- Haskell-Cafe - Haskell.org

Taking over maintainership of cautious-file (or does anyone know of an alternative?)
by Brent Yorgey 15 Feb '20

15 Feb '20

The cautious-file package http://hackage.haskell.org/package/cautious-file has not been updated by the maintainer, Robin Green, since 2013 (though there have been a few Hackage trustee updates since then). The linked source repository was hosted on patch-tag.com and no longer exists. I tried contacting the maintainer on January 25 but have not heard back. I hereby announce my intention to take over as maintainer of the package. (As a side note, as far as I know my diagrams-haddock package is the only thing on Hackage that depends on it.) Alternatively, if anyone knows of a different, actively maintained package that provides similar functionality, I'd love to hear about it! -Brent

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ghc runtime linker problem on i386
by Olaf Klinke 14 Feb '20

14 Feb '20

Dear Cafe, I'm experiencing strange behaviour on an old i386 machine when interpreting Haskell code on the fly: The same code runs from GHCi and fails as compiled executable. It might be a GHC runtime linker problem but I'm not sure. I successfully built haskintex and IHaskell with stack 2.1.3 on that machine. Both programs are supposed to interpret Haskell code at runtime: IHaskell uses the GHC API while haskintex uses hint, which itself is a wrapper for the GHC API. Therefore I suspect the problem lies in the usage of the GHC API itself. Both programs fail at runtime with the same error: $LIBDIR/ghc-prim-0.5.3/HSghc-prim-0.5.3.o: unknown symbol `_GLOBAL_OFFSET_TABLE_` When adding -dynamic to the ghc-options field in the package cabal file, the error goes away. Minimal code to reproduce is below. The i386 machine has no system ghc, no cabal, no ghcup and I wiped the $HOME/.stack directory before running "stack build". On x86-64 the error does not occur regardless of the -dynamic flag. Should I file a bug report or is this expected behaviour? If this is a bug, who should I file the bug against? Olaf {-- put this as app/Main.hs in a new stack project --} module Main where import Language.Haskell.Interpreter -- hint main :: IO () main = putStrLn =<< hintstuff hintstuff :: IO String hintstuff = fmap (either show show).runInterpreter $ do setImports ["Prelude"] interpret "1+2" (as :: Int)

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Interpreting synchronized streams (pre-IO monad Haskell)
by Jiri Jakes 13 Feb '20

13 Feb '20

Heλλo! Before introduction of IO monad, first versions of Haskell used synchronised streams [1]: main :: [Response] -> [Request] where Response and Request were ADTs containing all possible actions and responses: data Request = ReadFile Name | ... | AppendChan Name String | ... data Response = Success | Str String | Bn Bin | Failure ... I wanted to write an interpreter of this representation using a simplified version: import System.Environment (getArgs) data Response = Success | StrList [String] data Request = GetArgs | PutStr String eval :: Request -> IO Response eval GetArgs = StrList <$> getArgs eval (PutStr s) = putStrLn s >> return Success main' :: [Response] -> [Request] main' ~(StrList args : _) = [ GetArgs, PutStr (show args) ] main :: IO () main = ??? I can imagine how interpreting main' could work, thanks to laziness. However, when actually trying to implement it, I get lost. I cannot figure out how could I read requests (result of calling main') before having something to pass to main'. Having a look at ancient version of GHC [2] didn't help either. Is it actually possible without some low-level tricks? Perhaps using mutually recursive functions? Or by converting to continuations somehow? Thank you! Jiri [1] http://haskell.org/definition/haskell-report-1.0.ps.gz [2] https://downloads.haskell.org/~ghc/0.29/ghc-0.29-src.tar.gz

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Re: [Haskell-cafe] [ANN] Documentation for base-4.13.0.0 & GHC 8.8.1
by 石井大海 13 Feb '20

13 Feb '20

Oops, sorry I've sent the question only to Fumi mistakingly. Here I re-send to Cafe. Sorry! > 2020/02/13 13:28、石井大海 <konn.jinro(a)gmail.com>のメール: > > Hi, > > What's the difference with documentations already distributed with GHC Users' Guide? > > * https://downloads.haskell.org/~ghc/8.8.2/docs/html/ <https://downloads.haskell.org/~ghc/8.8.2/docs/html/> > * https://downloads.haskell.org/~ghc/8.8.2/docs/html/libraries/ghc-8.8.2/inde… <https://downloads.haskell.org/~ghc/8.8.2/docs/html/libraries/ghc-8.8.2/inde…> > * https://downloads.haskell.org/~ghc/8.8.2/docs/html/libraries/index.html <https://downloads.haskell.org/~ghc/8.8.2/docs/html/libraries/index.html> > > Are they hooglable? > >> 2020/02/13 13:20、Fumiaki Kinoshita <fumiexcel(a)gmail.com <mailto:fumiexcel@gmail.com>>のメール: >> >> It seems unlikely that they will be uploaded to Hackage anytime soon, so I decided to host them on my server. >> >> http://docs.hask.moe/base-4.13.0.0/index.html <http://docs.hask.moe/base-4.13.0.0/index.html> >> >> GHC 8.8.1: http://docs.hask.moe/ghc-8.8.1/index.html <http://docs.hask.moe/ghc-8.8.1/index.html> >> >> Hope this helps >> _______________________________________________ >> Haskell-Cafe mailing list >> To (un)subscribe, modify options or view archives go to: >> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe <http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe> >> Only members subscribed via the mailman list are allowed to post. >

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Re: [Haskell-cafe] [Job] Cloudseal seeks Haskell Software Engineers
by tomas gallegos 13 Feb '20

13 Feb '20

Hello there, My name is Tomas Gallegos and I specialize in functional programming using Haskell. I am very interested in this Haskell job position. It would be great if we could talk to discuss this position further and maybe schedule an interview. Thank you for your time and consideration, I look forward to hearing from you.(Attached to this email is my resume). Regards, Tomas Gallegos

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[ANN] Documentation for base-4.13.0.0 & GHC 8.8.1
by Fumiaki Kinoshita 13 Feb '20

13 Feb '20

It seems unlikely that they will be uploaded to Hackage anytime soon, so I decided to host them on my server. http://docs.hask.moe/base-4.13.0.0/index.html GHC 8.8.1: http://docs.hask.moe/ghc-8.8.1/index.html Hope this helps

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[ANN] BNFC-meta 0.6.1 release -- embedded Happy parsers
by Artem Pelenitsyn 13 Feb '20

13 Feb '20

Hello! BNFC-meta 0.6.1 has been released. The library [1,2] allows you to define simple parsers inside your source files using BNF-like formalism by the way of Template Haskell. A couple of small example applications are hosted here [3]. Details are described in the Haskell '11 paper [4] (preprint [5]). Compared with the previous release, support for recent GHCs is added. Also a minor problem with spaces after closing parenthesis in pretty-printer is fixed courtesy GitHub user @mbuszka. [1]: http://hackage.haskell.org/package/BNFC-meta [2]: https://github.com/ulysses4ever/BNFC-meta [3]: https://github.com/ulysses4ever/BNFC-meta-examples [4]: https://dl.acm.org/doi/10.1145/2096148.2034689 [5]: http://www.cse.chalmers.se/~patrikj/papers/MetaDSL_preprint_20110325.pdf -- Cheers, Artem

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Re: [Haskell-cafe] [Job] Cloudseal seeks Haskell Software Engineers
by tomas jose gallegos 12 Feb '20

12 Feb '20

Hello there, My name is Tomas Gallegos and I specialize in functional programming using Haskell. I am very interested in this Haskell job position. It would be great if we could talk to discuss this position further and maybe schedule an interview. Thank you for your time and consideration, I look forward to hearing from you.(Attached to this email is my resume). Regards, Tomas Gallegos Sent with [ProtonMail](https://protonmail.com) Secure Email.

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help designing a function
by PICCA Frederic-Emmanuel 12 Feb '20

12 Feb '20

Hello, I try to write a software, which takes a stack of images and produce a data cube. Depending on the user input obtain via an .ini file, these cube are computed from different kind of projection. For now I have only two projection QxQyQzProjection and HklProjection. I prepare the InputXXX for the processXXX functions from the BinocularConfiguration and a function (InputType -> a) mkInputQxQyQz :: FramesQxQyQzP a => BinocularsConfig -> (InputType -> a) -> IO (InputQxQyQz a) processQxQyQz :: FramesQxQyQzP a => InputQxQyQz a -> IO () mkInputHkl :: FramesHklP a => BinocularsConfig -> (InputType -> a) -> IO (InputHkl a b) processHkl :: FramesHklP a => InputHkl a b -> IO () now I want to write this kind of function, which use the right Projection depending on the type find in the BinocularsConfig processProjection :: Show a => BinocularsConfig -> (InputType -> a) -> IO () processProjection c' f = do print c' case (ptype . bProjection $ c') of QxQyQzProjection -> do i <- mkInputQxQyQz c' f print i processQxQyQz i HklProjection -> do i <- mkInputHkl c' f print i processHkl i return () Indeed when I compile this code, I have an Error explaining that a FramesHklP a constrain is missing from the processProjection function. and idem for the FramesQxQyQzP. so I can add both constrains, but in that case I need to implement the two interfaces for each type a. Indeed this is wrong the `a` is for a specific projection thus I can not create an instance for each kind of Projection. I do not know If I am clear, but I do not know how to organise my code in order to be able to write this processProjection method. any help would be appreciate. thanks Frederic

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[Job] Hackworth are hiring a Haskell developer, full time, on-site in London
by Drew Hess 11 Feb '20

11 Feb '20

[Hi Haskellers! Apologies if you’ve already seen this on Reddit or Hacker News.] Hackworth are hiring a full-time Haskell developer in London. This is an on-site role, at our office in Shoreditch. Salary range: £70,000-£80,000 per year In this role, you'll help lead the research phase of our first product: a programming language optimized for learning to program, rooted in functional programming concepts, with a particular focus on the visualization of program execution. You'll be responsible for designing several prototype languages, exploring the programming language and computer education research literature for ideas, and explaining these designs and their trade-offs to your colleagues. Once the research phase concludes, you'll help lead the development phase of the product, the result of which will be a novel interactive programming environment for children. We're targeting the end of 2021 for initial beta testing with schools and external organizations. We expect to open-source the product at some point during the development phase. You'll have the option of leading that open source effort, if you wish. This role does not include any on-call, devops, or customer support requirements. You'll be focused exclusively on writing Haskell and creating an innovative programming environment for kids. For more information, please see the full job posting on our website: https://www.hackworthltd.uk/jobs/20200204/. ## Tech Our software stack is entirely Haskell and Nix. We use macOS on the desktop, and NixOS and AWS everywhere else. If you prefer Linux on your desktop, we can probably arrange that. ## About us Hackworth Ltd is a well-financed, bootstrapped, private limited company based in London. Our purpose is to make programming relevant to the interests of children of all backgrounds. We're committed to building a sustainable, ethical, socially responsible business. We serve children and schools; therefore, we’ll never fund our business by selling ad placements or exploiting compulsion loops via loot boxes or micro-transactions. See here for more: https://www.hackworthltd.uk/about/ ## Applying To apply for this role, you should meet the following requirements: * The equivalent of (approximately) 2 years' experience writing Haskell, in either an industrial or research setting. It need not have been all at one organization, nor one contiguous block of time. * You can be on-site at our London office at least 4 days per week. * You're eligible to work in the United Kingdom. If you're familiar with any of the following topics, that's a definite plus, and you should mention it in your application; but please note that these are not required for the role: * Dependent types * Gradual typing * Refinement types * Total functional programming * Program synthesis * Structured editing a la Hazel or similar * Block-based programming (e.g., Scratch) * Virtual machines designed for functional languages, e.g., Landin's SECD. ## To apply To apply for this role, please submit a resume/CV to careers(a)hackworthltd.com. Even if you’re unsure about your fit, or if you have any additional questions about the role, or about working at Hackworth in general, please get in touch! Hackworth are committed to diversity. We are an equal opportunities employer and do not discriminate on the grounds of gender, sexual orientation, marital or civil partner status, pregnancy or maternity, gender reassignment, race, colour, nationality, ethnic or national origin, religion or belief, disability or age.

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