August 2018 - Glasgow-haskell-users

[ANNOUNCE] GHC 8.6.1-beta1 available
by Ben Gamari 11 Sep '18

11 Sep '18

Hello everyone, The GHC development team is very pleased to announce the first beta leading up to GHC 8.6.1 release. The usual release artifacts are available from https://downloads.haskell.org/~ghc/8.6.1-beta1 This beta fixes most of the bugs reported in the first two alphas and brings all of the core libraries up to their final release versions. The 8.6 release fixes over 300 bugs from the 8.4 series and introduces a number of exciting features. These most notably include: * Significantly better handling of macOS linker command size limits, avoiding linker errors while linking large projects * A new deriving mechanism, `deriving via`, providing a convenient way for users to extend Haskell's typeclass deriving mechanism * Quantified constraints, allowing forall quantification in contexts * An early version of the GHCi `:doc` command * The `ghc-heap-view` package, allowing introspection into the structure of GHC's heap * Valid hole fit hints, helping the user to find terms to fill typed holes in their programs * The BlockArguments extension, allowing the `$` operator to be omitted in some unambiguous contexts * The next phase of the MonadFail proposal, enabling -XMonadFailDesugaring by default A full list of the changes in this release can be found in the release notes: https://downloads.haskell.org/~ghc/8.6.1-beta1/docs/html/users_guide/8.6.1-… This will very likely be the last release before the final 8.6.1 so do give it a thorough testing and, as always, report any issues you encounter. Thanks for your help! Cheers, - Ben

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Fwd: Unable to compile ghc-8.2.2 with ghc-8.4.3
by Sven Panne 01 Sep '18

01 Sep '18

Am Fr., 31. Aug. 2018 um 11:11 Uhr schrieb Sam Halliday < sam.halliday(a)gmail.com>: > [...] It would make a lot of sense for the > "unregistered" sources to be made available as an optional download > alongside the source code, if haskell.org were open to that > possibility. IIRC, the generated C code is *not* platform-independent, at least that is what I remember from ancient times. Perhaps I'm wrong and/or this has changed, but if this is really the case, you would need an additional download per target platform. Cheers, S.

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Unable to compile ghc-8.2.2 with ghc-8.4.3
by Sam Halliday 31 Aug '18

31 Aug '18

Hello all, I am unable to compile ghc-8.2.2 with ghc-8.4.3 (which is otherwise working fine, e.g. to compile my own projects and xmonad). Could somebody please help? The error I get is ghc-cabal: Encountered missing dependencies: base >=4.4.1 && <4.11 libraries/hpc/ghc.mk:3: libraries/hpc/dist-boot/package-data.mk: No such file or directory make[1]: *** [libraries/hpc/ghc.mk:3: libraries/hpc/dist-boot/package-data.mk] Error 1 make: *** [Makefile:123: all] Error 2 I should give some background as to why I'm doing this: I am trying to build a back catalogue of ghc installations because the older binary downloads from haskell.org give me linking errors and I've lost faith in Archlinux's ability to package ghc. I plan on using these builds of ghc in stack, instead of their binaries. I don't like downloading binaries. I'd rather build them from source. I will also create a docker image for my own CI purposes. I'm using this script, but it's just a formalisation of the ghc installation instructions to help me automate the process. https://gitlab.com/fommil/ghc-env/blob/master/bin/ghc-env I am on Archlinux, which (I'm sure many of you know) has a very broken concept of ghc. I already lost 2 hours today because Archlinux broke my ~/.ghc, and therefore xmonad was unable to start and this locked me out of my desktop. I plan on using NixOS in the future. From a fresh OS install I do pacman -S ghc-static cabal-install to get me ghc 8.4.3 and the cabal CLI. From here I download and compile ghc 8.4.3 and cabal-install with ghc-env compile 8.4.3 cabal install cabal-install xmonad xmonad-contrib and now I can delete Arch's versions of ghc (yay!). But from here, if I try to compile ghc 8.2.2 (with a view to compile all the way back to the 7.x series) I get the failure at the top. An alternative solution would be if there were instructions for a fabled "phase0" compile, which doesn't require a ghc bootstrap. Does anybody know anything about that? Best regards, Sam

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Constructor as outermost match in RULE under GHC 8.2.2 & 8.4.3
by Conal Elliott 04 Aug '18

04 Aug '18

GHC 8.2.2 and 8.4.3 dislike the following rules: ``` haskell {-# RULES "pair fst snd" forall p. (,) (exl p) (exr p) = p "swap" forall p. (,) (exr p) (exl p) = swap p #-} ``` Error messages: ``` haskell /Users/conal/Haskell/concat/plugin/src/ConCat/Rebox.hs:485:1: warning: A constructor, (,), appears as outermost match in RULE lhs. This rule will be ignored. | 485 | "pair fst snd" forall p. (,) (exl p) (exr p) = p | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ /Users/conal/Haskell/concat/plugin/src/ConCat/Rebox.hs:489:1: warning: A constructor, (,), appears as outermost match in RULE lhs. This rule will be ignored. | 489 | "swap" forall p. (,) (exr p) (exl p) = swap p | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ``` GHC 8.0.2 didn't complain about these rules, though I'm unsure whether they worked as desired. Why disallow such rules (with constructors at the head)? -- Conal

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