- Haskell-Cafe - Haskell.org

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

1 2

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

2 1

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.

3 4

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/

1 0

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

4 4

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

1 0

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

2 2

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

1 0

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

2 1

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…

3 3