- Haskell-Cafe - Haskell.org

Hyrum's law (Was: [RFC] Support Unicode characters in instance Show String)
by Henning Thielemann 08 Jul '21

08 Jul '21

moving to Haskell Cafe On Thu, 8 Jul 2021, Bardur Arantsson wrote: > On 08/07/2021 17.53, Oleg Grenrus wrote: > > [--snip--] > >> >> 78 out of 2819 tests failed (35.88s) >> > > The use of Show in 'golden' test suites is interesting because Show > doesn't really guarantee any real form of stability in its output. > > I guess Hyrum's Law applies here too. > > Anyway... just an idle observation. Obviously, breaking loads of test > suites is going to be hard to swallow. I found this explanation: https://www.hyrumslaw.com/ Nice to have a name for this observation. I think the problem can be relaxed if there are multiple implementations for the same interface. But then you often find, that the implementations do not even adhere to the interface, thus people start guessing what the interface actually means. I hope that in the future we can describe interfaces more formally, such that a user knows what he can rely on.

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Where have the discussions moved to?
by Carette, Jacques 08 Jul '21

08 Jul '21

Haskell Café used to be quite active. But in the last 2 years, at least, there have been much less traffic. In the same time frame, Haskell's popularity and community has expanded greatly. The logical conclusion is that discussions have moved elsewhere. I know that, for example, there are at times a large amount of discussion happening via github on the proposals [1] (in fact, so much so that I unsubscribed). I am aware that the community page [2] does mention quite a few places - too many. Is there one of those places where the kinds of discussions that used to happen here have moved to? Jacques [1] https://github.com/ghc-proposals/ghc-proposals [2] https://www.haskell.org/community/

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[ANN] Copilot 3.4 - hard realtime C runtime verification
by Frank Dedden 08 Jul '21

08 Jul '21

Dear all, We are pleased to announce the release of Copilot 3.4, a stream-based DSL for writing and monitoring embedded C programs, with an emphasis on correctness and hard realtime requirements. Copilot is typically used as a high-level runtime verification framework, and supports temporal logic (LTL, PTLTL and MTL), clocks and voting algorithms. Among others, Copilot has been used at the Safety Critical Avionics Systems Branch of NASA Langley Research Center for monitoring test flights of drones. This release introduces a number of bug fixes and deprecates functions that have been superseded. The newest release is available on hackage [1]. For more information, including documentation, examples and links to the source code, please visit the webpage [2]. Current emphasis is on facilitating the use with other systems, and improving the codebase in terms of stability and test coverage. Users are encouraged to participate by opening issues and asking questions via our github repo [3]. Kind regards, The Copilot developers: - Frank Dedden - Alwyn Goodloe - Ivan Perez [1] https://hackage.haskell.org/package/copilot [2] https://copilot-language.github.io [3] https://github.com/Copilot-Language/copilot

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How to debug SQL disconnect error
by Olaf Klinke 07 Jul '21

07 Jul '21

Dear Café, How can I go about examining an SQL error [1] when using persistent- odbc to access an MS SQL database? Set up a pristine MS SQL server 2012. Installed the driver on Debian using apt-get install msodbcsql17. Upon running either of persitent's printMigration or runMigration, the disconnect produces an error: *** Exception: SqlError {seState = "["25000"]", seNativeError = -1, seErrorMsg = "freeDbcIfNotAlready/SQLDisconnect: ["0: [Microsoft][ODBC Driver 17 for SQL Server]Invalid transaction state"]"} Running the printed SQL statements with isql executes allright, so it is not the particular migration at fault here. Presently I don't even know whether persistent or persistent-odbc or any false assumptions about the connection configuration is the cause. Thanks in advance Olaf [1] https://github.com/gbwey/persistent-odbc/issues/26

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FMBC 2021 - Call for Participation
by Bruno Bernardo 05 Jul '21

05 Jul '21

[ Please distribute, apologies for multiple postings. ] ======================================================================== 3rd International Workshop on Formal Methods for Blockchains (FMBC) 2021 - Call for Participation https://fmbc.gitlab.io/2021 July 18 and 19, 2021, Online, 8AM-10AM PDT Co-located with the 33rd International Conference on Computer-Aided Verification (CAV 2021) http://i-cav.org/2021/ --------------------------------------------------------- The FMBC workshop is a forum to identify theoretical and practical approaches of formal methods for Blockchain technology. Topics include, but are not limited to: * Formal models of Blockchain applications or concepts * Formal methods for consensus protocols * Formal methods for Blockchain-specific cryptographic primitives or protocols * Design and implementation of Smart Contract languages * Verification of Smart Contracts The list of lightning talks and conditionally accepted papers is available on the FMBC 2021 website: https://fmbc.gitlab.io/2021/program.html There will be one keynote by David Dill, Lead Researcher on Blockchain at Novi/Facebook and professor emeritus at Stanford University, USA. Registration Registration to FMBC 2021 is done through the CAV 2021 registration form: http://i-cav.org/2021/attending/ (*Early bird deadline is July 9.*)

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ANN: hledger-1.22
by Simon Michael 04 Jul '21

04 Jul '21

I'm pleased to announce hledger 1.22 ! https://hledger.org/release-notes.html#hledger-1-22 describes the user-visible changes. Highlights include: - Optimisations: about 20% faster overall, with register about 2x faster and 4x more memory-efficient - Bugfixes, including fixes for several regressions. Thank you to the following release contributors this time around: Felix Yan, crocket, Eric Mertens, Damien Cassou, charukiewicz, Garret McGraw, and especially Stephen Morgan. hledger (https://hledger.org) is a dependable, cross-platform "plain text accounting" tool, with command-line, terminal and web interfaces. It is an actively maintained, largely compatible reimplementation of Ledger CLI with many improvements. You can use it to track money, time, investments, cryptocurrencies, inventory and more. See also the Plain Text Accounting site (https://plaintextaccounting.org) https://hledger.org/download shows all the ways to install hledger on mac, windows or unix (stack, cabal, brew, nix, CI binaries, your package manager..). Or, run this bash script to install or upgrade to the latest release: $ curl -sO https://raw.githubusercontent.com/simonmichael/hledger/master/hledger-insta… $ less hledger-install.sh # security review $ bash hledger-install.sh New users, check out https://hledger.org/quickstart or the tutorials (with pictures!) at hledger.org -> FIRST STEPS or the https://hledger.org/videos.html. To get help, see https://hledger.org#help, and join one of our chat rooms: - #hledger:matrix.org (http://matrix.hledger.org) - #hledger:libera.chat (http://irc.hledger.org) Beginners and experts, contributors, sponsors, and all feedback are most welcome! Wishing you health and prosperity, -Simon

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Spam Control
by Gershom B 30 Jun '21

30 Jun '21

On Jun 29, 2021, 4:57 AM -0400, Ivan Perez <ivanperezdominguez(a)gmail.com>, wrote: > Can we please permanently ban this person and everyone from the confscience.com domain? > > Thanks, > > Ivan Done. —Gershom

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Using Data.String.Conversions
by Galaxy Being 30 Jun '21

30 Jun '21

I would simply like to use Data.String.Conversions, specifically the cs function while I'm in my global ghci REPL. Here's the code I'm working on (from here <https://zacwood.me/posts/2020-12-29-dates-ihp/>) parseDay' :: String -> Maybe Day parseDay' = parseTimeM True defaultTimeLocale "%Y-%m-%d" then mydate = getCurrentTime (Data.Time imported just fine.) parseDay' $ takeWhile ('T' /=) (cs mydate) My problem is I can import and expose Data.Time, but Data.String.Conversions will not import to my global REPL. Any tips on doing this project-based would be enlightening too. ⨽ Lawrence Bottorff Grand Marais, MN, USA borgauf(a)gmail.com

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Re: [Haskell-cafe] Prolog-style list syntax?
by Johannes Waldmann 29 Jun '21

29 Jun '21

> `[ x, y, z | zs ]` is also valid; [...] > That structure is particularly ugly in Haskell syntax. how so? `x : y : z : zs` Prolog list syntax is ugly here because the "cons" operator (|) needs special parentheses. Well, a similar thing in Haskell ist the ".." (enumFromTo) operator. For syntactic generality, you could go full Agda https://agda.readthedocs.io/en/v2.6.0.1/language/mixfix-operators.html but I'm not sure whether brackets could be "name parts" - J.W.

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Re: [Haskell-cafe] [Haskell Cafe] How to debug stack build failure? (YAMAMOTO Yuji)
by David Banas 29 Jun '21

29 Jun '21

$ stack build -v Version 2.7.1, Git revision 8afe0c2932716b0441cf4440d6942c59568b6b19 x86_64 hpack-0.34.4 {snip} 2021-06-28 16:20:17.903335: [info] comonad > configure 2021-06-28 16:20:17.905709: [debug] Run process within /tmp/stack-d3c8d82a69b145e0/comonad-5.0.6/: /home/david/.stack/programs/x86_64-linux/ghc-8.8.4/bin/ghc-8.8.4 --make -odir /tmp/stack-d3c8d82a69b145e0/comonad-5.0.6/.stack-work/dist/x86_64-linux/Cabal-3.0.1.0/setup -hidir /tmp/stack-d3c8d82a69b145e0/comonad-5.0.6/.stack-work/dist/x86_64-linux/Cabal-3.0.1.0/setup -i -i. -clear-package-db -global-package-db -package-db=/home/david/.stack/snapshots/x86_64-linux/6d64ef72f82ddc8525a7ddc3720c5e56c966b1ecb86aceed15c48dc305ef2f2c/8.8.4/pkgdb -package-db=/home/david/prj/haskarch/.stack-work/install/x86_64-linux/6d64ef72f82ddc8525a7ddc3720c5e56c966b1ecb86aceed15c48dc305ef2f2c/8.8.4/pkgdb -hide-all-packages -package-id=Cabal-3.0.1.0 -package-id=base-4.13.0.0 -package-id=cabal-doctest-1.0.8-2wQRz9ec1yB5lMDRmEgBWB -optP-include -optP/tmp/stack-d3c8d82a69b145e0/comonad-5.0.6/.stack-work/dist/x86_64-linux/Cabal-3.0.1.0/setup/setup_macros.h /tmp/stack-d3c8d82a69b145e0/comonad-5.0.6/Setup.lhs /home/david/.stack/setup-exe-src/setup-shim-mPHDZzAJ.hs -main-is StackSetupShim.mainOverride -o /tmp/stack-d3c8d82a69b145e0/comonad-5.0.6/.stack-work/dist/x86_64-linux/Cabal-3.0.1.0/setup/setup -threaded 2021-06-28 16:20:17.943489: [warn] comonad > /home/david/.stack/programs/x86_64-linux/ghc-8.8.4/lib/ghc-8.8.4/bin/ghc: /lib64/libtinfo.so.5: no version information available (required by /home/david/.stack/programs/x86_64-linux/ghc-8.8.4/lib/ghc-8.8.4/bin/../haskeline-0.7.5.0/libHShaskeline-0.7.5.0-ghc8.8.4.so) 2021-06-28 16:20:17.944049: [warn] comonad > /home/david/.stack/programs/x86_64-linux/ghc-8.8.4/lib/ghc-8.8.4/bin/ghc: /lib64/libtinfo.so.5: no version information available (required by /home/david/.stack/programs/x86_64-linux/ghc-8.8.4/lib/ghc-8.8.4/bin/../ghc-8.8.4/libHSghc-8.8.4-ghc8.8.4.so) 2021-06-28 16:20:17.944266: [warn] comonad > /home/david/.stack/programs/x86_64-linux/ghc-8.8.4/lib/ghc-8.8.4/bin/ghc: /lib64/libtinfo.so.5: no version information available (required by /home/david/.stack/programs/x86_64-linux/ghc-8.8.4/lib/ghc-8.8.4/bin/../terminfo-0.4.1.4/libHSterminfo-0.4.1.4-ghc8.8.4.so) 2021-06-28 16:20:18.075957: [info] comonad > [1 of 2] Compiling Main ( /tmp/stack-d3c8d82a69b145e0/comonad-5.0.6/Setup.lhs, /tmp/stack-d3c8d82a69b145e0/comonad-5.0.6/.stack-work/dist/x86_64-linux/Cabal-3.0.1.0/setup/Main.o ) 2021-06-28 16:20:18.195209: [info] comonad > [2 of 2] Compiling StackSetupShim ( /home/david/.stack/setup-exe-src/setup-shim-mPHDZzAJ.hs, /tmp/stack-d3c8d82a69b145e0/comonad-5.0.6/.stack-work/dist/x86_64-linux/Cabal-3.0.1.0/setup/StackSetupShim.o ) 2021-06-28 16:20:18.353001: [info] comonad > Linking /tmp/stack-d3c8d82a69b145e0/comonad-5.0.6/.stack-work/dist/x86_64-linux/Cabal-3.0.1.0/setup/setup ... 2021-06-28 16:20:20.173612: [debug] Process finished in 2267ms: /home/david/.stack/programs/x86_64-linux/ghc-8.8.4/bin/ghc-8.8.4 --make -odir /tmp/stack-d3c8d82a69b145e0/comonad-5.0.6/.stack-work/dist/x86_64-linux/Cabal-3.0.1.0/setup -hidir /tmp/stack-d3c8d82a69b145e0/comonad-5.0.6/.stack-work/dist/x86_64-linux/Cabal-3.0.1.0/setup -i -i. -clear-package-db -global-package-db -package-db=/home/david/.stack/snapshots/x86_64-linux/6d64ef72f82ddc8525a7ddc3720c5e56c966b1ecb86aceed15c48dc305ef2f2c/8.8.4/pkgdb -package-db=/home/david/prj/haskarch/.stack-work/install/x86_64-linux/6d64ef72f82ddc8525a7ddc3720c5e56c966b1ecb86aceed15c48dc305ef2f2c/8.8.4/pkgdb -hide-all-packages -package-id=Cabal-3.0.1.0 -package-id=base-4.13.0.0 -package-id=cabal-doctest-1.0.8-2wQRz9ec1yB5lMDRmEgBWB -optP-include -optP/tmp/stack-d3c8d82a69b145e0/comonad-5.0.6/.stack-work/dist/x86_64-linux/Cabal-3.0.1.0/setup/setup_macros.h /tmp/stack-d3c8d82a69b145e0/comonad-5.0.6/Setup.lhs /home/david/.stack/setup-exe-src/setup-shim-mPHDZzAJ.hs -main-is StackSetupShim.mainOverride -o /tmp/stack-d3c8d82a69b145e0/comonad-5.0.6/.stack-work/dist/x86_64-linux/Cabal-3.0.1.0/setup/setup -threaded Progress 1/10 2021-06-28 16:20:20.191005: [error] Did not find executable at specified path: /tmp/stack-d3c8d82a69b145e0/comonad-5.0.6/.stack-work/dist/x86_64-linux/Cabal-3.0.1.0/setup/setup > On Jun 29, 2021, at 5:00 AM, haskell-cafe-request(a)haskell.org wrote: > > Try stack build -v firstable.

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