- Haskell-Cafe - Haskell.org

Munich Haskell Meeting, 2023-10-31 @ 19:30
by Leah Neukirchen 30 Oct '23

30 Oct '23

Dear all, Next week, our monthly Munich Haskell Meeting will take place again on Tuesday, October 31 at Iveria (Lindwurmstraße 159A) at 19h30. For details see here: http://muenchen.haskell.bayern/dates.html If you plan to join, please add yourself to this nuudel so we can reserve enough seats! It is OK to add yourself to the nuudel anonymously or pseudonymously. https://nuudel.digitalcourage.de/7ST4pxNRVj3rGLdO Everybody is welcome! cu, -- Leah Neukirchen <leah(a)vuxu.org> https://leahneukirchen.org/

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Re: [Haskell-cafe] Should GHC 9.4.7 be native on MacBook Air M2?
by David Banas 28 Oct '23

28 Oct '23

Ah, I needed this line in my stack.yaml file: arch: aarch64 Why is that? Shouldn’t it use the native architecture if it can support it? -db

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Should GHC 9.4.7 be native on MacBook Air M2?
by David Banas 28 Oct '23

28 Oct '23

I’m working on a new MacBook Air M2. I just bumped my current Haskell project to stack LTS-21.17, after catching up on the GHC porting effort news. I did a stack clean / stack build and saw GHC 9.4.7 being installed, as expected, but still to the x86_64-osx directory: % l ~/.stack/programs x86_64-osx % l ~/.stack/programs/x86_64-osx ghc-8.10.3 ghc-8.10.4.tar.bz2 ghc-8.6.3.installed ghc-9.0.2 ghc-9.2.2.tar.bz2 ghc-9.2.7.installed ghc-8.10.3.installed ghc-8.4.3 ghc-8.6.3.tar.bz2 ghc-9.0.2.installed ghc-9.2.5 ghc-9.2.7.tar.bz2 ghc-8.10.3.tar.bz2 ghc-8.4.3.installed ghc-8.6.5 ghc-9.0.2.tar.bz2 ghc-9.2.5.installed ghc-9.4.7 ghc-8.10.4 ghc-8.4.3.tar.bz2 ghc-8.6.5.installed ghc-9.2.2 ghc-9.2.5.tar.bz2 ghc-9.4.7.installed ghc-8.10.4.installed ghc-8.6.3 ghc-8.6.5.tar.bz2 ghc-9.2.2.installed ghc-9.2.7 ghc-9.4.7.tar.bz2 I was expecting a native version; do I misunderstand something?

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Simplest way to move a ... `using` ... line into the IO monad?
by David Banas 27 Oct '23

27 Oct '23

Hi all, What is the simplest way to translate a non-monadic line of Haskell code, such as: res = map foo xs `using` parList rseq For use in the IO monad? This doesn’t work: res <- mapM fooM xs `using` parTraversable rseq complaining: No Traversable instance for IO. Thanks, -db

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Re: [Haskell-cafe] when does ghc(i) expand type synonyms?
by Olaf Klinke 26 Oct '23

26 Oct '23

> ghci> :set +t > > ghci> "foo" > "foo" > it :: String > > ghci> reverse "foo" > "oof" > it :: [Char] I'm not a GHC expert, but my guess is: It must have something to do with unifying the argument types with the type signature of the function. In (<>), the two argument and the result types are identical. Hence it can be safely said that x <> whatever as long as this expression is valid, has the same type as x. In contrast, the result type of (++) is always of the shape [a]. Hence String gets unified with [a] which forces expansion of the type synonym. Consider: class Foo a where {rev :: a -> a; conc :: a -> a -> a} instance Foo [a] where {rev = reverse; conc = (++)} revconc :: Foo a => a -> a; revconc a = conc a (rev a) :t revconc ("foo" :: String) revconc ("foo" :: String) :: String So as long has you hide (++) in a type signature that proves input and output are the same, synonyms don't get expanded. Olaf

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when does ghc(i) expand type synonyms?
by Johannes Waldmann 25 Oct '23

25 Oct '23

Dear cafe, my students were asking: why are types printed differently here? ghci> :set +t ghci> "foo" "foo" it :: String ghci> reverse "foo" "oof" it :: [Char] ... and I add ghci> fst ("foo", 42) "foo" it :: String compiler docs do not really explain the difference https://downloads.haskell.org/ghc/latest/docs/users_guide/ghci.html#ghci-cm… (it says "display the type of .." while technically it is "display some representation of the type of ..."?) I found this explanation of a somewhat related issue https://gitlab.haskell.org/ghc/ghc/-/issues/9183#note_83743 While playing around with this, I noticed: ghci> let x = "foo" in (x <> reverse x) "foooof" it :: String ghci> let x = "foo" in (x ++ reverse x) "foooof" it :: [Char] Well, it's just optics: when I extract the type programmatically, the synonym necessarily does get expanded ghci> import Data.Data ghci> typeOf (let x = "foo" in (x <> reverse x)) [Char] it :: TypeRep - Johannes

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Hackage not building package
by Ivan Perez 23 Oct '23

23 Oct '23

Hi, I recently uploaded a package ( https://hackage.haskell.org/package/dunai-0.12.0) and hackage is not building it. I don't see info anywhere and I cannot re-trigger a build: attempting to do so shows the message "Report not found -Build report does not exist" Is everything ok with hackage? Thanks Ivan

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Where did pem-0.2.4 come from? a.k.a. is anyone compelled to take-over this project?
by Noon van der Silk 19 Oct '23

19 Oct '23

Glancing at hackage, I happened to noticed that pem is at 0.2.4 - https://hackage.haskell.org/package/pem-0.2.4 Glancing at the repo, I notice that pem is at 0.2.3 - https://github.com/vincenthz/hs-pem It seems there _is_ a tag for 0.2.4, but `master` has not been updated <https://github.com/vincenthz/hs-pem/compare/master..pem-v0.2.4>. Is there anyone out there that feels compelled or excited to fix this? And perhaps relatedly, given vincent has archived all these repos; perhaps there could be a kind of "global takeover" by the HF cryptography working group of these projects? -- Noon van der Silk, ن http://silky.github.io/ "My programming language is kindness."

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Request for take over: graphviz
by Daniel Casanueva 18 Oct '23

18 Oct '23

Hello, graphviz [1] maintenance has been inactive for a long time now. Revisions have been published, but the maintainer seems unresponsive. Last year, Bodigrim suggested the package needs a new maintainer in a GitHub thread [2] that one month ago I found while looking if someone had already done the fix I needed. I'm happy to help keeping the package alive so, about a month ago, I emailed Ivan (graphviz's author) to the e-mail address from his GitHub profile, offering my assistance with graphviz. I haven't gotten any answer yet, so I thought I should be making my offer public, as indicated by the "Taking over a package" wikipage [3]. I don't have big change plans for graphviz. Most likely I will just be patching it to keep it working with future GHC releases and reviewing/accepting PRs. Thank you, Daniel [1] https://hackage.haskell.org/package/graphviz [2] https://github.com/ivan-m/graphviz/pull/53#issuecomment-1261496914 [3] https://wiki.haskell.org/Taking_over_a_package

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Assistant Prof at Barnard College, Columbia U
by Mark Santolucito 17 Oct '23

17 Oct '23

Hi all, Barnard College, Columbia University has an opening for an Assistant Professor: https://cs.barnard.edu/assistant-professor-computer-science-2024 The deadline is Oct 27 for full consideration. Barnard is the women's college of Columbia and has a 2-2 teaching load (typically with additional reductions). If you are interested, please feel free to reach out to me directly to discuss more. This is a unique place that I have really enjoyed the past few years! Mark https://www.marksantolucito.com/

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