- Haskell-Cafe - Haskell.org

regex problem with ghc-8.6 and older
by Ben Franksen 29 May '23

29 May '23

Hi Everyone I was trying to fix a bug in a large program (darcs) and stumbled over a problem that I cooked down to the minimal test program below. The issue here is that with ghc-8.6 and earlier, properly handling an invalid regular expression (here: the empty string) does not work: somehow something calls "error". With ghc-8.8 and later it works as expected. In both cases the latest releases of the regex packages are used. {-# LANGUAGE GeneralizedNewtypeDeriving #-} import Prelude hiding (fail) import Control.Monad.Fail import Control.Exception import Text.Regex.Base import Text.Regex.TDFA newtype RegexFail a = RegexFail { runRegexFail :: Either String a } deriving (Functor, Applicative, Monad) instance MonadFail RegexFail where fail = RegexFail . Left test :: RegexFail Regex test = makeRegexM "" main = handle (\(ErrorCall _) -> putStrLn "error call") $ case runRegexFail test of Left _ -> putStrLn "clean error handling" Right x -> print (matchM x "" :: Maybe Bool) > runghc-8.6 test2.hs √ error call > runghc-8.8 test2.hs √ clean error handling (1) Is this a known problem with ghc < 8.8 / base < 4.13? (2) Is there a work-around for older ghc versions? Cheers Ben -- I would rather have questions that cannot be answered, than answers that cannot be questioned. -- Richard Feynman

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GHC handling of signals
by Ben Franksen 28 May '23

28 May '23

Consider the following program: import System.IO import System.IO.Error import System.Posix.Signals main = do installHandler sigPIPE Default Nothing c <- readFile "/usr/share/dict/words" putStrLn c `catchIOError` \e -> hPutStrLn stderr (show e) hPutStrLn stderr "I survived" Compile with ghc and run as ./test | true As expected, you see nothing further displayed, since according to `man 7 signal` the default for SIGPIPE is to terminate the program, which happens before the exception handler has a chance to run. Without the line where the signal handler gets installed the behavior is different: You'll see: <stdout>: commitBuffer: resource vanished (Broken pipe) I survived Apparently the GHC runtime does something like installHandler sigPIPE Ignore Nothing This is not a complaint, I find the behavior quite reasonable and much more predictable than the default (why should I not be able to catch EPIPE and continue?). The question is whether it is documented how the GHC runtime treats signals and if yes where? Cheers Ben -- I would rather have questions that cannot be answered, than answers that cannot be questioned. -- Richard Feynman

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Munich Haskell Meeting, 2023-05-29 @ 19:30
by Leah Neukirchen 28 May '23

28 May '23

Dear all, Next week, our monthly Munich Haskell Meeting will take place again on Monday, May 29 at 19h30. The weather should be good, so we'll meet at **Hirschgarten Biergarten**. For details see here: http://muenchen.haskell.bayern/dates.html If you plan to join, please add yourself to this nuudel so we can look out for you. It is OK to add yourself to the nuudel anonymously or pseudonymously. https://nuudel.digitalcourage.de/xduCn5pUNTlcl7dT Everybody is welcome! cu, -- Leah Neukirchen <leah(a)vuxu.org> https://leahneukirchen.org/

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Developer Surveys
by Dev Survey 26 May '23

26 May '23

Hello Developers, No login required, anonymous survey, and takes no more than 5-10 minutes. Developer Tools Survey Shortened URL : Developer Tools Survey (Anonymous) Thanks, have a great day

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Searching for dependent code
by Geraldus 26 May '23

26 May '23

Hello, dear Cafe! I have a mono repository and would like to do the following for CI: - take the files from the commit - Find all the code that depends on them explicitly or implicitly - make a list of executable files that need to be rebuilt This happens in CI and there is no cache of previous builds. Note that dependencies may not be direct, e.g: - there are packages A, B, C. - C depends only on B - B depends on A - C should be rebuilt if there were changes in A Can you please tell me if there is any ready-made solution for this?

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[Haskell] [ANNOUNCE] GHC 9.2.8 released
by Zubin Duggal 26 May '23

26 May '23

The GHC developers are happy to announce the availability of GHC 9.2.8. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org](https://downloads.haskell.org/ghc/9.2.8). This release is primarily a bugfix release addressing one issue found in 9.2.7: - Fix a bug with RTS linker failing with 'internal error: m32_allocator_init: Failed to map' on newer Linux kernels (#19421). We would like to thank Microsoft Azure, GitHub, IOG, the Zw3rk stake pool, Well-Typed, Tweag I/O, Serokell, Equinix, SimSpace, Haskell Foundation, and other anonymous contributors whose on-going financial and in-kind support has facilitated GHC maintenance and release management over the years. Finally, this release would not have been possible without the hundreds of open-source contributors whose work comprise this release. As always, do give this release a try and open a [ticket][] if you see anything amiss. Happy compiling, - Zubin [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new [release notes]: https://downloads.haskell.org/~ghc/9.2.8/docs/html/users_guide/9.2.8-notes.…

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JOB | Platform Lead (Singapore/London)
by James Tobin 26 May '23

26 May '23

Hello I'm working with an employer that is looking to hire someone in London or Singapore to take lead on the modernisation of their on-premises environment. Consequently, I had hoped that some members of this group may like to discuss. I can be reached using "JamesBTobin (at) Gmail (dot) Com". Kind regards, James

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Haskell Symposium'23 Calls For Papers
by Niki Vazou 26 May '23

26 May '23

Dear all, Reminder that the Haskell Symposium’23 Submission Deadline is one week away. We are looking forward for your papers. Best, Niki =============================================================================== ACM SIGPLAN CALL FOR SUBMISSIONS Haskell Symposium 2023 Seattle, WA, USA Fri 8 -- Sat 9 September, 2023 http://www.haskell.org/haskell-symposium/2023/ ================================================================================ The ACM SIGPLAN Haskell Symposium 2023 will be co-located with the 2023 International Conference on Functional Programming (ICFP). As with last year, Haskell'23 will use a single-track submission process. That is, we will only have the regular track and no early track. The Haskell Symposium presents original research on Haskell, discusses practical experience and future development of the language, and promotes other forms of declarative programming. Topics of interest include: * Language design, with a focus on possible extensions and modifications of Haskell as well as critical discussions of the status quo; * Theory, such as formal semantics of the present language or future extensions, type systems, effects, metatheory, and foundations for program analysis and transformation; * Implementations, including program analysis and transformation, static and dynamic compilation for sequential, parallel, and distributed architectures, memory management, as well as foreign function and component interfaces; * Libraries, that demonstrate new ideas or techniques for functional programming in Haskell; * Tools, such as profilers, tracers, debuggers, preprocessors, and testing tools; * Applications, to scientific and symbolic computing, databases, multimedia, telecommunication, the web, and so forth; * Functional Pearls, being elegant and instructive programming examples; * Experience Reports, to document general practice and experience in education, industry, or other contexts; * Tutorials, to document how to use a particular language feature, programming technique, tool or library within the Haskell ecosystem; * System Demonstrations, based on running software rather than novel research results. Regular papers should explain their research contributions in both general and technical terms, identifying what has been accomplished, explaining why it is significant, and relating it to previous work, and to other languages where appropriate. Experience reports and functional pearls need not necessarily report original academic research results. For example, they may instead report reusable programming idioms, elegant ways to approach a problem, or practical experience that will be useful to other users, implementers, or researchers. The key criterion for such a paper is that it makes a contribution from which other Haskellers can benefit. It is not enough simply to describe a standard solution to a standard programming problem, or report on experience where you used Haskell in the standard way and achieved the result you were expecting. Like an experience report and a functional pearl, tutorials should make a contribution from which other Haskellers can benefit. What distinguishes a tutorial is that its focus is on explaining an aspect of the Haskell language and/or ecosystem in a way that is generally useful to a Haskell audience. Tutorials for many such topics can be found online; the distinction here is that by writing it up for formal review it will be vetted by experts and formally published. System demonstrations should summarize the system capabilities that would be demonstrated. The proposals will be judged on whether the ensuing session is likely to be important and interesting to the Haskell community at large, whether on grounds academic or industrial, theoretical or practical, technical, social or artistic. Please contact the program chair with any questions about the relevance of a proposal. If your contribution is not a research paper, please mark the title of your experience report, functional pearl, tutorial or system demonstration as such, by supplying a subtitle (Experience Report, Functional Pearl, Tutorial Paper, System Demonstration). Submission Details ================== Formatting ---------- Submitted papers should be in portable document format (PDF), formatted using the ACM SIGPLAN style guidelines. Authors should use the `acmart` format, with the `sigplan` sub-format for ACM proceedings. For details, see: http://www.sigplan.org/Resources/Author/#acmart-format It is recommended to use the `review` option when submitting a paper; this option enables line numbers for easy reference in reviews. Functional pearls, experience reports, tutorials and demo proposals should be labelled clearly as such. Lightweight Double-blind Reviewing ---------------------------------- Haskell Symposium 2023 will use a lightweight double-blind reviewing process. To facilitate this, submitted papers must adhere to two rules: 1. Author names and institutions must be omitted, and 2. References to authors' own related work should be in the third person (e.g., not "We build on our previous work" but rather "We build on the work of "). The purpose of this process is to help the reviewers come to an initial judgement about the paper without bias, not to make it impossible for them to discover the authors if they were to try. Nothing should be done in the name of anonymity that weakens the submission or makes the job of reviewing the paper more difficult (e.g., important background references should not be omitted or anonymised). In addition, authors should feel free to disseminate their ideas or draft versions of their paper as they normally would. For instance, authors may post drafts of their papers on the web or give talks on their research ideas. A reviewer will learn the identity of the author(s) of a paper after a review is submitted. Page Limits ----------- The length of submissions should not exceed the following limits: Regular paper: 12 pages Functional pearl: 12 pages Tutorial: 12 pages Experience report: 6 pages Demo proposal: 2 pages There is no requirement that all pages are used. For example, a functional pearl may be much shorter than 12 pages. In all cases, the list of references is not counted against these page limits. Deadlines --------- Paper submission: 1 June 2023 (Thu) Notification: 4 July 2023 (Tue) Camera ready: 18 July 2023 (Tue) Deadlines are anywhere on Earth. Submission ---------- Submissions must adhere to SIGPLAN's republication policy (http://sigplan.org/Resources/Policies/Republication/) and authors should be aware of ACM's policies on plagiarism (https://www.acm.org/publications/policies/plagiarism) Program Committee members are allowed to submit papers, but their papers will be held to a higher standard. The paper submission deadline and length limitations are firm. There will be no extensions, and papers violating the length limitations will be summarily rejected. Papers should be submitted through HotCRP at: https://haskell23.hotcrp.com/ Improved versions of a paper may be submitted at any point before the submission deadline using the same web interface. Supplementary material: Authors have the option to attach supplementary material to a submission, on the understanding that reviewers may choose not to look at it. This supplementary material should not be submitted as part of the main document; instead, it should be uploaded as a separate PDF document or tarball. Supplementary material should be uploaded at submission time, not by providing a URL in the paper that points to an external repository. Authors can distinguish between anonymised and non-anonymised supplementary material. Anonymised supplementary material will be visible to reviewers immediately; non-anonymised supplementary material will be revealed to reviewers only after they have submitted their review of the paper and learned the identity of the author(s). Resubmitted Papers: authors who submit a revised version of a paper that has previously been rejected by another conference have the option to attach an annotated copy of the reviews of their previous submission(s), explaining how they have addressed these previous reviews in the present submission. If a reviewer identifies him/herself as a reviewer of this previous submission and wishes to see how his/her comments have been addressed, the conference chair will communicate to this reviewer the annotated copy of his/her previous review. Otherwise, no reviewer will read the annotated copies of the previous reviews. Proceedings =========== Accepted papers will be included in the ACM Digital Library. Their authors will be required to choose one of the following options: - Author retains copyright of the work and grants ACM a non-exclusive permission-to-publish license (and, optionally, licenses the work with a Creative Commons license); - Author retains copyright of the work and grants ACM an exclusive permission-to-publish license; - Author transfers copyright of the work to ACM. For more information, please see ACM Copyright Policy (http://www.acm.org/publications/policies/copyright-policy) and ACM Author Rights (http://authors.acm.org/main.html) Accepted proposals for system demonstrations will be posted on the symposium website but not formally published in the proceedings. Publication date: The official publication date of accepted papers is the date the proceedings are made available in the ACM Digital Library. This date may be up to two weeks prior to the first day of the conference. The official publication date affects the deadline for any patent filings related to published work. Artefacts ========= Authors are encouraged to make auxiliary material (artefacts like source code, test data, etc.) available with their paper. Authors can opt to have these artefacts published alongside their paper in the ACM Digital Library (copyright of artefacts remains with the authors). Artefacts must be included as part of their submission to HotCRP and should consist of a .zip file containing the artefact materials, a README explaining the contents of the artefact and how it should be used, and a LICENSE file. If an accepted paper's artefacts are made permanently available for retrieval in a publicly accessible archival repository like the ACM Digital Library, that paper qualifies for an Artefact badge (https://www.acm.org/publications/policies/artifact-review-badging) Program Committee ================= Alexander Green Standard Chartered, UK David Thrane Christiansen The Haskell Foundation, Denmark Edsko de Vries Well-Typed LLP, Netherlands Exequiel Rivas Tallinn University of Technology Facundo DomÃnguez Tweag Florian Zuleger TU Vienna, Austria Graham Hutton University of Nottingham, UK Jasper Van der Jeugt Snyk, Switzerland Jennifer Paykin Intel, USA Jesper Cockx Delft University of Technology, Netherlands Jose Nuno Oliveira University of Minho & INESC TEC, Portugal Michael Sperber Active Group GmbH, Germany Michel Steuwer University of Edinburgh, UK Niki Vazou (chair) IMDEA Software Institute, Spain Rumyana Neykova Brunel University London, UK Trevor L. McDonell (co-chair) Utrecht University, Netherlands Ugo Dal Lago University of Bologna, Italy & INRIA, France Wen Kokke University of Edinburgh, UK Leonidas Lampropoulos University of Maryland, College Park, USA If you have questions, please contact the chairs at niki.vazou(a)imdea.org and t.l.mcdonell(a)uu.nl. ================================================================================

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[ANN] Haskell Streamly 0.9.0 Release
by Harendra Kumar 25 May '23

25 May '23

We are glad to announce streamly 0.9.0 release. streamly-0.9.0 and streamly-core-0.1.0 have been available on Hackage for some time now. You can find the source at https://github.com/composewell/streamly and reference documentation and some guides are also available on https://streamly.composewell.com . The website also has functionality to search across multiple streamly packages. This release did a major revamp of the API to make it easier to comprehend and less error prone to use. Now there is a single "Stream" type instead of the polymorphic "IsStream" type class. There are explicit concurrency combinators to enable concurrent behavior on the same type instead of using different types for that purpose. Dependency on GHC rewrite rules has been removed for more robust behavior and better programmer control, though it required splitting the stream type into the default direct-style type "Stream" and the CPS type "StreamK". The package has been split into two, "streamly-core" intends to depend only on boot libraries (currently has some more deps due to backward compatibility), "streamly" provides higher level functionality like concurrency. Parser functionality has been released. Parsers fuse with streams and are compatible with folds i.e. parsers are folds with more power. Please see the following docs for more details: * Changelog: https://streamly.composewell.com/streamly-0.9.0/User/ProjectRelated/Changel… * Upgrade guide: https://streamly.composewell.com/streamly-0.9.0/User/ProjectRelated/Upgradi… Your feedback is important to us. We did the API revamp based on feedback from users. -harendra

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what are correct ways to translate haskell code ?
by profited＠tutanota.com 24 May '23

24 May '23

let's consider this example Alice has 1.hs like this v :: (,) Int Bool v = (,) 0 False main :: IO () main = putStrLn "print some magic number" >> print ( fst v ) Bob download 1.hs from Alice Bob would like to change 1.hs to 2.hs Bob want the programs [ 1.hs 2.hs ] to behave the same the reason that Bob want to modify 1.hs may be Bob does not like the type (,) in 1.hs Bob has Vector_2.hs module Vector_2 where data Vector_2 a b = C a b x1_of :: Vector_2 a b -> a x1_of ( C x1 _ ) = x1 x2_of :: Vector_2 a b -> b x2_of ( C _ x2 ) = x2 Bob like his Vector_2.hs Bob thinks the Vector_2 shall be good enough to replace (,) in 1.hs i want to create a translator.hs for Bob Bob tell the translator.hs that Bob want to replace (,) with Vector_2 in 1.hs translator.hs automatically translate 1.hs to 2.hs 2.hs shall look like this import Vector_2 ( Vector_2 ) import qualified Vector_2 v :: Vector_2 Int Bool v = Vector_2.C 0 False main :: IO () main = putStrLn "print some magic number" >> print ( Vector_2.x1_of v ) what shall i do ?

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