- Haskell-Cafe - Haskell.org

[Job] Muse Dev, a Galois spin-out, is hiring
by Thomas DuBuisson 15 Oct '19

15 Oct '19

Muse Dev is a Galois spin-out working to put the rest of Galois out of business by automating their jobs away [1]. By discovering "the right issues at the right time" and presenting to the developer, Muse seeks to bring static code analysis to the world as early in the development cycle as possible. We're currently working with early adopters to flesh-out the interface and add final must-haves. Oh, and we are hiring. If you like all-Haskell backends, have SaaS-related experience, and love build systems then please apply. We're interested in people with experience and enthusiasm in some of: * Haskell development * Static analysis * Build system interpretation * Kubernetes cluster deployment * AWS such as EC2, IAM, EKS * REST APIs * Enterprise system deployment, packaging, and support Location: Galois offices in Portland, Oregon or Arlington, Virginia. Resumes can be sent to careers(a)muse.dev See Also https://muse.dev <https://muse.dev/careers> https://lifeatgalois.com - We have inherited some culture from Galois but are a separate company. [1] Well, anything that can be automated about program analysis. Don't tell Galois. They'll kick us out of this nice, comfy, office.

1 0

Optional "Default" instances of classes in certain subcases (but too broad)
by Juan Casanova 15 Oct '19

15 Oct '19

Hello again, Before my question, I notice I am using this list quite a bit. I hope I am no abusing or misusing it by doing so, though. Sometimes I wonder what's the line between what I should ask here and what I should ask in StackOverflow, if that line even exists. If anyone feels I may be abusing or misusing, please let me know (in public or in private). Very simple question: Would it make sense, or does it already exist, a way to implement *optional* default instances of classes that can be used more directly than currently. I am *not* talking about providing a default implementation of a class when declaring it. I know you can do this. I am talking about when you know you can provide a generic instance of a class for a wide range of situations *which depends on some constraints*. For example: instance Bifunctor f => Functor (f a) where fmap = bimap id Of course, this is a terrible idea, because the constraints are not checked when verifying overlap and the like, and so this is very likely to break your program. What I tend to do nowadays is to add a function: fmapFromBiMap :: Bifunctor f => (b -> c) -> (f a b) -> (f a c) fmapFromBiMap = bimap id and then use it each time (the following is obviously a silly example): instance Functor (Either a) where fmap = fmapFromBiMap The only problem I see with this is that I need to remember (specially with my own type classes): 1. That I provided this "default" implementation. 2. Its name. I know these are fairly small things to complain about, but once again when you do it 100 times it becomes annoying, specially for a person who absolutely does not like doing things that I know would be able to explain how to automate. So, what I would expect is for it to be something like declaring the default instance but only use it for the types that explicitly ask for it. E.g.: optional instance Bifunctor f => Functor (f a) where fmap = bimap id instance Functor (Either a) using optional The main important point here is that I expect this to check the constraints in compile time for the class that I am giving (and if it contains type variables, only use those that are guaranteed to be complied, of course). This means that if I did: instance Functor (f a) using optional I *do not* expect it to be okay with it and automatically add the constraint Bifunctor f => to the instance. I expect it to give me a compile error: "No matching optional instance found". Of course, there could be several optional instances that overlap when using optional. But then, GHC would give me the error indicating what the options are *and I would know that it's because I put optional* and I could just replace it with the specific one to use. Maybe by giving them names? optional instance fmapFromBiMap Bifunctor f => Functor (f a) where fmap = bimap id instance Functor (Either a) using optional -- If this does not work because it overlaps with other optionals, then GHC tells me, indicates the options, and I replace with: instance Functor (Either a) using fmapFromBiMap This avoids the problem of defining the instance in general (that it will overlap with basically anything), should be easy to type check and prevents having to keep an index in your mind about useful functions that you implemented or didn't. I wonder if the "deriving" family of functionalities have anything like this, but my search has not been fruitful. Maybe using Generics? Maybe I just need good autocomplete so that I can find the function easily... it still feels like this would make sense. Juan. -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336.

2 4

Feedback First Application
by Casper Thule Hansen 14 Oct '19

14 Oct '19

Hi. I have created my first application that I expect will go live within the next couple of months and I would like to have some feedback. The application is here: https://github.com/into-cps-association/utilities_backend and will be a project that I keep updating as I learn new stuff. I consider myself somewhat a haskell beginner, and my goal is to learn more about Haskell's features, packages and similar. So I hope that someone can point me to some places in my code that can be written in a better fashion, concepts that can be applied or similar. Of course - please try to keep it within my reach 🙂 The application is not critical in any fashion. It is not necessary with optimal performance, extensive testing and similar. Currently, I am not particularly interested in testing, I will save that for later. I hope someone can give me a few pointers! Cheers, Casper Thule

1 0

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

2 2

[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.

1 0

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…>

1 0

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 08 Oct '19

08 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 07 Oct '19

07 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