August 2023 - Haskell-Cafe

OAuth on gitlab.haskell.org
by Julian Brunner 28 Aug '23

28 Aug '23

Hello, I last used gitlab.haskell.org in 2022 via OAuth on my GitHub account. However, this seems to no longer be an option. The account itself (https://gitlab.haskell.org/julianbrunner) seems to still exist, but I am unable to log in or request a password reset. I could not find any way to contact anyone on gitlab.haskell.org or any information on the removal of the OAuth option. Does anyone know how I can get my account back or who I should contact to get this sorted out? Cheers, Julian

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debugging <<loop>> exception
by Dennis Raddle 27 Aug '23

27 Aug '23

I'm getting Exception: <<loop>>. It doesn't print the line number. When I load the program into ghci, it still doesn't print the line number. When I trace the program in ghci it never gets to the point of emitting the exception. I set up my program in stack. I tried both "stack ghci" and just "ghci".. the latter to make sure it wasn't using any compiled code (at least in my own code). If it doesn't print a line number does this mean it's happening in compiled code? Any ideas how I can go about debugging this?

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Munich Haskell Meeting, 2023-08-30 @ 19:30
by Leah Neukirchen 26 Aug '23

26 Aug '23

Dear all, Next week, our monthly Munich Haskell Meeting will take place again on Wednesday, August 30 at Augustiner-Kurgarten (De-la-Paz-Straße 10, 80639 München) at 19h30. Different location as Rumpler is on summer holidays! 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/xYna3xETL2UACtzT Everybody is welcome! cu, -- Leah Neukirchen <leah(a)vuxu.org> https://leahneukirchen.org/

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IOSim on Hackage
by coot＠coot.me 26 Aug '23

26 Aug '23

Hello dear Haskell-Cafe, I realised that I haven't shared here that we (the networking team of IOG) released io-sim on Hackage. We found and fixed countless bugs thanks to it, including some concurrent ones. Here's a blog post which I wrote some time ago: https://engineering.iog.io/2023-04-14-io-sim-annoucement https://hackage.haskell.org/package/io-sim https://hackage.haskell.org/package/io-classes Cheers, Marcin Szamotulski

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[ANNOUNCE] GHC 9.4.7 is now available
by Zubin Duggal 26 Aug '23

26 Aug '23

The GHC developers are happy to announce the availability of GHC 9.4.7. Binary distributions, source distributions, and documentation are available at https://downloads.haskell.org/ghc/9.4.7 The GHC developers are happy to announce the availability of GHC 9.4.7. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org](https://downloads.haskell.org/ghc/9.4.7). This release is primarily a bugfix release addressing some issues found in 9.4.6. These include: * A bump to bytestring-0.11.5.2 allowing GHC to be bootstrapped on systems where the bootstrap compiler is built with the `pthread_condattr_setclock` symbol available (#23789). * A number of bug fixes for scoping bugs in the specialiser, preventing simplifier panics (#21391, #21689, #21828, #23762). * Distributing dynamically linked alpine bindists (#23349, #23828). * A bug fix for the release notes syntax, allowing them to built on systems with older python and sphinx versions (#23807, #23818). * ... and a few more. See the [release notes] for a full accounting. 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/9.4.7/docs/users_guide/9.4.7-notes.html

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[ANNOUNCE] GHC 9.4.6 is now available
by Ben Gamari 25 Aug '23

25 Aug '23

The GHC developers are happy to announce the availability of GHC 9.4.6. Binary distributions, source distributions, and documentation are available at https://downloads.haskell.org/ghc/9.4.6 This release is primarily a bugfix release addressing some issues found in 9.4.6. These include: * Many bug fixes for the simplifier, preventing compiler panics, loops and incorrect code generation (#22761, #22549, #23208, #22761, #22272, #23146, #23012, #22547). * Bug fixes for the typechecker involving newtype family instances, making type equalities more robust and bugs having to do with defaulting representation polymorphic type variables (#23329, #23333, #23143, #23154, #23176). * Some bug fixes for code generation, particularly on the aarch64 backend, including adding more memory barriers for array read operations (#23541, #23749). * Some bug fixes for windows builds, ensuring the reliablility of IO manager shutdown and a bug fix for the RTS linker on windows (#23691, #22941). * A bug fix for the non-moving GC ensuring mutator allocations are properly accounted for (#23312). * A bug fix preventing some segfaults by ensuring that pinned allocations respect block size (#23400). * Many bug fixes for the bytecode interpreter, allowing a greater subset of the language to be interpreted (#22376, #22840, #22051, #21945, #23068, #22958). * ... and a few more. See the [release notes] for a full accounting. As some of the fixed issues do affect correctness users are encouraged to upgrade promptly. 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 & Ben [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new [release notes]: https://downloads.haskell.org/~ghc/9.4.6/docs/users_guide/9.4.6-notes.html

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[ANNOUNCE] GHC 9.8.1-alpha3 is now available
by Ben Gamari 23 Aug '23

23 Aug '23

The GHC developers are very pleased to announce the availability of the third alpha prerelease of GHC 9.8.1. Binary distributions, source distributions, and documentation are available at https://downloads.haskell.org/ghc/9.8.1-alpha3 GHC 9.8 will bring a number of new features and improvements, including: * Preliminary support the `TypeAbstractions` language extension, allowing types to be bound in type declarations [TypeAbstractions]. * Support for the `ExtendedLiterals` extension, providing syntax for non-word-sized numeric literals in the surface language [extended-literals] * Improved rewrite rule matching behavior, allowing limited matching of higher-order patterns * Better support for user-defined warnings by way of the `WARNING` pragma [warnings] * The introduction of the new `GHC.TypeError.Unsatisfiable` constraint, allowing more predictable user-defined type errors [unsatisfiable] * Implementation of the export deprecation proposal, allowing module exports to be marked with `DEPRECATE` pragmas [deprecated-exports] * The addition of build semaphore support for parallel compilation; with coming support in `cabal-install` this will allow better use of parallelism in multi-package builds [jsem] * More efficient representation of info table provenance information, reducing binary sizes by over 50% in some cases when `-finfo-table-map` is in use A full accounting of changes can be found in the [release notes]. This alpha includes roughly a dozen changes relative to alpha 2, including what we believe should be nearly the last changes to GHC's boot libraries. We would like to thank GitHub, IOG, the Zw3rk stake pool, Well-Typed, Tweag I/O, Serokell, Equinix, SimSpace, the 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, ~ Ben [TypeAbstractions]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0425-d… [extended-literals]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0451-s… [unsatisfiable]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0433-u… [warnings]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0541-w… [deprecated-exports]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0134-d… [jsem]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0540-j… [release notes]: https://downloads.haskell.org/ghc/9.8.1-alpha3/docs/users_guide/9.8.1-notes…

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[ANNOUNCE] GHC 9.8.1-alpha2 is now available
by Ben Gamari 23 Aug '23

23 Aug '23

The GHC developers are very pleased to announce the availability of the second alpha prerelease of GHC 9.8.1. Binary distributions, source distributions, and documentation are available at https://downloads.haskell.org/ghc/9.8.1-alpha2 GHC 9.8 will bring a number of new features and improvements, including: * Preliminary support the `TypeApplications` language extension [type-binders], allowing types to be bound in type declarations. * Support for the `ExtendedLiterals` extension, providing syntax for non-word-sized numeric literals in the surface language [extended-literals] * Improved rewrite rule matching behavior, allowing limited matching of higher-order patterns * Better support for user-defined warnings by way of the `WARNING` pragma [warnings] * The introduction of the new `GHC.TypeError.Unsatisfiable` constraint, allowing more predictable user-defined type errors [unsatisfiable] * Implementation of the export deprecation proposal, allowing module exports to be marked with `DEPRECATE` pragmas [deprecated-exports] * The addition of build semaphore support for parallel compilation; with coming support in `cabal-install` this will allow better use of parallelism in multi-package builds [jsem] * More efficient representation of info table provenance information, reducing binary sizes by over 50% in some cases when `-finfo-table-map` is in use A full accounting of changes can be found in the [release notes]. This alpha includes around two dozen bug-fixes relative to alpha 1. We would like to thank GitHub, IOG, the Zw3rk stake pool, Well-Typed, Tweag I/O, Serokell, Equinix, SimSpace, the 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, ~ Ben [type-binders]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0425-d… [extended-literals]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0451-s… [unsatisfiable]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0433-u… [warnings]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0541-w… [deprecated-exports]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0134-d… [jsem]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0540-j… [release notes]: https://downloads.haskell.org/ghc/9.8.1-alpha2/docs/users_guide/9.8.1-notes… [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new

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Re: [Haskell-cafe] Can I get 'forall (a :: k). Typeable a => Dict (Typeable k)'?
by Ryan Scott 23 Aug '23

23 Aug '23

To respond to your original point: > Morally I think that > > class Typeable (a :: k) > > should have been > > class Typeable k => Typeable (a :: k) > > This has been considered before, although it is not entirely straightforward to implement. See [1] and [2], which track the idea of having GHC solve these constraints automatically, without the need for users to explicitly reach for `typeRepKind`. Best, Ryan ----- [1] https://gitlab.haskell.org/ghc/ghc/-/issues/14190 [2] https://gitlab.haskell.org/ghc/ghc/-/issues/16627

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Can I get 'forall (a :: k). Typeable a => Dict (Typeable k)'?
by Tom Ellis 23 Aug '23

23 Aug '23

Morally I think that class Typeable (a :: k) should have been class Typeable k => Typeable (a :: k) If I'm wrong, could someone please elaborate why? If I'm right, please read on ... That would be a breaking change, but could we at least get kindable :: forall (a :: k). Typeable a => Dict (Typable (a :: k)) in the meantime? Tom

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