August 2020 - Haskell-Cafe

New package: compact-sequences
by David Feuer 11 Aug '20

11 Aug '20

I've gotten the code I wrote for my Haskell Love talk into (just barely) good enough shape to make an initial release. So far, I have implemented stacks and queues that take n + O(log n) space, and whose basic operations take O(log n) time. I hope to add deques soon. More urgently, I need to write a test suite. Furthermore, I have written only "simple" versions, that directly use the mechanism described in my talk. To get decent performance, it will probably be necessary to add a layer on top of that. The package can be found at http://hackage.haskell.org/package/compact-sequences-0.1.0.0 David Feuer

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Third call for draft papers for IFL 2020 (Implementation and Application of Functional Languages)
by Jurriaan Hage 11 Aug '20

11 Aug '20

Hello, Please, find below the third call for draft papers for IFL 2020. Please forward these to anyone you think may be interested. Apologies for any duplicates you may receive. best regards, Jurriaan Hage Publicity Chair of IFL ================================================================================ IFL 2020 32nd Symposium on Implementation and Application of Functional Languages venue: online 2nd - 4th September 2020 https://www.cs.kent.ac.uk/events/2020/ifl20/ ================================================================================ ### Scope The goal of the IFL symposia is to bring together researchers actively engaged in the implementation and application of functional and function-based programming languages. IFL 2020 will be a venue for researchers to present and discuss new ideas and concepts, work in progress, and publication-ripe results related to the implementation and application of functional languages and function-based programming. Topics of interest to IFL include, but are not limited to: - language concepts - type systems, type checking, type inferencing - compilation techniques - staged compilation - run-time function specialisation - run-time code generation - partial evaluation - (abstract) interpretation - meta-programming - generic programming - automatic program generation - array processing - concurrent/parallel programming - concurrent/parallel program execution - embedded systems - web applications - (embedded) domain specific languages - security - novel memory management techniques - run-time profiling performance measurements - debugging and tracing - virtual/abstract machine architectures - validation, verification of functional programs - tools and programming techniques - (industrial) applications ### Post-symposium peer-review Following IFL tradition, IFL 2020 will use a post-symposium review process to produce the formal proceedings. Before the symposium authors submit draft papers. These draft papers will be screened by the program chair to make sure that they are within the scope of IFL. The draft papers will be made available to all participants at the symposium. Each draft paper is presented by one of the authors at the symposium. After the symposium every presenter is invited to submit a full paper, incorporating feedback from discussions at the symposium. Work submitted to IFL may not be simultaneously submitted to other venues; submissions must adhere to ACM SIGPLAN's republication policy. The program committee will evaluate these submissions according to their correctness, novelty, originality, relevance, significance, and clarity, and will thereby determine whether the paper is accepted or rejected for the formal proceedings. We plan to publish these proceedings in the International Conference Proceedings Series of the ACM Digital Library, as in previous years. ### Important dates Submission deadline of draft papers: 17 August 2020 Notification of acceptance for presentation: 19 August 2020 Registration deadline: 31 August 2020 IFL Symposium: 2-4 September 2020 Submission of papers for proceedings: 7 December 2020 Notification of acceptance: 3 February 2021 Camera-ready version: 15 March 2021 ### Submission details All contributions must be written in English. Papers must use the ACM two columns conference format, which can be found at: http://www.acm.org/publications/proceedings-template ### Peter Landin Prize The Peter Landin Prize is awarded to the best paper presented at the symposium every year. The honoured article is selected by the program committee based on the submissions received for the formal review process. The prize carries a cash award equivalent to 150 Euros. ### Programme committee Kenichi Asai, Ochanomizu University, Japan Olaf Chitil, University of Kent, United Kingdom (chair) Martin Erwig, Oregon State University,United States Daniel Horpacsi, Eotvos Lorand University, Hungary Zhenjiang Hu, Peking University, China Hans-Wolfgang Loidl, Heriot-Watt University, United Kingdom Neil Mitchell, Facebook, UK Marco T. Morazan, Seton Hall University, United States Rinus Plasmeijer, Radboud University, Netherlands Colin Runciman, University of York, United Kingdom Mary Sheeran, Chalmers University of Technology, Sweden Josep Silva, Universitat Politecnica de Valencia, Spain Jurrien Stutterheim, Standard Chartered, Singapore Josef Svenningsson, Facebook, UK Peter Thiemann, University of Freiburg, Germany Kanae Tsushima, National Institute of Informatics, Japan. Marcos Viera, Universidad de la Republica, Montevideo, Uruguay Janis Voigtlander, University of Duisburg-Essen, Germany ### Virtual symposium Because of the Covid-19 pandemic, this year IFL 2020 will be an online event, consisting of paper presentations, discussions and virtual social gatherings. Registered participants can take part from anywhere in the world. ### Acknowledgments This call-for-papers is an adaptation and evolution of content from previous instances of IFL. We are grateful to prior organisers for their work, which is reused here.

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[ANN] Darcs 2.14.5 release
by Ben Franksen 08 Aug '20

08 Aug '20

Hi all, on behalf of the Darcs team, I would like to announce the release of Darcs 2.14.5: https://hackage.haskell.org/package/darcs-2.14.5 This is a bug-fix release and will be the latest release in the 2.14 series. In no way does it reflect the state of our development branch; instead it contains only a very small amount of changes needed to fix an ugly bug we recently discovered and which affects all previous versions in the 2.12 and 2.14 series. Upgrading is advised to avoid future incompatibilities. See the CHANGELOG for details. We will soon release 2.16.1 which will contain the large amount of work that has gone into darcs since the release of 2.14.0 more than two years ago. Cheers Ben

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Where does the name "Algebraic data types" come from?
by Li-yao Xia 07 Aug '20

07 Aug '20

Dear Café, What makes "algebraic data types" algebraic? There are at least two common explanations in use: 1. Algebraic data types are defined using sums and products of types, by analogy with, well, concepts from algebra. 2. Algebraic data types are initial algebras. There are numerous blogs online explaining "algebraic data types" that way, with a large majority adopting the more approachable explanation (1). The question is, how did the appellation "algebraic" come about historically? Did it start with one or both of the meanings above? The language feature, independently of the name, seems attributed to the HOPE language[1] (see for instance A History of Haskell: Being Lazy with Class[2]). However, the paper introducing HOPE does not use the word "algebraic" anywhere. Other papers on the topic do not discuss the origins of the word. I am curious about citations regarding the history of the name "algebraic data types" itself. Regards, Li-yao [1]: http://citeseer.ist.psu.edu/viewdoc/summary?doi=10.1.1.18.8135 [2]: https://www.microsoft.com/en-us/research/wp-content/uploads/2016/07/history…

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Call for Tutorial Participation: ICFP 2020
by Sam Tobin-Hochstadt 07 Aug '20

07 Aug '20

CALL FOR TUTORIAL PARTICIPATION ICFP 2020 25th ACM SIGPLAN International Conference on Functional Programming August 23 - 28, 2020 Virtual https://icfp20.sigplan.org/ Early Registration ends August 8! The 25th ACM SIGPLAN International Conference on Functional Programming will be held virtually on August 23-28, 2020. ICFP provides a forum for researchers and developers to hear about the latest work on the design, implementations, principles, and uses of functional programming. This year, ICFP features a wide variety of tutorials on topics related to functional programming, including design, education, tools, and more. Tutorials are available to all ICFP participants with registration. Tutorials occur before or after ICFP, co-located with the associated workshops, on August 23 or August 27-28. The schedule of ICFP Tutorials can be found at: https://icfp20.sigplan.org/track/icfp-2020-tutorials#program ICFP Early Registration ends on August 8th, and is available at: https://icfp20.sigplan.org/attending/Registration

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Core optimizations affected by package provenance
by Li-yao Xia 07 Aug '20

07 Aug '20

Hello Café, I've been testing properties of some optimized Core using the inspection-testing library. Some functions appear to be optimized differently depending on whether one of the package dependencies comes from Hackage or elsewhere. As far as I can tell, the source code is identical, and the only difference is whether or not I add the path to the local package in my cabal.project. Why would a dependency be compiled differently depending on where it comes from? Any suggestions on how to troubleshoot this? To be more concrete, the relevant packages are generic-random and splitmix. The following commands should reproduce the issue: git clone https://github.com/Lysxia/generic-random git clone https://github.com/phadej/splitmix cd generic-random # With local splitmix echo "packages: . ../splitmix" > cabal.project cabal test --flags="enable-inspect" # PASS # With remote splitmix echo "packages: ." > cabal.project cabal test --flags="enable-inspect" # FAIL It would be useful to know whether anyone can reproduce this behavior or not. Cheers, Li-yao PS, link to Github issue: https://github.com/Lysxia/generic-random/issues/22

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ANN: network 3.1.2.0
by Evan Borden 07 Aug '20

07 Aug '20

I'm happy to announce the release of network 3.1.2.0. https://hackage.haskell.org/package/network-3.1.2.0 This version of network includes many improvements that allow more extensibility, portability, and greater test coverage. See the log below for more information. As well version 3.1.1.0 and 3.1.1.1 have been deprecated as they contain a bug in graceful close, more details below. - Added -f devel for test cases that are known to fail. #471 <https://github.com/haskell/network/pull/471> - Improved precedence-compliant Read/Show instances. Verified via QuickCheck. #465 <https://github.com/haskell/network/pull/465> #466 <https://github.com/haskell/network/pull/466> - Removed the racing graceful close implementation to avoid issues with CLOSE_WAIT. #460 <https://github.com/haskell/network/pull/438> - Gracefully handle binding of UNIX domain sockets. #460 <https://github.com/haskell/network/pull/460> - Replace Socket type and family with extensible CInt pattern and synonyms. #459 <https://github.com/haskell/network/pull/459> - Fixed race conditions in tests. #458 <https://github.com/haskell/network/pull/458> - Removed many legacy uses of undefined. #456 <https://github.com/haskell/network/pull/456> - Defined extensible CustomSockOpt via ViewPatterns. #455 <https://github.com/haskell/network/pull/455> - Defined openSocket in terms of AddrInfo. 5b0987197fe2ed7beddd7b2096522d624e71151e <https://github.com/haskell/network/commit/5b0987197fe2ed7beddd7b2096522d624…> - Improved FreeBSD portability for Control Messages and tests #452 <https://github.com/haskell/network/pull/452> - Support sendMsg and recvMsg #433 <https://github.com/haskell/network/pull/433> #445 <https://github.com/haskell/network/pull/445> #451 <https://github.com/haskell/network/pull/451> - Added sendMsg and recvMsg APIs - Redefined SocketOption as pattern synonym - Implement total Show functions for SockAddr #441 <https://github.com/haskell/network/pull/441> - Improve portability changing u_int32_t to uint32_t. #442 <https://github.com/haskell/network/pull/442> - Removed obsolete CPP statements. d1f4ee60ce6a4a85abb79532f64d4a4e71e2b1ce <https://github.com/haskell/network/commit/d1f4ee60ce6a4a85abb79532f64d4a4e7…> - Loads of improved test coverage. cbd67cc50a37770432eb978ac8b8eb6da3664817 <https://github.com/haskell/network/commit/cbd67cc50a37770432eb978ac8b8eb6da…> fcc2d86d53a6bec793f6a979a9e8fdf7fe3f4c22 <https://github.com/haskell/network/commit/fcc2d86d53a6bec793f6a979a9e8fdf7f…> 6db96969b3e8974abbfd50a7f073baa57376fd5e <https://github.com/haskell/network/commit/6db96969b3e8974abbfd50a7f073baa57…> As always, thank you to network's contributors!

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Second Call for Participation: ICFP 2020
by Sam Tobin-Hochstadt 06 Aug '20

06 Aug '20

===================================================================== Second Call for Participation ICFP 2020 25th ACM SIGPLAN International Conference on Functional Programming and affiliated events August 23 - August 28, 2020 Online http://icfp20.sigplan.org/ Early Registration ends August 8! ==================================================================== ICFP provides a forum for researchers and developers to hear about the latest work on the design, implementations, principles, and uses of functional programming. The conference covers the entire spectrum of work, from practice to theory, including its peripheries. Watch our new video, and Don't Stop ICFP: https://www.youtube.com/watch?v=Fte5wwnwCws Early Registration ends August 8th! Registration for students with an ACM or SIGPLAN membership is free, and anyone can apply for a fee waiver at: https://icfp20.sigplan.org/attending/Registration This year, the conference will be a virtual event. All activities will take place online. The main conference will take place from August 24-26, 2020 during two time bands. The first band will be 9AM-5:30PM New York, and will include both technical and social activities. The second band will repeat (with some variation) the technical program and social activities 12 hours later, 9AM-5:30PM Beijing, the following day. We've written a blog post about how conference mirroring will work for ICFP: https://blog.sigplan.org/2020/08/04/come-to-virtual-icfp/ We’re excited to announce our two invited speakers for 2020: Evan Czaplicki, covering the Elm programming language and hard lessons learned on driving adoption of new programming languages; and Audrey Tang, Haskeller and Taiwan’s Digital Minister, on how software developers can contribute to fighting the pandemic. ICFP has officially accepted 37 exciting papers, and (as a fresh experiment this year) there will also be presentations of 8 papers accepted recently to the Journal of Functional Programming. Co-located symposia and workshops will take place the day before and two days immediately after the main conference. Registration is now open. The early registration deadline is August 8th, 2020. Registration is not free, but is significantly lower than usual. Students who are ACM or SIGPLAN members may register for FREE before the early deadline. https://regmaster.com/2020conf/ICFP20/register.php New this year: Attendees will be able to sign-up for the ICFP Mentoring Program (either to be a mentor, receive mentorship or both). * Overview and affiliated events: http://icfp20.sigplan.org/home * Full Schedule: https://icfp20.sigplan.org/program/program-icfp-2020 * Accepted papers: http://icfp20.sigplan.org/track/icfp-2020-papers#event-overview * JFP Talks: https://icfp20.sigplan.org/track/icfp-2020-jfp-talks#event-overview * Registration is available via: https://regmaster.com/2020conf/ICFP20/register.php Early registration ends 8 August, 2020. * Programming contest: https://icfpcontest2020.github.io/ * Student Research Competition: https://icfp20.sigplan.org/track/icfp-2020-Student-Research-Competition * Follow us on Twitter for the latest news: http://twitter.com/icfp_conference This year, there are 10 events co-located with ICFP: * Erlang Workshop (8/23) * Haskell Implementors' Workshop (8/28) * Haskell Symposium (8/27-8/28) * Higher-Order Programming with Effects (8/23) * miniKanren Workshop (8/27) * ML Family Workshop (8/27) * OCaml Workshop (8/28) * Programming Languages Mentoring Workshop (8/23) * Scheme Workshop (8/28) * Type-Driven Development (8/23) ### ICFP Organizers General Chair: Stephanie Weirich (University of Pennsylvania, USA) Program Chair: Adam Chlipala (MIT, USA) Artifact Evaluation Co-Chairs: Brent Yorgey (Hendrix College, USA) Ben Lippmeier (Ghost Locomotion, Australia) Industrial Relations Chair: Alan Jeffrey (Mozilla Research, USA) Programming Contest Organizer: Igor Lukanin (Kontur, Russia) Publicity and Web Chair: Sam Tobin-Hochstadt (Indiana University, USA) Student Research Competition Chair: Youyou Cong (Tokyo Institute of Technology, Japan) Workshops Co-Chair: Jennifer Hackett (University of Nottingham, UK) Leonidas Lampropoulos (University of Pennsylvania, USA) Video Chair: Leif Andersen (Northeastern University, USA) Student Volunteer Co-Chair: Hanneli Tavante (McGill University, Canada) Victor Lanvin (IRIF, Université Paris Diderot, France)

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stack: pandoc fails to build as dependency
by Olaf Klinke 06 Aug '20

06 Aug '20

Dear cafe, I am baffled to learn that stack does not provide builds as reproducible as advertised. I have a project that depends on pandoc. It builds fine on my Debian 9 machine. Then I check out the project on a Debian 8 machine. Downloading and building pandoc-2.7.3 with the latest stack-2.1.3 on the Debian 8 machine runs fine. Now I create a new project, using the same stack.yaml as in the pandoc-2.7.3 package, except now pandoc-2.7.3 is an extra-dep. The project's only module contains nothing but: module Test where import Text.Pandoc Building this project with the same stack results in a linker error: pandoc > Preprocessing executable 'pandoc' for pandoc-2.7.3.. pandoc > Building executable 'pandoc' for pandoc-2.7.3.. pandoc > [1 of 2] Compiling Main pandoc > [2 of 2] Compiling Paths_pandoc pandoc > Linking .stack-work/dist/x86_64-linux/Cabal-2.4.0.1/build/pandoc/pandoc ... pandoc > collect2: error: ld returned 1 exit status pandoc > `gcc' failed in phase `Linker'. (Exit code: 1) This seems to be independent of the LTS version (the stack.yaml in pandoc-2.7.3 says lts-13.17 although lts-13.17 contains pandoc-2.5 and pandoc-2.7.3 is available only in 14.9). Can somebody hint what I am doing wrong? Should I file a bug report? Thanks Olaf

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dates...
by Gregory Guthrie 06 Aug '20

06 Aug '20

I don't understand why the Julian conversion are given relative to 2019, instead of 2020, and don't seem to actually show the date index. Must be misreading the library specs? toJulianYearAndDay :: Day<https://hackage.haskell.org/package/time-1.6/docs/Data-Time-Calendar.html#t…> -> (Integer<https://hackage.haskell.org/package/base-4.8.1.0/docs/Prelude.html#t:Integer>, Int<https://hackage.haskell.org/package/base-4.8.1.0/docs/Data-Int.html#t:Int>) convert to proleptic Julian year and day format. First element of result is year (proleptic Julian calendar), second is the day of the year, with 1 for Jan 1, and 365 toJulian :: Day<https://hackage.haskell.org/package/time-1.6/docs/Data-Time-Calendar.html#t…> -> (Integer<https://hackage.haskell.org/package/base-4.8.1.0/docs/Prelude.html#t:Integer>, Int<https://hackage.haskell.org/package/base-4.8.1.0/docs/Data-Int.html#t:Int>, Int<https://hackage.haskell.org/package/base-4.8.1.0/docs/Data-Int.html#t:Int>) Source<https://hackage.haskell.org/package/time-1.6/docs/src/Data-Time-Calendar-Ju…> convert to proleptic Julian calendar. First element of result is year, second month number (1-12), third day (1-31). ---------------------------------------------------------------------------------- ds = "1/8/2020" day = parseTimeOrError True defaultTimeLocale "%-m/%-d/%Y" ds :: UTCTime getDay = toGregorian . utctDay getDayOfYear = toJulian . utctDay getDayYear = toJulianYearAndDay. utctDay main = do print day print $ getDay day print $ getDayYear day print $ getDayOfYear day 2020-01-08 00:00:00 UTC (2020,1,8) (2019,360) (2019,12,26) And; 2020-02-08 00:00:00 UTC (2020,2,8) (2020,26) (2020,1,26) Dr. Gregory Guthrie Maharishi International University ----------------------------------------------------------------

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