April 2023 - Glasgow-haskell-users

[Haskell] [ANNOUNCE] GHC 9.4.5 released
by Zubin Duggal 18 Apr '23

18 Apr '23

The GHC developers are happy to announce the availability of GHC 9.4.5. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org](https://downloads.haskell.org/ghc/9.4.5). Download Page: https://www.haskell.org/ghc/download_ghc_9.4.5.html Blog Post: https://www.haskell.org/ghc/blog/20230418-ghc-9.4.5-released.html This release is primarily a bugfix release addressing a few issues found in 9.4.4. These include: * Fixes for a number of bug fixes in the simplifier (#22623, #22718, #22913, 22695, #23184, #22998, #22662, #22725). * Many bug fixes to the non-moving and parallel GCs (#22264, #22327, #22926, #22927, #22929, #22930, #17574, #21840, #22528) * A fix a bug with the alignment of RTS data structures that could result in segfaults when compiled with high optimisation settings on certain platforms (#22975 , #22965). * Bumping `gmp-tarballs` to a version which doesn't use the reserved `x18` register on AArch64/Darwin systems, and also has fixes for CVE-2021-43618 (#22497, #22789). * A number of improvements to recompilation avoidance with multiple home units (#22675, #22677, #22669, #22678, #22679, #22680) * Fixes for regressions in the typechecker and constraint solver (#22647, #23134, #22516, #22743) * Easier installation of binary distribution on MacOS platforms by changing the installation Makefile to remove the quarantine attribute when installing. * ... and many 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 [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new [release notes]: https://downloads.haskell.org/~ghc/9.4.5/docs/html/users_guide/9.4.5-notes.…

1 0

Pattern Synonym decls only at top level
by Anthony Clayden 18 Apr '23

18 Apr '23

" Pattern synonym declarations can only occur in the top level of a module. In particular, they are not allowed as local definitions. " says the User Guide. And the 2016 paper says likewise. But there's no explanation why. PattSyns are not necessarily declared in the same module as the underlying Datatype, so there can be a region of scope with the data constructor but without the PattSyn. If PattSyns are declared in the same module as their datatype, you can export the PattSyns but not the data constructors -- indeed that's a common way to keep the Datatype implementation abstract. Or (unusually) you can export the data constructors but not PattSyns. So there seems to be no close tie-up of Datatype/constructors and PattSyns. Then why couldn't a PattSyn be declared in local scope only? The builder function behind a PattSyn is just like any other function, so could be local(?) The paper's Implementation section 7 says the matcher also is an "ordinary function". Relatedly, PattSyns can in effect be overloaded: define the PattSyn in terms of a ViewPattern function. That can be a method of some class. Then why not more directly declare PattSyns within a class? [I have a feeling I answered a similar question on some forum, saying the PattSyn has to follow around its data constructors, like a dog on a lead. Can't find that now. If that was me, I apologise and withdraw.] AntC

1 0

[ANNOUNCE] GHC 9.6.1 is now available
by Ben Gamari 02 Apr '23

02 Apr '23

The GHC team is very pleased to announce the availability of GHC 9.6.1. As usual, binaries and source distributions are available at downloads.haskell.org: https://downloads.haskell.org/ghc/9.6.1/ Beginning with GHC 9.6.1, GHC can be built as a cross-compiler to WebAssembly and JavaScript. This is an important step towards robust support for compiling Haskell to the Web, but there are a few caveats to be aware of in the 9.6 series: - Both the Javascript and WebAssembly backends are still at an early stage of development and are present in this release as a technology preview - Using GHC as a cross-compiler is not as easy as we would like it to be; in particular, there are challenges related to Template Haskell - GHC is not yet run-time retargetable; a given GHC binary targets exactly one platform, and both WebAssembly and JavaScript are considered platforms for this purpose. Cross-compilers must be built from source by their users We hope to lift all of these limitations in future releases. Additionally, 9.6.1 includes: - Significant latency improvements in the non-moving garbage collector - Efficient runtime support for delimited continuations - Improvements in compiler error messages - Numerous improvements in the compiler's memory usage See the [release notes] for a comprehensive accounting of changes in this release. As always, one can find a migration guide to aid in transitioning from older releases on the [GHC Wiki][migration-guide]. We have also recently started extending our release process to cover a wider set of Linux distributions. In particular, we now offer Rocky 8 and Ubuntu 20.04 binary distributions which cover RedHat-derivative and distributions using older glibc releases (namely 2.27), respectively. Thanks to everyone who has contributed code, documentation, testing, and tickets to this release process. As this release represents upstream GHC's first step towards supporting web targets, we are very excited to have this release out the door! Cheers, - Ben [ticket]: https://gitlab.haskell.org/ghc/ghc/issues/ [migration-guide]: https://gitlab.haskell.org/ghc/ghc/-/wikis/migration/9.6 [release notes]: https://downloads.haskell.org/ghc/9.6.1/docs/users_guide/9.6.1-notes.html

2 1