- Haskell-Cafe - Haskell.org

Fwd: State of BNFC-meta and friends
by Artem Pelenitsyn 14 Jan '20

14 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 13 Jan '20

13 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 13 Jan '20

13 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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