December 2016 - Haskell-Cafe

Gitter Haskell Community
by Ben Spencer 13 Dec '16

13 Dec '16

Hello all, We have a small group of Haskellers over in our Gitter community chat. If you're inclined, come check us out at https://gitter.im/haskell-chat/Lobby. We have about 40 Haskell enthusiasts so far! Why Gitter you might ask? Gitter was designed for open communities. It's free for unlimited users and you get full access to your chat history. And you only need your Github account to sign up. Plus if we generate enough activity, Gitter will feature Haskell as a suggested community! Best, Ben

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Supporting Haskell.org in 2016
by Adam Foltzer 12 Dec '16

12 Dec '16

Dear Haskellers, A great deal of core infrastructure, including HaskellWiki, Hackage, Hoogle, and build infrastructure for GHC are hosted and managed with the help of donations to haskell.org, from you, the Haskell community. As many of us are in tax jurisdictions where December 31st is a deadline for charitable giving, I’d like to remind you that donations to support these activities are tax-deductible. You can donate online right now through the donate button on the wiki: https://wiki.haskell.org/Donate_to_Haskell.org. Mailing information for checks is also on that page. New for this year, individual donations may be made directly via Paypal rather than the clickandpledge service, and Haskell.org is also can now accept donations through employers via Benevity using the unique ID 475236502. This year we had a successful first Summer of Haskell, offering 8 stipends of $5,500 to students making valuable contributions to our shared tooling and infrastructure such as ghc, ghcjs, and hackage, and engaging them in what we hope becomes a long succession of contributions to open source software. The exciting results are available at https://mail.haskell.org/ pipermail/haskell-cafe/2016-December/125702.html; this work is only made possible by your generous support, and that of the sponsors listed at https://summer.haskell.org/. We also have continued improving our infrastructure, using committee funds to help the development of a new performance tracker for ghc, with the aim of opening this up to a broader range of projects as well. With your support, we hope to continue these activities and more in 2017. Best wishes, Adam Foltzer on behalf of the Haskell.org committee

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A Procedural-Functional Language (WIP)
by Rik Howard 12 Dec '16

12 Dec '16

Dear Haskell Cafe Subscribers on the recommendation of someone for whom I have great respect, I have just subscribed to this list, it having been suggested as being a good place for me to get feedback regarding a project that I have been working on. I am humbled by the level of discussion and it feels to be a very bold step for me to request anybody's time for my words. The linked document is a four-page work-in-progress summary: the length being stipulated, potential novelty being the other main requirement. Given the requirements, the summary necessarily glosses over some details and is not yet, I fear, completely correct. The conclusion is, more or less, the one at which I am aiming; the properties are, more or less, the ones that are needed. http://www.dcs.bbk.ac.uk/~rik/gallery/work-in-progress/document.pdf The work arises from an investigation into functional programming syntax and semantics. The novelty seems to be there but there is too a question as to whether it is simply a gimmick. I try to suggest that it is not but, by that stage, there have been many assumptions so it is hard to be sure whether the suggestion is valid. If anyone has any comments, questions or suggestions, they would be gratefully received. Yours sincerely Rik Howard

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PhD studentships at Leeds
by David Duke 12 Dec '16

12 Dec '16

The School of Computing at the University of Leeds is advertising a number of PhD studentships open to UK, EU and international applicants. Two of the projects are at the overlap between functional programming and visualization, one on performance analysis, one on explaining type inference. Please see the following URL for further information including how to apply: https://engineering.leeds.ac.uk/research-opportunity/201323/research-degree… Closing date: 06/01/2017 --- 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/

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[Ann] Haskell Ecosystem Proposals
by Alan & Kim Zimmerman 11 Dec '16

11 Dec '16

Earlier this year Simon Peyton Jones wrote about respect [1], and said "It's worth separating two things 1. Publicly debating an issue where judgements differ 2. Using offensive or adversarial language in that debate" There is now a repository[2] for us as a community to have the first kind of discussion about issues that affect the community as a whole. The intention is that this becomes a neutral place where discussion can take place about coordinating the various services offered to the haskell community. This is partly to expose the thinking and constraints on a particular approach, so proponents of other approaches can have a better understanding of how things can evolve. The idea is that through an honest understanding of the various parts we can achieve consensus on how to improve things. If this all sounds a bit handwavy, the first concrete example of this approach is a pull request [3] discussing the management of implicit or speculative version bounds between cabal-install/hackage and stack/stackage. This has reached a point where there is a clearer understanding of the actual problem, and a viable solution must be agreed. The structure of the repository is shamelessly copied from the one for GHC proposals, so the actual process description is way off. It should probably just state that we discuss until consensus is reached if possible, but that we are always open for further discussion. It is up to all of us to make this work. Regards Alan [1] https://mail.haskell.org/pipermail/haskell/2016-September/024995.html [2] https://github.com/haskell/ecosystem-proposals [3] https://github.com/haskell/ecosystem-proposals/pull/1

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what is lens-based parsing?
by Ruben Astudillo 10 Dec '16

10 Dec '16

Dear Cafe I've reading the tutorial for pipes-parse, and I got some references that it supports lens-based parsing. I know lens, yet I don't really know what is that about. Also looking in google doesn't get any detailed blogpost. Can anybody help me out on what is this? -- -- Ruben

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Partial Evaluation & Program Manipulation (PEPM'17): Call for Participation
by Jeremy Yallop 09 Dec '16

09 Dec '16

CALL FOR PARTICIPATION Workshop on PARTIAL EVALUATION AND PROGRAM MANIPULATION (PEPM 2017) http://conf.researchr.org/home/PEPM-2017 Paris, France, January 16th - 17th, 2017 (co-located with POPL 2017) Registration ------------ http://popl17.sigplan.org/attending/registration Early registration deadline: Saturday 17th Dec 2016 Programme --------- Monday 16th January 09:00-10:00: Keynote Compiling Untyped Lambda Calculus to Lower-Level Code by Game Semantics and Partial Evaluation Neil D. Jones (with Daniil Berezun) 10:30-12:00: Programming languages Lightweight Soundness for Towers of Language Extensions Alejandro Serrano, Jurriaan Hage Detecting code clones with gaps by function applications Tsubasa Matsushita, Isao Sasano PEG Parsing in Less Space Using Progressive Tabling and Dynamic Analysis Fritz Henglein, Ulrik Terp Rasmussen 14:00-15:30: Tutorial and Poster Session Idris, Inside-Out: A Tutorial on Extending Idris in Idris David Christiansen Language-integrated Query with Ordering, Grouping and Outer Joins (poster) Tatsuya Katsushima, Oleg Kiselyov 16:00-17:00: Transformation (part I) Verification of Code Generators via Higher-Order Model Checking Takashi Suwa, Takeshi Tsukada, Naoki Kobayashi, Atsushi Igarashi Interactive data representation migration: Exploiting program dependence to aid program transformation Krishna Narasimhan, Julia Lawall, Christoph Reichenbach Tue 17th January 09:00-10:00: Tutorial Reversible computing from a programming language perspective Robert Glück 10:30-12:00: Types Cost versus Precision for Approximate Typing for Python Levin Fritz, Jurriaan Hage Refining types using type guards in TypeScript Ivo Gabe de Wolff, Jurriaan Hage Predicting Resource Consumption of Higher-Order Workflows Markus Klinik, Jurriaan Hage, Jan Martin Jansen, Rinus Plasmeijer 14:00-15:30: Tutorial Practical Partial Evaluation for Language Implementation with Graal & Truffle Gilles Duboscq 16:00-17:00: Transformation (part II) Functional Parallels of Sequential Imperatives Tiark Rompf, Kevin J. Brown A Functional Reformulation of UnCAL Graph-Transformations: Or, Graph Transformation as Graph Reduction Kazutaka Matsuda, Kazuyuki Asada

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Dockerfile for building ghc8.0 with ubuntu 16.04LTS
by Takenobu Tani 09 Dec '16

09 Dec '16

Hi cafe, I pushed Dockerfile for building ghc8.0 with ubuntu 16.04LTS. (If you need Debian and Arcanist, please use Greg's Dockerfile[1].) Dockerfile for Haskell GHC building https://github.com/takenobu-hs/ghc-build-docker Let's get familiar with ghc building and validating :) [1]: https://github.com/gregwebs/ghc-docker-dev [2]: https://ghc.haskell.org/trac/ghc/wiki/Building Enjoy, Takenobu

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Summer of Haskell 2016 Wrap-Up
by Gershom B 08 Dec '16

08 Dec '16

We wanted to let folks know what happened with all our Summer of Haskell projects, and thank again all those who donated as individuals or sponsored students to make this possible. As a reminder, the accepted projects were announced on reddit at: https://www.reddit.com/r/haskell/comments/4kp6zg/summer_of_haskell_2016_acc… * * * 1) Native Metaprogramming in Haskell This very ambitious project made significant progress, though is not yet ready for a full merge into GHC. A talk and paper on work relating to it were presented at the Haskell Implementors Workshop at ICFP, and a page on the GHC wiki describes the current status. - https://www.youtube.com/watch?v=DSWoGdfYt68 - https://arxiv.org/abs/1610.04799 - https://ghc.haskell.org/trac/ghc/wiki/NativeMetaprogramming 2) GHCVM - A JVM Backend for GHC Again, significant progress made on a very ambitious project, which has now been renamed to “eta”. A talk on the work done was given at the HIW, and the project is considered ready for “hobbyist use”. - https://www.youtube.com/watch?v=G4m7xFVzd50 - https://github.com/typelead/eta 3) Completing the LLVM backend for Accelerate All operators of the LLVM backend are now implemented, and we’re told that the accelerate-llvm project, already usable, will be get a more proper announcement as ready for widespread use real soon now (tm). - https://github.com/AccelerateHS/accelerate-llvm - https://github.com/AccelerateHS/accelerate-llvm/commits?author=ZihengJiang 4) Hackage Improvements A whole raft of usability improvements to hackage (including the long-awaited rollout of reverse dependency tracking, and a very usable package browser interface) are undergoing final code review and polish in a PR before being rolled out. The student’s blog contains more information about what’s on the way. - http://sooryanarayan.me/blog/hsoc-testimonial/ 5) Derivable Storable and Prim instances This work resulted in both a package (usable today) and a plugin to improve the performance of the derived code. Updates on the decisions made and work done were posted to the numerical-haskell group - https://hackage.haskell.org/package/derive-storable - http://hackage.haskell.org/package/derive-storable-plugin - https://groups.google.com/forum/#!forum/numericalhaskell 6) Visual functional block-based programming language for CodeWorld This work went well and is described on the student’s blog. It is usable today at https://code.world/blocks and apparently has already begun to be integrated into CodeWorld lesson plans. - http://stefanj.me/funblocks/ - https://code.world/blocks 7) Jupyter for GHCJS Apparently this ran into a far amount of difficulties and didn’t make significant progress, though not for lack of effort. The student is anticipated to write up an experience report describing some of the problems encountered and how others might work around them in the future. 8) Live Profiling and Performance Monitoring Server A lot of work was accomplished on various fronts here. A number of changes to the GHC RTS are in review and pending merge. A tool has been written to take advantage of the newly available information. And various other small packages that met needs along the way were extracted and contributed to hackage. A fuller write-up of progress and future work is available at the student’s blog. - https://phabricator.haskell.org/D2522 - https://github.com/NCrashed/live-profile-monitor - http://ncrashed.github.io/blog/posts/2016-09-11-hsoc-results.html * * * Apologies for the delays in assembling this information -- as they say, man plans, the fates laugh. Thanks to all our students for their dedicated work and contributions to the ecosystem. We hope to see much more from all of you in the future. And thanks to all our mentors for donating their time to guide, teach, and make this possible. And a very special thanks to Edward Kmett for co-ordinating much of the administrative work here, as well as fundraising towards this great Summer of Haskell. * * * Sponsors (listed on summer.haskell.org) - haskell.org kicked things off this year by funding a student and organizing the Summer of Haskell. - Awake Networks is building a next generation network security and analytics platform. They are a proud sponsor of the Summer of Haskell and contribute broadly to the Haskell community. - Haskell Book is a proud sponsor of the Summer of Haskell and provides a complete and up-to-date resource for learning Haskell, suitable whether you're completely new to Haskell or are at an intermediate level and want to deepen your understanding. - YOW! Australia is a proud sponsor of the Summer of Haskell and organizes conferences throughout Australia. - Chris Smith volunteered to fund two students to work on CodeWorld in particular. - Edward Kmett and Gershom Bazerman volunteered to personally fund a student project. Best, Gershom Bazerman Haskell.org Committee

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Bits.bitSize
by ALeX Kazik 08 Dec '16

08 Dec '16

Hi, I think it would be a good idea to provide a default implementation for bitSize, example: bitSize b = fromMaybe (error "bitSize is undefined") (bitSizeMaybe b) The advantage is that from now on new instances of Bits no longer need to define bitSize. And once bitSize has been removed there will be no errors about it not being a method of class Bits. ALeX.

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