - Successful applications of textual modeling languages - Case studies on industrial applications of textual modeling languages - Experience reports -- usage of textual modeling languages and tools in complex domains, -- usability of textual modeling languages and tools for end-users - Empirical studies about the benefits and drawbacks of textual modeling languages - Innovative textual modeling tools - Comparison, evaluation and integration of modeling languages - Correlation between modeling languages and modeling tasks This year, we particularly encourage submissions describing tools that support - in a very broad sense - textual modeling languages (if you have implemented OCL.js to run OCL in a web browser, this is the right workshop to present your work) as well as textual model transformations. Venue ===== The workshop will be organized as a part of MODELS 2015 Conference in Ottawa, Canada. It continues the series of OCL workshops held at UML/MODELS conferences: York (2000), Toronto (2001), San Francisco (2003), Lisbon (2004), Montego Bay (2005), Genova (2006), Nashville (2007), Toulouse (2008), Denver (2009), Oslo (2010), Zurich (2011, at the TOOLs conference), 2012 in Innsbruck, 2013 in Miami, and 2014 in Valencia, Spain. Similar to its predecessors, the workshop addresses both people from academia and industry. The aim is to provide a forum for addressing integration of OCL and other textual modeling languages, as well as tools for textual modeling, and for disseminating good practice and discussing the new requirements for textual modeling. Workshop Format =============== The workshop will include short (about 15 min) presentations, parallel sessions of working groups, and sum-up discussions. Submissions =========== Three types of papers will be considered: * short papers (between 6 and 8 pages) describing ideas, * tool papers (between 6 and 8 pages), and * full papers (between 12 and 16 pages) in LNCS format. Submissions should be uploaded to EasyChair (https://easychair.org/conferences/?conf=ocl20150) The program committee will review the submissions (minimum 2 reviews per paper, usually 3 reviews) and select papers according to their relevance and interest for discussions that will take place at the workshop. Accepted papers will be published online in a pre-conference edition of CEUR (http://www.ceur-ws.org) Important Dates =============== Submission of papers: July 17, 2015 Notification: August 21, 2015 Workshop date: September 28, 2015 Organizers ========== Achim D. Brucker, SAP SE, Germany Marina Egea, Indra Sistemas S.A., Spain Martin Gogolla, University of Bremen, Germany Frederic Tuong, Univ. Paris-Sud - IRT SystemX - LRI, France Programme Committee =================== Mira Balaban, Ben-Gurion University of the Negev, Israel Tricia Balfe, Nomos Software, Ireland Achim D. Brucker, SAP SE, Germany Fabian Buettner, Inria - Ecole des Mines de Nantes, France Jordi Cabot, Inria - Ecole des Mines de Nantes, France Dan Chiorean, Babes-Bolyai University, Romania Robert Clariso, Universitat Oberta de Catalunya, Spain Tony Clark, Middlesex University, UK Manuel Clavel, IMDEA Software Institute, Spain Carolina Dania, IMDEA Software Institute, Spain Birgit Demuth, Technische Universitat Dresden, Germany Marina Egea, Indra Sistemas S.A., Spain Geri Georg, Colorado State University, USA Martin Gogolla, University of Bremen, Germany Shahar Maoz, Tel Aviv University, Israel Istvan Rath, Budapest University of Technology and Economics, Hungary Bernhard Rumpe, RWTH Aachen, Germany Frederic Tuong, Univ. Paris-Sud - IRT SystemX - LRI, France Claas Wilke, Technische Universitat Dresden, Germany Edward Willink, Willink Transformations Ltd., UK Burkhart Wolff, Univ. Paris-Sud - LRI, France Steffen Zschaler, King's College, UK -- Dr. Achim D. Brucker, SAP SE, Vincenz-Priessnitz-Str. 1, D-76131 Karlsruhe Phone: +49 6227 7-52595, http://www.brucker.ch/

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Re: [Haskell-cafe] Haskell users on Chile
by Anupam Jain 19 Jun '15

19 Jun '15

Also, I am a part of the Startup Chile community. I would be happy to promote this group on their mailing list. On Friday, June 19, 2015, Ismael Figueroa <ismael.figueroa(a)ucv.cl> wrote: > Hi all, > > I definitely love the idea of having a chilean Haskell user group :-) > Even more so if it is in the V Region ;-) > > -- > Ismael > > On 18/06/15 18:14, Éric Tanter wrote: > >> I’m a CS professor at Universidad de Chile, doing research in PL, some >> of it in Haskell. I also use Haskell for part of my PL courses, so there >> might be some Haskellers that came out of these experiences. >> >> Also, Ismael Figueroa (in cc) graduated from his PhD under my >> supervision last year. His PhD thesis was entirely around Haskell >> (monadic embedding of aspects, compositional reasoning about >> interference), and we’ve done some other stuff on Haskell too (effect >> capabilities). Ismael is now professor at Universidad Católica de >> Valparaíso. >> >> -- Éric >> >> >> On Jun 18, 2015, at 2:44 PM, Roman Dzvinkovsky <romand.ne(a)gmail.com >>> <mailto:romand.ne@gmail.com>> wrote: >>> >>> Living in Viña del Mar, would love to participate. >>> >>> 2015-06-09 9:46 GMT-03:00 Anupam Jain <ajnsit(a)gmail.com >>> <mailto:ajnsit@gmail.com>>: >>> >>> Great idea! Though not a native Chilean, I lived in Chile (Santiago) >>> for the better part of a year in 2014-2015, where my favourite >>> activity was infiltrating JS meetups and evangelizing Haskell :) >>> >>> It would be great to have a dedicated Haskell community there. >>> >>> -- Anupam >>> >>> On Tue, Jun 9, 2015 at 5:44 PM, Ruben Astudillo >>> <ruben.astud(a)gmail.com <mailto:ruben.astud@gmail.com>> wrote: >>> > Hi all >>> > >>> > I would like to see how many haskellers are living on Chile with >>> hopes of >>> > forming a user group. If you are in here, you should reply this >>> thread and >>> > see >>> > how many of us there are. You can also contact me to my mail. >>> > >>> > -- >>> > Ruben Astudillo. pgp: 0x3C332311 , usala en lo posible :-) >>> > Crear un haiku, en diecisiete silabas, es complica... >>> > _______________________________________________ >>> > Haskell-Cafe mailing list >>> > Haskell-Cafe(a)haskell.org <mailto:Haskell-Cafe@haskell.org> >>> > http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe >>> _______________________________________________ >>> Haskell-Cafe mailing list >>> Haskell-Cafe(a)haskell.org <mailto:Haskell-Cafe@haskell.org> >>> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe >>> >>> >>> _______________________________________________ >>> Haskell-Cafe mailing list >>> Haskell-Cafe(a)haskell.org <mailto:Haskell-Cafe@haskell.org> >>> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe >>> >> >> > -- > Ismael > -- Sent from my hyper-communicator

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Haskell users on Chile
by Ruben Astudillo 18 Jun '15

18 Jun '15

Hi all I would like to see how many haskellers are living on Chile with hopes of forming a user group. If you are in here, you should reply this thread and see how many of us there are. You can also contact me to my mail. -- Ruben Astudillo. pgp: 0x3C332311 , usala en lo posible :-) Crear un haiku, en diecisiete silabas, es complica...

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phantom types and record syntax
by Dimitri DeFigueiredo 18 Jun '15

18 Jun '15

Hi All, My apologies if this is not the right forum, but am not satisfied with my current understanding. I am surprised that this program compiles in GHC: ----- data UserSupplied = UserSupplied -- i.e. unsafe data Safe = Safe data Username a = Username { first :: String, last :: String} sanitize :: Username UserSupplied -> Username Safe sanitize name = name { first = "John" } main = putStrLn "Hi!" ----- My trouble is that it seems the record syntax is*implicitly* converting from one type to the other. It seems I would have to remove the phantom type by adding a tag to avoid this: ----- data Username a = Username { first :: String, last :: String, tag :: a } sanitize :: Username UserSupplied -> Username Safe sanitize name = name { first = "John" } -- FAIL as expected!! :-) ----- But this makes me unwilling to use phantom types for security as I would be worried of unwittingly making the conversion. Could somebody sprinkle some insight into why this is "converted automatically" for phantom types? Is there another way around this? Thanks! Dimitri

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Haskell and Spark
by Vasili I. Galchin 18 Jun '15

18 Jun '15

Hello, There was a posting from a Polish guy(Wojcieh .,,,, been trying to contact him) on implementing a library/wrapper for Spark. Does anybody know the status? Vasili

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RFC: "Native -XCPP" Proposal
by Herbert Valerio Riedel 18 Jun '15

18 Jun '15

Hello *, As you may be aware, GHC's `{-# LANGUAGE CPP #-}` language extension currently relies on the system's C-compiler bundled `cpp` program to provide a "traditional mode" c-preprocessor. This has caused several problems in the past, since parsing Haskell code with a preprocessor mode designed for use with C's tokenizer has caused already quite some problems[1] in the past. I'd like to see GHC 7.12 adopt an implemntation of `-XCPP` that does not rely on the shaky system-`cpp` foundation. To this end I've created a wiki page https://ghc.haskell.org/trac/ghc/wiki/Proposal/NativeCpp to describe the actual problems in more detail, and a couple of possible ways forward. Ideally, we'd simply integrate `cpphs` into GHC (i.e. "plan 2"). However, due to `cpp`s non-BSD3 license this should be discussed and debated since affects the overall-license of the GHC code-base, which may or may not be a problem to GHC's user-base (and that's what I hope this discussion will help to find out). So please go ahead and read the Wiki page... and then speak your mind! Thanks, HVR [1]: ...does anybody remember the issues Haskell packages (& GHC) encountered when Apple switched to the Clang tool-chain, thereby causing code using `-XCPP` to suddenly break due to subtly different `cpp`-semantics?

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Canberra Functional Programming Group
by Ivan Lazar Miljenovic 18 Jun '15

18 Jun '15

In case you live in Canberra, Australia and were unaware of this already, Alex Mason (aka Axman6) is helping to arrange/organise a new functional programming group. The first meeting for it is next week on 24 June (including free pizza!). For more information please see http://www.meetup.com/CanFPG/ -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com http://IvanMiljenovic.wordpress.com

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Haskell Weekly News
by Kim-Ee Yeoh 18 Jun '15

18 Jun '15

*Top Picks:* - Andrew Gibiansky <http://www.reddit.com/r/haskell/comments/37uqqk/ihaskell_online_help_choose…> announces the Mathematica-inspired REPL 2.0 IHaskell as a web-app you can play with right now <http://try.jupyter.org/>. Bouquets include: "This is an awesome step up from the tryhaskell window." Also, "I love IHaskell. I've already started preferring it to ghci since it's so much easier to use." More /r/haskell love here <https://www.reddit.com/r/haskell/comments/376aqh/ihaskell_on_tryjupyterorg/> . - Mihai Maruseac and Alejandro Serrano Mena publish the 28th Haskell Communities and Activities Report <https://www.haskell.org/communities/05-2015/html/report.html>. Top comment on HN <https://news.ycombinator.com/item?id=9627260>: "Haskell is backed by a truly amazing community. Haskell will continue to inspire people to build better, safer software. I hope that the values of tolerance, respect and benevolence that most of the Haskell community is supporting will also contribute to make tech a more friendly and equal place for everyone." - Bicycling in circles just to find parking in Utrecht? Bas van Dijk launches a city-wide monitoring system that guides you to a space that's free, dry, and safe <https://bicycledutch.wordpress.com/2015/06/09/bicycle-parking-guidance-syst…>. Written in Haskell 'natch, even the front-end leverages GHCJS. Devops'ed in NixOS. He tips off his fellow redditors <http://www.reddit.com/r/haskell/comments/3959r0/haskellbased_bicycle_parkin…> about using blaze-react to wrap Facebook's React library. HN-worthy <https://news.ycombinator.com/item?id=9690683>. - Announcing on haskell-cafe <http://haskell.1045720.n5.nabble.com/A-Dockerfile-to-provision-a-build-envi…> and /r/haskell <http://www.reddit.com/r/haskell/comments/387uct/building_an_android_game_wr…>, Sean Seefried open sources a Docker script that instantly gets you a Haskell build environment for Android game development <https://github.com/sseefried/docker-epidemic-build-env>. No more fiddling with cross-compiles. He even gives you an open source game <https://github.com/sseefried/open-epidemic-game> all mobile-ready. Thanks, Sean! - Vincent Hanquez releases cryptonite <http://hackage.haskell.org/package/cryptonite>, a single package that consolidates 10-20 other crypto packages. Why? Because maintaining multiple packages is a pain involving fiddling with dependency version bounds and changelog/cabal/version metadata. Benefit for the user? Easier discovery of crypto widgets now that they are all in one haddock, as opposed to hidden in a package whose name eludes you. Kibbitz on /r/haskell <http://www.reddit.com/r/haskell/comments/389tpg/announcing_cryptonite/>. - Joe Nelson <https://news.ycombinator.com/item?id=9642665#up_9643923>discovered Haskell two years ago <http://www.wagonhq.com/blog/first-two-weeks-haskell-wagon> and calls it "moon language." Now he works full-time at Wagon, an all-Haskell start-up offering "a modern data collaboration tool." He's proud of his team that "excels at debugging gnarly issues, including a memory leak caused by a useful yet tricky language feature called lazy evaluation." But what's the buzz that HN <https://news.ycombinator.com/item?id=9703500> and /r/haskell <http://www.reddit.com/r/haskell/comments/39izi6/my_first_two_weeks_of_haske…> latch on? Answer: The pros and cons of effectful point-free refactoring. - Fredrik Olsen migrates from Ruby on Rails (RoR) to Haskell <https://medium.com/@folsen/haskell-in-production-bdellium-1df48de40e19> at fintech start-up Bdellium. Unlike RoR where he "always had a much harder time" with an existing codebase, he testifies that "Haskell let me quickly browse the code, read the types and almost instantly understand the structure and layout of the program." Hiring for RoR nets him "a few hundred applications" where only "10–20% I’d say are people that I’d actually be interested in hiring." Hiring for Haskell gets "50 responses to the Reddit post, all of them were people that I could have hired. Many of the applicants were even grossly over-qualified and were willing to take the job just because it would let them work in Haskell." Ben Ford of Fynder.io corroborates Fredrik in the top comment on /r/haskell <http://www.reddit.com/r/haskell/comments/38nooh/haskell_in_production_bdell…> . Phil Wadler reblogs <http://wadler.blogspot.com/2015/06/haskell-in-production-bdellium.html> the story and zooms in on how Fredrik gained 3.7x parallelism from 4 cores by merely tweaking a single line of code. Control.Parallel.Strategies <http://hackage.haskell.org/package/parallel-3.2.0.6/docs/Control-Parallel-S…> ftw! - Arnaud Bailly <https://news.ycombinator.com/item?id=9642665#up_9643923> shares on HN that he had "no issue finding talent" for Haskell jobs in Singapore. "150 qualified applicants (i.e. passed the test, which was to design an inventory management system in Haskell) for ~10 positions, all foreign; the majority came from the US, Germany and Scandinavia." - If type errors can be deferred, why not also "name not found"? Tom Ellis asks <http://haskell.1045720.n5.nabble.com/fdefer-more-errors-tp5809991.html>. He thinks it would make Haskell "gentler for newcomers." For veterans: even more stub-driven-dev opportunities. Coincidentally, Dan Burton spitballed the same on /r/haskell <http://www.reddit.com/r/haskell/comments/37km7e/fdeferscopeerrors_anyone/>. This idea has a history stretching back at least 3 years: see trac ticket #5910 <https://ghc.haskell.org/trac/ghc/ticket/5910#comment:19>. - David Luposchainsky proposes to move the fail method out of the Monad type class <https://github.com/quchen/articles/blob/master/monad_fail.md>. With the deeply thought out blueprint he provides, /r/haskell reports <http://www.reddit.com/r/haskell/comments/397k1a/monadfail_proposal_mfp_movi…> that the community's already working on it. Discussion on libraries list <http://haskell.1045720.n5.nabble.com/MonadFail-proposal-MFP-Moving-fail-out…> . - Anthony Cowley proposes a shorter syntax for imports on haskell-cafe <http://haskell.1045720.n5.nabble.com/Proposal-Shorter-Import-Syntax-td58104…> and trac <https://ghc.haskell.org/trac/ghc/ticket/10478>. He withdraws his proposal five days later because the "disdainful mockery" and "strongly worded rebuttals" have him overwhelmed on what is only a "nights and weekends project." Reddit discussion here <https://www.reddit.com/r/haskell/comments/38vsef/proposal_shorter_import_sy…> . - Henk-Jan van Tuyl <http://haskell.1045720.n5.nabble.com/a-files-not-found-td5810165.html> runs smack into a library .a-extension File Not Found problem when installing data-default-instances-old-locale on 7.10. Culprit? Windows! And its %&@#! 255-character filepath limit. He is not alone <https://github.com/haskell/cabal/issues/2502>. Why is 7.8 ok? Because package names in the filepath used to be abbreviated. Workaround? Instead of cabal install X, download it first: cabal get X, then cabal install ./X. Thanks to Matej Borovec and Michal Antkiewicz for sorting it out. - FP Complete announces Stack <https://www.fpcomplete.com/blog/2015/06/announcing-first-public-beta-stack>, a replacement for cabal-install <https://hackage.haskell.org/package/cabal-install> the command-line tool (not Cabal the library infrastructure). Stack leverages Stackage <https://www.stackage.org/> Long-Term Support (LTS) releases for a speedy escape from cabal hell. Warmly received on /r/haskell <http://www.reddit.com/r/haskell/comments/3957e1/announcing_first_public_bet…>. Dan Burton blogs on how Stack eases development by removing the need to remember a sequence of cabal commands <http://www.reddit.com/r/haskell/comments/3a6p9h/how_stack_lowers_the_barrie…>. HN-worthy <https://news.ycombinator.com/item?id=9687274> and a troll that Haskell's "an esoteric language that no one uses" provokes many a valiant, evidence-backed defense <https://news.ycombinator.com/item?id=9687274#up_9688248>. - Redditor beerdude26 nudges folks on /r/haskell <http://www.reddit.com/r/haskell/comments/37y1yi/my_approach_to_centralizing…> to continue cultivating the haskell wiki <https://wiki.haskell.org/Haskell>. He sets an example by splicing in the common newtype workaround <https://wiki.haskell.org/Orphan_instance#Common_workaround> into the entry on orphan instances. - In HN news <https://news.ycombinator.com/item?id=9662705>: Cloud Haskell <http://haskell-distributed.github.io/> -- Erlang-style concurrent and distributed programming. Top comment notes that whereas the web site suggests that activity stopped in 2014, CH actually thrives on Github <https://github.com/haskell-distributed>. - In HN news <https://news.ycombinator.com/item?id=9696086>: Haskell wiki entry on Frag <https://wiki.haskell.org/Frag>, a 2005 undergrad project by Mun Hon Cheong who recreated a Quake3-like First-Person Shooter (FPS) game using Yampa FRP. Although a decade old, Cody Goodman <https://news.ycombinator.com/item?id=9696086#up_9696700> reports that he's gotten it to compile. - In HN news <http://news.ycombinator.com/item?id=9704851>: APL lives! A functional programmer investigates APL <http://theburningmonk.com/2015/06/fear-and-loathing-with-apl/>, discovers that it "looks every bit as mind-bending and unbelievable as scenes from Johnny Depp’s *Fear and Loathing in L**as Vegas*", and summarizes the syntax for the benefit of all. *Quotes of the Week:* - A typeclass with only one instance is nonsensical, and often a symptom of trying to use typeclasses as OO classes. -- Brandon Allbery <http://haskell.1045720.n5.nabble.com/Disambiguating-a-Num-RealFrac-instance…> - That Haskell shows the developer things about themselves even they didn't know is enough to make it worth learning. It's mind-bending and ideology-exposing. -- Redditor on /r/haskell <http://www.reddit.com/r/haskell/comments/39ci9j/coming_from_php_working_in_…> - Haskell's great for writing an ugly solution and fixing it later because refactoring is so cheap. No need to get it right the first time. -- Gabriel Gonzalez on Twitter <https://twitter.com/GabrielG439/status/606831084655902720> -- Kim-Ee nights and weekends project

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More instances for Identity?
by Niklas Hambüchen 17 Jun '15

17 Jun '15

Hi, I just noticed that Data.Functor.Identity [1] lacks many useful instances like Eq, Ord, Show ... etc. Is there a reason for this? Otherwise, shouldn't we make a proposal for it? In my opinion, if the seven-tuple has an instance, then Identity deserves it as well. Niklas [1]: https://downloads.haskell.org/~ghc/7.8.3/docs/html/libraries/transformers-0…

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