- ghc-devs - Haskell.org

Searching on GitLab
by Richard Eisenberg 07 Nov '20

07 Nov '20

Hi all, Some time ago, I set up a keyword bookmark (https://www-archive.mozilla.org/docs/end-user/keywords.html <https://www-archive.mozilla.org/docs/end-user/keywords.html>) to search in tickets and MRs, by using a Google "site:gitlab.haskell.org/ghc/ghc/issues/ <http://gitlab.haskell.org/ghc/ghc/issues/> %s" query. About a year ago, I noticed that the quality of results decreased to the point of uselessness, and I started to use GitLab's built-in search. This works fine, but it's not as good as Google's. Today, I discovered why the quality went down: GitLab changed its URLs. Previously, a ticket lived at e.g. gitlab.haskell.org/ghc/ghc/issues/1234 <http://gitlab.haskell.org/ghc/ghc/issues/1234>. Today, it lives at gitlab.haskell.org/ghc/ghc/-/issues/1234 <http://gitlab.haskell.org/ghc/ghc/-/issues/1234>. GitLab automatically redirects from the former to the latter, so old links/bookmarks still work great. But Google's search doesn't! The solution was easy: just update my keyword bookmarks to include the extra /-. Better search results, cooked up fresh. Perhaps you want some, too -- hence this email. Enjoy, Richard

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Re: Status of #10071 (class method deprecations)
by Richard Eisenberg 06 Nov '20

06 Nov '20

My take (not authoritative) is that some good ideas were floated, but nothing was decided on. Given that we now have a proper process for deciding on new features, I think we should use it, and go via a proposal. Note that I've fixed the link in the original description to point to https://gitlab.haskell.org/ghc/ghc/-/wikis/design/deprecation-mechanisms/ty… Richard > On Nov 6, 2020, at 1:22 AM, Fumiaki Kinoshita <fumiexcel(a)gmail.com> wrote: > > I stumbled upon a case where I want to deprecate a class method in favour of another (https://github.com/fumieval/witherable/pull/68 <https://github.com/fumieval/witherable/pull/68>), which reminded me of some discussion around Monad-of-no-return proposal. > > There seems to be an old ticket, but I'm not sure what the status is -- > is this approved and waiting for implementation, or something which needs to be resubmitted to ghc-proposals? > https://gitlab.haskell.org/ghc/ghc/-/issues/10071 <https://gitlab.haskell.org/ghc/ghc/-/issues/10071> > _______________________________________________ > ghc-devs mailing list > ghc-devs(a)haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs

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Announcing the Haskell Foundation
by Richard Eisenberg 04 Nov '20

04 Nov '20

I'm very pleased to announce the creation of the Haskell Foundation (HF), an independent, non-profit organisation dedicated to broadening Haskell adoption. Website: https://haskell.foundation/ <https://haskell.foundation/> Twitter: @haskellfound Founding whitepaper: https://haskell.foundation/whitepaper/ <https://haskell.foundation/whitepaper/> Simon Peyton Jones's announcement, with lots of Q&A: https://www.youtube.com/watch?v=MEmRarBL9kw <https://www.youtube.com/watch?v=MEmRarBL9kw> The "official" ask-me-anything on Reddit: https://www.reddit.com/r/haskell/comments/jnwg7i/haskell_foundation_ama/ <https://www.reddit.com/r/haskell/comments/jnwg7i/haskell_foundation_ama/> Mailing list for future HF announcements: https://mail.haskell.org/cgi-bin/mailman/listinfo/hf-announce <https://mail.haskell.org/cgi-bin/mailman/listinfo/hf-announce> Mailing list for HF discussion / involvement: https://mail.haskell.org/cgi-bin/mailman/listinfo/hf-discuss <https://mail.haskell.org/cgi-bin/mailman/listinfo/hf-discuss> Please join the conversation. We need your participation to realize the vision of the foundation as *our* foundation, not *their* foundation. Looking forward to seeing where this all leads! Richard

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Re: msys woes
by Shayne Fletcher 04 Nov '20

04 Nov '20

On Sun, Nov 1, 2020 at 12:44 PM Ben Gamari <bgamari(a)gmail.com> wrote: > Shayne Fletcher <shayne.fletcher.50(a)gmail.com> writes: > > > On Thu, Oct 8, 2020 at 1:18 PM Phyx <lonetiger(a)gmail.com> wrote: > > > >> From the looks of it the repo.msys2.org system doesn't have enough > space > >> to restore all these old packages. > >> > >> So we'll have to handle it on our end. The easiest way to get your > builds > >> working again is by applying a patch with the fix to the source tree. > >> > >> > > New problems in this space as of today. This time with > > ```bash > > > > stack --stack-yaml stack.yaml --resolver nightly-2020-01-08 exec -- > > pacman -S autoconf automake-wrapper make patch python tar mintty > > --noconfirm > > ``` > > > > which produces 404 errors > > Oh dear; thank you for raising this with upstream, Shayne! Let's hope > there is action soon. > > After looking into it a bit, I'm beginning to think that it is in fact on us (stack as it happens) to upgrade our msys installer. I have a workaround for now: ``` stack exec -- curl -O http://repo.msys2.org/msys/x86_64/msys2-keyring-r21.b39fb11-1-any.pkg.tar.xz stack exec -- pacman -U msys2-keyring-r21.b39fb11-1-any.pkg.tar.xz --noconfirm stack exec -- pacman -Syu autoconf automake-wrapper make patch python tar mintty --noconfirm" ``` -- Shayne Fletcher

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Tomorrow: Simon PJ announces Haskell Foundation
by Richard Eisenberg 03 Nov '20

03 Nov '20

Tomorrow (Wednesday Nov 4) at 12:00 UTC, Simon PJ will announce the formation of the Haskell Foundation, an independent, non-profit organization dedicated to broadening Haskell adoption. This will be a part of Haskell eXchange, but this announcement will be free to attend, via YouTube. Much of the presentation will be time for Q&A; questions can be posed both within the Haskell eXchange HopIn platform and via comments on YouTube. Attend at https://youtu.be/MEmRarBL9kw <https://youtu.be/MEmRarBL9kw> Just to forestall any disappointment: I won't be answering any questions here until at least after the announcement -- but do please come and ask questions there and afterwards. Richard

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Re: msys woes
by Shayne Fletcher 01 Nov '20

01 Nov '20

On Thu, Oct 8, 2020 at 1:18 PM Phyx <lonetiger(a)gmail.com> wrote: > From the looks of it the repo.msys2.org system doesn't have enough space > to restore all these old packages. > > So we'll have to handle it on our end. The easiest way to get your builds > working again is by applying a patch with the fix to the source tree. > > New problems in this space as of today. This time with ```bash stack --stack-yaml stack.yaml --resolver nightly-2020-01-08 exec -- pacman -S autoconf automake-wrapper make patch python tar mintty --noconfirm ``` which produces 404 errors ``` 2020-11-01T16:02:47.2564782Z :: Retrieving packages... 2020-11-01T16:02:49.0237771Z error: failed retrieving file 'diffutils-3.6-1-x86_64.pkg.tar.xz' from repo.msys2.org : The requested URL returned error: 404 2020-11-01T16:02:49.3752086Z error: failed retrieving file 'diffutils-3.6-1-x86_64.pkg.tar.xz' from downloads.sourceforge.net : The requested URL returned error: 404 2020-11-01T16:02:49.8476086Z error: failed retrieving file 'diffutils-3.6-1-x86_64.pkg.tar.xz' from www2.futureware.at : The requested URL returned error: 404 2020-11-01T16:02:49.8482030Z warning: failed to retrieve some files 2020-11-01T16:02:51.2288388Z error: failed retrieving file 'autoconf-2.69-3-any.pkg.tar.xz' from repo.msys2.org : The requested URL returned error: 404 2020-11-01T16:02:51.3674499Z error: failed retrieving file 'autoconf-2.69-3-any.pkg.tar.xz' from downloads.sourceforge.net : The requested URL returned error: 404 2020-11-01T16:02:51.4787091Z error: failed retrieving file 'autoconf-2.69-3-any.pkg.tar.xz' from www2.futureware.at : The requested URL returned error: 404 2020-11-01T16:02:51.4791763Z warning: failed to retrieve some files ... ``` I've raised https://github.com/msys2/MSYS2-packages/issues/2225 with msys2. -- Shayne Fletcher

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GitLab down
by Ben Gamari 26 Oct '20

26 Oct '20

Hi all, GitLab will be down for a bit while I do a bit of maintenance. Cheers, - Ben

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GHC's internal confusion about Ints and Words
by Moritz Angermann 22 Oct '20

22 Oct '20

Hi there! So there is a procedure calling convention that for reasons I did not fully understand, but seem to be historically grown, uses packed arguments for those that are spilled onto the stack. On top of that, CInt is 32bit, Word is 64bits. This provides the following spectacle: While we know in STG that the CInt is 32bits wide, when lowered into Cmm, it's represented as I64 in the arguments to the C function. Thus packing based on the format of the Cmm type would yield 8 bytes. And now, all further packed arguments have the wrong offset (by four). Specifically in GHC.Cmm.Utils we find: primRepCmmType :: Platform -> PrimRep -> CmmType primRepCmmType platform IntRep = bWord platform mkIntCLit :: Platform -> Int -> CmmLit mkIntCLit platform i = CmmInt (toInteger i) (wordWidth platform) The naive idea to just fix this and make them return cIntWidth instead, seemingly produces the correct Cmm expressions at a local level, but produces a broken compiler. A second approach could be to extend the Hints into providing sizes, and using those during the foreign call generation to pack spilled arguments. This however appears to be more of a patching up of some fundamental underlying issue, instead of rectifying it properly. Maybe I'll have to go down the Hint path, it does however break current Eq assumptions, as they are sized now, and what was equal before, is only equal now if they represent the same size. >From a cursory glance at the issues with naively fixing the width for Int, it seems that GHC internally assumes sizeof(Int) = sizeof(Word). Maybe there is a whole level of HsInt vs CInt discrimination missing? Cheers, Moritz

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GitLab e-mails: down for everyone, or just me?
by Ryan Scott 22 Oct '20

22 Oct '20

Since yesterday, I haven't been receiving any e-mail notifications from GitLab. Are other people having this problem too, or is it a problem on my end? Ryan S.

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Fwd: Restricted sums in BoxedRep
by David Feuer 15 Oct '20

15 Oct '20

Forwarded from Andrew Martin below. I think we want more than just Maybe (more than one null), but the nesting I described is certainly more convenience than necessity. ---------- Forwarded message --------- From: Andrew Martin <andrew.thaddeus(a)gmail.com> Date: Wed, Oct 14, 2020, 4:14 PM Subject: Re: Restricted sums in BoxedRep To: David Feuer <david.feuer(a)gmail.com> You'll have to forward this to the ghc-devs list to share it with others since I'm not currently subscribed to it, but I've had this same thought before. It is discussed at https://github.com/andrewthad/impure-containers/issues/12. Here's the relevant excerpt: > Relatedly, I was thinking the other day that after finishing implementing > https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0203-p…, > I should really look at seeing if it's possible to add this > maybe-of-a-lifted value trick straight to GHC. I think that with: > > data RuntimpRep > = BoxedRep Levity > | MaybeBoxedRep Levity > | IntRep > | ... > > data BuiltinMaybe :: forall (v :: Levity). TYPE v -> TYPE ('MaybeBoxedRep v) > > This doesn't have the nesting issues because the kind system prevents > nesting. But anyway, back to the original question. I would recommend not > using Maybe.Unsafe and using unpacked-maybe instead. The latter is > definitely safe, and it only costs an extra machine word of space in each > data constructor it gets used in, and it doesn't introduce more > indirections. > On Tue, Oct 13, 2020 at 5:47 PM David Feuer <david.feuer(a)gmail.com> wrote: > Null pointers are widely known to be a lousy language feature in general, > but there are certain situations where they're *really* useful for compact > representation. For example, we define > > newtype TMVar a = TMVar (TVar (Maybe a)) > > We don't, however, actually use the fact that (Maybe a) is lifted. So we > could represent this much more efficiently using something like > > newtype TMVar a = TMVar (TVar a) > > where Nothing is represented by a distinguished "null" pointer. > > While it's possible to implement this sort of thing in user code (with > lots of fuss and care), it's not very nice at all. What I'd really like to > be able to do is represent certain kinds of sums like this natively. > > Now that we're getting BoxedRep, I think we can probably make it happen. > The trick is to add a special Levity constructor representing sums of > particular shapes. Specifically, we can represent a type like this if it is > a possibly-nested sum which, when flattened into a single sum, consists of > some number of nullary tuples and at most one Lifted or Unlifted type. > Then we can have (inline) primops to convert between the BoxedRep and the > sum-of-sums representations. > > Anyone have thoughts on details for what the Levity constructor arguments > might look like? > -- -Andrew Thaddeus Martin

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