- Haskell-Cafe - Haskell.org

Supporting The Haskell Foundation
by Rebecca Skinner 24 Dec '20

24 Dec '20

This has been an eventful year for many of us, and haskell.org is no different. This year we've continued to support a significant part of the Haskell community infrastructure- including haskell.org, Hackage, Hoogle, and GHC build infrastructure. We're able to do this thanks to the support of the Haskell community. In addition to our ongoing work maintaining Haskell community infrastructure, we once again participated in the Google Summer of Code this year, supporting 12 projects. You can read more about the projects here: https://summer.haskell.org/news/2020-10-12-final-results.html As many of you are likely aware, this year also saw some of our community successfully launch a new initiative, the Haskell Foundation. We are thrilled for the Haskell Foundation and congratulate them on their successful launch. Haskell.org is an independent organization, and while we welcome any opportunities to collaborate with the Haskell Foundation, we will continue to pursue our mission of managing and supporting Haskell community infrastructure. If you would like to support Haskell.org in our mission, you can donate via several method, including PayPay and check: https://www.haskell.org/donations/ 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. Another way to help haskell.org is to serve on the committee. We have three positions opening in 2021, and our call for nominations is open through Jan 7th 2021. Please email the committee at committee(a)haskell.org if you would like to nominate yourself or someone else for a position. We look forward to continuing this work with your support in 2021 as well as exploring new projects to improve the Haskell community infrastructure. Best wishes, Rebecca Skinner on behalf of the haskell.org committee.

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cabal build fails: sidebyside
by Gregory Guthrie 23 Dec '20

23 Dec '20

I have a fairly simple Haskell program which I build with cabal, which ends up seemingly successful with an executable (apl.exe). (but what a path(!): . \dist-newstyle\build\x86_64-windows\ghc-8.10.1\apl-0.0.1\build\apl\apl.exe Running that gives an error: Program 'apl.exe' failed to run: The application has failed to start because its side-by-side configuration is incorrect. Please see the application event log or use the command-line sxstrace.exe tool for more detailAt line:1 char:1 + ./apl + ~~~~~. At line:1 char:1 + ./apl + ~~~~~ + CategoryInfo : ResourceUnavailable: (:) [], ApplicationFailedException + FullyQualifiedErrorId : NativeCommandFailed Looking in the Windows event viewer, it reports: Activation context generation failed for "...\apl.exe". Error in manifest or policy file "...apl.exe" on line 2. Invalid Xml syntax. Sxstrace did not seem to give any additional information: Begin Activation Context Generation. Input Parameter: Flags = 0 ProcessorArchitecture = AMD64 CultureFallBacks = en-US;en ManifestPath = D:\CS\Courses\CS505 -APL\Labs & Hmwks\Dsem Labs -Haskell Solns\dist-newstyle\build\x86_64-windows\ghc-8.10.1\APL-0.0.1\build\APL\apl.exe AssemblyDirectory = D:\CS\Courses\CS505 -APL\Labs & Hmwks\Dsem Labs -Haskell Solns\dist-newstyle\build\x86_64-windows\ghc-8.10.1\APL-0.0.1\build\APL\ Application Config File = ----------------- INFO: Parsing Manifest File D:\CS\Courses\CS505 -APL\Labs & Hmwks\Dsem Labs -Haskell Solns\dist-newstyle\build\x86_64-windows\ghc-8.10.1\APL-0.0.1\build\APL\apl.exe. INFO: Manifest Definition Identity is (null). ERROR: Line 2: XML Syntax error. ERROR: Activation Context generation failed. End Activation Context Generation. Online some posts suggest installing a current VC_redist - I did that, no relief. Any suggestions on what is causing this, and a fix? Running GCH: 8.10.1 Cabal: 3.2.0.0 Windows 10 Dr. Gregory Guthrie

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Enable -Wall by default?
by Fumiaki Kinoshita 23 Dec '20

23 Dec '20

I mean literally. An article [0] reminded me of the fact that I enable -Wall in 99% of time -- and most packages I use have it enabled too. It's well known that -Wall doesn't enable* all *warnings, but a subset of warnings that * are well accepted by the community * rarely produce false positives Well, they look like good reasons to enable the warnings by default. Same goes for -Wcompat, except that it is not as popular as -Wall. Seeing potential problems when compiling code is far less of a pain than leaving breakages unnoticed. Am I missing some obvious reason not to do this? [0] https://www.snoyman.com/blog/2020/12/haskell-bad-parts-3

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Re: [Haskell-cafe] type class Boolean
by Johannes Waldmann 22 Dec '20

22 Dec '20

> most useful kind of instance would be symbolic booleans Yes. Ersatz has this: https://hackage.haskell.org/package/ersatz-0.4.8/docs/Ersatz-Bit.html#t:Boo… I also use this class (re-exported) in https://hackage.haskell.org/package/obdd Then modules typically start with import Prelude hiding ( not, and, or, (&&), (||) ) -- possibly more import Ersatz slightly annoying but you get used to it ... - J.

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(Co-)Maintainer-needed: imagemagick, binary-conduit
by Alexander V Vershilov 21 Dec '20

21 Dec '20

Hello, I'm searching for the (co-)maintainers for packages that I don't use at my daily work. If anyone use those, please volunteer: https://hackage.haskell.org/package/imagemagick https://hackage.haskell.org/package/binary-conduit https://hackage.haskell.org/package/network-transport-zeromq -- Alexander Vershilov

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Where do trivial functions on the usual containers live?
by Olaf Klinke 21 Dec '20

21 Dec '20

> I am looking for a place where I can find or put some simple > functions that I > expect but do not find in the `containers` or elsewhere in the > standard > libraries. Many hackage contributors seem to maintain their own <maintainer>-utils package containing bits and bobs they personally deem useful but can not find elsewhere. I might add my own one soon. Not saying this is a good thing, though. > Some examples I have in mind: > > * Group a collection by an equivalence relation: > > classify ∷ Ord π ⇒ (a → π) → [a] → [[a]] GHC.Exts.groupWith or Data.List.groupBy might do want you want, depending on whether you want to aggregate globally or only consecutive runs of equivalent elements. > > * From a finite map, get a map from its range to its fibers: > > fibers ∷ (Ord k, Ord v) ⇒ Map k v → Map v (NonEmpty k) The usual Semigroup instance of Map k v destroys data upon key collision. For problems like this I have a newtype wrapper newtype SemiMap f v = SemiMap {getSemiMap :: f v} instance (Semigroup v, Ord k) => Semigroup (SemiMap (Map k) v) so that one can implement 'fibers' using foldMapWithKey. Is this worth its own package? > > * Put a type into the diagonal of its square: > > diagonal = λx → (x, x) This may be too trivial to be a library function, and its proper type should rather be x -> Pair x since we know both components have the same type. Pair is a Monad and this function is its return. In package ghc Pair has an Applicativeinstance at least. Regards, Olaf

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Intermediate Modern Haskell
by Jacques Carette 21 Dec '20

21 Dec '20

I will be teaching a second Haskell course next semester. Let's assume that Introducing functional programming Getting started with Haskell and GHCi Basic types and definitions Designing and writing programs Data types, tuples and lists Programming with lists Defining functions over lists Playing the game: I/O in Haskell Reasoning about programs Generalization: patterns of computation Higher-order functions Developing higher-order programs Overloading, type classes and type checking Algebraic types (i.e. the first chapters of Thompson's Haskell: the Craft of Functional Programming book is "beginner, classic Haskell". The next few chapters, namely Abstract data types Lazy programming Programming with monads Domain-Specific Languages Time and space behaviour would be (re)done at the start of such a second course. The question for cafe is: what else? I will likely cover: - Typeclassopedia - finally tagless - Template Haskell - Optics - GADTs - recursion schemes I should probably cover parser combinators, pretty-printing, cabal&stack. I know that http://dev.stephendiehl.com/hask/ <http://dev.stephendiehl.com/hask/> gives me one heck of a smorgasbord of options, which is kind of a problem. Things I know I will not cover: - dependent types (if I was going to do that, I'd switch to Idris/Agda) - concurrency (don't ask) Jacques

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Where do trivial functions on the usual containers live?
by Ignat Insarov 21 Dec '20

21 Dec '20

Hello. I am looking for a place where I can find or put some simple functions that I expect but do not find in the `containers` or elsewhere in the standard libraries. Some examples I have in mind: * Group a collection by an equivalence relation: classify ∷ Ord π ⇒ (a → π) → [a] → [[a]] * From a finite map, get a map from its range to its fibers: fibers ∷ (Ord k, Ord v) ⇒ Map k v → Map v (NonEmpty k) * Put a type into the diagonal of its square: diagonal = λx → (x, x) These are all very common and trivial mathematical constructions and I really want such things to be common place in Haskell, so that they may have a canonical, polished definition. It is unfeasible to put them into the standard libraries. _(Attempts were made.)_ So I wonder if there is a package around that would accept them!

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[CFP]Automatic Debugging, Error and Impact Reporting Approaches workshop
by mgajda＠mimuw.edu.pl 20 Dec '20

20 Dec '20

International workshop on Automatic Debugging, Error and Impact Reporting Approaches ==================================================================================== Automatic debugging, error fixing, and reporting is getting more and more popularity across different research communities. We aim to provide a forum for exchange of latest work and document best practices across different disciplines. - Automatic reproducers like those generated by LLDB - Automatic unit test extraction and using decorators and code inspection - Automatic reproducer/error case minimization - Interactive error recovery systems and their applications - Error algebras and error-tracing algebras - Formalizations of debugging - Fault impact reporting and accuracy estimation - Provenance tracking in term rewriting - Error analytics pipelines and databases - Error monitoring in intrusion detection systems - Delta debugging - Automatic generation of error dashboards - Global fault analysis of systems with both computational and human component, and cyber-physical systems. Note that workshop particularly encourage treatment of all kinds of errors, be they compile-time, run-time, discrepancies between intent and specification, hardware failures, or human errors to the degree to which they are amenable to automatic analysis and reporting. Intended audience ----------------- - Experts in automated debugging, error fixing wishing to exchange knowledge with their peers. - Industry practitioners interested to learn more about approaches to automated analysis of errors. - Academics in quest for formalization of automated error analysis and fixing - Financial industry practitioners interested in computer science approaches to satisfy risk reporting guidelines with respect to error impact tracing and reporting of accuracy - Management scientist looking for automatic global fault reporting and impact reporting methodologies. Because of this, we encourage you to reference used theories and methodologies, and provide a introductions with use cases. The workshop is held as a part of [Programming Conference 2021](https://2021.programming-conference.org/). Goals ----- - Our main goal is to encourage social exchange of ideas related to automatic error analysis and impact reporting. - We call for position papers, research expositions, early stage work, and industry experience papers to encourage exchange of on-going research and implementation efforts. Important dates =============== Abstract registration deadline : January 15th, 2021 Submission deadline : January 20th, 2021 Author response period : February 14th-21st, 2021 Acceptance notification : March 1st, 2021 Programme committee ------------------- - Kenichi Asai, [Ochanomizu University](http://pllab.is.ocha.ac.jp/~asai/) - Michał J. Gajda, [Migamake Pte Ltd](https://migamake.com) *(chair)* - Michał "phoe" Herda [\#lisp @ Freenode IRC](https://netsplit.de/channels/details.php?room=%23lisp&net=freenode) - Henrik Nilsson [University of Nottingham](http://www.cs.nott.ac.uk/~psznhn/) - Vladimir Panteleev [DustMite](https://github.com/CyberShadow/DustMite) - Francesco Spegni [Università Politecnica delle Marche](https://www.dii.univpm.it/francesco.spegni) - Dmitry Vostokov [DumpAnalysis.org](https://DumpAnalysis.org) - Vadim Zaytsev [Universiteit Twente](http://grammarware.net) Submissions =========== We welcome original, unpublished papers of the following forms: full articles, extended abstracts, case studies. Please submit your paper or extended abstract [by EasyChair](https://easychair.org/conferences/?conf=adeira2021). You may [contact the committee chair](https://www.linkedin.com/in/mjgajda/) with any questions you have about submission. The paper evaluation will use the following criteria: \* Novelty \* Clarity of exposition \* Transferrability of innovation(s) to other domains \* Scientific rigour and form of the article \* Cross-pollination potential with other papers \* Preliminary papers will be offered feedback on how to improve the quality in all these factors before and during the workshop All submissions should use [ACM DL template](https://www.acm.org/publications/proceedings-template).

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[CFP]Automatic Debugging, Error and Impact Reporting Approaches workshop
by mgajda＠mimuw.edu.pl 20 Dec '20

20 Dec '20

Dear Friends, The emerging interest in the rigorous and agile data science and functional ETL pipelines has driven the developments of many new libraries, frameworks and methodologies. We invite industry practitioners and academics to present their latest work on agile functional data pipelines as a workshop at the EDI'2021 conference. Call for papers =============== The following would be accepted: - Exposures of methodologies for building agile functional data pipelines - Presentations of frameworks used for data pipelines in industry and academia - Experience reports from building of data pipelines in industry and academia - Benchmarks and optimization of agile data pipeline frameworks - Solutions to data integration and exchange problems within ETL pipelines. In particular, we encourage: - Agile functional data methodologists - Authors of ETL frameworks, streaming libraries and databases, reactive streaming, streaming benchmarks, high-performance workflow engines - Position papers on the use of agile and functional data methodologies - Descriptions of environments for interactive and live programming with data - Benchmarks of state-of-the-art solutions for agile functional data pipelines. Details at https://afdp.github.io Important dates =============== Abstract registration deadline : December 27th, 2020 (extended) Submission deadline : January 3rd, 2020 (extended) Acceptance notification : January 12th 2021 Final manuscripts : January 23rd, 2021 Presentation at the conference : March 23rd-26th 2021 Submission instructions ======================= Original, unpublished papers are solicited for presentation at the AFDP workshop. Prospective authors are invited to submit papers (electronically, PDF only) that are no longer than 6 pages for full papers, including all figures and references. For work-in-progress, we also solicit extended abstracts for presentations. The submitted paper must be formatted according to the guidelines of Procedia Computer Science. All accepted papers will be published in Procedia Computer Science. Location ======== This workshop will be held as a part of [The 4th International Conference on Emerging Data and Industry 4.0 (EDI40)](http://cs-conferences.acadiau.ca/EDI40-21/) held on March 23 - 26, 2021 in Warsaw, Poland. -- Best regards Michał

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