- Haskell-Cafe - Haskell.org

Twitter-conduit author not responding
by Corentin Dupont 12 Oct '19

12 Oct '19

Hi community, I have a small problem with the "Twitter-conduit" package: https://github.com/himura/twitter-conduit Their are several opened issues and pull requests, in particular the Twitter API changed so the package is relatively broken. I mailed the author some month ago, without response. What is the recommended course of action? Regards Corentin

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[TFP'20] one month left for pre-symposium submissions for Trends in Functional Programming 2020, 13-14 February, Krakow, Poland
by Peter Achten 11 Oct '19

11 Oct '19

------------------------------------------------------------------------- Second call for papers 21st Symposium on Trends in Functional Programming tfp2020.org ------------------------------------------------------------------------- The symposium on Trends in Functional Programming (TFP) is an international forum for researchers with interests in all aspects of functional programming, taking a broad view of current and future trends in the area. It aspires to be a lively environment for presenting the latest research results, and other contributions. * TFP is moving to new winter dates, to provide an FP forum in between the annual ICFP events. * TFP offers a supportive reviewing process designed to help less experienced authors succeed, with two rounds of review, both before and after the symposium itself. Authors have an opportunity to address reviewers' concerns before final decisions on publication in the proceedings. * TFP offers two "best paper" awards, the John McCarthy award for best paper, and the David Turner award for best student paper. * This year we are particularly excited to co-locate with Lambda Days in beautiful Krakow. Lambda Days is a vibrant developer conference with hundreds of attendees and a lively programme of talks on functional programming in practice. TFP will be held in the same venue, and participants will be able to session-hop between the two events. Important Dates --------------- Submission deadline for pre-symposium review: 15th November, 2019 Submission deadline for draft papers: 10th January, 2020 Symposium dates: 13-14th February, 2020 Visit tfp2020.org for more information.

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Hiring Using Opensource? - Haskell Community
by Alex Mesropians 10 Oct '19

10 Oct '19

Hey All, I wanted to grab your thoughts on hiring using opensource! I wanted to talk open source! Open Source issues is a new feature we have just launched on our platform Workshub <https://t.sidekickopen79.com/s1t/c/5/f18dQhb0S7lC8dDMPbW2n0x6l2B9nMJW7t5XZs…> and it’s going to make hiring even easier!Our one click GitHub integration allows you to share your companies open source issues,alongside your jobs and company profile. Once your issue are posted you can start to build a network of candidates that have a specific interest in your code base. You can also add a $ incentive to any or all of your issues if you want to reward Engineers for completing the work! Here are just a few of the benefits:- - 89% of Engineers on our site would prefer to join a company with active open source software: - Get contributions to real problems your tech team are trying to solve - Streamline the recruitment process and get to know how each candidate really works - Candidates are more likely to apply to roles at a company where they have already contributed to their code base - We will recommend your OS issues directly to our community You can find our more here! <https://t.sidekickopen79.com/s1t/c/5/f18dQhb0S7lC8dDMPbW2n0x6l2B9nMJW7t5XZs…> You can also see an example of how we are building our own OS community with contributions to our the WorksHub code base here <https://t.sidekickopen79.com/s1t/c/5/f18dQhb0S7lC8dDMPbW2n0x6l2B9nMJW7t5XZs…> ! Look forward to hearing your thoughts! thanks, -- [image: Functional Works] <https://t.sidekickopen79.com/s1t/c/5/f18dQhb0S7lC8dDMPbW2n0x6l2B9nMJW7t5XZs…> Alex Mesropians +447949853457 Founder [image: GitHub] <https://t.sidekickopen79.com/s1t/c/5/f18dQhb0S7lC8dDMPbW2n0x6l2B9nMJW7t5XZs…> [image: LinkedIn] <https://t.sidekickopen79.com/s1t/c/5/f18dQhb0S7lC8dDMPbW2n0x6l2B9nMJW7t5XZs…> [image: Twitter] <https://t.sidekickopen79.com/s1t/c/5/f18dQhb0S7lC8dDMPbW2n0x6l2B9nMJW7t5XZs…>

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Hedgehog: returning a list from `commandExecute` and getting to the items in an update function
by Magnus Therning 10 Oct '19

10 Oct '19

Hello, I'm trying to use Hedgehog to test a web app at work. Yesterday I ran into an issue with getting to the value returned from my `commandExecute` in an `Update` `Callback`. Basically my model looks like this ~~~ newtype State (v :: * -> *) = State (M.Map (Var UUID v) DataPerItem) deriving (Eq, Show) ~~~ and I have an action, `Command gen exec [Update update]` where ~~~ exec :: action -> m [UUID] ~~~ which results in ~~~ update :: State v -> action -> Var [UUID] v -> State v ~~~ AFAICS I need to, in order to actually update my model, turn that `Var [UUID] v` into `[Var UUID v]`. I've been staring at the functions in Hedgehog for a while now but nothing jumps out... or am I, once again, thinking about it all wrong? :) /M I also asked at stackoverflow: https://stackoverflow.com/questions/58157292/returning-a-list-and-getting-t… This is just to widen the net a bit... -- Magnus Therning OpenPGP: 0x927912051716CE39 email: magnus(a)therning.org twitter: magthe http://magnus.therning.org/ Ah, good taste! What a dreadful thing! Taste is the enemy of creativeness. — Pablo Picasso

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Re: [Haskell-cafe] Publish slides of talks in HIW 2019 (Or whom to ask about it)
by Yuji Yamamoto 07 Oct '19

07 Oct '19

Confirmed my profile and the link to the slides. Thanks! 2019年10月7日(月) 19:10 niki.vazou <niki.vazou(a)imdea.org>: > Hi Yuji, Richard, > > Yuji, I added the link to your lightning talk here: > https://icfp19.sigplan.org/home/hiw-2019#event-overview > > I did not collect links for the slides this year, but if more speakers > want to share their slides, will be happy to upload them. > > Best, > Niki > > > On 02.10.2019 10:59, Richard Eisenberg wrote: > > I have cc'd Niki Vazou, the chair of this year's HIW. She'll have the > > best answers. > > > > Richard > > > >> On Oct 2, 2019, at 2:39 AM, Yuji Yamamoto > >> <whosekiteneverfly(a)gmail.com> wrote: > >> > >> Hello Haskellers, > >> > >> I'm not sure where is the best place to ask about this, > >> so please tell me if there is better place. > >> > >> Does anyone know when the slides of HIW 2019 will be published in > >> the web site [1] like the last year's [2]? > >> I see some of the talks are "File Attached", but most of them are > >> not. > >> > >> In addition, can I attach the URL of my lightning talk slides > >> https://the.igreque.info/slides/2019-08-23-indexed-applicative.html > >> to the web site? > >> > >> According to the last year's page, some of the lightning talks are > >> also "File Attached" or "Media Attached". > >> > >> Thanks in advance! > >> > >> -- > >> > >> 山本悠滋 > >> twitter: https://twitter.com/igrep > >> GitHub: https://github.com/igrep > >> GitLab: https://gitlab.com/igrep > >> Facebook: http://www.facebook.com/igrep > >> _______________________________________________ > >> Haskell-Cafe mailing list > >> To (un)subscribe, modify options or view archives go to: > >> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe > >> Only members subscribed via the mailman list are allowed to post. > > > > > > > > Links: > > ------ > > [1] https://icfp19.sigplan.org/home/hiw-2019#program > > [2] https://icfp18.sigplan.org/track/hiw-2018-papers#event-overview > -- 山本悠滋 twitter: https://twitter.com/igrep GitHub: https://github.com/igrep GitLab: https://gitlab.com/igrep Facebook: http://www.facebook.com/igrep

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Problematic fixed "stack ghci" temporary script (parent) directory
by Viktor Dukhovni 06 Oct '19

06 Oct '19

When I run "stack ghci", an attempt is made to create a temporary directory named: /tmp/haskell-stack-ghci/<unique-subdir> in which various temporary artefacts are stored. The parent directory is created with permissions (0777 & ~umask). Security issues aside, this can't work reliably on a multi-user system. Does anyone know whether this is something peculiar to my FreeBSD setup, or a systemic issue with "stack ghci"? I don't see the same behaviour with "stack script", though if I create a script to run in "/tmp", then ghc is, somewhat unexpectely, executed with "-i/tmp/", which also has security implications... -- Viktor.

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hie + neovim + coc.nvim on NixOS
by Marc Busqué 05 Oct '19

05 Oct '19

Hi Cafe, this is an adapted version of a question I already posted on NixOS discussion forum, so far with no luck [1]: I’m trying to replicate the configuration from an article on a NixOS machine [2]. That’s, I’m trying to use hie on neovim, through coc.nvim, with NixOS as operating system. For now, I want it to work for a project which uses GHC 8.6.5 through Stack. So far I’ve been able to: - Install hie version for GHC 8.6.5: ``` let all-hies = import (fetchTarball "https://github.com/infinisil/all-hies/tarball/master") {}; in { environment.systemPackages = with pkgs; [ (all-hies.selection { selector = p: { inherit (p) ghc865; }; }) ]; ``` - Install neovim 4.x to have floating window feauture, which is only available in master, as far as I know: ``` let nixPkgsMaster = import (fetchTarball "https://github.com/NixOS/nixpkgs/tarball/master") {}; in { environment.systemPackages = with pkgs; [ nixPkgsMaster.neovim ]; } ``` - I configured coc.nvim [3] to use hie, together with `haskell-vim` plugin. I'm using Plug for this: ``` Plug 'neoclide/coc.nvim', { 'do': 'yarn install --frozen-lockfile' } Plug 'neovimhaskell/haskell-vim' ``` And I have configured coc.nvim as its documentation suggests [4]. - I found that having hie for GHC 8.6.5 was not enough and that I had to install manually the compiler for 8.6.5. I think it is needed in NixOS. If I’m wrong, please, tell me. So, I added `haskell.compiler.ghc865` in `environment.systemPackages`. - Besides, I have following haskell tools: `haskellPackages.hlint`, `haskellPackages.apply-refact` and `haskellPackages.hindent`. With all of that, hie is somehow working on neovim, but there are a lot of things missing. For example, one thing that is working is `:call CocAction('format')`. It also points me to some hlint warnings underlying their lines. However, there are a lot of functionalities missing. - Autocompletion is anything but intellisense. - I can’t quickfix hlint warnings. It says `[coc.nvim] No quickfix action available` - Trying to rename returns `[coc.nvim] Error on 'rename': rename: "HaRe: file not loaded for refactoring"` - It gives me no type information when I press K on a word (being K mapped as coc.nvim suggests) I think that my NixOS configuration is the culprit here, because I’m not too experienced with it and I see it needs to be very specific when configuring haskell. I’m wondering if I’m missing some extra haskell package. I tried with `haskell.packages.ghc865.hoogle` hoping it would make a difference in showing me types or documentation, but no luck here. Thanks for any insight you can give me. - [1] https://discourse.nixos.org/t/configuration-needed-for-haskell-ide-environm… - [2] http://marco-lopes.com/articles/Vim-and-Haskell-in-2019/ - [3] https://github.com/neoclide/coc.nvim - [4] https://github.com/neoclide/coc.nvim#example-vim-configuration Marc Busqué http://waiting-for-dev.github.io/about/

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Parametric polymorphism and promoted types
by Marcin Szamotulski 04 Oct '19

04 Oct '19

Hello Haskell Cafe, It seems that GHC has a trouble recognising that a variable of type `forall (x :: (a, b))` can be reduced to `forall ((u, v) :: (a, b))`. For example in the following snippet `unsafeCoerce` is unavoidable: ``` data P a = P data Proxy (p :: (a, b)) where Proxy :: P a -> P b -> Proxy '(a, b) both0 :: forall (s :: (a, b)). Proxy s both0 = unsafeCoerce (Proxy P P) ``` A slightly nicer solution can be written with type families: ``` type family Fst (p :: (a, b)) :: a where Fst '(x, y) = x type family Snd (p :: (a, b)) :: b where Snd '(x, y) = y data Dict (a :: k) (b :: k) where Dict :: a ~ b => Dict a b instance Category Dict where id = Dict Dict . Dict = Dict proof :: forall (s :: (a, b)). Dict s '(Fst s, Snd s) proof = unsafeCoerce Dict both1 :: forall (s :: (a, b)). Proxy s both1 = case proof :: Dict s '(Fst s, Snd s) of Dict -> Proxy P P ``` Did I missed how to avoid `unsafeCoerce` all together? Best regards, Marcin Szamotulski

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LGtk
by Seph Shewell Brockway 04 Oct '19

04 Oct '19

Does anyone know what happened to the LGtk project? I really like its declarative approach to writing GUIs, but it doesn’t seem to be being actively maintained. -- Seph Shewell Brockway, BSc MSc (Glas.) Pronouns: she/her

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Publish slides of talks in HIW 2019 (Or whom to ask about it)
by Yuji Yamamoto 02 Oct '19

02 Oct '19

Hello Haskellers, I'm not sure where is the best place to ask about this, so please tell me if there is better place. Does anyone know when the slides of HIW 2019 will be published in the web site <https://icfp19.sigplan.org/home/hiw-2019#program> like the last year's <https://icfp18.sigplan.org/track/hiw-2018-papers#event-overview>? I see some of the talks are "File Attached", but most of them are not. In addition, can I attach the URL of my lightning talk slides https://the.igreque.info/slides/2019-08-23-indexed-applicative.html to the web site? According to the last year's page, some of the lightning talks are also "File Attached" or "Media Attached". Thanks in advance! -- 山本悠滋 twitter: https://twitter.com/igrep GitHub: https://github.com/igrep GitLab: https://gitlab.com/igrep Facebook: http://www.facebook.com/igrep

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New book: Haskell from the Very Beginning
by John Whitington 01 Oct '19

01 Oct '19

Hello, I've prepared a new book "Haskell from the Very Beginning", which has now been published. A printed copy may be obtained from Amazon for $29.99: https://www.amazon.com/dp/095767113X/ (or your equivalent local Amazon) Alternatively, a PDF copy may be obtained for $19.99 from the book's website: https://www.haskellfromtheverybeginning.com Thanks to all those who have helped in recent weeks with useful comments on an earlier draft. And of course, thank-you for Haskell! Here's the blurb: In Haskell from the Very Beginning John Whitington takes a no-prerequisites approach to teaching the basics of a modern general-purpose programming language. Each small, self-contained chapter introduces a new topic, building until the reader can write quite substantial programs. There are plenty of questions and, crucially, worked answers and hints. Haskell from the Very Beginning will appeal both to new programmers, and to experienced programmers eager to explore functional languages such as Haskell. It is suitable both for formal use within an undergraduate or graduate curriculum, and for the interested amateur. Thanks, -- John Whitington Director, Coherent Graphics Ltd

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hackage issues
by Richard Senington 01 Oct '19

01 Oct '19

Hi list, I have been trying to set up an account on Hackage to upload a project. I have created the account, but cannot get in contact with trustees to enable uploading. My mail servers (a university server) says that it cannot deliver the messages. Can anyone advise or assist? Richard

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how to profile my code
by PICCA Frederic-Emmanuel 30 Sep '19

30 Sep '19

Hello, I would like to profile my code in order to find what is wrong with it. When I run it , I have a lot's of time took by the GC. 13,374,664,736 bytes allocated in the heap 16,149,779,248 bytes copied during GC 8,449,239,784 bytes maximum residency (617 sample(s)) 52,988,816 bytes maximum slop 15265 MB total memory in use (6808 MB lost due to fragmentation) Tot time (elapsed) Avg pause Max pause Gen 0 7281 colls, 7281 par 80.304s 3.389s 0.0005s 0.0279s Gen 1 617 colls, 616 par 2508.056s 105.538s 0.1711s 0.6128s Parallel GC work balance: 32.20% (serial 0%, perfect 100%) TASKS: 51 (1 bound, 50 peak workers (50 total), using -N24) SPARKS: 0 (0 converted, 0 overflowed, 0 dud, 0 GC'd, 0 fizzled) INIT time 0.013s ( 0.030s elapsed) MUT time 927.150s (101.039s elapsed) GC time 2349.743s ( 98.933s elapsed) RP time 0.000s ( 0.000s elapsed) PROF time 238.618s ( 9.993s elapsed) EXIT time 0.007s ( 0.001s elapsed) Total time 3515.531s (209.997s elapsed) Alloc rate 14,425,560 bytes per MUT second Productivity 26.4% of total user, 48.1% of total elapsed gc_alloc_block_sync: 524769 whitehole_spin: 2 gen[0].sync: 1375 gen[1].sync: 2139389 But If I use the Strict Extension in one of my file[1], this amount of time reduce drastically (the first run was done with a cold cache) This is why the MUT time is different. 13,364,299,032 bytes allocated in the heap 6,460,918,752 bytes copied during GC 8,423,062,112 bytes maximum residency (294 sample(s)) 55,571,872 bytes maximum slop 15265 MB total memory in use (6813 MB lost due to fragmentation) Tot time (elapsed) Avg pause Max pause Gen 0 7455 colls, 7455 par 54.623s 2.330s 0.0003s 0.0279s Gen 1 294 colls, 293 par 782.773s 33.293s 0.1132s 0.5003s Parallel GC work balance: 61.24% (serial 0%, perfect 100%) TASKS: 51 (1 bound, 50 peak workers (50 total), using -N24) SPARKS: 0 (0 converted, 0 overflowed, 0 dud, 0 GC'd, 0 fizzled) INIT time 0.013s ( 0.026s elapsed) MUT time 340.862s ( 64.620s elapsed) GC time 749.604s ( 31.920s elapsed) RP time 0.000s ( 0.000s elapsed) PROF time 87.791s ( 3.703s elapsed) EXIT time 0.011s ( 0.002s elapsed) Total time 1178.282s (100.271s elapsed) Alloc rate 39,207,331 bytes per MUT second Productivity 28.9% of total user, 64.4% of total elapsed gc_alloc_block_sync: 439663 whitehole_spin: 11 gen[0].sync: 922 gen[1].sync: 1129310 It is nice, but I would like to understand the real problem. I used hp2ps in order to monitor the memory usage, but my code is dominated by PINNED values (attached file) so I do not know where to start ? thanks for your advices. Frederic [1] https://repo.or.cz/hkl.git/blob/4cff5145d095683a40bc93cf8a0c0076f308244b:/c…

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Munich Haskell Meeting, 2019-09-30 @ 19:30
by Leah Neukirchen 27 Sep '19

27 Sep '19

Dear all, Next week, our monthly Munich Haskell Meeting will take place again on Monday, September 30 at Augustiner-Gaststätte Rumpler at 19h30. For details see here: http://muenchen.haskell.bayern/dates.html If you plan to join, please add yourself to this dudle so we can reserve enough seats! It is OK to add yourself to the dudle anonymously or pseudonymously. https://dudle.inf.tu-dresden.de/haskell-munich-sep-2019/ Everybody is welcome! cu, -- Leah Neukirchen <leah(a)vuxu.org> https://leahneukirchen.org/

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Stack overflow with ReadP
by Henry Laxen 25 Sep '19

25 Sep '19

Dear Haskell gurus, There has to be something very simple that I am misunderstanding here. I have tried sticking in trace statement, using the ghci debugger, but it just makes no sense to me. Please tell me what I am missing. Best wishes, Henry Laxen -------------------------------------------------------------------------------- module S where import Text.ParserCombinators.ReadP import Data.Char data Exp = Num Int | Add Exp Exp deriving (Eq, Show) expr :: ReadP Exp expr = do e <- (parseNumber +++ parseAdd) return e parseAdd :: ReadP Exp parseAdd = do e1 <- expr _ <- char '+' e2 <- expr return (Add e1 e2) parseNumber :: ReadP Exp parseNumber = do ds <- (munch1 isDigit) return . Num . read $ ds parse s = let parses = (readP_to_S expr) s in case parses of (p : _) -> fst (last parses) _ -> error "parse error" main = do print $ parse "1" λ> main *** Exception: stack overflow λ> parse "1+2" *** Exception: stack overflow -------------------------------------------------------------------------------- -- Nadine and Henry Laxen The rest is silence Villa Alta #6 Calle Gaviota #10 Never try to teach a pig to sing Chapala It wastes your time +52 (376) 765-3181 And it annoys the pig

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Foldable, Traversable and choosing an order
by Juan Casanova 25 Sep '19

25 Sep '19

Hello again, haskell-cafe. I was trying to implement the Unifiable typeclass from Control.Unification on one of my types, and did so fine, but then realized I needed a Traversable instance. So I thought about it, and concluded: Yes, my type definitely is Traversable, and I implemented Traversable. But then I realized I needed a Foldable instance for that. And then I wasn't so sure anymore. I *can* implement a Foldable instance, but it requires a choice of the order in which my structure is traversed that I don't really want to make? A.k.a: I can think of at least two different ways of implementing Foldable that would give different results if the function passed to foldr was not associative. So I looked online a bit, and it seems this is a topic people have talked about, but maybe not precisely in the context of the order. What I have gathered is that: yes, if a functor is Traversable, then there is at least one way to implement a Foldable in it. And I understand this, but then, I don't really grasp how that works in my specific case. Because my Traversable instance does not make a choice of this order (at least I think so), and I do need to make that choice to implement Foldable (at least I think so), and I don't see how the "default" implementation of foldMap in terms of traverse makes that choice. But the choice must be made somewhere if it is made in the Foldable. So what is going on? Of course, here's the code. My types: data SOTermPF fn p f = ConstF fn | Proj Int | CompF p [f] deriving Eq newtype SOTermF fn f = SOF (SOTermPF fn f f) deriving Eq My Traversable instance (with comments on intermediate types because otherwise it can get pretty obscure): instance Traversable (SOTermF fn) where traverse f (SOF (ConstF c)) = pure (SOF (ConstF c)) traverse f (SOF (Proj idx)) = pure (SOF (Proj idx)) -- f g :: f b -- map f sargs = [f b] -- CompF :: a -> ([a] -> SOTermPF fn p a) -- (\h -> \ts -> SOF (CompF h ts)) :: ([a] -> SOTermF fn a) -- fmap (\h -> \ts -> SOF (CompF h ts)) (f g) :: f ([b] -> SOTermF fn b) -- traverse :: (aa -> ff bb) -> [aa] -> ff [bb] -- traverse :: (f b -> f b) -> [f b] -> f [b] -- ((fmap (\h -> \ts -> SOF (CompF h ts)) (f g)) <*>) :: f [b] -> f (SOTermF fn b) -- traverse id (map f sargs) :: f [b] -- (fmap (\h -> \ts -> SOF (CompF h ts)) (f g)) <*> (traverse id (map f sargs)) :: f (SOTermF fn b) traverse f (SOF (CompF g sargs)) = (fmap (\h -> \ts -> SOF (CompF h ts)) (f g)) <*> (traverse id (map f sargs)) But to implement Foldable I need to choose an order because in the case where I do have elements under the functor (CompF), I have them in two shapes: The "head" and the "arguments" (the p and the [f] in CompF p [f]). So, of course, the arguments are traversed in the order of the list, but the order that I need to choose is: Do I apply the head first and the arguments later or do I apply the arguments first and the head later? But my traverse seems so natural. Am I making that choice there? Maybe if I made the fmap over the arguments (while traversing the list) instead of over the head, and then did a flipped application of <*>? Does that mean my traverse instance has implicitly assumed that the head will be done first? All of this is really out of curiosity and making sure I know what I'm doing: I will not use foldr on my structure and I'm pretty sure that the traversal that Control.Unification needs is associative. But I don't like seeing arbitrary choices appear out of nowhere in my code, I want to make sure of why I made them. :P Thanks in advance, Juan. -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336.

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JOB | Web Architect (London, UK)
by James Tobin 25 Sep '19

25 Sep '19

Hello, I'm working with an employer that is looking to hire a permanent front end architect to join their London office. You should have experience with Javascript and frameworks such as (but not only) React. Consequently, I had hoped that some members of this mailing list may like to discuss further off-list using "JamesBTobin (at) Gmail (dot) Com". Kind regards, James

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ANN: network 3.1.1.0
by Evan Borden 23 Sep '19

23 Sep '19

I'm happy to announce the release of network 3.1.1.0. http://hackage.haskell.org/package/network-3.1.1.0 Changes: - A new API: gracefulClose. #417 <https://github.com/haskell/network/pull/417> Also see Kazu's blog post on the design choices in this function https://kazu-yamamoto.hatenablog.jp/entry/2019/09/20/165939 - touchSocket, unsafeFdSocket: Allow direct access to a socket's file descriptor while providing tools to prevent it from being garbage collected. This also deprecated fdSocket in favor of unsafeFdSocket and withFdSocket. #423 <https://github.com/haskell/network/pull/423> - socketToFd: Duplicates a socket as a file descriptor and closes the source socket. #424 <https://github.com/haskell/network/pull/424> As always thank you to network's contributors.

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FMBC 2019 Call for Participation - Porto (Portugal), October 11
by Bruno Bernardo 23 Sep '19

23 Sep '19

[Please accept our apologies for duplicates.] ===================================================== Call for Participation 1st Workshop on Formal Methods for Blockchains (FMBC) 2019 https://sites.google.com/view/fmbc/home Porto, Portugal, October 11 Part of the 3rd World Congress on Formal Methods http://formalmethods2019.inesctec.pt/ ===================================================== About FMBC ---------------- Blockchains are decentralized transactional ledgers that rely on cryptographic hash functions for guaranteeing the integrity of the stored data. Participants on the network reach agreement on what valid transactions are through consensus algorithms. Blockchains may also provide support for Smart Contracts. Smart Contracts are scripts of an ad-hoc programming language that are stored in the blockchain and that run on the network. They can interact with the ledger’s data and update its state. These scripts can express the logic of possibly complex contracts between users of the blockchain. Thus, Smart Contracts can facilitate the economic activity of blockchain participants. With the emergence and increasing popularity of cryptocurrencies such as Bitcoin and Ethereum, it is now of utmost importance to have strong guarantees of the behavior of blockchain so ware. These guarantees can be brought by using Formal Methods. Indeed, Blockchain software encompasses many topics of computer science where using Formal Methods techniques and tools are relevant: consensus algorithms to ensure the liveness and the security of the data on the chain, programming languages specifically designed to write smart contracts, cryptographic protocols, such as zero-knowledge proofs, used to ensure privacy, etc. This workshop is a forum to identify theoretical and practical approaches of formal methods for blockchain technology. Topics include, but are not limited to: * Design and implementation of Smar Contract languages * Formal models of blockchain applications or concepts * Formal methods for consensus protocols * Formal methods for blockchain-specific cryptographic primitives or protocols * Formal languages for Smart Contracts * Verification of Smart Contracts Invited Speaker -------------------- Ilya Sergey (Yale-NUS College / NUS School of Computing) Contributed papers -------------------------- See the workshop program at: https://sites.google.com/view/fmbc/program Registration ---------------- Registration is shared for all FM events: http://formalmethods2019.inesctec.pt/?page_id=2363 Attending ------------- See the FM webpage at: http://formalmethods2019.inesctec.pt/?page_id=140 Contact ---------- mailto:fmbc19@easychair.org

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Re: [Haskell-cafe] How are we helping? Climate Strike / Earth Strike fri 20, fri 27
by Olaf Klinke 22 Sep '19

22 Sep '19

Haskeller working in the renewable energy sector here. Richard O'Keefe has good points, it is hard for the average programmer to have a real impact on climate change. Power consumption of computing equipment, though, is indeed a huge part of our electricity usage, so any progress will be very welcome in this sector. Ask your cloud computing vendor where the data center sources its power. <shameless advertising> It ought to look like this. [*] </shameless advertising> My suggestion is to help make renewables the cheapest power source in the market. It already is in some countries, and both China and India are investing massively in wind and solar power, not beause of morale, but beause it is cheap. So go ahead and develop good SCADA software, help the grid operators balance their volatile loads, use deep learning and so-called AI to make maintenance cheaper and life cycles longer. And, but this has nothing to do with programming, keep pestering your first-world governments. Even if your country's share in the global emissions is minute, showing that even industrialized countries can reduce their emissions hopefully leads to others following. But this is only going to work if saving the environment is also cheaper compared to going on as usual. Olaf [*] http://windcores.de/en/homepage/#!/who

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How are we helping ? Climate Strike / Earth Strike fri 20, fri 27
by Simon Michael 22 Sep '19

22 Sep '19

Hi all, There's world-wide "strike" event, to raise awareness and stimulate climate action, happening tomorrow and also on friday 27th. Some folks will observe one, the other, both, or the whole period between. We probably don't all share the same awareness or even concern about climate change.. but this is changing rapidly. I wanted to start a discussion and figure out something we could do to support these events.. earlier. But I'm working, preparing for a trip, etc. etc. and "ran out of time". I'll send this now at least. If the site goes green or something, this is the reason. Re the sep 20 and sep 27 events: Thanks to Open Collective, for their leadership and blog post: https://blog.opencollective.com/digital-climate-strike hledger's opencollective, though we're not really using it yet, is opted in for tomorrow: https://opencollective.com/hledger Origin and recent history of this event: https://en.wikipedia.org/wiki/School_strike_for_climate#'Intergenerational'_Global_Climate_Strikes_in_September_2019 There are probably a bunch of "home" sites for this, here are two: https://www.fridaysforfuture.org https://www.earth-strike.com Going forward: I think "How are we helping?" is a standard question every individual, project, institution should be answering. For the hledger project, I've had a few ideas for a long time but haven't managed to manifest them yet. Looking into the near future, some days it feels like working on hledger is a waste of time. Probably many of you can relate. If you are working on anything in this direction I'd love to hear more. Best! -Simon PS I ran out of time even more for crafting a mail to haskell-cafe; cc'ing this anyway.

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Changing a function definition causes an error at link-time
by Vanessa McHale 21 Sep '19

21 Sep '19

Hi all, I have a function ft :: CMode -> FileType ft i = toEnum (fromIntegral i) which is used to marshal a function defined with c2hs, viz. {# fun archive_entry_filetype as ^ { `ArchiveEntryPtr' } -> `FileType' ft #} This all works fine under GHC 8.8.1-GHC-8.2.2. When I try to compile the test suite with GHC 8.0.2 I get Linking /home/vanessa/programming/haskell/done/libarchive/dist-newstyle/build/x86_64-linux/ghc-8.0.2/libarchive-2.0.0.0/t/libarchive-test/build/libarchive-test/libarchive-test ... /usr/bin/ld: /home/vanessa/programming/haskell/done/libarchive/dist-newstyle/build/x86_64-linux/ghc-8.0.2/libarchive-2.0.0.0/build/libHSlibarchive-2.0.0.0-inplace.a(ArchiveEntry.o): in function `rg6i_info': (.text+0x9cd6): undefined reference to `archive_entry_acl_next_w' /usr/bin/ld: /home/vanessa/programming/haskell/done/libarchive/dist-newstyle/build/x86_64-linux/ghc-8.0.2/libarchive-2.0.0.0/build/libHSlibarchive-2.0.0.0-inplace.a(ArchiveEntry.o): in function `cjVN_info': (.text+0x128c6): undefined reference to `archive_entry_acl_next_w' collect2: error: ld returned 1 exit status `gcc' failed in phase `Linker'. (Exit code: 1) When I define the marshaling function with ft :: CMode -> FileType ft 0 = error "here" ft i = toEnum (fromIntegral i) I can no longer compile the test suite; it fails with a linker error, even with GHC 8.8.1-GHC-8.2.2. I get Linking /home/vanessa/programming/haskell/done/libarchive/dist-newstyle/build/x86_64-linux/ghc-8.8.1/libarchive-2.0.0.0/t/libarchive-test/build/libarchive-test/libarchive-test ... /home/vanessa/programming/haskell/done/libarchive/dist-newstyle/build/x86_64-linux/ghc-8.8.1/libarchive-2.0.0.0/build/libHSlibarchive-2.0.0.0-inplace.a(ArchiveEntry.o)(.text+0x9d86): error: undefined reference to 'archive_entry_acl_next_w' /home/vanessa/programming/haskell/done/libarchive/dist-newstyle/build/x86_64-linux/ghc-8.8.1/libarchive-2.0.0.0/build/libHSlibarchive-2.0.0.0-inplace.a(ArchiveEntry.o):function libarchivezm2zi0zi0zi0zminplace_CodecziArchiveziForeignziArchiveEntry_zdwarchiveEntryAclNextW_info: error: undefined reference to 'archive_entry_acl_next_w' collect2: error: ld returned 1 exit status `gcc' failed in phase `Linker'. (Exit code: 1) You can have a look at some of some of the code in this branch here: https://github.com/vmchale/libarchive/blob/ghc-potential-bug/src/Codec/Arch… and here: https://github.com/vmchale/libarchive/blob/ghc-potential-bug/src/Codec/Arch… Cheers, Vanessa McHale

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Re: [Haskell-cafe] [Haskell] ANNOUNCE: mm2: The library that can be used for optimization of multiple (Ord a) => a -> b transformations
by Henning Thielemann 21 Sep '19

21 Sep '19

On Sat, 21 Sep 2019, olexandr543--- via Haskell wrote: > My library that can help to optimize using 'case ... of ...' construction if there are multiple (more than at > least 5) variants. > mm2: The library that can be used for optimization of multiple (Ord a) => a -> b transformations Isn't this a problem you would solve using Data.Map?

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Re: [Haskell-cafe] Explicitly calling syntactic equality on datatypes
by Olaf Klinke 18 Sep '19

18 Sep '19

IMHO Tom's suggestion is the way to go, because: (1) The normalized values form a sub-set of the general ones. If you have just one data type for both, then you'll have no static guarantee of normalization, and this will lead to mistakes once you fail to track the normalize calls. (2) Since the normalized values are a sub-set, coercing a normalized value back into the super-type is cheap. (3) Two distinct types guarantee that you won't do the same work twice. Your proposal of (==) `on` normalize will re-calculate the normalization every time you call (==), if no memoization happens. (4) The existing machinery of the compiler suffices to do what you want. If you consider the two forms semantically equal then maybe the non-normalized form should be represented as a thunk. Isn't that what the ShowS type is about? Just my 2 cents. Olaf

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Explicitly calling syntactic equality on datatypes
by Juan Casanova 18 Sep '19

18 Sep '19

Hello, Pretty simple question here really. I think I've searched for it several times in the past and ended up surprised I did not find an answer. Simple example: sum expressions. One way to define this, one that is comfortable to construct new sums, would be: data Sum = Value Int | Sum Sum Sum Another one, one that is comfortable to check equality with (and other similar things that rely on some notion of normal form), would be (essentially non-empty lists of ints): data Sum = Value Int | Sum Int Sum Now, in many cases you really want to go with the first one for several reasons. You just do not care about normalization in most cases, or maybe you do something more abstract and complicated on top of it that delays the possibility or the sensibility of normalization until something else happens later. So say, that I have the first definition. But then, I want to define equality semantically. An obvious way to go is to produce a function that normalizes Sums (from the first definition) to guarantee that the first sub-sum is always going to be a value, and then check that these two are "equal". And this is where my question comes in, because, of course, the following is infinite recursion: instance Eq Sum where a == b = (normalize a) == (normalize b) What I'd like is to be able to override the default implementation of Eq, but be able to *explicitly* call syntactic equality in calculating it, so that I can do: instance Eq Sum where a == b = (syntacticEq (normalize a) (normalize b)) So, I can see how this is not as straightforward as a function. You cannot correctly produce a polymorphic function syntacticEq :: a -> a -> Bool that works on the SYNTAX of a because it is hidden inside the polymorphic function. What (deriving Eq) does (as I understand it) is to produce an instance at compilation time by looking at how the specific type is presented. But that same compilation time producing could be done to produce it as a function instead of as an implementation of Eq, so that syntacticEq would not be an actual function, but some sort of "macro" that, on compile time, creates the default implementation of equality, but instead of defining it as (==) it defines it as a new function that is only used there. Of course, I can just implement syntactic equality myself explicitly, but when I have to do this for 3, 4, 7 types, some of which have many cases, and a lot of these are polymorphic, so that I have to put all the (Eq arg1, Eq arg2, Eq arg3, ...) => constraints before all of them, it gets old quick. So, is there something like this? Am I saying something really dumb? Of course, I am thinking about equality here, but the same could be said for any standard derivation of classes, like Functor, Show, etc. ALL of them sound like I've wanted to do them at some point in the past. Thanks, Juan. -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336.

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Practical Aspects of Declarative Languages PADL2020: 2nd CFP
by Ekaterina Komendantskaya 18 Sep '19

18 Sep '19

22nd International Symposium on Practical Aspects of Declarative Languages (PADL 2020) <https://popl20.sigplan.org/home/PADL-2020#22nd-international-symposium-on-p…> <https://popl20.sigplan.org/home/PADL-2020#httpspopl20sigplanorghomepadl-2020> https://popl20.sigplan.org/home/PADL-2020,20-21 January 2020, New Orleans, Louisiana, United States <https://popl20.sigplan.org/home/PADL-2020#20-21-january-2020-new-orleans-lo…>Co-located with ACM POPL 2020 ( <https://popl20.sigplan.org/home/PADL-2020#co-located-with-acm-popl-2020-htt…> https://popl20.sigplan.org/) ------------------------------ *Declarative languages* is an umbrella term that include functional, logic, and constraint programming languages. These languages have been successfully applied to many different real-world situations, ranging from database management to active networks to software engineering to decision support systems. New developments in theory and implementation have opened up new application areas. At the same time, applications of declarative languages to challenging problems raise intriguing research questions, such as scalable design and implementation, language extensions for application deployment, and programming environments. PADL is a well-established forum for researchers and practitioners to present original work emphasizing novel applications and implementation techniques for all forms of declarative programming, including functional and logic programming, database and constraint programming, and theorem proving. Topics of interest include, but are not limited to: - Innovative applications of declarative languages - Declarative domain-specific languages and applications - Practical applications of theoretical results - New language developments and their impact on applications - Declarative languages for software engineering - Evaluation of implementation techniques on practical applications - Practical experiences and industrial applications - Novel uses of declarative languages in the classroom - Practical languages and extensions such as probabilistic and reactive languages *PADL 2020* especially welcomes new ideas and approaches pertaining to applications, design and implementation of declarative languages going beyond the scope of the past PADL symposia, for example, advanced database languages and contract languages, as well as verification and theorem proving methods that rely on declarative languages. Important Dates and Submission Guidelines: <https://popl20.sigplan.org/home/PADL-2020#important-dates-and-submission-gu…> - Abstracts due: 11 October 2019 - Papers due: 18 October 2019 - Notification to authors: 18 November 2019 - Camera-ready: 29 November 2020 - Symposium dates: 20 - 21 January 2020 Submission instructions can be found at: https://popl20.sigplan.org/home/PADL-2020#Call-for-Papers Looking forward to receiving your submission, PADL19 PC members: https://popl20.sigplan.org/home/PADL-2020#About

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Re: [Haskell-cafe] Attach a finalizer to a FunPtr
by Roman Cheplyaka 17 Sep '19

17 Sep '19

On 17/09/2019 10.50, Shao Cheng wrote: > Hi Roman, > > mkWeak# 's "key" and "value" arguments must both be lifted types, see https://gitlab.haskell.org/ghc/ghc/blob/master/rts/PrimOps.cmm#L699. Your code directly passes the raw Addr# which is not a managed pointer, thus the segfault. Ah, that makes sense — thanks Cheng (and Matthew). I modeled my code after mkWeakIORef, and I assumed that MutVar# and Addr# were in the same category. > I recommend using ForeignPtr in this case. You can add finalizers to ForeignPtr properly, and coerce from ForeignPtr to FunPtr when using it, since they're both containing the Addr# under the hood. I considered doing that, but that'd require quite a bit of code to be constantly converting between ForeignPtr and FunPtr and also converting IO () finalizers to FunPtr (...) finalizers. System.Mem.Weak looks like a better fit because it uses IO () finalizers. I think I'll try attaching a finalizer to ForeignPtr itself and be careful to retain a pointer to ForeignPtr (perhaps with the help of a StablePtr) while it's in use. Or, if that doesn't work, I might implement a reference counter instead. Roman

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[ANN] Call for Contributions: BOB 2020 [Feb 28, Deadline Nov 8]
by Stefan Wehr 17 Sep '19

17 Sep '19

BOB Conference 2020 "What happens when we use what's best for a change?" http://bobkonf.de/2020/cfc.html Berlin, February 28 Call for Contributions Deadline: November 8, 2019 You are actively engaged in advanced software engineering methods, implement ambitious architectures and are open to cutting-edge innovation? Attend this conference, meet people that share your goals, and get to know the best software tools and technologies available today. We strive to offer a day full of new experiences and impressions that you can use to immediately improve your daily life as a software developer. If you share our vision and want to contribute, submit a proposal for a talk or tutorial! NOTE: The conference fee will be waived for presenters. Travel expenses will not be covered (for exceptions see "Speaker Grants"). Speaker Grants BOB has Speaker Grants available to support speakers from groups under-represented in technology. We specifically seek women speakers and speakers who are not be able to attend the conference for financial reasons. Shepherding ----------- The program committee offers shepherding to all speakers. Shepherding provides speakers assistance with preparing their sessions, as well as a review of the talk slides. Topics ------ We are looking for talks about best-of-breed software technology, e.g.: - functional programming - persistent data structures and database - event-based modelling and architectures - types - formal methods for correctness and robustness - abstractions for concurrency and parallelism - metaprogramming - probabilistic programming - math and programming - controlled side effects - beyond REST and SOAP - effective abstractions for data analytics - ... everything really that isn’t mainstream, but you think should be. Presenters should provide the audience with information that is practically useful for software developers. We're especially interested in experience reports. Other topics are also relevant, e.g.: - introductory talks on technical background - overviews of a given field - demos and how-tos Requirements ------------- We accept proposals for presentations of 45 minutes (40 minutes talk + 5 minutes questions), as well as 90 minute tutorials for beginners. The language of presentation should be either English or German. Your proposal should include (in your presentation language of choice): - An abstract of max. 1500 characters. - A short bio/cv - Contact information (including at least email address) - A list of 3-5 concrete ideas of how your work can be applied in a developer's daily life - additional material (websites, blogs, slides, videos of past presentations, …) Submit here: https://bobcfc.active-group.de/en/bob2020/cfp Organisation ------------ - Direct questions to contact at bobkonf dot de - Proposal deadline: November 8, 2019 - Notification: November 22, 2019 - Program: December 6, 2019 Program Committee ----------------- (more information here: https://bobkonf.de/2020/programmkomitee.html) - Matthias Fischmann, Wire - Matthias Neubauer, SICK AG - Nicole Rauch, Softwareentwicklung und Entwicklungscoaching - Michael Sperber, Active Group - Stefan Wehr, factis research Scientific Advisory Board - Annette Bieniusa, TU Kaiserslautern - Torsten Grust, Uni Tübingen - Peter Thiemann, Uni Freiburg

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Class of ordered tuples
by Olaf Klinke 17 Sep '19

17 Sep '19

Dear Cafe, I had a lengthy discussion with GHC but so far it won't let me do the following. (Code below is simplified to transport the idea. Type families don't seem to do the trick, either.) A finite set of types A, B, C, ... is totally ordered. This can be expressed e.g. by a multi-parameter type class and type-level natural numbers: instance Index A 0 where instance Index B 1 where etc. Now I want a type class Range and an appropriate set of instance declarations that has A, B, (A,B), (A,C), (A,(B,C)) etc. as members but not (B,A) or (C,C). That is, each type appears at most once and in the defined order. The problem is overlapping instances of the base case with the inductive case. instance Index a n => Range a n n instance (Range a x y, Range b x' y', y < x') => Range (a,b) x y' Then the compiler rightfully complains that someone could write an instance Index (a,b) n which would lead to conflicting instances of Range (a,b) n n. I can not make either of the type classes Index nor Range closed because there will be several of those sets of types. This problem is like smart constructors for ordered lists, but on the type level. Thanks in advance for any hints. Olaf

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Attach a finalizer to a FunPtr
by Roman Cheplyaka 17 Sep '19

17 Sep '19

Hi all, I'd like to attach a finalizer to FunPtrs (which point to JIT-compiled functions that need to be deallocated). However, the act of running the finalizer (no matter what it does) results in a segfault. Here's a minimal example: {-# LANGUAGE UnboxedTuples, MagicHash #-} import GHC.Exts (FunPtr(..)) import GHC.Base import Foreign.Ptr import System.Mem attachFinalizer :: FunPtr a -> IO () -> IO () attachFinalizer fptr@(FunPtr addr) (IO fin) = IO $ \s0 -> case mkWeak# addr fptr fin s0 of (# s1, _ #) -> (# s1, () #) foreign import ccall "wrapper" mkIO :: IO () -> IO (FunPtr (IO ())) main = do fptr <- mkIO $ return () attachFinalizer fptr $ do -- The exact contents of the finalizer doesn't seem to matter putStrLn "+++ finalizer ran" freeHaskellFunPtr fptr putStrLn "+++ attached successfully" performGC Is there a proper way to do this? (GHC 8.6.5) Roman

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Fusion & Laziness
by Hilco Wijbenga 17 Sep '19

17 Sep '19

Hi all, I'd like to have a better understanding of fusion and (maybe?) laziness. Let's say I have an (exported) type "data EndResult = ... !(Vector Thing) ..." and an intermediate, unexported type "data IntermediateResult = ... !(Vector Thing) ...". (I suppose it doesn't need to be Vector, it could be Set, or some other data structure that (I imagine) is relatively expensive to map over, unlike, say [].) [To start off, I want to state my, possibly incorrect, understanding of fusion and how it does not (in my expectation) apply to Vector, Set, et cetera. A List can essentially disappear as it's replaced by a loop but a Vector would not: the executing code would create and garbage collect multiple intermediate Vectors before finally returning the end result.] Assume that I need my algorithm to go from initial input to IntermediateResult to subsequent IntermediateResult (a few times) to EndResult. In my case, each subsequent IntermediateResult is a bit smaller than the previous one but that's probably irrelevant. Should I prefer IntermediateResult to be lazy? Should I use [] instead of Vector in the IntermediateResult? What about the functions that actually operate on IntermediateResult, should I prefer to use [] or Vector there? I'm currently able to use Data.Vector.concatMap in some places, is that just as optimized? I realize that the correct answer more than likely is "don't worry about it". And that I'm being very vague. :-) I'm not looking for anything definitive, I'm just hoping to improve my understanding and intuition. What should I consider when thinking about these types of things? If I don't want to create two separate implementations and profile them, are there "obvious" signs one way or another? Cheers, Hilco

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Default "type" in type class
by Hilco Wijbenga 16 Sep '19

16 Sep '19

Hi all, I'm trying to create a "HasToList" type class. It starts off really simple: class HasToList collection where toList ∷ collection element → [element] instance HasToList Set where toList = Data.Set.toList Unfortunately, this breaks down with Data.EnumSet.EnumSet. So instance HasToList EnumSet where toList = Data.EnumSet.toList doesn't compile and I could not find a way to add "Enum a =>" to either the instance or "toList". (Well, not without making the compiler upset.) With the aid of ConstraintKinds and TypeFamilies (and not much understanding on my end, obviously) I created class HasToList collection where type Requirement collection element :: Constraint toList ∷ Requirement collection element => collection element → [element] instance HasToList Set where type Requirement Set a = () toList = Data.Set.toList instance HasToList EnumSet where type Requirement EnumSet a = Enum a toList = Data.EnumSet.toList This works but now I have to add the constraint to every instance even though only a tiny minority actually need it. Is there a way to add a default "type implementation"? I tried the obvious type Requirement collection element :: Constraint = () and type Requirement collection element :: Constraint type Requirement collection element :: Constraint = () but neither compiles. Another problem is that the compiler can't compile something like this: isteps ∷ HasToList collection ⇒ collection String → [(Int, String)] isteps steps = Data.List.Index.indexed (toList steps) because it doesn't know which constraint to apply ("Could not deduce: Requirement hasToList String"). That seems fair but also irrelevant at this point. I feel like this is all far too complicated for what I'm trying to accomplish. :-) While I would like to have an answer to the questions above, I guess what I really want is a simpler way to implement HasToList. Cheers, Hilco

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MPC 2019 - final call for participation
by Graham Hutton 16 Sep '19

16 Sep '19

Dear all, Final call for participation for the Mathematics of Program Construction (MPC) conference in Portugal. MPC 2019 will feature 15 research papers and 4 keynotes, and is co-located with Formal Methods 2019 and many other events. See you in Porto! https://tinyurl.com/MPC-Porto Best wishes, Graham Hutton Program Chair, MPC 2019 ====================================================================== *** FINAL CALL FOR PARTICIPATION -- MPC 2019 *** 13th International Conference on Mathematics of Program Construction 7-9 October 2019, Porto, Portugal Co-located with Formal Methods 2019 https://tinyurl.com/MPC-Porto ====================================================================== PROGRAM: https://tinyurl.com/yxvvc5vb ACCEPTED PAPERS: https://tinyurl.com/yyuhy8ze REGISTRATION AND TRAVEL: https://tinyurl.com/y4uetlsr KEYNOTE SPEAKERS: Assia Mahboubi (MPC) INRIA, France Annabelle McIver (MPC) Macquarie University, Australia Tony Hoare (UTP) Oxford University, UK Shriram Krishnamurthi (FM) Brown University, USA BACKGROUND: The International Conference on Mathematics of Program Construction (MPC) aims to promote the development of mathematical principles and techniques that are demonstrably practical and effective in the process of constructing computer programs. MPC 2019 will be held in Porto, Portugal from 7-9 October 2019, and is co-located with the International Symposium on Formal Methods, FM 2019. Previous conferences were held in Königswinter, Germany (2015); Madrid, Spain (2012); Québec City, Canada (2010); Marseille, France (2008); Kuressaare, Estonia (2006); Stirling, UK (2004); Dagstuhl, Germany (2002); Ponte de Lima, Portugal (2000); Marstrand, Sweden (1998); Kloster Irsee, Germany (1995); Oxford, UK (1992); Twente, The Netherlands (1989). PROGRAM COMMITTEE: Patrick Bahr IT University of Copenhagen, Denmark Richard Bird University of Oxford, UK Corina Cîrstea University of Southampton, UK Brijesh Dongol University of Surrey, UK João F. Ferreira University of Lisbon, Portugal Jennifer Hackett University of Nottingham, UK William Harrison University of Missouri, USA Ralf Hinze University of Kaiserslautern, Germany Zhenjiang Hu National Institute of Informatics, Japan Graham Hutton (chair) University of Nottingham, UK Cezar Ionescu University of Oxford, UK Mauro Jaskelioff National University of Rosario, Argentina Ranjit Jhala University of California, USA Gabriele Keller Utrecht University, The Netherlands Ekaterina Komendantskaya Heriot-Watt University, UK Chris Martens North Carolina State University, USA Bernhard Möller University of Augsburg, Germany Shin-Cheng Mu Academia Sinica, Taiwan Mary Sheeran Chalmers University of Technology, Sweden Alexandra Silva University College London, UK Georg Struth University of Sheffield, UK For any queries about the program please contact the program chair, Graham Hutton <graham.hutton(a)nottingham.ac.uk>. CONFERENCE VENUE: The conference will be held at the Alfândega Porto Congress Centre, a 150 year old former custom's house located in the historic centre of Porto on the bank of the river Douro. The venue was renovated by a Pritzer prize winning architect and has received many awards. LOCAL ORGANISER: José Nuno Oliveira University of Minho, Portugal For any queries about local issues please contact the local organiser, José Nuno Oliveira <jno(a)di.uminho.pt>. ====================================================================== This message and any attachment are intended solely for the addressee and may contain confidential information. If you have received this message in error, please contact the sender and delete the email and attachment. Any views or opinions expressed by the author of this email do not necessarily reflect the views of the University of Nottingham. Email communications with the University of Nottingham may be monitored where permitted by law.

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[ANN] lzlib bindings in Haskell
by Vanessa McHale 15 Sep '19

15 Sep '19

Hi all, I have released a library containing a high-level API for lzlib (and bindings to the full lzlib), viz. http://hackage.haskell.org/package/lzlib Cheers, Vanessa McHale

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parallele tolistM of the pipes module
by PICCA Frederic-Emmanuel 12 Sep '19

12 Sep '19

Hello, I would like to know how to write a parallele version of the pipes function: toListM :: Monad m => Producer a m () -> m [a] toListM = fold step begin done where step x a = x . (a:) begin = id done x = x [] {-# INLINABLE toListM #-} I want to extract all the a from th epipes but concurrently. is it possible ? Cheers Frederic

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[POPL2020] Call for student volunteers
by Hanneli Tavante 11 Sep '19

11 Sep '19

Hello! The call for Student Volunteers at POPL2020 is opened until October 17th! The 2020 edition will be in New Orleans, USA, January19th-25th. More information here: https://popl20.sigplan.org/attending/students We encourage all the students to apply - with or without experience, local and non-local, undergrads and graduate students.

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Taking over regex-base on Hackage
by Troels Henriksen 10 Sep '19

10 Sep '19

regex-base is at the bottom of the regex-* package hierarchy and has remarkably remained unchanged and working since the last release in 2010. Alas, the MonadFail change in GHC 8.8 breaks it and the maintainer, Christopher Kuklewicz, seems to have been absent for a while. Most of his other packages have long since been taken over by others. I would like to take over regex-base in order to patch it to work with GHC 8.8. -- \ Troels /\ Henriksen

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Concurrent reads, ordered writes?
by amindfv＠gmail.com 09 Sep '19

09 Sep '19

I've implemented a solution for this problem, but it seems a bit less clean than it could be, which leaves me wondering if there's a data structure or algorithm specifically for this purpose: We've got multiple concurrent thereads reading items from a (TBQueue A), calling f :: A -> B, and writing to a (TBQueue B). We must, though, write items into the (TBQueue B) in the order that the corresponding As were read (the order they were put in the (TBQueue A)). Are there existing libraries which solve this or a similar problem? Ideally with niceties like configuring whether the pending out-of-order writes block the worker threads, and a way of signalling there's no more work to perform. Thanks! Tom

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[CC2020] 2nd CFP for the ACM SIGPLAN 2020 International Conference on Compiler Construction
by Gabriel Rodríguez Álvarez 09 Sep '19

09 Sep '19

ACM SIGPLAN 2020 International Conference on Compiler Construction (CC'20) co-located with CGO, PPoPP and HPCA San Diego, CA, USA February 22 - 23, 2020 https://conf.researchr.org/home/CC-2020 The ACM SIGPLAN 2020 International Conference on Compiler Construction (CC 2020) is interested in work on processing programs in the most general sense: analyzing, transforming or executing input programs that describe how a system operates, including traditional compiler construction as a special case. Original contributions are solicited on the topics of interest which include, but are not limited to: - Compilation and interpretation techniques, including program representation, analysis, and transformation; code generation, optimization, and synthesis; the verification thereof - Run-time techniques, including memory management, virtual machines, and dynamic and just-in-time compilation - Programming tools, including refactoring editors, checkers, verifiers, compilers, debuggers, and profilers - Techniques for specific domains, such as secure, parallel, distributed, embedded or mobile environments - Design and implementation of novel language constructs, programming models, and domain-specific languages CC 2020 is the 29th edition of the conference. From this year onwards, CC is an ACM SIGPLAN conference and will implement guidelines and procedures recommended by SIGPLAN https://www.sigplan.org. ================================================================================================= To subscribe to the CC announce mailing list, see cc_conference_announce(a)googlegroups.com To subscribe to the CC announce Twitter account, see @cc2020conf (https://twitter.com/cc2020conf) ================================================================================================= IMPORTANT DATES Abstract Submission: 23 October 2019 Paper Submission : 30 October 2019 Rebuttal : 4-6 December 2019 Artifact Submission: 13 December 2019 Author Notification: 24 December 2019 Final papers due : 15 January 2020 Conference : 22–23 February 2020 All submissions must be made electronically through the conference web site and include an abstract (100–400 words), author contact information, the full list of authors and their affiliations. Full paper submissions must be in PDF formatted printable on both A4 and US letter size paper. All papers must be prepared in ACM Conference Format using the 2-column acmart format. Papers should contain a maximum of 10 pages of text (in a typeface no smaller than 10 point) or figures, NOT INCLUDING references. There is no page limit for references and they must include the name of all authors (not {et al.}). Appendices are not allowed, but the authors may submit supplementary material, such as proofs or source code; all supplementary material must be in PDF or ZIP format. Looking at supplementary material is at the discretion of the reviewers. Submission is double blind and authors will need to identify any potential conflicts of interest with PC, as defined here: http://www.sigplan.org/Resources/Policies/Review/ (ACM SIGPLAN policy). Authors are encouraged to submit their artifacts for the Artifact Evaluation (AE). The Artifact Evaluation process is run by a separate committee whose task is to assess how the artifacts support the work described in the papers. To ease the organization of the AE committee, we kindly ask authors to submit their artifact at the latest 10 days after the rebuttal. Papers that go through the Artifact Evaluation process successfully will receive a seal of approval printed on the papers themselves. Additional information will be made available on the CC AE web page. Deadlines expire at midnight anywhere on earth. ORGANIZERS General Chair Louis-Noel Pouchet Colorado State University <pouchet AT colostate.edu> Program Chair Alexandra Jimborean Uppsala University <alexandra.jimborean AT it.uu.se> Artifact Evaluation Chairs Michel Steuwer University of Glasgow <Michel.Steuwer AT glasgow.ac.uk> Martin Kong University of Oklahoma Publicity Chair Gabriel Rodriguez University of A Coruna Web Chair Mihail Popov Uppsala University Steering Committee Bjorn Franke University of Edinburgh <bfranke AT inf.ed.ac.uk> Sebastian Hack Saarland University Manuel Hermenegildo IMDEA SW Institute and Technical U. of Madrid Peng Wu Huawei America Research Lab Ayal Zaks Intel and Technion, Israel Jingling Xue University of New South Wales, Australia Christophe Dubach University of Edinburgh Nelson J. Amaral University of Alberta Milind Kulkarni Purdue University Program Committee Apan Qasem AMD/Texas State University Bernhard Scholz University of Sydney Bettina Heim Microsoft Bilha Mendelson Optitura Brian Demsky UC Irvine Changhee Jung Virginia Tech Christian Schulte KTH EJ Park Los Alamos National Laboratory Delphine Demange Inria Dongyoon Lee Virginia Tech Fernando Magno Quintao Pereira UFMG Brazil Haowei Wu Google Manuel Hermenegildo IMDEA and T.U. Madrid Matin Hashemi Sharif University of Technology Michel Steuwer University of Glasgow Mila Dalla Preda University of Verona Nelson J. Amaral University of Alberta Philippe Clauss University of Strasbourg Pavlos Petoumenos University of Edinburgh Rumyana Neykova Brunel London Santosh Nagarakatte Rutgers University Sebastian Hack University of Saarland Tomofumi Yuki Inria Xu Liu College of William and Mary

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Re: [Haskell-cafe] [ANNOUNCE] GHC 8.8.1 and cabal-install version
by Carter Schonwald 06 Sep '19

06 Sep '19

V1 or v2 install? On Mon, Sep 2, 2019 at 11:42 AM George Colpitts <george.colpitts(a)gmail.com> wrote: > https://www.haskell.org/ghc/blog/20190825-ghc-8.8.1-released.html says > > cabal-install users should note that cabal-install-3.0 or later is > required for use with GHC 8.8. > > but this seems wrong or have I done something wrong? > > $ cabal install cabal-install > cabal install cabal-install > ... > > Resolving dependencies... > cabal: Could not resolve dependencies: > [__0] trying: cabal-install-3.0.0.0 (user goal) > [__1] next goal: time (dependency of cabal-install) > [__1] rejecting: time-1.9.3/installed-1.9... (conflict: cabal-install => > base>=4.8 && <4.13, time => base==4.13.0.0/installed-4.1...) > [__1] trying: time-1.9.3 > [__2] next goal: stm (dependency of cabal-install) > [__2] rejecting: stm-2.5.0.0/installed-2.5... (conflict: cabal-install => > base>=4.8 && <4.13, stm => base==4.13.0.0/installed-4.1...) > [__2] trying: stm-2.5.0.0 > [__3] next goal: process (dependency of cabal-install) > [__3] rejecting: process-1.6.5.1/installed-1.6... (conflict: cabal-install > => > base>=4.8 && <4.13, process => base==4.13.0.0/installed-4.1...) > [__3] trying: process-1.6.5.1 > [__4] next goal: pretty (dependency of cabal-install) > [__4] rejecting: pretty-1.1.3.6/installed-1.1... (conflict: cabal-install > => > base>=4.8 && <4.13, pretty => base==4.13.0.0/installed-4.1...) > [__4] trying: pretty-1.1.3.6 > [__5] next goal: network (dependency of cabal-install) > [__5] rejecting: network-3.1.0.1/installed-CeX... (conflict: cabal-install > => > base>=4.8 && <4.13, network => base==4.13.0.0/installed-4.1...) > [__5] trying: network-3.1.0.1 > [__6] trying: hackage-security-0.5.3.0 (dependency of cabal-install) > [__7] next goal: template-haskell (dependency of hackage-security) > [__7] rejecting: template-haskell-2.15.0.0/installed-2.1... (conflict: > cabal-install => base>=4.8 && <4.13, template-haskell => > base==4.13.0.0/installed-4.1...) > [__7] rejecting: template-haskell-2.15.0.0, template-haskell-2.14.0.0, > template-haskell-2.13.0.0, template-haskell-2.12.0.0, > template-haskell-2.11.1.0, template-haskell-2.11.0.0, > template-haskell-2.10.0.0, template-haskell-2.9.0.0, > template-haskell-2.8.0.0, > template-haskell-2.7.0.0, template-haskell-2.6.0.0, > template-haskell-2.5.0.0, > template-haskell-2.4.0.1, template-haskell-2.4.0.0, > template-haskell-2.3.0.1, > template-haskell-2.3.0.0, template-haskell-2.2.0.0 (constraint from > non-upgradeable package requires installed instance) > [__7] fail (backjumping, conflict set: cabal-install, hackage-security, > template-haskell) > After searching the rest of the dependency tree exhaustively, these were > the > goals I've had most trouble fulfilling: base, cabal-install, directory, > template-haskell, process, time, network, pretty, hackage-security, > deepseq, > HTTP, stm, cabal-install:lib > > > On Mon, Aug 26, 2019 at 6:25 AM Ben Gamari <ben(a)well-typed.com> wrote: > >> >> Hello everyone, >> >> The GHC team is pleased to announce the release candidate for GHC 8.8.1. >> The source distribution, binary distributions, and documentation are >> available at >> >> https://downloads.haskell.org/ghc/8.8.1 >> >> This release is the culmination of over 3000 commits by over one hundred >> contributors and has several new features and numerous bug fixes >> relative to GHC 8.6: >> >> * Visible kind applications are now supported (GHC Proposal #15) >> >> * Profiling now works correctly on 64-bit Windows (although still may >> be problematic on 32-bit Windows due to platform limitations; see >> #15934) >> >> * A new code layout algorithm for amd64's native code generator >> significantly improving the runtime performance of some kernels >> >> * The introduction of a late lambda-lifting pass which may reduce >> allocations significantly for some programs. >> >> * Further work on Trees That Grow, enabling improved code re-use of the >> Haskell AST in tooling >> >> * Users can write `forall` in more contexts (GHC Proposal #7) >> >> * The pattern-match checker is now more precise in the presence of >> strict fields with uninhabited types. >> >> * A comprehensive audit of GHC's memory ordering barriers has been >> performed, resulting in a number of fixes that should significantly >> improve the reliability of programs on architectures with >> weakly-ordered memory models (e.g. PowerPC, many ARM and AArch64 >> implementations). >> >> * A long-standing linker limitation rendering GHCi unusable with >> projects with cyclic symbol dependencies has been fixed (#13786) >> >> * Further work on the Hadrian build system >> >> * Countless miscellaneous bug-fixes >> >> Unfortunately, due to a build issue (#17108) found late in the release >> process >> i386 Windows builds are currently unavailable. These will be provided in >> the coming weeks. >> >> As always, if anything looks amiss do let us know. >> >> Happy compiling! >> >> Cheers, >> >> - Ben >> >> >> [1] >> https://downloads.haskell.org/ghc/8.8.1/docs/html/users_guide/8.8.1-notes.h… >> _______________________________________________ >> Glasgow-haskell-users mailing list >> Glasgow-haskell-users(a)haskell.org >> http://mail.haskell.org/cgi-bin/mailman/listinfo/glasgow-haskell-users >> > _______________________________________________ > Glasgow-haskell-users mailing list > Glasgow-haskell-users(a)haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/glasgow-haskell-users >

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How to write a Monad instance for this type
by PICCA Frederic-Emmanuel 06 Sep '19

06 Sep '19

Hello, I try to write a monad instance for this type which represent the content of an hdf5 file. This file format is similar to a filesystem, where directories are Group and files Dataset. I end up with this type. data Hdf5M a = H5Root (Hdf5M a) | H5Group ByteString [Hdf5M a] -- A group can contain other groups and/or datasets | forall sh b. (NativeType b, Shape sh) => H5Dataset ByteString (Array F sh b) type Hdf5 = Hdf5M () hdf5 :: Hdf5 -> Hdf5 hdf5 = H5Root group :: ByteString -> [Hdf5] -> Hdf5 group g = H5Group g dataset :: (NativeType b, Shape sh) => ByteString -> (Array F sh b) -> Hdf5 dataset = H5Dataset I tryed to inspire myself from the blaze-html Markup type. And I would like to be able to describe a contain like this hdf5 $ do group "name" $ do dataset "name1" array1 dataset "name2" array2 group "other-name" $ do etc... instead of H5Root ( H5Group "name" [ dataset ]...) the final idea, is to be able to serialize object via a class ToHdf5 where toHdf5 :: a -> Hdf5 So my question is someone can help me design this ? thanks for your help Frederic

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Stack & Test Coverage
by Hilco Wijbenga 06 Sep '19

06 Sep '19

Hi all, I have a very simple newtype Index = Index Int deriving (Eq, Ord, Enum) for which I have written tests with both HSpec and QuickCheck. Specifically, I have written tests for "==", "/=", "compare" (for all of EQ, LT, and GT), and "toEnum" & "fromEnum". So I thought I had _very_ thoroughly covered that one line. :-) Unfortunately, after running "stack clean ; stack test --coverage" I see in the HTML report that only Eq has been tested and that Ord and Enum have _no_ coverage (i.e. "never executed"). (The module also has some regular functions and an explicit Show instance [all with tests] and those are apparently fine. So coverage does seem to work but not the way I expect?) What am I doing wrong? Cheers, Hilco

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c2hs syntax highlighting in vim
by Vanessa McHale 05 Sep '19

05 Sep '19

Hi all, I wrote a vim plugin to highlight c2hs files, viz. https://github.com/vmchale/c2hs-vim Cheers, Vanessa McHale

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ANN: optics-0.1
by Adam Gundry 02 Sep '19

02 Sep '19

We are delighted to announce the first Hackage release of optics, a Haskell library for defining and using lenses, traversals, prisms and more. For further information: https://www.well-typed.com/blog/2019/09/announcing-the-optics-library/ https://hackage.haskell.org/package/optics The optics library is broadly similar in functionality to the well-established lens library, but uses an abstract interface rather than exposing the underlying implementation of each optic kind. It aims to be easier to understand than lens, with clearer interfaces, simpler types and better error messages, while retaining as much functionality as possible. It is being developed by Andrzej Rybczak and Adam Gundry, with significant contributions from Oleg Grenrus and Andres Löh, and much copy-pasting of code and selective copying of ideas from lens. -- Adam Gundry, Haskell Consultant Well-Typed LLP, https://www.well-typed.com/ Registered in England & Wales, OC335890 118 Wymering Mansions, Wymering Road, London W9 2NF, England

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ghc and OpenMP
by PICCA Frederic-Emmanuel 01 Sep '19

01 Sep '19

Hello, I would like your help, in order to understand how to modify a cabal file in order to compile an Haskell modules with .c files (containing OpenMP pragma). I use FFI and a bunch of .c and .h files for the computation part. thanks for your help. I am runnng hc on Debian stable. Cheers Frederic

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ANN: hledger 1.15
by Simon Michael 01 Sep '19

01 Sep '19

I'm pleased to announce hledger 1.15 ! Thanks to release contributors Caleb Maclennan, Jakob Schöttl, Henning Thielemann, Dmitry Astapov, Ben Creasy, zieone, Boyd Kelly, Gabriel Ebner, Hans-Peter Deifel, and Andreas Pauley. hledger is a robust, cross-platform, multicurrency, plain text accounting tool, with command-line, console and web UIs. It is one of the leading implementations of plain text accounting, and is a modern and largely compatible reimplementation of Ledger. Use it for tracking money, time, stocks, cryptocurrencies or any other commodity, Learn more at http://hledger.org and http://plaintextaccounting.org . WHAT'S NEW: A new website, faster and more flexible valuation, more accurate close command, tags --values, new descriptions/payees/notes/diff commands, misc. fixes. For details, see https://hledger.org/release-notes#hledger-1-15 . GETTING STARTED: Many install methods are described at http://hledger.org/download . Some of these might take a few days to become up to date. You can build the latest by doing: stack install --resolver=lts-14.4 hledger-lib-1.15 hledger-1.15 hledger-web-1.15 hledger-ui-1.15 --verbosity=error or: cabal v2-update && cabal v2-install hledger-1.15 hledger-web-1.15 hledger-ui-1.15 To start recording transactions: "hledger add". To list more commands: "hledger". See http://hledger.org for tutorials and support, or join #hledger on Freenode (http://irc.hledger.org) or join via Matrix (http://riot.hledger.org) New and old users, contributors, sponsors, and all feedback are most welcome! Best, -Simon

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Book reviewers wanted
by John Whitington 31 Aug '19

31 Aug '19

Hello, I've prepared a book "Haskell from the Very Beginning" in the same manner as my earlier "OCaml from the Very Beginning". It would be useful to find some people to look it over before release. I did this with the OCaml book, and it improved it markedly. I'm particularly looking for people who have taught or learned Haskell as a first programming language (either in an academic setting or not). I should point out that the book has already benefited from a full, paid, technical review, so you would not be being used as a substitute for that. Do drop me an email if you're interested. There would be, of course, no obligation. Thanks, John -- John Whitington Director, Coherent Graphics Ltd

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[CFP] Final Day for submissions to Functional Conf 2019 in Bengaluru!
by John Sinclair 31 Aug '19

31 Aug '19

Are you using Haskell in innovative ways? Do you have expertise the community would benefit from? Functional Conf 2019 is India's premier Functional programming conference, and we would love to hear from you! Submit your session proposal here: https://confng.in/zmRYXh7N <https://llink.to/?u=https:%2F%2Fconfng.in%2FzmRYXh7N&e=b3dafcbd9791228f91b8…> Hurry! Submissions close today (Aug 31)! Functional Conf is the premiere event for Functional programmers in India. Our goal is to support the community with access to high quality speakers, who are innovating in this field. https://twitter.com/FnConf <https://llink.to/?u=https:%2F%2Ftwitter.com%2FFnConf&e=df52b49527f43fa29bda…> https://www.linkedin.com/showcase/functional-conf <https://llink.to/?u=https:%2F%2Fwww.linkedin.com%2Fshowcase%2Ffunctional-co…>

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A faithful strictly-accumulating writer
by David Feuer 30 Aug '19

30 Aug '19

It's widely known that the classic WriterT tends to leak space, and that in some cases this leak can be resolved by using StateT instead. The implementations I've seen of this idea both use the module system to prevent the computation from gaining unauthorized access to the state. I believe I've found a way to avoid this. Does this look right? {-# language RankNTypes, FlexibleInstances, MultiParamTypeClasses #-} import qualified Control.Monad.Writer.Class as W import Control.Monad.State.Strict import Control.Monad.Reader import Control.Applicative -- The key idea is that the computation -- can't inspect the state because it doesn't know the type newtype WriterT w m a = WriterT { unWriterT :: forall s. ReaderT ((w -> w) -> s -> s) (StateT s m) a } runWriterT :: Monoid w => WriterT w m a -> m (a, w) runWriterT m = runStateT (runReaderT (unWriterT m) id) mempty instance Functor m => Functor (WriterT w m) where fmap f m = WriterT $ fmap f (unWriterT m) instance Monad m => Applicative (WriterT w m) where pure a = WriterT (pure a) liftA2 f m n = WriterT $ liftA2 f (unWriterT m) (unWriterT n) instance Monad m => Monad (WriterT w m) where m >>= f = WriterT $ unWriterT m >>= unWriterT . f instance MonadTrans (WriterT w) where lift m = WriterT $ lift . lift $ m tell :: (Monad m, Semigroup w) => w -> WriterT w m () tell w = WriterT $ do p <- ask modify' $ p (<> w) pass :: Monad m => WriterT w m (a, w -> w) -> WriterT w m a pass m = WriterT $ do p <- ask (a, ww) <- unWriterT m modify' (p ww) pure a instance (Monoid w, Monad m) => W.MonadWriter w (WriterT w m) where tell = tell listen m = do aw@(_a, w) <- lift $ runWriterT m tell w pure aw pass = pass

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Call for scholarship applications: PLMW @ POPL 2020
by Robbert Krebbers 30 Aug '19

30 Aug '19

CALL FOR SCHOLARSHIP APPLICATIONS (** DEADLINE: OCTOBER 7 **) ACM SIGPLAN Programming Languages Mentoring Workshop, New Orleans, Louisiana Tuesday, January 21, 2020 Co-located with POPL 2020 Web page: https://popl20.sigplan.org/home/PLMW-POPL-2020 After the success of the first eight Programming Languages Mentoring Workshops at POPL 2012-2019 we are announcing the 9th SIGPLAN Programming Languages Mentoring Workshop (PLMW), co-located with POPL 2020 and organized by Stephanie Balzer, Justin Hsu, Robbert Krebbers, and Nobuko Yoshida. The purpose of this mentoring workshop is to encourage graduate students and senior undergraduate students to pursue careers in programming language research. This workshop will bring together world leaders in programming languages research and teaching from academia and industry to provide (a) technical sessions on cutting-edge PL research and (b) mentoring sessions on how to prepare for a research career. The workshop will help students imagine how they might contribute to our research community. We especially encourage women and underrepresented minority students, and people with disabilities to attend PLMW. This workshop is part of the activities surrounding POPL, the Symposium on Principles of Programming Languages, and takes place the day before the main conference. One goal of the workshop is to make the POPL conference more accessible to newcomers. We hope that participants will stay through the entire conference. A number of sponsors (listed below) have generously donated scholarship funds for qualified students to attend PLMW. These scholarships should cover reasonable expenses (airfare, hotel, and registration fees) for attendance at both the workshop and the POPL conference. Students attending this year will get one year free student membership of SIGPLAN, unless they prefer to opt out during their application. The workshop registration is open to all. Students with alternative sources of funding are welcome as well. APPLICATION for PLMW scholarship: The scholarship application can be accessed at the following URL: https://forms.gle/dzV8ELgQUx2xfEjm9 The deadline for full consideration of funding is Monday, October 7. Selected participants will be notified by October 21. Confirmed speakers (so far): * Adriana Compagnoni, Stevens Institute of Technology * Isil Dillig, UT Austin * Derek Dreyer, MPI-SWS * Marco Gaboardi, SUNY Buffalo * Lindsey Kuper, UC Santa Cruz * Xavier Leroy, Inria Confirmed sponsors (so far): * An Anonymous Donor * NSF * ACM SIGPLAN * Amazon

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