- Haskell-Cafe - Haskell.org

job opportunity at Luna
by Sylwia Brodacka 23 May '19

23 May '19

Luna (http://luna-lang.org) is an award-winning data-science platform and a general-purpose functional programming language, selected by NASA and Singularity University as 1 of the 20 most impressive technologies worldwide. It spans the entire stack, from high-level visualisation and communication, to the nitty-gritty of running backend services in a single language. With inbuilt capabilities for visualisation and a dual-syntax architecture, the possibilities are limitless. We are looking for talented and extraordinary people with strong technical skills and a passion for functional programming. Since majority of Luna codebase is written in Haskell we have available positions for senior Haskell developers for a variety of roles, including Compiler Engineer, DevOps Engineer, GUI Architect, and Cloud Software Engineer. If you want to learn more about possibilities please check out detailed job description: https://stackoverflow.com/jobs/264670/senior-haskell-developer-luna Cheers, Sylwia

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Re: [Haskell-cafe] Announce: Haskell Platform 8.6.5 (Gershom B) - clarification
by Pierre_van_der_Laar (Functional Account) 21 May '19

21 May '19

Dear All, The license issue can be summarized as follows: Whenever a program is compiled with GHC and is distributed on another platform than OS X, anybody can claim that the source code of that program must be provided due to the LGPL license, since integer-gmp, the ghc code, and that program's code are statically linked! Not convinced? Read e.g. https://gitlab.haskell.org/ghc/ghc/wikis/replacing-gmp-notes that discussed both the LGPL license and the usage of static libraries by GHC. For convenience, I have include the most relevant parts: ``` GMP is licensed under the GNU Lesser General Public License (LGPL), a kind of "copyleft" license. According to the terms of the LGPL, paragraph 5, you may distribute a program that is designed to be compiled and dynamically linked with the library under the terms of your choice (i.e., commercially) but if your program incorporates portions of the library, if it is linked statically, then your program is a "derivative"--a "work based on the library"--and according to paragraph 2, section c, you "must cause the whole of the work to be licensed" under the terms of the LGPL (including for free). The LGPL licensing for GMP is a problem for the overall licensing of binary programs compiled with GHC because most distributions (and builds) of GHC use static libraries. (Dynamic libraries are currently distributed only for OS X.) The LGPL licensing situation may be worse: even though The Glasgow Haskell Compiler License is essentially a "free software" license (BSD3), according to paragraph 2 of the LGPL, GHC must be distributed under the terms of the LGPL! ``` So the problem is real and seems to be underestimated by the Haskell user community based on the many (partly) incorrect responses on this mailing list. I still would like to know what GHC's strategy is to tackle this problem! Greetings, Pierre ________________________________ The information contained in this message may be confidential and legally protected under applicable law. The message is intended solely for the addressee(s). If you are not the intended recipient, you are hereby notified that any use, forwarding, dissemination, or reproduction of this message is strictly prohibited and may be unlawful. If you are not the intended recipient, please contact the sender by return e-mail and destroy all copies of the original message.

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[TFP'19 and TFPIE'19] call for participation
by Peter Achten 21 May '19

21 May '19

--------------------------------- C A L L F O R P A R T I C I P A T I O N --------------------------------- ====== TFP 2019 ====== 20th Symposium on Trends in Functional Programming 12-14 June, 2019 Vancouver, BC, CA https://www.tfp2019.org/index.html ====== TFPIE 2019 ====== 8th International Workshop on Trends in Functional Programming in Education 11 June, 2019 Vancouver, BC, CA http://www.staff.science.uu.nl/~hage0101/tfpie2019/index.html The symposium on Trends in Functional Programming (TFP) is an international forum for researchers with interests in all aspects of functional programming, taking a broad view of current and future trends in the area. It aspires to be a lively environment for presenting the latest research results, and other contributions (see below at scope). Please be aware that TFP uses two distinct rounds of submissions (see below at submission details). TFP 2019 will be the main event of a pair of functional programming events. TFP 2019 will be accompanied by the International Workshop on Trends in Functional Programming in Education (TFPIE), which will take place on June 11. == Invited Speakers == TFP 2019 is pleased to announce keynote talks by the following two invited speakers: Nikhil Swamy, Microsoft Research: Structuring the Verification of Imperative Programs with Functional Programming Frank Wood, University of British Columbia: Probabilistic Programming TFPIE 2019 is pleased to have the following invited speaker: Gregor Kiczales: Functional Programming at the Core of a High Throughput Software Engineering Curriculum == Scope == The symposium recognizes that new trends may arise through various routes. As part of the Symposium's focus on trends we therefore identify the following five article categories. High-quality articles are solicited in any of these categories: Research Articles: Leading-edge, previously unpublished research work Position Articles: On what new trends should or should not be Project Articles: Descriptions of recently started new projects Evaluation Articles: What lessons can be drawn from a finished project Overview Articles: Summarizing work with respect to a trendy subject Articles must be original and not simultaneously submitted for publication to any other forum. They may consider any aspect of functional programming: theoretical, implementation-oriented, or experience-oriented. Applications of functional programming techniques to other languages are also within the scope of the symposium. Topics suitable for the symposium include, but are not limited to: Functional programming and multicore/manycore computing Functional programming in the cloud High performance functional computing Extra-functional (behavioural) properties of functional programs Dependently typed functional programming Validation and verification of functional programs Debugging and profiling for functional languages Functional programming in different application areas: security, mobility, telecommunications applications, embedded systems, global computing, grids, etc. Interoperability with imperative programming languages Novel memory management techniques Program analysis and transformation techniques Empirical performance studies Abstract/virtual machines and compilers for functional languages (Embedded) domain specific languages New implementation strategies Any new emerging trend in the functional programming area If you are in doubt on whether your article is within the scope of TFP, please contact the TFP 2019 program chairs, William J. Bowman and Ron Garcia. == Best Paper Awards == To reward excellent contributions, TFP awards a prize for the best paper accepted for the formal proceedings. TFP traditionally pays special attention to research students, acknowledging that students are almost by definition part of new subject trends. A student paper is one for which the authors state that the paper is mainly the work of students, the students are listed as first authors, and a student would present the paper. A prize for the best student paper is awarded each year. In both cases, it is the PC of TFP that awards the prize. In case the best paper happens to be a student paper, that paper will then receive both prizes. == Instructions to Author == Papers must be submitted at: https://easychair.org/conferences/?conf=tfp2019 Authors of papers have the choice of having their contributions formally reviewed either before or after the Symposium. == Pre-symposium formal review == Papers to be formally reviewed before the symposium should be submitted before an early deadline and receive their reviews and notification of acceptance for both presentation and publication before the symposium. A paper that has been rejected in this process may still be accepted for presentation at the symposium, but will not be considered for the post-symposium formal review. == Post-symposium formal review == Papers submitted for post-symposium review (draft papers) will receive minimal reviews and notification of acceptance for presentation at the symposium. Authors of draft papers will be invited to submit revised papers based on the feedback received at the symposium. A post-symposium refereeing process will then select a subset of these articles for formal publication. == Paper categories == There are two types of submission, each of which can be submitted either for pre-symposium or post-symposium review: Extended abstracts. Extended abstracts are 4 to 10 pages in length. Full papers. Full papers are up to 20 pages in length. Each submission also belongs to a category: research position project evaluation overview paper Each submission should clearly indicate to which category it belongs. Additionally, a draft paper submission—of either type (extended abstract or full paper) and any category—can be considered a student paper. A student paper is one for which primary authors are research students and the majority of the work described was carried out by the students. The submission should indicate that it is a student paper. Student papers will receive additional feedback from the PC shortly after the symposium has taken place and before the post-symposium submission deadline. Feedback is only provided for accepted student papers, i.e., papers submitted for presentation and post-symposium formal review that are accepted for presentation. If a student paper is rejected for presentation, then it receives no further feedback and cannot be submitted for post-symposium review. == Format == Papers must be written in English, and written using the LNCS style. For more information about formatting please consult the Springer LNCS web site (http://www.springer.com/lncs) == Program Committee == Program Co-chairs William J. Bowman University of British Columbia Ronald Garcia University of British Columbia Matteo Cimini University of Massachusetts Lowell Ryan Culpepper Czech Technical Institute Joshua Dunfield Queen's University Sam Lindley University of Edinburgh Assia Mahboubi INRIA Nantes Christine Rizkallah University of New South Wales Satnam Singh Google AI Marco T. Morazán Seton Hall University John Hughes Chalmers University and Quviq Nicolas Wu University of Bristol Tom Schrijvers KU Leuven Scott Smith Johns Hopkins University Stephanie Balzer Carnegie Mellon University Viktória Zsók Eötvös Loránd University

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Re: [Haskell-cafe] Announce: Haskell Platform 8.6.5 (Gershom B)
by Pierre_van_der_Laar (Functional Account) 21 May '19

21 May '19

Dear Gershom / GHC development team, The provided windows version of GHC contains lib-gmp. Hence, this version enforces a LGPL license on my code (see e.g. https://gitlab.haskell.org/ghc/ghc/wikis/replacing-gmp-notes for more info) . Unfortunately, this license is unacceptable for me. For me this raises the question: What is the strategy of GHC with respect to licensing? In particularly, * Why considers GHC a LGPL license for all the code developed by their users acceptable? * Is GHC considering to allow their user to standardly develop their code under a license of their own choice? * Are there plans to offer the GHC users an opportunity to choose the license in the near future? e.g. by distributing GHC binary distributions with integer-gmp and integer-simple. Thanks in advance for your answers, Pierre van de Laar --------------------------------------------------------------------- Date: Wed, 8 May 2019 16:28:21 -0400 From: Gershom B <gershomb(a)gmail.com> To: haskell-cafe <haskell-cafe(a)haskell.org>, haskell(a)haskell.org Subject: [Haskell-cafe] Announce: Haskell Platform 8.6.5 Message-ID: <CAM8RHpGB=mhYLJ_qDd__Td8vcJYBvZ66h0fErTU98H9DnWawmQ(a)mail.gmail.com> Content-Type: text/plain; charset="UTF-8" On behalf of the Haskell Platform team, I'm happy to announce the release of Haskell Platform 8.6.5 Now available at https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.haske… This includes GHC 8.6.5, cabal-install 2.4.1.0, and stack 1.9.3. It is an incremental release over 8.6.3 intended mainly to make available bugfixes for windows in subsequent revisions in the 8.6 series and otherwise leave everything the same. These windows fixes are important, and it is recommended all windows users upgrade to 8.6.5 whether through the platform installer or some other mechanism. For detail on these changes and fixes see https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.haske… https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.haske… As with the 8.6.3 release, we are only providing core builds. Further, in 8.6.3 we moved from generic linux installers to recommending users install ghc through ghcup. As discussed in the last announcement, we have now moved to recommending os x users also use ghcup rather than a dedicated binary installer. For more details, please see the 8.6.3 announcement at https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fmail.hask… Happy Haskell Hacking all, Gershom ________________________________ The information contained in this message may be confidential and legally protected under applicable law. The message is intended solely for the addressee(s). If you are not the intended recipient, you are hereby notified that any use, forwarding, dissemination, or reproduction of this message is strictly prohibited and may be unlawful. If you are not the intended recipient, please contact the sender by return e-mail and destroy all copies of the original message.

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Second Call for Tutorial Proposals: ICFP 2019
by Sam Tobin-Hochstadt 20 May '19

20 May '19

*EXTENDED DEADLINE* - CALL FOR TUTORIAL PROPOSALS ICFP 2019 24th ACM SIGPLAN International Conference on Functional Programming August 18 - 23, 2019 Berlin, Germany https://icfp19.sigplan.org/ The 24th ACM SIGPLAN International Conference on Functional Programming will be held in Berlin, Germany on August 18-23, 2019. ICFP provides a forum for researchers and developers to hear about the latest work on the design, implementations, principles, and uses of functional programming. Proposals are invited for tutorials, lasting approximately 3 hours each, to be presented during ICFP and its co-located workshops and other events. These tutorials are the successor to the CUFP tutorials from previous years, but we also welcome tutorials whose primary audience is researchers rather than practitioners. Tutorials may focus either on a concrete technology or on a theoretical or mathematical tool. Ideally, tutorials will have a concrete result, such as "Learn to do X with Y" rather than "Learn language Y". Tutorials may occur after ICFP co-located with the associated workshops, from August 22 till August 23. ---------------------------------------------------------------------- Submission details Deadline for submission: June 3rd, 2019 Notification of acceptance: June 10th, 2019 Prospective organizers of tutorials are invited to submit a completed tutorial proposal form in plain text format to the ICFP 2018 workshop co-chairs (Jennifer Hackett and Christophe Scholliers), via email to icfp-workshops-2019(a)googlegroups.com by June 3rd, 2019. Please note that this is a firm deadline. Organizers will be notified if their event proposal is accepted by June 10th, 2019. The proposal form is available at: http://www.icfpconference.org/icfp2019-files/icfp19-tutorials-form.txt ---------------------------------------------------------------------- Selection committee The proposals will be evaluated by a committee comprising the following members of the ICFP 2019 organizing committee. Tutorials Co-Chair: Jennifer Hackett (University of Nottingham) Tutorials Co-Chair: Christophe Scholliers (University of Ghent) General Chair: Derek Dreyer (MPI-SWS) Program Chair: François Pottier ( Inria, France) ---------------------------------------------------------------------- Further information Any queries should be addressed to the tutorial co-chairs (Jennifer Hackett and Christophe Scholliers), via email to icfp-workshops-2019(a)googlegroups.com

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How to dynamic plan in Haskell?
by Magicloud Magiclouds 20 May '19

20 May '19

Hi, I solved the question. But I could not figure out a FP style solution. Question: 1 - 9, nine numbers. Show all the possible combinations that sum up to 10. Different orders are counted as the same. For example, [1, 4, 5].

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zstd package. Proposal to take over maintenance
by Luis Pedro Coelho 20 May '19

20 May '19

Hi everyone, The zstd package contains important bugs (it produces malformed output in some cases) and seems unmaintained. I would like to take over maintenance of it. I have actually forked the package and fixed the bugs, releasing it as hs-zstd: https://github.com/luispedro/hs-zstd http://hackage.haskell.org/package/hs-zstd I was advised to consider taking over maintenance of zstd as an earlier attempt to contact the maintainers of zstd was not answered. I would still prefer not to have this responsibility, but I would also like to use zstd in my work. * The zstd issues are not obvious because 99% of the time it works well, so we actually used it in a release of ngless, but after 3 days in the wild, we had to release a "bugfix". This is because most code paths work well, but there is one which produces a broken file. http://ngless.embl.de/whatsnew.html#version-0-11 Thanks, Luis Luis Pedro Coelho | Fudan University | http://luispedro.org https://orcid.org/0000-0002-9280-7885

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First Call for Papers for IFL 2019 (Implementation and Application of Functional Languages)
by J. Stutterheim 19 May '19

19 May '19

Dear all, Please, find below the first call for papers for IFL 2019. Please forward these to anyone you think may be interested. Apologies for any duplicates you may receive. Best regards, Jurriën Stutterheim --- ================================================================================ IFL 2019 31st Symposium on Implementation and Application of Functional Languages National University of Singapore September 25th-27th, 2019 http://2019.iflconference.org ================================================================================ ### 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 2019 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 specialization - run-time code generation - partial evaluation - (abstract) interpretation - metaprogramming - 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 ### Keynote Speaker * Olivier Danvy, Yale-NUS College ### Submissions and peer-review Differently from previous editions of IFL, IFL 2019 solicits two kinds of submissions: * Regular papers (12 pages including references) * Draft papers for presentations ('weak' limit between 8 and 15 pages) Regular papers will undergo a rigorous review by the program committee, and will be evaluated according to their correctness, novelty, originality, relevance, significance, and clarity. A set of regular papers will be conditionally accepted for publication. Authors of conditionally accepted papers will be provided with committee reviews along with a set of mandatory revisions. Regular papers not accepted for publication will be considered as draft papers, at the request of the author. Draft papers will be screened to make sure that they are within the scope of IFL, and will be accepted for presentation or rejected accordingly. Prior to the symposium: Authors of conditionally accepted papers and accepted presentations will submit a pre-proceedings version of their work that will appear in the draft proceedings distributed at the symposium. The draft proceedings does not constitute a formal publication. We require that at least one of the authors present the work at IFL 2019. After the symposium: Authors of conditionally accepted papers will submit a revised versions of their paper for the formal post-proceedings. The program committee will assess whether the mandatory revisions have been adequately addressed by the authors and thereby determines the final accept/reject status of the paper. Our interest is to ultimately accept all conditionally accepted papers. If you are an author of a conditionally accepted paper, please make sure that you address all the concerns of the reviewers. Authors of accepted presentations will be given the opportunity to incorporate the feedback from discussions at the symposium and will be invited to submit a revised full article for the formal post-proceedings. 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. ### Publication The formal proceedings will appear in the International Conference Proceedings Series of the ACM Digital Library. At no time may work submitted to IFL be simultaneously submitted to other venues; submissions must adhere to ACM SIGPLAN's republication policy: http://www.sigplan.org/Resources/Policies/Republication ### Important dates Submission of regular papers: May 31, 2019 Submission of draft papers: July 15, 2019 Regular and draft papers notification: August 1, 2019 Deadline for early registration: August 15, 2019 Submission of pre-proceedings version: September 15, 2019 IFL Symposium: September 25-27, 2019 Submission of papers for post-proceedings: November 30, 2019 Notification of acceptance: January 31, 2020 Camera-ready version: February 29, 2020 ### 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 Authors submit through EasyChair: https://easychair.org/conferences/?conf=ifl2019 ### Peter Landin Prize The Peter Landin Prize is awarded to the best paper presented at the symposium every year. The honored 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. ### Organization and Program committee Chairs: Jurrien Stutterheim (Standard Chartered Bank Singapore), Wei Ngan Chin (National University of Singapore) Program Committee: - Olaf Chitil, University of Kent - Clemens Grelck, University of Amsterdam - Daisuke Kimura, The University of Tokyo - Pieter Koopman, Radboud University - Tamás Kozsik, Eötvös Loránd University - Roman Leschinskiy, Facebook - Ben Lippmeier, The University of New South Wales - Marco T. Morazan, Seton Hall University - Sven-Bodo Scholz, Heriot-Watt University - Tom Schrijvers, Katholieke Universiteit Leuven - Alejandro Serrano, Utrecht University - Tony Sloane, Macquarie University - Simon Thompson, University of Kent - Marcos Viera, Universidad de la República - Wei Ngan Chin, NUS - Jurriën Stutterheim, Standard Chartered Bank ### Venue The 30th IFL is organized by the University of Massachusetts Lowell. The City of Lowell is located at the heart of the Merrimack Valley just 30 miles northwest of Boston. Lowell can be easily reached by train or taxi. See the website for more information on the venue. ### Acknowledgments This call-for-papers is an adaptation and evolution of content from previous instances of IFL. We are grateful to prior organizers for their work, which is reused here. A part of IFL 2019 format and CFP language that describes conditionally accepted papers has been adapted from call-for-papers of OOPSLA conferences.

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Mocking out external services
by Francesco Ariis 19 May '19

19 May '19

(literate Haskell follows) Hello -cafe, I recently read "Three Layer Haskell Cake" [1] and decided to give it a go. I am stuck on a simple problem and feel like I am missing something easy. One of the first examples is a mocking of an `IO UTCTime` function. > > {-# Language FlexibleInstances #-} > > data UTCTime = UTCTime Int > > class MonadTime m where > getCurrentTime :: m UTCTime > > instance MonadTime ((->) UTCTime) where > getCurrentTime = id > > -- instance IO omitted > Everything is clear. I decided to write another function, mocking a stream-of-Char input. > > class MonadKeys m where > getKeys :: m [Char] > > instance MonadKeys ((->) [Char]) where > getKeys = id > > -- instance IO omitted > Again, fine. But now, if I want to write a function which combines the two external services, like: > > someFun :: (MonadTime m, MonadKeys m) => m () > someFun = undefined > there is no non-IO instance satisfying the two constraints. I could of course write a type > > data Env = Env UTCTime [Char] > and make it instance of MonadTime and MonadKeys, but then I am passing non-relevant arguments to a mocked function like getCurrentTime, which would only need UTCTime. What am I doing incorrectly? -F [1] https://www.parsonsmatt.org/2018/03/22/three_layer_haskell_cake.html

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Identity operator for types
by Juan Miguel Vilar 17 May '19

17 May '19

Hi, Café: I am not sure how to make the question, but the idea is to have a type operator that returns the same type. Let me show what I need. I have some type like this: data Example f t = Example (f t) So if I want a type variable that contains a list of integers, I can use Example [] Int and then treat the content like a list: f :: Example [] Int -> Int f (Example l) = length l Now, the problem is what can I do to have a type that contains a single Int? Is there a sort of id for types so that I can write f :: Example ?? Int -> Int f (Example i) = 2 * i ? Thanks in advance Juan Miguel Vilar -- Juan Miguel Vilar Torres Profesor titular de universidad Departamento de Lenguajes y Sistemas Informáticos Escuela Superior de Tecnología y Ciencias Experimentales Universitat Jaume I Av. de Vicent Sos Baynat s/n 12071 Castelló de la Plana (Spain) Tel: +34 964 72 8365 Fax: +34 964 72 8435 jvilar(a)uji.es

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