- Haskell-Cafe - Haskell.org

A Specification for GADTs in Haskell?
by Xuanrui Qi 27 Nov '19

27 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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Planet Haskell
by Joachim Breitner 22 Nov '19

22 Nov '19

Hi, I am reading planet haskell through a feed reader that pulls https://planet.haskell.org/atom.xml and I get new posts. But it seems that that https://planet.haskell.org/ is stuck in January 2019. Or, upon closer inspection, new posts _are_ on planet.haskell.org, but they are not on top. I guess in the times of reddit and slack, few people are following the planet, but maybe still some people do? Cheers, Joachim -- Joachim Breitner mail(a)joachim-breitner.de http://www.joachim-breitner.de/

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Re: [Haskell-cafe] Transforming from on State-transformer to another
by Olaf Klinke 22 Nov '19

22 Nov '19

> Am 21.11.2019 um 22:56 schrieb Jacques Carette <carette(a)mcmaster.ca>: > > On 2019-Nov.-21 15:57 , Olaf Klinke wrote: >>> Is there a way to have a function of type (a -> b) -> State a c -> State >>> b c ? >> djinn says no. The reason ist that the a occurs both positively and negatively in State a c, that is, on the left and the right hand side of the -> in State. >> >>> In the particular case of interest, I am interested in is actually b -> >>> State a c -> (State (a,b) c), which is of course a special case of the >>> above. >> djinn says yes. The suggested term is >> >> \f -> \(a,b) -> let (a,c) = f a in ((a,b),c) > > > Thanks. I tried to play with the online djinn to ask about exactly this - and failed! How should I be asking? I downloaded the djinn package and built it with cabal. > > Also, something is weird about that term, since it doesn't match "b -> State a c -> (State (a,b) c)" at all. It does match "(b -> State a c) -> (State (a,b) c)" which is a completely different type (and not interesting...) Sorry, I tried to simplify djinn's output and failed. The term should be \f -> \(a,b) -> let (c,a') = f a in (c,(a',b)) :: (a -> (c, a3)) -> (a, b) -> (c, (a3, b)) where you can let a3 = a to get State a c -> State (a,b) c That is, it maps a transformer of state a into a transformer of state (a,b) that leaves the b component unchanged. Olaf

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Re: [Haskell-cafe] filepath
by Johannes Waldmann 21 Nov '19

21 Nov '19

Dear Cafe, is there a library that provides an "abstract representation of file and directory pathnames"? This had been discussed before - e.g., https://mail.haskell.org/pipermail/libraries/2007-December/008769.html (it's one message of a longer thread) That message references an obsolete (?) Java library, they now have https://docs.oracle.com/en/java/javase/13/docs/api/java.base/java/nio/file/… It seems that https://hackage.haskell.org/package/filepattern-0.1.1/docs/System-FilePatte… does cover typical usage. It is based on FilePath = String, and its implementation has some "++"-ing. That indicates that an abstraction layer is missing - or, that such a layer is indeed not required? - J.W.

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Transforming from on State-transformer to another
by Jacques Carette 21 Nov '19

21 Nov '19

Is there a way to have a function of type (a -> b) -> State a c -> State b c ? In the particular case of interest, I am interested in is actually b -> State a c -> (State (a,b) c), which is of course a special case of the above. This matches 'first' on Data.Bifunctor, but State is not a Bifunctor. Nor a Profunctor, AFAIK. Use case: a Stateful computation where a local sub-computation needs more (local) state that will be, in-time, de-allocated. I guess the usual solution is probably to use 2 stacked State, but I'm curious if there's another way. Jacques

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Summer internship with a Haskell-related project (DAAD Rise Germany)
by Niels Bunkenburg 20 Nov '19

20 Nov '19

My department (PL and compiler construction) at the University of Kiel, Germany, offers a summer internship in 2020 sponsored by DAAD Rise Germany [1]. The topic of the project is verification of effectful Haskell programs in Coq. For a brief overview of the internship and the topic, please have a look at the project page [2]. We'd be very happy to host a motivated student who likes working with our haskell-to-coq compiler. Depending on personal interests, the focus of the internship can be the compiler itself or its output and the Coq framework for reasoning about the generated code. Previous knowledge of Coq is not required! If you have any questions beforehand, feel free to reply directly or email us at the addresses listed on the project page. The program funding is based on the number of applications, so please spread the news to your colleagues, students or classmates! Best regards, Niels [1] https://www.daad.de/rise/en/rise-germany/find-an-internship/ [2] https://bunkenburg.net/projects/2019-11-01-daad-rise.html

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[Job] PureScript and Haskell, Tokyo or remote
by Ramin Honary 19 Nov '19

19 Nov '19

*[Job] PureScript and Haskell, Tokyo or remote* Cross Compass <https://www.cross-compass.com/en> in Tokyo is hiring programmers to build a data science IDE on top of JupyterLab <https://jupyterlab.readthedocs.io/en/stable/> , with a Haskell backend and a PureScript/React frontend. The JupyterLab stack is new and we're building new technology. This is a small team and we want to add generalists to work full-time. We are looking for candidates with these areas of interest and experience. - Browser-based GUI applications, especially React and PureScript - Functional programming, especially Haskell - Devops, especially Docker and Nix - Python and the Jupyter ecosystem - Machine learning and data science *About Cross Compass* Cross Compass is a Japanese AI consultancy founded in 2015 in Tokyo <https://goo.gl/maps/79wQbmfbGYgLZgYd9>. It is a leader in AI for manufacturing and industrial robotics with 80~100 projects per year. There are 66 employees (43 engineers), and the office conversation is about half Japanese, half English, with 15 nationalities represented among our staff. The number of self-described Haskellers at Cross Compass currently stands at 4 in Tokyo and 2 remote. github.com/xc-jp - Ramin Honary https://github.com/RaminHAL9001 <https://github.com/RaminHAL9001> - Dennis Gosnell https://github.com/cdepillabout <https://github.com/cdepillabout> - Jonas Carpay https://github.com/jonascarpay <https://github.com/jonascarpay> - Viktor Kronvall https://github.com/considerate <https://github.com/considerate> - Robert Prije https://github.com/rprije <https://github.com/rprije> - James Brock https://github.com/jamesdbrock <https://github.com/jamesdbrock> *Application* We would like to see examples of how you work, so if you have any work published on the internet, please tell us where to look for it, and explain what is interesting about it. Please apply by email to recruit(a)cross-compass.com <recruit@cross-compass.com?subject=Programmer+Data+Science+IDE+RECR-371> and include the following: - Highlights of work history - Highlights of education history - Open source software links - Papers, articles, social media, anything which reflects well on you - Request to work in Tokyo office or remote If you want to talk about this position or anything else, please email me at james.brock(a)cross-compass.com. Salary will be based on experience and shall be determined by market pay rates for programming positions in Tokyo. The application process will include a one month trial period. Remote work is possible but we prefer candidates who live, or want to live, in Tokyo, for a larger interaction with our teams. We provide visa sponsorship.

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Reverse of -ddump-splices
by Markus Läll 19 Nov '19

19 Nov '19

Hi list! Is it so that there is no reverse for -ddump-splices? In ghci I can set it with :set -ddump-splices and it turns on, but adding "no" to the flag appears not to work. Found this https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/flags.html so probably there is no reverse? -- Markus Läll

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