- Haskell-Cafe - Haskell.org

cabal errors
by Gregory Guthrie 28 Dec '20

28 Dec '20

I'm having some issues with Cabal , wonder if they are known issues. 1) I had a previously working installation of files, hadn't used them for some time, did Haskell upgrades (chocolatey), and tried to recompile. I got a weird error on running the build - 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 Chasing this all around - no solutions so I started over, in a new location, adding one file at a time. Worked fine. 2) So I then has a current working build in some top level xTest temporary directory. (Just a direct copy of all the files, and "cabal v2-build") 3) So I then just copied all the source files back to a desired installation place, with a longer path name. 4) But there it fails to build: PS D:\CS\Courses\long path\Solns\All Solutions> cabal v2-install Wrote tarball sdist to D:\CS\Courses\long path\Solns\All Solutions\dist-newstyle\sdist\apl-0.0.1.tar.gz Resolving dependencies... Build profile: -w ghc-8.10.1 -O1 In order, the following will be built (use -v for more details): - apl-0.0.1 (exe:apl) (requires build) cabal.exe: Failed to unpack apl-0.0.1. The exception was: dieVerbatim: user error (cabal.exe: Package .cabal file not found in the tarball: C:\Users\guthrie\AppData\Local\Temp\cabal-install.-2584\dist-newstyle\tmp\src-2584\apl-0.0.1\apl.cabal) 5) Just copying (again) the same folder of files which is failing to a top level new folder (yTest), deleting the dist-newstyle folder, And running "cabal v2-buld" again, all works fine, no errors, executable built. Three directories, all with the same files - one fails. ?? The only difference I can see is the long path name with blanks in it - is that an issue? Dr. Gregory Guthrie Maharishi International University ----------------------------------------------------------------

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Re: [Haskell-cafe] [Ann] group-theory
by Olaf Klinke 26 Dec '20

26 Dec '20

Koji Miyazato wrote: > > You can use `MonoidNull`. from monoid-subclasses to avoid an `Eq` > constraint. > > For groups, there is no difference between `MonoidNull` and `Eq`, as > you can define `x == y` be > `null (x <> inv y)`. There are monoids which `==` is not even > decidable but `null` is (e.g. context-free grammars > with equality defined by the language it defines), but such monoid > necessarily has no `Group` instance. A beautiful example of topological groups: Their topology is completely determined by the neighbourhoods of the identity element. If the identity element is isolated, the entire group is discrete. Olaf

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[Ann] group-theory
by Emily Pillmore 26 Dec '20

26 Dec '20

Hello all, I am pleased to announce the release of the group-theory ( https://hackage.haskell.org/package/group-theory ) package: a package aimed at implementing the theory of finite groups in a reasonably ergonomic, well-documented, and featureful way. It's hardly finished, but my co-maintainer, Reed Mullanix (@totbwf) and I thought this was a good mvp with which we could announce. Contributions are very welcome, and I hope everyone enjoys. Cheers, Emily Pillmore

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Haskell-language-server is looking for a logo
by Alan & Kim Zimmerman 24 Dec '20

24 Dec '20

Hi all, The haskell language server is coming up for its first birthday in January. To celebrate we would like to collectively choose a logo. So if you have a creative streak and would like to donate a lasting contribution to the project, please submit for consideration at [1]. We will aim to close the judging on 25 Jan 2021, being the anniversary of the Bristol Hackathon[2] where HLS was born. Alan [1] https://github.com/haskell/haskell-language-server/issues/694 [2] https://mpickering.github.io/bristol2020.html

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Supporting Haskell.org
by Rebecca Skinner 23 Dec '20

23 Dec '20

Hi everyone. Apologies for the second email here. I originally sent this message with an incorrect subject, and I wanted to re-post here with a correct subject for visibility. 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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Supporting The Haskell Foundation
by Rebecca Skinner 23 Dec '20

23 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 22 Dec '20

22 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 22 Dec '20

22 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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