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10 PhD studentships in Nottingham for Home/EU applicants
by Graham Hutton 20 Jan '20

20 Jan '20

Dear all, The School of Computer Science at the University of Nottingham is seeking applications for 10 fully-funded PhD studentships for Home/EU students: https://tinyurl.com/ten-phds-2020 Applicants in the area of the Functional Programming Laboratory (https://tinyurl.com/fp-notts) are strongly encouraged! If you are interested in applying, please contact a potential supervisor as soon as possible (the application deadline is 6th March): Thorsten Altenkirch - constructive logic, proof assistants, homotopy type theory, category theory, lambda calculus. Venanzio Capretta - type theory, mathematical logic, corecursive structures, proof assistants, category theory, epistemic logic. Graham Hutton - not taking on any new students this year, but you may find these notes useful: https://tinyurl.com/scbkxkr Henrik Nilsson - functional reactive programming, domain- specific languages, generalised notions of computation. These positions are only open to Home/EU applicants. An advert for international students was posted earlier and is now closed. Best wishes, Graham +-----------------------------------------------------------+ 10 Fully-Funded International PhD Studentships School of Computer Science University of Nottingham, UK https://tinyurl.com/ten-phds-2020 Applications are invited for 10 fully-funded PhD studentships for Home/EU students in the School of Computer Science at the University of Nottingham, starting on 1st October 2020. The topics for the studentships are open, but should relate to the interests of one of the School’s research groups: Agents Lab; Computational Optimisation and Learning Lab; Computer Vision Lab; Functional Programming; Intelligent Modelling and Analysis; Mixed Reality Lab; Data Driven Algorithms, Systems and Design and Uncertainty in Data and Decision Making The studentships are for three and a half years and include a stipend of £15,009 per year and tuition fees. Applicants are normally expected to have a first-class Masters or Bachelors degree in Computer Science or a related discipline, and must obtain the support of a potential supervisor in the School prior to submitting their application. Initial contact with supervisors should be made at least two weeks prior to the closing date for applications. Eligible successful applicants are expected to apply for a EU VC Scholarship. Informal enquiries may be addressed to Kathleen.Fennemore(a)nottingham.ac.uk. To apply, please submit the following items by email to: Marc.Williams(a)nottingham.ac.uk: (1) a copy of your CV, including your actual or expected degree class(es), and results of all University examinations; (2) an example of your technical writing, such as a project report or dissertation; (3) contact details for two academic referees. (4) a research proposal – max 2 x sides A4 You may also include a covering letter but this is optional. Closing date for applications: Friday 6 March 2020. +-----------------------------------------------------------+ This message and any attachment are intended solely for the addressee and may contain confidential information. If you have received this message in error, please contact the sender and delete the email and attachment. Any views or opinions expressed by the author of this email do not necessarily reflect the views of the University of Nottingham. Email communications with the University of Nottingham may be monitored where permitted by law.

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Haskell.org Committee Nomination Results
by Emily Pillmore 20 Jan '20

20 Jan '20

Hello Everyone, I'm pleased to announce that the results for the Haskell.org ( http://haskell.org/ ) committee nominations are in, and voting has completed. The following tally is the final result: Jaspe Van der Jeugt: 6 Alexandre Garcia de Oliveira: 5 April Gonçalves: 2 Rebecca Skinner: 5 With no votes for anyone else. This means that Jasper's renomination was successful, and we get to welcome 2 new faces to the Haskell.org ( http://haskell.org/ ) ; congratulations Rebecca and Alexandre! Thanks, Emily

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persistent and safe-money packages
by Debasish Ghosh 17 Jan '20

17 Jan '20

Hi - I am using "persistent" for database access in Haskell. However in my domain model I have used the Dense data type from safe-money ( https://hackage.haskell.org/package/safe-money) as the money datatype. It looks like this data type is not supported by default in persistent. Is there a way around ? Thanks in advance. -- Debasish Ghosh http://manning.com/ghosh2 http://manning.com/ghosh Twttr: @debasishg Blog: http://debasishg.blogspot.com Code: http://github.com/debasishg

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[ANN] 2nd Call for Participation: BOB 2020 (February 28, Berlin, early-bird until Jan 20)
by Stefan Wehr 15 Jan '20

15 Jan '20

================================================================================ BOB 2020 Conference “What happens if we simply use what’s best?” February 28, 2020, Berlin http://bobkonf.de/2020/ Program: http://bobkonf.de/2020/en/program.html Registration: http://bobkonf.de/2020/en/registration.html ================================================================================ BOB is the conference for developers, architects and decision-makers to explore technologies beyond the mainstream in software development, and to find the best tools available to software developers today. Our goal is for all participants of BOB to return home with new insights that enable them to improve their own software development experiences. The program features 14 talks and 8 tutorials on current topics: http://bobkonf.de/2020/en/program.html The subject range of talks includes functional programming, formal methods, architecture documentation, functional-reactive programming, and language design. The tutorials feature introductions to Idris, Haskell, F#, TLA+, ReasonML, and probabilistic programming. Heather Miller will give the keynote talk. Registration is open online: http://bobkonf.de/2020/en/registration.html NOTE: The early-bird rates expire on January 20, 2020! BOB cooperates with the Racketfest conference on the day before BOB: https://racketfest.com/ BOB cooperates with the :clojureD conference on the day after BOB: https://clojured.de/

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[Job] Hiring Numerical Programmers at Anduril Industries
by Travis Whitaker 15 Jan '20

15 Jan '20

Greetings Fellow Haskellers, Anduril Industries is hiring Haskellers for numerical programming work. Quick Details: - Seeking Haskellers familiar with numerical programming techniques. - Familiarity with LLVM, FORTRAN, Linux, and compiler engineering is advantageous. - Positions for internships and new graduates are available. - Regrettably, no remote opportunities are available at this time. We are located in southern California, USA. Anduril is looking for engineers to rapidly develop high-reliability solutions to numerical problems by leveraging lightweight formal methods. We are working on problems from a wide range of disciplines, including robotics, flight control, guidance & navigation, and radar signal processing. If you're interested in numerical programming, physics, and lightweight formal verification techniques, then you'd likely enjoy working on our team! With respect to internships, our program is extremely flexible and we can adapt to whatever structure your university might require. If this sounds interesting, please drop me a line at travis(a)anduril.com. Thanks for your time, Travis Whitaker

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database programming with Haskell
by Debasish Ghosh 14 Jan '20

14 Jan '20

Hello - I am looking for some good practices on how to design database access APIs in applications using Haskell. I have been going through various libraries like persistent, Esqueleto etc. All of them have nice APIs. However I am looking for practices around designing APIs that also offer testability without plugging in a concrete database engine. Like the one we can design using tagless final approaches where we can switch out the Database monad with some mocked one (maybe that uses some hashmap instead of a real database) for unit tests. Is there any recommended practice on this or may be some sample application that's designed around these practices ? Or is this at all a recommended practice in Haskell ? regards. -- Debasish Ghosh http://manning.com/ghosh2 http://manning.com/ghosh Twttr: @debasishg Blog: http://debasishg.blogspot.com Code: http://github.com/debasishg

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[TFP'20] call for participation: Trends in Functional Programming 2020, 13-14 February, Krakow, Poland
by Peter Achten 14 Jan '20

14 Jan '20

------------------------------------------------------------------------- Call for participation 21st Symposium on Trends in Functional Programming tfp2020.org ------------------------------------------------------------------------- The list of accepted papers is available at http://www.cse.chalmers.se/~rjmh/tfp/ 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. * TFP is moving to new winter dates, to provide an FP forum in between the annual ICFP events. * TFP offers a supportive reviewing process designed to help less experienced authors succeed, with two rounds of review, both before and after the symposium itself. Authors have an opportunity to address reviewers' concerns before final decisions on publication in the proceedings. * TFP offers two "best paper" awards, the John McCarthy award for best paper, and the David Turner award for best student paper. * This year we are particularly excited to co-locate with Lambda Days in beautiful Krakow. Lambda Days is a vibrant developer conference with hundreds of attendees and a lively programme of talks on functional programming in practice. TFP will be held in the same venue, and participants will be able to session-hop between the two events. Important Dates --------------- Submission deadline for pre-symposium review: 15th November, 2019 -- passed -- Submission deadline for draft papers: 10th January, 2020 -- passed -- Registration (regular): 2nd February, 2020 Registration (late): 13th February, 2020 Symposium dates: 13-14th February, 2020 Visit tfp2020.org for more information.

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Fwd: State of BNFC-meta and friends
by Artem Pelenitsyn 13 Jan '20

13 Jan '20

Dear cafe, I tried to contact Jonas, the maintainer of BNFC-meta[1], twice (a week ago and 1.5 months ago, see below the copies of emails) with regards to updating the package to recent GHC, but with no luck. I'm interested in taking over the package if nobody minds... [1]: http://hackage.haskell.org/package/BNFC-meta -- Kind regards, Artem ---------- Forwarded message --------- From: Artem Pelenitsyn <a.pelenitsyn(a)gmail.com> Date: Sun, 5 Jan 2020 at 15:06 Subject: Re: State of BNFC-meta and friends To: <jonas.duregard(a)gmail.com> Hey Jonas, Just wanted to check if you saw my mail… -- Best, Artem On Thu, 21 Nov 2019 at 20:44, Artem Pelenitsyn <a.pelenitsyn(a)gmail.com> wrote: > Hello Jonas, > > I'm writing to let you know that your Hackage packages > > * BNFS-meta, > * happy-meta, > * alex-meta > > fail to build with current versions of GHC (8.6, 8.8). I wonder if you > intend to update them? > > All of them require bumping the template-haskell upper bound to <2.16. > > happy-meta seems to have weird interactions with newer Cabal because of > "Build-type: Custom" along the lines > https://github.com/haskell/cabal/issues/5278 Given that your Setup.hs > uses Distribution.Simple, I don't really see the point of having Custom. > Switching to "Build-type: Simple" seems to work just fine. > > alex-meta has one broken Monoid instance as per SMP proposal. Easily > upgraded. > > With these changes, I was able to build BNFC-meta successfully with GHC > 8.6.5, cabal 2.4. I'd be happy to supply pull requests but I don't see > {alex,happy}-meta repositories anywhere, and I noticed BNFC-meta repo on > GitHub has the version of the package different from what is on Hackage. > > There is a bunch of deprecation and tabs warnings also. > > Kind regards, > Artem Pelenitsyn > PhD student at Northeastern U. > http://www.ccs.neu.edu/~artem/ > >

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Possibly an error in Tutorial?
by Ignat Insarov 13 Jan '20

13 Jan '20

In this line: > For example, the principal type of `head` is `[a]->a`; `[b]->a`, `a->a`, or even `a` are correct types, but too general, whereas something like `[Integer]->Integer` is too specific. — It is not clear how `a → a` can be a correct type for `head`, insofar as all occurrences of a type variable must be instantiated to the same concrete type. If this sentence is actually correct, perhaps it could be clarified to address the issue? This concern was raised on Reddit: https://www.reddit.com/r/haskellquestions/comments/enqhu0/how_does_head_hav… Link to tutorial: https://www.haskell.org/tutorial/goodies.html

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[GSoC 2020] Call for Ideas
by Jasper Van der Jeugt 12 Jan '20

12 Jan '20

Google Summer of Code [1] will take place again in 2020! Haskell.org has been able to take part in this program in the past two years, and we'd like to keep this momentum up since it greatly benefits the community. Google is not extremely open about what factors it considers for applications from organizations, but they have stated multiple times that a well-organized ideas list is crucial. For that, we would like to count on all of you again. If you are the maintainer or a user of a Haskell project, and you have an improvement in mind which a student could work on during the summer, please submit an idea here: https://summer.haskell.org/ideas.html For context, Google Summer of Code is a program where Google sponsors students to work on open-source projects during the summer. Haskell.org has taken part in this program in 2006-2015, and 2018-2019. Many important improvements to the ecosystem have been the direct or indirect result of Google Summer of Code projects, and it has also connected new people with the existing community. Projects should benefit as many people as possible – e.g. an improvement to GHC will benefit more people than an update to a specific library or tool, but both are definitely valid. New libraries and applications written in Haskell, rather than improvements to existing ones, are also accepted. Projects should be concrete and small enough in scope such that they can be finished by a student in three months. Past experience has shown that keeping projects "small" is almost always a good idea. [1]: https://summerofcode.withgoogle.com/ Warm regards Jasper

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ETAPS Workshop on Trends, Extensions, Applications and Semantics of Logic Programming (TEASE-LP 2020)
by Ekaterina Komendantskaya 12 Jan '20

12 Jan '20

Call for Contributions Workshop on Trends, Extensions, Applications and Semantics of Logic Programming (TEASE-LP 2020) Dublin, Ireland, 25 April 2020 (co-located with ETAPS 2020) www.coalg.org/tease-lp Logic programming is a framework for expressing programs, propositions and relations as Horn clause theories, with the purpose of performing automatic inference in these theories. Horn clause theories are famous for their well-understood declarative semantics, in which models of logic programs are given inductively or coinductively. At the same time, Horn clauses give rise to efficient inference procedures, usually involving resolution. Logic programming found applications in type inference, verification, and AI. While logic programming was originally conceived for describing simple facts, it was extended to account for much more complex theories. This includes higher-order theories, inductive and coinductive data, and stochastic/probabilistic theories. The aim of this workshop is to bring together researchers that work on extensions of logic programming and inference methods, and to foster an exchange of methods and applications that have emerged in different communities. Topics --------------------------- The central idea of this workshop is to discuss the theory of logic programming and associated topics that have as well the goal to automatically infer knowledge and proofs. Our intention is to bring together researchers that work on the numerous topics that contribute to automatic proof inference and foster an exchange that may lead to advances in the theory of logic programming. Topics of interest include, but are not limited to, the following: * Proof theory (e.g. focalised and uniform proofs), * Logic programming beyond the classical Horn clause theories (e.g. coinduction, higher-order Horn clauses, probabilities, categorical logic, inductive LP), * Extensions of logic programming (e.g. DataLog, description logic, relational programming), * Advanced implementations (e.g. λProlog, ELPI, miniKanren), * Type theory (e.g. polarised λ-calculus, proofs-as-programs, types for logic programming), * Semantics (e.g. classical, categorical, algebraic, coalgebraic) , and * Applications. Venue and Event --------------------------- TEASE-LP 2020 will be held in Dublin, Ireland, co-located with ETAPS 2020 on 25 April 2020. Important Dates --------------------------- Abstract submission Wednesday, 26 February 2020 AoE Notification Wednesday, 25 March 2020 AoE Camera-ready copy Wednesday, 1 April 2020 AoE Workshop Saturday, 25 April 2020 Programme Committee --------------------------- Henning Basold (chair), Leiden University, NLD William Byrd, University of Alabama at Birmingham, USA Gopal Gupta, The University of Texas at Dallas, USA Ekaterina Komendantskaya (chair), Heriot-Watt University, GBR Dale Miller, INRIA and LIX/Ecole Polytechnique, FRA Gopalan Nadathur, University of Minnesota, USA Frank Pfenning, Carnegie Mellon University, USA Hiroshi Unno, University of Tsukuba, JPN Noam Zeilberger, University of Birmingham, GBR Submission Instructions --------------------------- Since the aim of the workshop is to foster exchange and discussions on trends, extensions, applications and semantics of logic programming, we invite presentations of possibly already published as well as ongoing work. Submissions should be abstracts of at most two pages in EPTCS style (http://style.eptcs.org/) and will be only be published in the informal pre-proceedings and on the website of the workshop. Post-proceedings volume may be solicited by the PC, based on the quality of contributions. Contributions should be submitted via the Easychair system: https://easychair.org/my/conference?conf=teaselp2020 All contributions will be refereed by the programme committee and it is expected that at least one of the authors will be present during the workshop.

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Road map for moving to new Haskell Platform?
by David Banas 12 Jan '20

12 Jan '20

It looks like the method of installing the Haskell Platform (at least, on MacOS) changed majorly, since the last time I updated. Is there any kind of “road map” to help us make the switch. Some questions that occurred to me, while I was doing the new install (via `curl … | sh`, as opposed to downloading a binary installer): It looks like there’s a new default install root: `~/.ghcup/`; does that mean I should rip out `/Library/Haskell/` and `~/Library/Haskell/`? Is `new-…` now the default (cabal v3.0.0.0), as previously threatened, or does the `new-` still need to be given explicitly? I’m getting different results using: `cabal install …` and `cabal new-install …`, and the `cabal install …` is complaining about a missing configuration variable: `installdir`, which I can’t find in my existing `~/.cabal/config` file. (Are the old `install_dirs` sections, with their several sub-variables, being ignored now?) Is `~/.cabal/config` still the default location for the config. file? How does one generate a new-format config. file? (Should one do this?) It looks like things are being sym-linked into `/usr/local/bin/` now; should I give that directory higher priority in my PATH variable? Any needed updates to Emacs config., to keep everything running smoothly? Thanks, -db

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[TFP'20] draft paper deadline open (January 10 2020) Trends in Functional Programming 2020, 13-14 February, Krakow, Poland
by Peter Achten 07 Jan '20

07 Jan '20

------------------------------------------------------------------------- Final call for papers 21st Symposium on Trends in Functional Programming tfp2020.org ------------------------------------------------------------------------- Did you miss the deadline to submit a paper to Trends in Functional Programming http://www.cse.chalmers.se/~rjmh/tfp/? No worries -- it's not too late! Submission is open until January 10th 2020, for a presentation slot at the event and post-symposium reviewing. 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. * TFP is moving to new winter dates, to provide an FP forum in between the annual ICFP events. * TFP offers a supportive reviewing process designed to help less experienced authors succeed, with two rounds of review, both before and after the symposium itself. Authors have an opportunity to address reviewers' concerns before final decisions on publication in the proceedings. * TFP offers two "best paper" awards, the John McCarthy award for best paper, and the David Turner award for best student paper. * This year we are particularly excited to co-locate with Lambda Days in beautiful Krakow. Lambda Days is a vibrant developer conference with hundreds of attendees and a lively programme of talks on functional programming in practice. TFP will be held in the same venue, and participants will be able to session-hop between the two events. Important Dates --------------- Submission deadline for pre-symposium review: 15th November, 2019 -- passed -- Submission deadline for draft papers: 10th January, 2020 Symposium dates: 13-14th February, 2020 Visit tfp2020.org for more information.

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Supporting Haskell.org
by Tikhon Jelvis 06 Jan '20

06 Jan '20

A significant part of the Haskell community infrastructure—including the haskell.org website, Hackage, Hoogle and the build infrastructure for GHC—runs on donations from the Haskell community administered by Haskell.org. Haskell.org also organizes Haskell's participation in the Google Summer of Code program. We had 18 projects this year, 15 of which were completed successfully, a solid completion ratio. If you would like to support Haskell.org, you can donate via several methods including PayPal and check: https://wiki.haskell.org/Donate_to_Haskell.org Haskell.org can also accept donations through employers via Benevity using the unique ID 475236502. Haskell.org is a 501(c)(3) non-profit, so donations may be tax-deductible in your jurisdiction. We look forward to continuing this work with your support in 2020 as well as exploring new projects to improve the Haskell community infrastructure. Best wishes, Tikhon Jelvis on behalf of the haskell.org committee.

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separate compilation for library profiling
by Henning Thielemann 05 Jan '20

05 Jan '20

Why does GHC start a separate compilation when I build with cabal --enable-library-profiling? At least parsing and type-checking should be the same as in the non-profiling compilation. Why aren't these steps shared between profiling and non-profiling compilation? I remember that in the past GHC also started a separate compilation for shared object generation. However, starting with GHC-7.8 dyn-files are just generated along with static compilation.

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Lift data from IO to Validation
by Debasish Ghosh 05 Jan '20

05 Jan '20

Hi - I am not an experienced Haskell programmer and would like to have some help with the following problem .. I am trying to validate a bunch of inputs and found the package Data.Validation. I am also using Data.Time for date and time. I have a function like this .. validateOpenDate :: ZonedTime -> Validation [String] ZonedTime It's supposed to validate a date for which I need to fetch the current date and time. I can do that with getZonedTime :: IO ZonedTime. I want to check if the current time is less than the date time I pass to the function and return an appropriate Validation. The question is how do I lift the result from IO into the Validation ? Or is there any alternative strategy that I should consider for this validation ? I have a number of other validations which follow the same strategy but don't have the IO. My final goal is to be able to compose all these validations applicatively to prepare a final ADT in a smart constructor. Any help will be appreciated .. regards. -- Debasish Ghosh

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[ANN] rdf4h-4.0.0 released - working with RDF in Haskell
by Rob Stewart 03 Jan '20

03 Jan '20

Hi, rdf4h-4.0.0 has been released. This library [1,2] is for working with semantic web RDF data. It includes multiple graph representations, RDF parsers/serialisers, and an API for querying and modifying RDF graphs. Version 4.0.0 is significant because it is the first release of the rdf4h library to be 100% compliant [3] with the parser unit tests defined by the W3C RDF Test Suite Curation Community Group [4] for parsing NTriple, Turtle and XML RDF formats. [1] https://hackage.haskell.org/package/rdf4h-4.0.0 [2] https://github.com/robstewart57/rdf4h [3] https://travis-ci.org/robstewart57/rdf4h [4] https://www.w3.org/community/rdf-tests/ Special thanks to Slava Kravchenko, Pierre Le Marre and Renzo Carbonara whose efforts contributed to this milestone. -- Rob Stewart

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WST 2020 Call for Papers
by Samir Genaim 02 Jan '20

02 Jan '20

========================================================================== WST 2020 - Call for Papers 17th International Workshop on Termination http://costa.fdi.ucm.es/wst2020 July 4-5, 2020, Paris, France co-located with IJCAR and FSCD 2020. ========================================================================== The Workshop on Termination (WST) traditionally brings together, in an informal setting, researchers interested in all aspects of termination, whether this interest be practical or theoretical, primary or derived. The workshop also provides a ground for cross-fertilization of ideas from the different communities interested in termination (e.g., working on computational mechanisms, programming languages, software engineering, constraint solving, etc.). The friendly atmosphere enables fruitful exchanges leading to joint research and subsequent publications. The workshop is co-located with IJCAR and FSCD 2020. https://ijcar2020.org/ https://fscd2020.org/ IMPORTANT DATES: * submission deadline: April 12, 2020 * notification: May 10, 2020 * final version due: May 31, 2020 * workshop: July 4-5, 2020 TOPICS: The 17th International Workshop on Termination welcomes contributions on all aspects of termination. In particular, papers investigating applications of termination (for example in complexity analysis, program analysis and transformation, theorem proving, program correctness, modeling computational systems, etc.) are very welcome. Topics of interest include (but are not limited to): * abstraction methods in termination analysis * certification of termination and complexity proofs * challenging termination problems * comparison and classification of termination methods * complexity analysis in any domain * implementation of termination methods * non-termination analysis and loop detection * normalization and infinitary normalization * operational termination of logic-based systems * ordinal notation and subrecursive hierarchies * SAT, SMT, and constraint solving for (non-)termination analysis * scalability and modularity of termination methods * termination analysis in any domain (lambda calculus, declarative programming, rewriting, transition systems, etc.) * well-founded relations and well-quasi-orders COMPETITION: Since 2003, the catalytic effect of WST to stimulate new research on termination has been enhanced by the celebration of the Termination Competition and its continuously developing problem databases containing thousands of programs as challenges for termination analysis in different categories, see http://termination-portal.org/wiki/Termination_Competition In 2020, the Termination Competition will run shortly before WST and the main venues (IJCAR-FSCD), and the results will be presented at IJCAR or FSCD. PROGRAM COMMITTEE: Martin Avanzini - INRIA Sophia, Antipolis Florian Frohn - Max-Planck-Institut für Informatik, Saarbrücken Carsten Fuhs - Birkbeck, U. of London Samir Genaim (chair) - U. Complutense de Madrid Jürgen Giesl - RWTH Aachen Matthias Heizmann - U. of Freiburg Cynthia Kop - Radboud U. Nijmegen Salvador Lucas - U. Politècnica de València Étienne Payet - U. de La Réunion Albert Rubio - U. Complutense de Madrid René Thiemann - U. of Innsbruck Johannes Waldmann - HTWK Leipzig INVITED SPEAKERS: tba SUBMISSION: Submissions are short papers/extended abstracts which should not exceed 5 pages. There will be no formal reviewing. In particular, we welcome short versions of recently published articles and papers submitted elsewhere. The program committee checks relevance and provides additional feedback for each submission. The accepted papers will be made available electronically before the workshop. Papers should be submitted electronically via the submission page: https://easychair.org/conferences/?conf=wst2020 Please, use LaTeX and the LIPIcs style file http://drops.dagstuhl.de/styles/lipics/lipics-authors.tgz to prepare your submission.

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SBLP 2020 - first call for papers
by Simon Thompson 31 Dec '19

31 Dec '19

Call for Papers - XXIV Brazilian Symposium on Programming Languages (SBLP 2020) Natal, Brazil, September 21-25, 2020 Submission link: https://easychair.org/conferences/?conf=sblp2020 SBLP 2020 is the 24th edition of the Brazilian Symposium on Programming Languages. It is promoted by the Brazilian Computer Society (SBC) and constitutes a forum for researchers, students and professionals to present and discuss ideas and innovations in the design, definition, analysis, implementation and practical use of programming languages. SBLP's first edition was in 1996. Since 2010, it is part of CBSoft, the Brazilian Conference on Software: Theory and Practice. Submission Guidelines ________________________________________________________________________________ Papers can be written in Portuguese or English. Submissions in English are encouraged because the proceedings will be indexed in the ACM Digital Library. The acceptance of a paper implies that at least one of its authors will register for the symposium to present it. Papers must be original and not simultaneously submitted to another journal or conference. SBLP 2020 will use a lightweight double-blind review process. The manuscripts should be submitted for review anonymously (i.e., without listing the author’s names on the paper) and references to own work should be made in third person. Papers must be submitted electronically (in PDF format) via the Easychair System: http://www.easychair.org/conferences/?conf=sblp2020 The following paper categories are welcome (page limits include figures, references and appendices): Full papers: up to 8 pages long in ACM 2-column conference format, available at http://www.acm.org/publications/proceedings-template Short papers: up to 3 pages in the same format. Short papers can discuss new ideas which are at an early stage of development or can report partial results of on-going dissertations or theses. List of Topics (related but not limited to the following) ________________________________________________________________________________ • Programming paradigms and styles, scripting and domain-specific languages and support for real-time, service-oriented, multi-threaded, parallel, and distributed programming • Program generation and transformation • Formal semantics and theoretical foundations: denotational, operational, algebraic and categorical • Program analysis and verification, type systems, static analysis and abstract interpretation • Programming language design and implementation, programming language environments, compilation and interpretation techniques Publication ________________________________________________________________________________ SBLP proceedings will be published in ACM's digital library. As in previous editions, authors of selected regular papers will be invited to submit an extended version of their work to be considered for publication in a journal's special issue. Since 2009, selected papers of each SBLP edition are being published in a special issue of Science of Computer Programming, by Elsevier. Important dates ________________________________________________________________________________ Abstract submission: 31 May, 2020 Paper submission: 7 June, 2020 (strict) Author notification: 24 July, 2020 Camera ready deadline: 9 August 2020 Program Committee ________________________________________________________________________________ Alex Garcia Instituto Militar de Engenharia Alvaro Moreira Universidade Federal do Rio Grande do Sul Anamaria Moreira Universidade Federal do Rio de Janeiro André Murbach Maidl Pontifícia Universidade Católica do Paraná Bernhard Scholz The University of Sydney Beta Ziliani Universidad Nacional de Córdoba Christiano Braga Universidade Federal Fluminense Cristiano Vasconcellos Universidade do Estado de Santa Catarina Fernando Castor Universidade Federal de Pernambuco Fernando Pereira Universidade Federal de Minas Gerais Francisco Sant'Anna Unversidade Estadual do Rio de Janeiro Hans-Wolfgang Loidl Heriot-Watt University Henrique Rebêlo Universidade Federal de Pernambuco João Paulo Fernandes University of Coimbra Krishna Nandivada IIT Madras Laure Gonnord University of Lyon Leonardo Reis Universidade Federal de Juiz de Fora Lucilia Figueiredo Universidade Federal de Ouro Preto Marisa Bigonha Universidade Federal de Minas Gerais Martin Musicante Universidade Federal do Rio Grande do Norte Pavlos Petoumenos University of Manchester Renato Cerqueira IBM Research Roberto Ierusalimschy PUC-Rio Rodrigo Ribeiro Universidade Federal de Ouro Preto Sandro Rigo Universidade de Campinas Sérgio Medeiros Universidade Federal do Rio Grande do Norte (Chair) Simon Thompson University of Kent Tomofumi Yuki INRIA Contact ________________________________________________________________________________ All questions about submissions should be emailed to Sérgio Medeiros (sergiomedeiros(a)ect.ufrn.br) Simon Thompson | Professor of Logic and Computation School of Computing | University of Kent | Canterbury, CT2 7NF, UK s.j.thompson(a)kent.ac.uk | M +44 7986 085754 | W www.cs.kent.ac.uk/~sjt

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A Generic Ordering over Types
by Justin Paston-Cooper 29 Dec '19

29 Dec '19

Hello, I've defined a module which defines a Data.Type.Ordering over types which are instances of Generic: https://github.com/jpcooper/generic-type-ordering/blob/master/src/Data/Type…. I was considering submitting it to Hackage if anyone finds this useful. I am using it in conjunction with Data.Type.Set (type-level-sets), which requires an ordering over the used types. The ordering works by first comparing the package, then the module, then the type name. I take it that the ordering as defined is correct over all types which are an instance of Generic. I wanted to check first whether this is done anywhere else, or in a different, better way. Can anyone advise? Cheers, Justin

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Re: [Haskell-cafe] Which is easier to ship on windows, a gi-gtk or fltk-hs project?
by Ruben Astudillo 25 Dec '19

25 Dec '19

On 25-12-19 02:13, Patrick Chilton wrote: > Hi, maybe you could host it somewhere and give it a web interface? > Google Compute Engine has a pretty generous free tier and you can > install Nix on it, which would take care of the packaging issues. I would prefer to not. Conceptually that is a harder sell as there is not a good technical reason to depend on webstuff apart of inconvenience. Also TeX compilation should be done on a web service if it's on the web (I think). This is a side project, which for me it's a opportunity to learn something new. That is right now shipping programs to windows that use bindings and depend on other programs. -- -- Rubén -- pgp: 4EE9 28F7 932E F4AD

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Which is easier to ship on windows, a gi-gtk or fltk-hs project?
by Ruben Astudillo 25 Dec '19

25 Dec '19

Dear list Currently for work I am doing a technical document generator using HaTex. The user primarily uses windows so I would like to ship to it. He is not a technical user, so a GUI is a must. FLTK is lighter than gtk but it seems the community has less experience shipping haskell GUIs with it on windows than with gi-gtk. So which toolkit binding would you use for a windows project? Also how would you ship such a project, which depends on a toolkit and TeX-engine on windows? I am used to a nix world-view. -- -- Rubén -- pgp: 4EE9 28F7 932E F4AD

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[ANN] ascii-holidays
by amindfv＠gmail.com 24 Dec '19

24 Dec '19

For those of you celebrating Christmas this week, I've just uploaded an early version of the ascii-holidays package to Hackage. At the moment it's a reimplementation of two ASCII art Christmas tree animations, one originally written in Bash and the other in Perl. Over time I plan to add animations for other holidays as well. You can install it with cabal install, then run it like: ascii-holidays xmas-1 I hope this adds a bit of Haskelly Christmas cheer to a few homes, and happy holidays to all! Tom

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Records, type-changing update, type inference
by Roman 21 Dec '19

21 Dec '19

I wrote a post about the records problem, in particular about type-changing update and how to get it without sacrificing type inference: https://github.com/effectfully/sketches/tree/master/has-lens-done-right The ideas are rather raw, but look promising to me. Any comments would be appreciated.

1 0

PhD and Postdoc positions at IMDEA
by Niki Vazou 21 Dec '19

21 Dec '19

Dear all, IMDEA Software Institute has open PhD and Postdoc positions. The selected candidate will work on liquid relational types and the application deadline is February 1st: https://software.imdea.org/open_positions.html Feel free to contact me for more information. Best, Niki

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Third call for draft papers for TFPIE 2020 (Trends in Functional Programming in Education)
by Jurriaan Hage 20 Dec '19

20 Dec '19

Hello, Please, find below the third call for draft papers for TFPIE 2020. Please forward these to anyone you think may be interested. Apologies for any duplicates you may receive. best regards, Jurriaan Hage Chair of TFPIE 2020 ======================================================================== TFPIE 2020 Call for papers http://www.staff.science.uu.nl/~hage0101/tfpie2020/index.html February 12th 2020, Krakow, Poland (co-located with TFP 2020 and Lambda Days) *NEW* Invited Speaker We are happy to announce the invited speaker for TFPIE 2020, Thorsten Altenkirch, who also speaks at Lambda Days. At TFPIE 2020 he shall be talking about his new book, Conceptual Programming With Python. *NEW* Registration This year TFPIE takes place outside of the Lambda Days/TFP organisation, although it takes place near their location. This means you do need to register separately for TFPIE; it also means you can register for TFPIE without registering for TFP/LambdaDays, and vice versa. Registration is mandatory for at least one author of every paper that is presented at the workshop. Only papers that have been presented at TFPIE may be submitted to the post-reviewing process. Registration is 25 euro per person. TFPIE 2020 welcomes submissions describing techniques used in the classroom, tools used in and/or developed for the classroom and any creative use of functional programming (FP) to aid education in or outside Computer Science. Topics of interest include, but are not limited to: FP and beginning CS students FP and Computational Thinking FP and Artificial Intelligence FP in Robotics FP and Music Advanced FP for undergraduates FP in graduate education Engaging students in research using FP FP in Programming Languages FP in the high school curriculum FP as a stepping stone to other CS topics FP and Philosophy The pedagogy of teaching FP FP and e-learning: MOOCs, automated assessment etc. Best Lectures - more details below In addition to papers, we are requesting best lecture presentations. What's your best lecture topic in an FP related course? Do you have a fun way to present FP concepts to novices or perhaps an especially interesting presentation of a difficult topic? In either case, please consider sharing it. Best lecture topics will be selected for presentation based on a short abstract describing the lecture and its interest to TFPIE attendees. The length of the presentation should be comparable to that of a paper. On top of the lecture itself, the presentation can also provide commentary on the lecture. Submissions Potential presenters are invited to submit an extended abstract (4-6 pages) or a draft paper (up to 20 pages) in EPTCS style. The authors of accepted presentations will have their preprints and their slides made available on the workshop's website. Papers and abstracts can be submitted via easychair at the following link: https://easychair.org/conferences/?conf=tfpie2020 . After the workshop, presenters will be invited to submit (a revised version of) their article for review. The PC will select the best articles that will be published in the Electronic Proceedings in Theoretical Computer Science (EPTCS). Articles rejected for presentation and extended abstracts will not be formally reviewed by the PC. Dates Submission deadline: January 14th 2020, Anywhere on Earth. Notification: January 17th 2020 TFPIE Registration Deadline: January 20th 2020 Workshop: February 12th 2020 Submission for formal review: April 19th 2020, Anywhere on Earth. Notification of full article: June 6th 2020 Camera ready: July 1st 2020 Program Committee Olaf Chitil - University of Kent Youyou Cong - Tokyo Institute of Technology Marko van Eekelen - Open University of the Netherlands and Radboud University Nijmegen Jurriaan Hage (Chair) - Utrecht University Marco T. Morazan - Seton Hall University, USA Sharon Tuttle - Humboldt State University, USA Janis Voigtlaender - University of Duisburg-Essen Viktoria Zsok - Eotvos Lorand University Note: information on TFP is available at http://www.cse.chalmers.se/~rjmh/tfp/

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[ANN] Venzone, an ASCII adventure/platformer
by Francesco Ariis 20 Dec '19

20 Dec '19

Hello -cafe, I am pleased to announce the release of `venzone`, an ASCII platform/adventure game. See it in action here: http://www.ariis.it/static/articles/venzone/venzone-cast.gif Get it (binaries or source) in the game page [1] or check Discourse [2] for a more details on the release. Happy festivities everyone! -F [1] http://www.ariis.it/static/articles/venzone/page.html [2] https://discourse.haskell.org/t/venzone-an-ascii-adventure-platformer-writt…

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Haskell 2010 report nit?
by Viktor Dukhovni 18 Dec '19

18 Dec '19

Not sure where to post about this, and it has likely been noted elsewhere already, but reading through the report I see in Section 3.17.2 > • Consider the following declarations: > > newtype N = N Bool > data D = D !Bool > > These examples illustrate the difference in pattern matching between types defined by data and newtype: > > (\ (N True) -> True) ⊥ ⇒ ⊥ > (\ (D True) -> True) ⊥ ⇒ ⊥ > (\ ~(D True) -> True) ⊥ ⇒ True > > Additional examples may be found in Section 4.2.3. But unlike the examples in 4.2.3, which do show differences between "newtype" and "data", the above does not seem to show any actual difference. For that the pattern after the constructor would I believe have to be irrefutable, which "True" is not. Thus, e.g. the below (which duplicates 4.2.3) would do the job: (\ (N _) -> True) ⊥ ⇒ True (\ (D _) -> True) ⊥ ⇒ ⊥ Perhaps I misunderstood something, but if not, and this has not been noted before, it may be worth fixing in the next revision. -- Viktor.

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Practical Aspects of Declarative Languages (PADL 2020) Call for Participation
by Ekaterina Komendantskaya 18 Dec '19

18 Dec '19

PADL 2020 Final Call for Participation: Please see many exciting talks and events at PADL 2020: The 22nd Symposium on Practical Aspects of Declarative Languages https://popl20.sigplan.org/home/PADL-2020 (Early registration by 12/18) Invited Talks Nikolaj Bjørner, Microsoft Research Logical Engines for Cloud Configurations Adnan Darwiche, UCLA Symbolic Reasoning About Machine Learning Systems Invited Experience and Direction Session Invited Talks Molham Aref, Relational AI Relational Artificial Intelligence Mayur Naik, University of Pennsylvania Learning Interpretable Rules from Structured Data Grant Passmore, Imandra Inc. and Cambridge University An Introduction to the Imandra Automated Reasoning System Philip Wadler, University of Edinburgh We Are All Poor Schmucks: On the Value of Gradual Types [image: Nikolaj Bjørner][image: Adnan Darwiche][image: Molham Aref][image: Grant Passmore][image: Mayur Naik][image: Phil Wadler] Complete Program https://popl20.sigplan.org/home/PADL-2020#program This includes also presentations of 10 full papers and 4 short papers; four discussion panels: (1) Programming with Logic for the Masses, (2) Memory and Real-Time Programming in Practice, (3) Reasoning for Machine Learning at Large, and (4) Experience and Direction; and a competitive programming experience session. Registration https://regmaster4.com/2020conf/POPL20/register.php Early rate closes on December 18th

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[ANNOUNCE] lzlib - lzma compression/decompression for Haskell
by Vanessa McHale 17 Dec '19

17 Dec '19

Hi all, I have written http://hackage.haskell.org/package/lzlib, a high-level interface to the lzlib library. Cheers, Vanessa McHale

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10 PhD studentships in Nottingham
by Graham Hutton 17 Dec '19

17 Dec '19

Dear all, The School of Computer Science at the University of Nottingham is seeking applications for 10 fully-funded international PhD studentships: https://tinyurl.com/10-phds-2020 Applicants in the area of the Functional Programming Laboratory (https://tinyurl.com/fp-notts) are strongly encouraged! If you are interested in applying, please contact a potential supervisor as soon as possible (the application deadline is 17th January): Thorsten Altenkirch - constructive logic, proof assistants, homotopy type theory, category theory, lambda calculus. Venanzio Capretta - type theory, mathemZZatical logic, corecursive structures, proof assistants, category theory, epistemic logic. Graham Hutton - not taking on any new students this year, but you may find these notes useful: https://tinyurl.com/scbkxkr Henrik Nilsson - functional reactive programming, domain- specific languages, generalised notions of computation. These positions are only open to international applicants. An advert for UK/EU applicants will be posted in January 2020. Best wishes, Graham +-----------------------------------------------------------+ 10 Fully-Funded International PhD Studentships School of Computer Science University of Nottingham, UK https://tinyurl.com/10-phds-2020 Applications are invited for 10 fully-funded international PhD studentships in the School of Computer Science at the University of Nottingham, starting on 1st October 2020. The topics for the studentships are open, but should relate to the interests of one of the School’s research groups: Agents Lab; Computational Optimisation and Learning Lab; Computer Vision Lab; Functional Programming; Intelligent Modelling and Analysis; Mixed Reality Lab; Data Driven Algorithms, Systems and Design and Uncertainty in Data and Decision Making The studentships are for three and a half years and include a stipend of £15,009 per year and tuition fees. Applicants are normally expected to have a first-class Masters or Bachelors degree in Computer Science or a related discipline, and must obtain the support of a potential supervisor in the School prior to submitting their application. Initial contact with supervisors should be made at least two weeks prior to the closing date for applications. Successful applicants are expected to apply for an International VC Scholarship. Informal enquiries may be addressed to Kathleen.Fennemore(a)nottingham.ac.uk. To apply, please submit the following items by email to: Marc.Williams(a)nottingham.ac.uk: (1) a copy of your CV, including your actual or expected degree class(es), and results of all University examinations; (2) an example of your technical writing, such as a project report or dissertation; (3) contact details for two academic referees. (4) a research proposal – max 2 x sides A4 You may also include a covering letter but this is optional. Closing date for applications: Friday 17 January 2020. +-----------------------------------------------------------+ This message and any attachment are intended solely for the addressee and may contain confidential information. If you have received this message in error, please contact the sender and delete the email and attachment. Any views or opinions expressed by the author of this email do not necessarily reflect the views of the University of Nottingham. Email communications with the University of Nottingham may be monitored where permitted by law.

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[ANN] Call for Participation: BOB 2020 (February 28, Berlin)
by Stefan Wehr 16 Dec '19

16 Dec '19

================================================================================ BOB 2020 Conference “What happens if we simply use what’s best?” February 28, 2020, Berlin http://bobkonf.de/2020/ Program: http://bobkonf.de/2020/en/program.html Registration: http://bobkonf.de/2020/en/registration.html ================================================================================ BOB is the conference for developers, architects and decision-makers to explore technologies beyond the mainstream in software development, and to find the best tools available to software developers today. Our goal is for all participants of BOB to return home with new insights that enable them to improve their own software development experiences. The program features 14 talks and 8 tutorials on current topics: http://bobkonf.de/2020/en/program.html The subject range of talks includes functional programming, formal methods, architecture documentation, functional-reactive programming, and language design. The tutorials feature introductions to Idris, Haskell, F#, TLA+, ReasonML, and probabilistic programming. Heather Miller will give the keynote talk. Registration is open online: http://bobkonf.de/2020/en/registration.html NOTE: The early-bird rates expire on February 19, 2020! BOB cooperates with racketfest and :clojureD on the day before/after BOB: https://racketfest.com/ https://clojured.de/

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Why many .tix files are generated in Haskell Program Coverage
by F L 16 Dec '19

16 Dec '19

I am using Haskell Program Coverage (HPC) to collect coverage information for Pandoc (https://github.com/jgm/pandoc) However, after adding the -fhpc option to GHC and running the program, two .tix files are generated. One is test-pandoc.tix in the main directory and the other is pandoc.tix under the "test" directory (test/pandoc.tix). These two files have different contents and I just cannot see the meaning of them from their names. Moreover, I tried to execute "hpc show xxx.tix" for them and test/pandoc.tix gives "hpc: hash in tix file for module Main does not match hash in ./.hpc/Main.mix". So, I wonder the specific generation rules of HPC tix files (possibly including the number and location) and how I can get the correct coverage information. Thanks very much!

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[ANNOUNCE] GHC 8.8.2-rc1 is now available
by Ben Gamari 13 Dec '19

13 Dec '19

Hello everyone, The GHC team is proud to announce the first release candidate of GHC 8.8.2. The source distribution, binary distributions, and documentation are available at https://downloads.haskell.org/~ghc/8.8.2-rc1 Release notes are also available [1]. This release fixes a handful of issues affecting 8.8.1: - A bug (#17088) in the compacting garbage collector resulting in segmentations faults under specific circumstances. Note that this may affect user programs even if they did not explicitly request the compacting GC (using the -c RTS flag) since GHC may fallback to compacting collection during times of high memory pressure. - A code generation bug (#17334) resulting in GHC panics has been fixed. - A bug in the `process` library causing builds using `hsc2hs` to fail non-deterministically on Windows has been fixed (Trac #17480) - A typechecker bug (#12088) resulting in programs being unexpectedly rejected has been fixed. - A bug in the implementation of compact normal forms resulting in segmentation faults in some uses (#17044) has been fixed. - A bug causing GHC to incorrectly complain about incompatible LLVM versions when using LLVM 7.0.1 has been fixed (#16990). As always, if anything looks amiss do let us know. Happy compiling! Cheers, - Ben [1] https://downloads.haskell.org/ghc/8.8.2-rc1/docs/html/users_guide/8.8.2-not…

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"Deep" Coding Support in Haskell
by Dušan Kolář 12 Dec '19

12 Dec '19

Dear Café, let me allow quite naive question, is there any library/tool/plugin supporting rapid application development in Haskell? I mean something that supports code completion, hints, help, code refactoring etc. Similar to Java support in e.g. Eclipse or IntelliJ IDEA. So far, I've found support for Vim, Eclipse. Nevertheless, my question goes farther - for implicit GUI editor/application development environment like Eclipse. Several years ago, I was able to run something in Eclipse, but not with good results. These days it seems dead (since 2015). Similarly, for IntelliJ IDEA - installed community version, downloaded Haskell plugin, tried to install additional plugins inside IntelliJ IDE, but after that no support for Haskell project (I'm on Arch linux, IDE from AUR, plugin install inside failed, downloaded it from https://plugins.jetbrains.com/plugin/8258-intellij-haskell/ versions[1] and it worked, at least installation, other plugins installed inside IDE worked partially - some of them were disabled by GUI after error). I'm sorry if I'm asking natural question. I've not found any additional how-tos to make it work... Best regards, Dusan -------- [1] https://plugins.jetbrains.com/plugin/8258-intellij-haskell/versions

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stack install ghcide fails
by Dušan Kolář 11 Dec '19

11 Dec '19

Hello Café, Using stack, I've tried stack install ghcide, it reported to put the following into my global extra-deps: - haskell- lsp-0.17.0.0@sha256:ddfcc2798f04bcb1ec20fafc02c03faa197322192578e879cef5852 aba43ebcb,5264 - haskell-lsp- types-0.17.0.0@sha256:9078237412d0596a7d09d432389c8fa21d6f3e21ed2ed761b3 093a21607d6c28,2941 - hie- bios-0.2.1@sha256:5f98a3516ce65e0a3ffd88bf6fb416b04cc084371d0fbf0e1762780d e1d652ce,3219 - rope-utf16- splay-0.3.1.0@sha256:15a53c57f8413d193054bb5f045929edae3b2669def4c6af6319 7b30dc1d5003,2029 Nevertheless, the build failed anyway: stack install ghcide ghcide> configure ghcide> Configuring ghcide-0.0.4... ghcide> build ghcide> Preprocessing library for ghcide-0.0.4.. ghcide> Building library for ghcide-0.0.4.. ghcide> [ 1 of 33] Compiling Development.IDE.Core.Debouncer ghcide> [ 2 of 33] Compiling Development.IDE.Core.PositionMapping ghcide> [ 3 of 33] Compiling Development.IDE.GHC.Compat ghcide> [ 4 of 33] Compiling Development.IDE.GHC.CPP ghcide> [ 5 of 33] Compiling Development.IDE.Spans.Type ghcide> [ 6 of 33] Compiling Development.IDE.Types.Location ghcide> [ 7 of 33] Compiling Development.IDE.Types.Diagnostics ghcide> [ 8 of 33] Compiling Development.IDE.LSP.Protocol ghcide> [ 9 of 33] Compiling Development.IDE.GHC.Util ghcide> [10 of 33] Compiling Development.IDE.GHC.Orphans ghcide> [11 of 33] Compiling Development.IDE.Import.DependencyInformation ghcide> [12 of 33] Compiling Development.IDE.GHC.Error ghcide> [13 of 33] Compiling Development.IDE.Import.FindImports ghcide> [14 of 33] Compiling Development.IDE.GHC.Warnings ghcide> [15 of 33] Compiling Development.IDE.Core.Preprocessor ghcide> [16 of 33] Compiling Development.IDE.Core.RuleTypes ghcide> [17 of 33] Compiling Development.IDE.Types.Logger ghcide> [18 of 33] Compiling Development.IDE.Types.Options ghcide> [19 of 33] Compiling Development.IDE.Core.Shake ghcide> ghcide> /tmp/stack204611/ghcide-0.0.4/src/Development/IDE/Core/Shake.hs:106:5: error: ghcide> • No instance for (Control.Monad.Fail.MonadFail Rules) ghcide> arising from a do statement ghcide> with the failable pattern ‘Just x’ ghcide> • In a stmt of a 'do' block: ghcide> Just x <- getShakeExtraRules @ShakeExtras ghcide> In the expression: ghcide> do Just x <- getShakeExtraRules @ShakeExtras ghcide> return x ghcide> In an equation for ‘getShakeExtrasRules’: ghcide> getShakeExtrasRules ghcide> = do Just x <- getShakeExtraRules @ShakeExtras ghcide> return x ghcide> | ghcide> 106 | Just x <- getShakeExtraRules @ShakeExtras ghcide> | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ghcide> -- While building package ghcide-0.0.4 using: /home/kolar/.stack/setup-exe-cache/x86_64-linux-tinfo6/Cabal- simple_mPHDZzAJ_2.4.0.1_ghc-8.6.3 --builddir=.stack-work/dist/x86_64-linux-tinfo6/ Cabal-2.4.0.1 build --ghc-options " -fdiagnostics-color=always" Process exited with code: ExitFailure 1 Does that mean the ghcide is broken? Or am I doing something wrong? Best regards, Dusan

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Request for Nominations to the GHC Steering Committee
by Joachim Breitner 11 Dec '19

11 Dec '19

Dear Haskell community, the GHC Steering committee is seeking nominations for one new member. The committee scrutinizes, nitpicks, improves, weights and eventually accepts or rejects proposals that extend or change the language supported by GHC and other (public-facing) aspects of GHC. Our processes are described at https://github.com/ghc-proposals/ghc-proposals which is also the GitHub repository where proposals are proposed. We are looking for a member who has the ability * to understand such language extension proposals, * to find holes and missing corner cases in the specifications, * foresee the interaction with other language features and specifications, * comment constructively and improve the proposals, * judge the cost/benefit ratio and * finally come to a justifiable conclusion. We look for committee members who have some of these properties: * have substantial experience in writing Haskell applications or libraries, which they can use to inform judgements about the utility or otherwise of proposed features, * have made active contributions to the Haskell community, for some time, * have expertise in language design and implementation, in either Haskell or related languages, which they can share with us. The committee’s work requires a small, but non-trivial amount of time, especially when you are assigned a proposal for shepherding. We estimate the workload to be around 2 hours per week, and our process works best if members usually respond to technical emails within 1-2 weeks (within days is even better). Please keep that in mind if your email inbox is already overflowing. The GHC developers themselves are already well represented already. We seek Haskell _users_ more than GHC hackers. There is no shortage of people who are eager to get fancy new features into the language, both in the committee and the wider community. But each new feature imposes a cost, to implement, to learn, (particularly) through its unexpected interaction with other features. We need to strike a balance, one that encourages innovation (as GHC always has) while still making Haskell attractive for real-world production use and for teaching. We therefore explicitly invite “conservative” members of the community to join the committee. To make a nomination, please send an email to me (as the committee secretary) at mail(a)joachim-breitner.de until January 2nd. I will distribute the nominations among the committee, and we will keep the nominations and our deliberations private. We explicitly encourage self-nominations. You can nominate others, but please obtain their explicit consent to do so. (We don’t want to choose someone who turns out to be unable to serve.) On behalf of the committee, Joachim Breitner -- Joachim Breitner mail(a)joachim-breitner.de http://www.joachim-breitner.de/

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Call for Haskell.org Committee Nominations
by Jasper Van der Jeugt 09 Dec '19

09 Dec '19

Dear Haskellers, It is time to put out a call for new nominations (typically but not necessarily self-nominations) to the Haskell.org committee. We have three members of our committee due for retirement -- Jasper Van der Jeugt, Niki Vazou, and Mitsutoshi Aoe. To nominate yourself, please send an email to committee at haskell.org by the 7th of January, 2020. The retiring members are eligible to re-nominate themselves. Please feel free to include any information about yourself that you think will help us to make a decision. The Haskell.org committee serves as a board of directors for Haskell.org, a 501(c)3 nonprofit which oversees technical and financial resources related to Haskell community infrastructure. Being a member of the committee does not necessarily require a significant amount of time, but committee members should aim to be responsive during discussions when the committee is called upon to make a decision. Strong leadership, communication, and judgement are very important characteristics for committee members. The role is about setting policy, providing direction/guidance for Haskell.org infrastructure, planning for the long term, and being fiscally responsible with the Haskell.org funds (and donations). As overseers for policy regarding the open source side of Haskell, committee members must also be able to set aside personal or business related bias and make decisions with the good of the open source Haskell community in mind. We seek a broad representation from different segments of the Haskell world -- including but not limited to those focused on education, those focused on industrial applications, those with background in organizing users-groups, and those focused directly on our technical infrastructure. More details about the committee's roles and responsibilities are on https://wiki.haskell.org/Haskell.org_committee If you have any questions about the process, please feel free to e-mail us at committee at haskell.org, or contact one of us individually. Warm regards, Jasper Van der Jeugt

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ZuriHac 2020 (12-14 June) registration is now open
by Jasper Van der Jeugt 06 Dec '19

06 Dec '19

Hi Haskell friends! We are happy to announce that ZuriHac 2020 will take place from Friday the 12th to Sunday the 14th of June, hosted again at the HSR (https://www.hsr.ch/) on the shores of beautiful Lake Zurich. You can find all the information on: https://zurihac.com The Zurich Haskell Hackathon is a free, international, grassroots, and collaborative coding festival. Our goal is to nourish the Haskell community, learn exciting new things, and to have fun working on projects together. This year, we are already excited to announce talks by: - Alexis King - Rob Rix More speakers will be announced later. In addition to talks, we will offer beginner, intermediate, and advanced tracks, similar to last year. The details of this will also be communicated in the coming months. The event is open to any experience level, from beginners to gurus. If you are completely new to Haskell, rest assured that there will be tutorials for you to take, and a bunch of friendly advanced Haskellers to answer your questions and help you along. We will have space for 500 attendees, making this the largest Haskell gathering that we know of! Registration is free and open as of right now: https://zurihac.com/#registration We would also like to thank the Hochschule für Technik Rapperswil for their amazing support and for hosting us again this year. Without them, an event of this scale and quality would be extremely difficult to pull off. We can't wait to see you in June, The Zurich Friends of Haskell (https://zfoh.ch/)

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[RFC] Constraint based arrow notation (GHC proposal)
by Alexis King 06 Dec '19

06 Dec '19

Hello all, I have recently written a GHC proposal to change the typechecking rules for arrow notation (aka `proc`) to better support custom control operators. Specifically, it reverses a change made in GHC 7.8 due to technical limitations that requires control operators to have significantly uglier types. Although arrows have fallen out of favor with the Haskell community in recent years, presumably there are still at least a few users. If you use `proc` notation, and especially if you use its support for custom control operators (i.e. (| banana brackets |)), your feedback would be highly valued. To read or comment on the proposal, follow this link: https://github.com/ghc-proposals/ghc-proposals/pull/303 Thanks, Alexis

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ANN: hledger 1.16
by Simon Michael 04 Dec '19

04 Dec '19

I'm pleased to announce hledger 1.16.1 ! hledger 1.16 was released on schedule on 2019-12-01, but only to hackage and github, since I was travelling and behind a rain-disrupted microwave link. Today brings the release notes & docs updates on hledger.org, and a 1.16.1 point release with some packaging updates. Thanks to release contributors Dmitry Astapov, Mykola Orliuk, Brian Wignall, Alejandro García Montoro, Timofey ZAKREVSKIY, Amitai Burstein, and Michael Kainer. hledger is a robust, cross-platform, multicurrency, plain text accounting tool, with command-line, terminal and web UIs. It is one of the leading implementations of plain text accounting, and is a modern and largely compatible reimplementation of Ledger. Use it for tracking money, time, stocks, cryptocurrencies or any other commodity, Learn more at http://hledger.org and http://plaintextaccounting.org . WHAT'S NEW: GHC 8.8 support, much more powerful CSV conversion rules, percentage balance reports, misc improvements. https://hledger.org/release-notes#hledger-1-16 . GETTING STARTED: Many install methods are described at http://hledger.org/download . Some of these might take a few days to become up to date; look for the green badges. You can build the latest by doing: stack update; stack install --resolver=lts hledger-lib-1.16.1 hledger-1.16.1 hledger-ui-1.16.1 hledger-web-1.16.1 --silent or: cabal v2-update; cabal v2-install hledger-1.16.1 hledger-web-1.16.1 hledger-ui-1.16.1 To start recording transactions: "hledger add". To list more commands: "hledger". See http://hledger.org for docs and support, or join #hledger on Freenode (http://irc.hledger.org) or join via Matrix (http://riot.hledger.org) New and old users, contributors, sponsors, and all feedback are most welcome! Best, -Simon

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Open Position: Lecturer in Cybersecurity - University of Exeter
by Achim D. Brucker 03 Dec '19

03 Dec '19

Dear all, As part of the expansion of the Department of Computer Science [1] at the University of Exeter, we are recruiting for a Lecturer in Cybersecurity. The lecturer will be part of the newly formed Security and Trust of Advanced Systems Group [2]. This is a *unique* opportunity to join a new group and to influence its future research and teaching. We are looking for a candidate with an outstanding research record in any area of cybersecurity such as (but not limited to): language-based security, access control, usable security, software security, formal methods for security, security analytics, security protocols, human aspects of security, security economics, security by design, applied cryptography, security testing. We are particularly keen on research areas that either extend the current strength in software security and formal methods in security or that complement these existing focus area. Please apply by 12th of December 2019! See the full announcement and application details at https://jobs.exeter.ac.uk/hrpr_webrecruitment/wrd/run/ETREC107GF.open?VACAN… Feel free to contact me for informal inquires about the post. Best, Achim [1] https://www.exeter.ac.uk/computer-science/ [2] https://emps.exeter.ac.uk/computer-science/research/cyber-security/ -- Prof. Achim Brucker | Chair in Cybersecurity & Head of Group | University of Exeter https://www.brucker.ch | https://logicalhacking.com/blog @adbrucker | @logicalhacking

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ANN: reflex-libtelnet-0.1.0.0
by Jack Kelly 03 Dec '19

03 Dec '19

I have just pushed an initial release of reflex-libtelnet[1] to Hackage. reflex-libtelnet wraps libtelnet[2] in a Reflex interface, so that you can describe data flows through a telnet state tracker using Reflex Events. Even if you're not using Telnet in 2019, you might find it interesting as a study in binding Reflex to a callback-oriented library. A telnet echo server is provided as an example[3]. Bug reports[4] and questions/patches[5] are welcome on Sourcehut. Best, -- Jack [1]: https://hackage.haskell.org/package/reflex-libtelnet-0.1.0.0 [2]: https://hackage.haskell.org/package/libtelnet [3]: https://git.sr.ht/~jack/reflex-libtelnet/tree/master/reflex-libtelnet-examp… [4]: https://todo.sr.ht/~jack/reflex-libtelnet [5]: https://lists.sr.ht/~jack/reflex-libtelnet-discuss

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Re: [Haskell-cafe] Is UndecidableInstances unavoidable in heterogenous Show derivation?
by Anthony Clayden 01 Dec '19

01 Dec '19

> ... was mildly surprised by the need for -XUndecidableInstances > when deriving the 'Show' instance for the heterogenous N-ary product 'NP': Hi Viktor, yes 'Undecidable' sounds scary, but it isn't. There's been much debate: should we find a less scary name? Presumably your program compiles and runs OK with that switched on(?) Providing your program compiles, it is type-safe. The risk with -XUndecidableInstances is that you might throw the compiler into a loop, in which case you'll get a stack depth check, with an unhelpful error message. See the Users Guide on UndecidableInstances, also this is a faq on StackOverflow. > deriving instance All (Compose Show f) xs => Show (NP f xs) Yes the constraint on that instance violates the Paterson Conditions (see Users Guide), the constraint is no smaller than the instance head. The P Conditions aim to make each step of instance resolution smaller, by strictly decreasing "constructors and variables (taken together ...". But that constraint has a count of 4, same as the head. > I guess I should also ask whether there's a way to define something equivalent > to 'Compose' without 'UndecidableSuperClasses', and perhaps the two are not unrelated. Not exactly related, but again superclass instance resolution wants to make the problem smaller at each step. The definition for class Compose has a constraint no smaller than the class head (3 variables). > [ Perhaps I should be more blasé about enabling these extensions, but I prefer > to leave sanity checks enabled when possible. ] Yes that's a sensible policy. The trouble with -XUndecidableInstances is that it's a module-wide setting, so lifts the check for all instances of all classes. There are/were several proposals to make this a per-instance or per-class pragma. But they got no support in the proposals process. AntC

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Is UndecidableInstances unavoidable in heterogenous Show derivation?
by Viktor Dukhovni 30 Nov '19

30 Nov '19

I was reading: Summer School on Generic and Effectful Programming Applying Type-Level and Generic Programming in Haskell Andres Löh, Well-Typed LLP https://www.cs.ox.ac.uk/projects/utgp/school/andres.pdf and trying out the various code fragments, and was mildly surprised by the need for -XUndecidableInstances when deriving the 'Show' instance for the heterogenous N-ary product 'NP': deriving instance All (Compose Show f) xs => Show (NP f xs) Without "UndecidableInstances" I get: • Variable ‘k’ occurs more often in the constraint ‘All (Compose Show f) xs’ than in the instance head ‘Show (NP f xs)’ (Use UndecidableInstances to permit this) • In the stand-alone deriving instance for ‘All (Compose Show f) xs => Show (NP f xs)’ This is not related to automatic deriving, as a hand-crafted instance triggers the same error: instance All (Compose Show f) xs => Show (NP f xs) where show Nil = "Nil" show (x :* xs) = show x ++ " :* " ++ show xs Is there some other way of putting together the building blocks that avoids the need for 'UndecidableInstances', or is that somehow intrinsic to the type of NP construction? I guess I should also ask whether there's a way to define something equivalent to 'Compose' without 'UndecidableSuperClasses', and perhaps the two are not unrelated. [ Perhaps I should be more blasé about enabling these extensions, but I prefer to leave sanity checks enabled when possible. ] -- Viktor. {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE DataKinds #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE KindSignatures #-} {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE RankNTypes #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE StandaloneDeriving #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeOperators #-} {-# LANGUAGE UndecidableInstances #-} {-# LANGUAGE UndecidableSuperClasses #-} import GHC.Exts (Constraint) -- | Map a constraint over a list of types. type family All (c :: k -> Constraint) (xs :: [k]) :: Constraint where All _ '[] = () All c (x ': xs) = (c x, All c xs) -- | With @g@ a type constructor and @f@ a constraint, define @Compose f g@ as -- a contraint on @x@ to mean that @g x@ satisfies @f@. -- -- Requires: -- -- 'ConstraintKinds' -- 'FlexibleInstances' -- 'MultiParamTypeClasses' -- 'TypeOperators' -- 'UndecidableSuperClasses' -- class (f (g x)) => (Compose f g) x instance (f (g x)) => (Compose f g) x -- | Type-level 'const'. newtype K a b = K { unK :: a } deriving instance Show a => Show (K a b) -- | N-ary product over an index list of types @xs@ via an interpretation -- function @f@, constructed as a list of elements @f x@. -- data NP (f :: k -> *) (xs :: [k]) where Nil :: NP f '[] (:*) :: f x -> NP f xs -> NP f (x ': xs) infixr 5 :* -- | If we can 'show' each @f x@, then we can 'show' @NP f xs@. -- -- Requires: 'UndecidableInstances' -- deriving instance All (Compose Show f) xs => Show (NP f xs)

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ANN brittany-0.12.0.0
by Evan Borden 28 Nov '19

28 Nov '19

Hello, I am happy to announce the release of brittany version 0.12.0.0. This version includes a number of fantastic improvements from many excellent contributors. Additionally brittany will soon be added back to stackage. In the meantime it can be built with the stack.yaml in its source or with cabal v2-build. https://hackage.haskell.org/package/brittany-0.12.0.0 Contributors ============ * Benjamin Kovach @5outh * Doug Beardsley @mightybyte * Evan Borden @eborden * Lennart Spitzner @lspitzner * Matt Noonan @moatt-noonan * Phil Hazelden @ChickenProp * Rupert Horlick @ruhatch * Sergey Vinokurov @sergv New Collaborators ================= You may be wondering why I am sending this message instead of Lennart. Taylor Fausak and I are taking on some of the maintenance for brittany. We will hopefully lift some of the burden from Lennart so he can remain the guiding light and driving force behind the project. Changes ========== This release includes many bug fixes, additional support for a number of syntactic constructs and a few layouting modifications. For full details check the change log on github: https://github.com/lspitzner/brittany/blob/master/ChangeLog.md Again thank you to brittany's fantastic contributors for helping making this release happen. -- Evan

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[Announcement] Copilot 3.1, hard realtime C generator and runtime verification framework
by Ivan Perez 27 Nov '19

27 Nov '19

Dear all, We are very pleased to announce the release of Copilot 3.1, a stream-based DSL for writing and monitoring embedded C programs, with an emphasis on correctness and hard realtime requirements. Copilot is typically used as a high-level runtime verification framework, and supports temporal logic (LTL, PTLTL and MTL), clocks and voting algorithms. Among others, Copilot has been used at the Safety Critical Avionics Systems Branch of NASA Langley Research Center for monitoring test flights of drones. This new release contains a number of bug fixes and simplifications: * The installation instructions have been updated to work with new versions of cabal and GHC. * Random stream generators were not being used and have been removed. * External functions are no longer supported by the language (to prevent side-effects in streams). * Minor bug related to labels, nested locals, and pretty printing Copilot core, have been fixed. * Code internals have been simplified for a more future proof codebase. Copilot 3.1 is available on hackage [1]. For more information, including documentation, examples and links to the source code, please visit the webpage [2]. Current emphasis is on providing better documentation, facilitating the use with other systems, and generally improving the codebase. Users are encouraged to participate by opening issues and asking questions via our github repo [3]. Kind regards, The Copilot developers: - Frank Dedden (maintainer) - Alwyn Goodloe (maintainer) - Ivan Perez (maintainer) [1] http://hackage.haskell.org/package/copilot [2] https://copilot-language.github.io [3] https://github.com/Copilot-Language/copilot

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A Specification for GADTs in Haskell?
by Xuanrui Qi 26 Nov '19

26 Nov '19

Hello all, I recently came a cross a comment by Richard Eisenberg that there's actually no specification for GADTs and creating one would be a major research project (in a GHC proposal somewhere, I recall, but I don't remember exactly where). I was wondering what exactly does Richard's comment mean. What constitutes a specification for GADTs in Haskell? I suppose typing rules and semantics are necessary; what are the major roadblocks hindering the creation of a formal specification for GADTs in Haskell? Thanks! Xuanrui -- Xuanrui Qi Graduate School of Mathematics, Nagoya University https://www.xuanruiqi.com

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[TFP'20] draft paper deadline open (January 10 2020) Trends in Functional Programming 2020, 13-14 February, Krakow, Poland
by Peter Achten 26 Nov '19

26 Nov '19

------------------------------------------------------------------------- Third call for papers 21st Symposium on Trends in Functional Programming tfp2020.org ------------------------------------------------------------------------- Did you miss the deadline to submit a paper to Trends in Functional Programming http://cse.chalmers.se/~rjmh/tfp/? No worries -- it's not too late! Submission is open until January 10th 2020, for a presentation slot at the event and post-symposium reviewing. 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. * TFP is moving to new winter dates, to provide an FP forum in between the annual ICFP events. * TFP offers a supportive reviewing process designed to help less experienced authors succeed, with two rounds of review, both before and after the symposium itself. Authors have an opportunity to address reviewers' concerns before final decisions on publication in the proceedings. * TFP offers two "best paper" awards, the John McCarthy award for best paper, and the David Turner award for best student paper. * This year we are particularly excited to co-locate with Lambda Days in beautiful Krakow. Lambda Days is a vibrant developer conference with hundreds of attendees and a lively programme of talks on functional programming in practice. TFP will be held in the same venue, and participants will be able to session-hop between the two events. Important Dates --------------- Submission deadline for pre-symposium review: 15th November, 2019 -- passed -- Submission deadline for draft papers: 10th January, 2020 Symposium dates: 13-14th February, 2020 Visit tfp2020.org for more information.

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Munich Haskell Meeting, 2019-11-27 @ 19:30
by Leah Neukirchen 25 Nov '19

25 Nov '19

Dear all, This week, our monthly Munich Haskell Meeting will take place again on Wednesday, November 27 at Cafe Puck(!) 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-nov-2019/ Everybody is welcome! cu, -- Leah Neukirchen <leah(a)vuxu.org> https://leahneukirchen.org/

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