- Haskell-Cafe - Haskell.org

Haskell eXchange 2018 CFP (London, Thursday, 11th - Friday, 12th October)
by Oliver Charles 15 May '18

15 May '18

Hi all, The Haskell eXchange is an annual conference created for and by the Skills Matter community. An opportunity for Haskellers to meet, learn and share skills, discover emerging technologies and help evolve the Haskell ecosystem. Everyone is welcome to join, whether you are an expert or a beginner, whether you are a commercial user, an academic or a hobbyist, we'd love it if you join us this year at the Haskell eXchange! For 2018, we are planning to have three types of sessions: 1. Regular talks (35 minutes) 2. Hands-on workshops (approximately 90 minutes) 3. Lightning talks (5-10 minutes to be determined in the formal confirmation) The Haskell eXchange is a broad conference, and we'll consider anything with a clear Haskell connection. For example, talks about Haskell libraries and applications, experience reports of using Haskell for work, and tutorials on programming techniques are all fantastic proposals - but please feel free to submit anything that you think is interesting. The committee are happy to work with you if you're unsure if your talk is a good fit, and can be reached at haskellx(a)skillsmatter.com Most importantly, we're looking for talks that inspire and educate. If your proposal doesn't fit into any of the above categories, it doesn't matter! To submit, please see the form in https://skillsmatter.com/conferences/10237-haskell-exchange-2018#get_involv… We look forward to your submissions!

1 0

Maintaining cpphs
by Markus Ongyerth 15 May '18

15 May '18

Hi Malcolm, Are you still interested in maintaining cpphs? I have posted an issue to your github tracker [1] (linked at [2]) and didn't get any response in a week. While that's not a terribly long time, the reason for this patch is trickling down to different distributions repositories (arch and debian-sid) which is making it harder for me to support users because of a dependency. If you are not planing to maintain cpphs in future, I'd like to take over the package on hackage. Cheers, ongy [1] https://github.com/malcolmwallace/cpphs/issues/16 [2] http://hackage.haskell.org/package/cpphs

1 0

PSA for Cabal 2.2 new-* users regarding .ghc.environment files
by Gershom B 15 May '18

15 May '18

There is an important change in the cabal new- commands for 2.2 that the release docs should have highlighted more significantly. Cabal new-* commands now produce a .ghc.environment file by default. These files [1] are picked up by ghc and ghci automatically (since 8.0.1), and allow them to operate directly with the same package environment used by the new-* commands. This lets you, for example, run `ghci` in a project where you are using `new-build` and get the proper dependencies in scope. Herbert has written an experimental tool to make it easier to create and manipulate these environments [2]. However: there is a drawback (on which some discussion at [3] and [4]. In particular, there is not good information provided by ghc about when these files are picked up and used. So if you are admixing new-* commands and other commands for the time being, jumping between the two, or admixing ghc and ghcjs, etc., then you may run into unexpected behavior! [5] The simplest solution for now is to delete the local .ghc.environment file in those cases (i.e. where you're mixing commands and get unexpected behavior). A particular gotcha is that these files are picked up not just in the current directory but also in any parent directory. Cheers, Gershom [1] documented at https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/packages.ht… [2] https://github.com/hvr/cabal-env [3] https://github.com/haskell/cabal/issues/4542 [4] https://ghc.haskell.org/trac/ghc/ticket/13753 [5] Error messages may be like ".cabal/store/ghc-8.0.2/package.db/package.cache: openBinaryFile: does not exist (No such file or directory)" or complaints about missing inplace dependencies.

8 9

Re: [Haskell-cafe] Problem with submitting papers for haskell 2018
by Nicolas Wu 14 May '18

14 May '18

Hello Winter, Thanks for getting in touch, I’m glad to hear that you’re preparing a submission to the Haskell Symposium this year. You haven’t missed any deadlines: we’re still reviewing the early track papers and so EasyChair is closed for regular submissions until notifications for those papers are released. This will happen on 18 May 2018. Best wishes, Nick Dr Nicolas Wu Department of Computer Science University of Bristol > On 14 May 2018, at 14:19, Brent Yorgey <byorgey(a)gmail.com> wrote: > > Hi Nick, > > Did you see this message that was sent to haskell-cafe a few hours ago? > > -Brent > > ---------- Forwarded message --------- > From: winter <drkoster(a)qq.com> > Date: Mon, May 14, 2018 at 4:15 AM > Subject: [Haskell-cafe] Problem with submitting papers for haskell 2018 > To: <haskell-cafe(a)haskell.org> > > > Dear all, > > Currently i and my friends @sighingnow are writing a paper on our > new I/O manager based on libuv. We planed to submit it to Haskell 2018, > and according to the official site's info, the deadline should be next > month: https://icfp18.sigplan.org/track/haskellsymp-2018-papers > > But here is my problem, i registered an account on easychair as Haskell > 2019 required and logged in, but when i click the submit link, a page > with following info are provided: > > > Paper submission for Haskell 2018 is closed.,,You seem to have no > previous roles at Haskell 2018, so > you cannot enter its pages. If you > have questions about the conference, please contact Haskell 2018 > chairs. > > What does this mean? Did i miss the submission window? Or do i have to > do some extra preparations? Please help! > > > Cheers~ > > Winter > > > > _______________________________________________ > Haskell-Cafe mailing list > To (un)subscribe, modify options or view archives go to: > http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe > Only members subscribed via the mailman list are allowed to post.

2 1

Current state of dependent types in Haskell
by Serguey Zefirov 14 May '18

14 May '18

Can anyone kindly point me at blog posts and/or articles on the subject? I would like to brush off my Haskell skills in that area with whatever new things that are hot. I once implemented type-level arithmetic in Haskell for sizing various hardware things but it is ages ago now. I would like to experiment with current state of affairs with type-level arithmetic and possibly experiment with adding structured values into the constraints.

2 2

Problem with submitting papers for haskell 2018
by winter 14 May '18

14 May '18

Dear all, Currently i and my friends @sighingnow are writing a paper on our new I/O manager based on libuv. We planed to submit it to Haskell 2018, and according to the official site's info, the deadline should be next month: https://icfp18.sigplan.org/track/haskellsymp-2018-papers But here is my problem, i registered an account on easychair as Haskell 2019 required and logged in, but when i click the submit link, a page with following info are provided: > Paper submission for Haskell 2018 is closed.,,You seem to have no previous roles at Haskell 2018, so > you cannot enter its pages. If you have questions about the conference, please contact Haskell 2018 > chairs. What does this mean? Did i miss the submission window? Or do i have to do some extra preparations? Please help! Cheers~ Winter

1 0

Call for Papers: Workshop in OCL and Textual Modeling (OCL 2018)
by Achim D. Brucker 11 May '18

11 May '18

(Apologies for duplicates) CALL FOR PAPERS 18th International Workshop on OCL and Textual Modeling Co-located with MODELS 2018: ACM/IEEE 21th International Conference on Model Driven Engineering Languages and System, October 14 (tbc), 2018, Copenhagen, Denmark http://oclworkshop.github.io Modeling started out with UML and its precursors as a graphical notation. Such visual representations enable direct intuitive capturing of reality, but they have weaknesses: for example, detailed visual representations bear the risk of becoming overcrowded faster than textual models and some of the visual features lack the level of precision required to create complete and unambiguous specifications. These weaknesses of graphical notations encouraged the development of text-based modeling languages that either integrate with or replace graphical notations for modeling. Typical examples of such languages are OCL, textual MOF, Epsilon, and Alloy. Textual modeling languages have their roots in formal language paradigms like logic, programming and databases. The goal of this workshop is to create a forum where researchers and practitioners interested in building models using OCL or other kinds of textual languages can directly interact, report advances, share results, identify tools for language development, and discuss appropriate standards. In particular, the workshop will encourage discussions for achieving synergy from different modeling language concepts and modeling language use. The close interaction will enable researchers and practitioners to identify common interests and options for potential cooperation. ## Topics of interest Topics of interest include (but are not limited to): - Mappings between textual modeling languages and other languages/formalisms - Mathematical models and/or formal semantics for textual modeling languages - Algorithms, evaluation strategies and optimizations in the context of textual modeling languages for: - validation, verification, and testing, - model transformation and code generation, - meta-modeling and DSLs, and - query and constraint specifications - Alternative graphical/textual notations for textual modeling languages - Evolution, transformation and simplification of textual modeling expressions - Libraries, templates and patterns for textual modeling languages - Tools that support textual modeling languages (e.g., verification of OCL formulae, runtime monitoring of invariants) - Model-driven security using textual modeling languages - Complexity results for textual modeling languages - Quality models and benchmarks for comparing and evaluating textual modeling tools and algorithms - Successful applications of textual modeling languages - Case studies on industrial applications of textual modeling languages - Experience reports: - usage of textual modeling languages and tools in complex domains, - usability of textual modeling languages and tools for end-users - Empirical studies about the benefits and drawbacks of textual modeling languages - Innovative textual modeling tools - Comparison, evaluation and integration of modeling languages - Correlation between modeling languages and modeling tasks We particularly encourage submissions describing applications and case studies of textual modeling as well as test suites and benchmark collections for evaluating textual modeling tools. ## Venue This workshop will be organized as a part of MODELS 2018 Conference in Copenhagen, Denmark. Similar to its predecessors, the workshop addresses both people from academia and industry. The aim is to provide a forum for addressing integration of OCL and other textual modeling languages, as well as tools for textual modeling, and for disseminating good practice and discussing the new requirements for textual modeling. ## Workshop Format The workshop will include short (about 15 min) presentations, parallel sessions of working groups, and sum-up discussions. ## Submissions Two types of papers will be considered: * Short contributions (between 5 and 7 pages) describing new ideas, innovative tools or position papers. * Full papers (between 10 and 14 pages). in LNCS format. Submissions should be uploaded to [EasyChair](https://easychair.org/conferences/?conf=ocl2018). The program committee will review the submissions (minimum 2 reviews per paper, usually 3 reviews) and select papers according to their relevance and interest for discussions that will take place at the workshop. Accepted papers will be published online, as part of the MODELS workshop proceedings, in [CEUR](http://www.ceur-ws.org). ## Important Dates - Submission of papers: July 17, 2018 - Notification: August 17, 2018 - Workshop date: October 14, 2018 (tbc) -- Dr. Achim D. Brucker | Software Assurance & Security | University of Sheffield https://www.brucker.ch | https://logicalhacking.com/blog @adbrucker | @logicalhacking

1 0

Taking over `data-default-*`
by Marco Zocca 11 May '18

11 May '18

Dear all, I've been increasingly relying on data-default-class, but sadly it doesn't look like it's currently maintained; there are some tickets on the github issue tracker that would need some attention. I have tried contacting the authro/current maintainer Lukas Mai (CC'd) by email but have not received an answer so far (I hope he's doing well, btw). This is my first public request for taking over the `data-default` family of packages: data-default-class data-default-instances-base data-default-instances-containers data-default-instances-dlist data-default-instances-old-locale data-default Kind regards, Marco Zocca (http://hackage.haskell.org/user/ocramz)

11 17

Re: [Haskell-cafe] How to expose if a constraint is satisfiable
by Anthony Clayden 09 May '18

09 May '18

Thanks David, Oliver, I'll leave it so Clinton whether that helps his use case. I see the write-ups for both the Constraint Unions package and ifCxt mentioned on the reddit thread talk about needing large amounts of boilerplate. That is, an instance for each class and type that effectively tells the class has an instance for that type. So that's the same as the AdvancedOverlap I linked to -- from Oleg + SPJ. IIUC, what Clinton's asking is: since there are already instances for `Show Int`, `Ord Float`, etc (declared in the Prelude), why can't ghc 'just know' that and expose it to type-level logic that can say: if there's `Show a` do this, otherwise do that? AntC > On *Tue May 8 22:29:20 UTC 2018*, David Feuer wrote: > Maybe look at https://www.reddit.com/r/haskell/comments/6k86je/constraint_unions_bringing… > (relating to the repository Oliver links to) and note also Edward Kmett's response. Eurrm. Could somebody explain that response using familiar language. I think the `:-` operator might be referring to Edward's & David's 'constraints' package on github, for which I've asked if there's human-facing documentation. Also asked if it'll be superseded by the 'Qualified Constraints' new development. >> On Tue, May 8, 2018 at 9:52 AM, Oliver Charles <ollie at ocharles.org.uk <http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe>> wrote: >>* I've only skimmed the thread, so sorry if this is a red herring, but could *>>* this be helpful?*

1 0

Scoped Type Variables discussion forum [was: open up the issues tracker on ghc-proposals]
by Anthony Clayden 09 May '18

09 May '18

This thread is a discussion about discussions, not the discussion itself ;-) I'm cc'ing to the cafe; but I'd prefer replies to come to glasgow-haskell-users. >> I can volunteer to at least scrape together all the objections to ScopedTypeVariables as currently. It's not yet a proposal, so not on github. Start a wiki page? A cafe thread? (It'll get lost.) A ghc-users thread? (It'll get ignored.) > ... don’t care what forums or list or whatever. As long as it’s collated and such > It could even be on the prime issue tracker for prime proposals. Just that it’s written down :) Thanks Carter, but I understand Haskell Prime to be to assess mature/stable proposals (preferably already delivered as extensions). This discussion is at first going to be more exploratory: * likes and dislikes about ScopedTypeVariables as currently. * confusions experienced by users (especially newbies) -- although absolute newbies wouldn't be using it(?), so intermediates? * feedback from those teaching Haskell. * wild ideas for possible alternative designs. * possible improvements to the current design. * I think we're all agreed that ScopedTypeVariables should have been in Haskell from the beginning; but it wasn't, so now we have to worry about backwards compatibility for programs that worked around the omission. Or do we? What code would break? How much pain would that cause? * anything else? > We have lots of forums, but your point is that certain sorts of discussions never get going with the right audience – you especially point to “confused beginners”. > ... It’s quite a challenge because beginners tend not to be vocal, and yet they are a crucial set of Haskell users. Every Haskell user started as a beginner. On this particular topic, there's plenty of confused people asking questions on StackOverflow. (Heads up: they're especially asking why they need explicit `forall` whereas in reguar Haskell that 'intermediates' see, the forall is implicit.) Can other people point me to questions/likes/dislikes on other forums? Reddit for example. If you've read this far, you now understand what we're trying to cover. It's going to be random/varied thoughts at first, then perhaps coalescing to an approach or two. At that point a formal proposal on github proper; and the random stuff might be interesting background but will essentially get archived/thrown away. I do agree with David's suggestion that github Issue tracker looks like a suitable solution. We can write formatted code and text. We can add links and references. What do others think? Joachim has opened up Issues tracker, as a try-out. If using it doesn't work out, that's fine and in keeping with my "thrown away" above. Also where else should I post links to this message to 'advertise' the thread? I don't reddit much, so if that's suitable, please someone post there. Thank you AntC

2 1