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Representing a type system in Haskell
by Talha Qamar 10 Jul '23

10 Jul '23

Hello everyone, I'm working on a game engine in Haskell. The thing is, while I want to write the architecture in Haskell, I'm thinking of using something else as the actual scripting language. Long story short, how would I represent a type system in Haskell? I've gotten _something_ together that works a bit like this: ``` data Type = -- ...all possible types data Value = -- ...all possible types again data TypedValue = TypedValye Type Value ``` But I'm concerned if this is the ideal way of doing things, particularly when I get to complex types like structs or tagged unions. Any help would be appreciated. Sent from Proton Mail mobile

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Re: [Haskell-cafe] Representing a type system in Haskell
by Talha Qamar 10 Jul '23

10 Jul '23

This looks perfect! I think I'll spend a couple days looking this over and grokking it. Thanks for your time. Sent from Proton Mail mobile -------- Original Message -------- On Jul 10, 2023, 6:56 PM, Brandon Allbery wrote: > You might look at https://web.cecs.pdx.edu/~mpj/thih/thih.pdf which shows how to implement Haskell's own type system (minus various GHC extensions) in Haskell, and adapt to whatever language you're implementing. On Mon, Jul 10, 2023 at 8:36 AM Talha Qamar via Haskell-Cafe wrote: > > > Hello everyone, I'm working on a game engine in Haskell. The thing is, while I want to write the architecture in Haskell, I'm thinking of using something else as the actual scripting language. > > Long story short, how would I represent a type system in Haskell? I've gotten _something_ together that works a bit like this: > > ``` > data Type = -- ...all possible types > data Value = -- ...all possible types again > data TypedValue = TypedValye Type Value > ``` > But I'm concerned if this is the ideal way of doing things, particularly when I get to complex types like structs or tagged unions. > > Any help would be appreciated. > > Sent from Proton Mail mobile > > > _______________________________________________ > 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. -- brandon s allbery kf8nh allbery.b(a)gmail.com

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servant streaming question
by Zoran Bošnjak 10 Jul '23

10 Jul '23

Hi all, I would like to reuse some streaming functions from the turtle package in the context of the servant streaming handler. Relevant references: https://hackage.haskell.org/package/turtle-1.6.1/docs/Turtle-Shell.html https://hackage.haskell.org/package/turtle-1.6.1/docs/Turtle-Prelude.html https://hackage.haskell.org/package/servant-0.20/docs/Servant-Types-SourceT… As a simple example: Turtle.Prelude.ls function represents stream of FilePaths (directory listing of some path) ls :: FilePath -> Shell FilePath Servant streaming is based around SourceT IO a, for example: type ListFiles = "ls" :> StreamGet NewlineFraming PlainText (SourceT IO FilePath) The problem is that the streaming (Shell a) is not exactly the same as servant's (SourceT IO a). But as far as I understand, they both represent "stream of values of type 'a'". My question is: Is a generic conversion function possible? Something like: shellToSource :: forall a. Shell a -> SourceIO a shellToSource = ?? ... such that I could reuse the 'ls' and write a streaming servant handler like this: listFilesHandler :: Handler (SourceIO FilePath) listFilesHandler = pure $ shellToSource $ Turtle.Prelude.ls "somePath" Appreciate any suggestion. regards, Zoran

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[ANN] Copilot 3.16
by Ivan Perez 09 Jul '23

09 Jul '23

Hi everyone, We are very excited to announce Copilot 3.16 [2]. Copilot is a stream-based EDSL in Haskell for writing and monitoring embedded C programs, with an emphasis on correctness and hard realtime requirements. Copilot is typically used as a high-level runtime verification framework, and supports temporal logic (LTL, PTLTL and MTL), clocks and voting algorithms. Copilot has been used at NASA in drone test flights. Through the NASA tool Ogma [1] (also written in Haskell), Copilot also serves as a runtime monitoring backend for NASA's Core Flight System, Robot Operating System (ROS2), and FPrime (the software framework used in the Mars Helicopter) applications. This new version provides comprehensive tests for the C99 backend, and introduces a breaking change in the definition of the type `Arg` in copilot-language. For details, see [2]. The new version is already available on Hackage [4]. As always, we're releasing exactly 2 months since the last release. Our next release is scheduled for Sep 7th, 2023. We are also extremely excited to announce that Copilot has received full approval for release as NASA Class D open-source software. Current emphasis is on increasing test coverage for the two remaining libraries without tests (copilot-language and copilot-theorem), removing unnecessary dependencies, hiding internal definitions, and formatting the code to meet our new coding standards. Users are encouraged to participate by opening issues and asking questions via our github repo [3]. There have been many updates on the Copilot front in the last few months. We'll be able to announce more soon. Stay tuned. Happy Haskelling! Ivan [1] https://github.com/nasa/ogma [2] https://github.com/Copilot-Language/copilot/releases/tag/v3.16 [3] https://github.com/Copilot-Language/copilot [4] https://hackage.haskell.org/package/copilot

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PhD position at KU Leuven
by Tom Schrijvers 06 Jul '23

06 Jul '23

Dear Haskell Cafe, I have a PhD position available for a candidate with a master degree in computer science, mathematics or similar and a passion for Haskell, functional programming and programming language theory. For more information and applications, see: https://www.kuleuven.be/personeel/jobsite/jobs/60229600?hl=en&lang=en -- prof. dr. ir. Tom Schrijvers Research Professor KU Leuven Department of Computer Science Celestijnenlaan 200A 3001 Leuven Belgium Phone: +32 16 327 830 http://people.cs.kuleuven.be/~tom.schrijvers/

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Final Call for Talks: Haskell Implementors' Workshop 2023
by Ryan Scott 02 Jul '23

02 Jul '23

The 2023 Haskell Implementors' Workshop deadline is just under one month away. We are looking forward to your talk submissions. Best, Ryan ================================== ACM SIGPLAN Haskell Implementors' Workshop https://icfp23.sigplan.org/home/hiw-2023 Seattle, Washington, United States, September 4, 2023 Co-located with ICFP 2023 https://icfp23.sigplan.org/ Important dates --------------- Deadline: July 4, 2023 (AoE) Notification: August 4, 2023 Workshop: September 4, 2023 The 15th Haskell Implementors' Workshop is to be held alongside ICFP 2023 this year in Seattle. It is a forum for people involved in the design and development of Haskell implementations, tools, libraries, and supporting infrastructure to share their work and to discuss future directions and collaborations with others. Talks and/or demos are proposed by submitting an abstract, and selected by a small program committee. There will be no published proceedings. The workshop will be informal and interactive, with open spaces in the timetable and room for ad-hoc discussion, demos, and short lightning talks. Scope and target audience ------------------------- It is important to distinguish the Haskell Implementors' Workshop from the Haskell Symposium which is also co-located with ICFP 2023. The Haskell Symposium is for the publication of Haskell-related research. In contrast, the Haskell Implementors' Workshop will have no proceedings -- although we will aim to make talk videos, slides, and presented data available with the consent of the speakers. The Implementors' Workshop is an ideal place to describe a Haskell extension, describe works-in-progress, demo a new Haskell-related tool, or even propose future lines of Haskell development. Members of the wider Haskell community are encouraged to attend the workshop -- we need your feedback to keep the Haskell ecosystem thriving. Students working with Haskell are especially encouraged to share their work. The scope covers any of the following topics. There may be some topics that people feel we've missed, so by all means submit a proposal even if it doesn't fit exactly into one of these buckets: * Compilation techniques * Language features and extensions * Type system implementation * Concurrency and parallelism: language design and implementation * Performance, optimisation and benchmarking * Virtual machines and run-time systems * Libraries and tools for development or deployment Talks ----- We invite proposals from potential speakers for talks and demonstrations. We are aiming for 20-minute talks with 5 minutes for questions and changeovers. We want to hear from people writing compilers, tools, or libraries, people with cool ideas for directions in which we should take the platform, proposals for new features to be implemented, and half-baked crazy ideas. Please submit a talk title and abstract of no more than 300 words. Submissions can be made via HotCRP at https://icfphiw23.hotcrp.com until July 4 (anywhere on earth). We will also have a lightning talks session. These have been very well received in recent years, and we aim to increase the time available to them. Lightning talks should be ~7mins and are scheduled on the day of the workshop. Suggested topics for lightning talks are to present a single idea, a work-in-progress project, a problem to intrigue and perplex Haskell implementors, or simply to ask for feedback and collaborators. Program Committee ----------------- * Gergő Érdi (Standard Chartered Bank) * Sebastian Graf (Karlsruhe Institute of Technology) * Wen Kokke (University of Strathclyde) * Ryan Scott (Galois, Inc.) * Rebecca Skinner (Mercury) * Li-yao Xia (University of Edinburgh) Contact ------- * Ryan Scott <ryan.gl.scott at gmail.com>

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Re: [Haskell-cafe] type error when specializing lens zooms in ghc >= 9.0
by Olaf Klinke 27 Jun '23

27 Jun '23

> Hm, yikes, I tend to agree this is a very general error message. Here > are > all the places "83865" shows up in the code base: > > > https://gitlab.haskell.org/search?search=83865&project_id=1&group_id=2&sear… > > I opened https://gitlab.haskell.org/ghc/ghc/-/issues/23466 to follow > up. > Feel free to weigh in. (Contact me if you need an account - spam > measures > currently include manual approvals for new accounts.) > Thanks, Bryan. This made me wonder what the current system behind assignment of error codes is. I'd expect five-digit error codes to be *more* specific than the general shape of error message emitted by ghc, but here it is evidently less specific. 82865 stands for the error message constructor TypeEqMismatch [1] which is a record [2] with many fields. In particular, the teq_mismatch_expected and teq_mismatch_actual fields hold structural information: a ForAllTy [3] may hint at simplified subsumption. Thus my proposal would be that error codes are composite values, with one part (as currently implemented) in bijection to the error message constructor and another part determined by a function of the actual error value. This function has to be chosen to provide sufficient abstraction from the actual situation but e.g. differentiate between constructors of the Type type. For example, why don't the cases differentiated by the pretty-printer [4] not own their own error codes? Olaf [1] https://gitlab.haskell.org/ghc/ghc/-/blob/master/compiler/GHC/Types/Error/C… [2] https://hackage.haskell.org/package/ghc-9.6.1/docs/src/GHC.Tc.Errors.Types.… [3] https://hackage.haskell.org/package/ghc-9.6.1/docs/src/GHC.Core.TyCo.Rep.ht… [4] https://hackage.haskell.org/package/ghc-9.6.1/docs/src/GHC.Tc.Errors.Ppr.ht…

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ICFP 2023: Call for Volunteers (Deadline: 30 June!)
by ICFP Publicity 27 Jun '23

27 Jun '23

ICFP 2023 CALL FOR VOLUNTEERS 28th ACM SIGPLAN International Conference on Functional Programming https://icfp23.sigplan.org/track/icfp-2023-volunteers Sign up to be a Volunteer and help us make ICFP 2023 a unique experience for all attendants! ICFP 2023 is pleased to offer a number of opportunities for volunteers, who are vital to the efficient operation and continued success of the conference each year. The volunteer program is a chance for people from around the world to participate in the conferences whilst assisting us in preparing and running the event. The Volunteer Program helps more people attend the ICFP conference by covering conference fees, including access to the banquet (but not travel or lodging expenses) in exchange for a fixed number of work hours (usually from 12 to 15) helping with the conference organization. ## How to apply Please apply using this form (https://forms.gle/27pzbztJq5PVCZeW9) The deadline is June 30th ## Eligibility Everyone is welcome to apply. Priority is given to junior members of our community, e.g. full- or part-time students of computer science and related fields. ## Expectation Applicants must be available for at least four (4) full days between September 4th and September 9th, 2023, and will be expected to provide a total of 12-15 hours of volunteering work in that time. The skills, talents, and dedication of our Volunteers contribute to the overall quality of the conference. The Volunteer role this year will mainly involve working with the organizers to prepare for the conference by providing technical assistance to attendees, managing online Q&A and poster sessions, and supporting active communication in our online environment. ## Compensation * A Complimentary Conference Registration, offering access to all open sessions (i.e., parallel paper presentations, demonstrations, and workshops) and conference proceedings. * Free lunches and refreshments during breaks. * Volunteer garments. * Free admission to all social events. Please note that volunteers are responsible for their own travel and accommodation arrangements. If you need additional travel funding, please consider SIGPLAN PAC Funding (http://www.sigplan.org/PAC/) and PLMW (https://icfp23.sigplan.org/track/plmw-icfp-2023)

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Munich Haskell Meeting, 2023-06-27 @ 19:30
by Leah Neukirchen 26 Jun '23

26 Jun '23

Dear all, Next week, our monthly Munich Haskell Meeting will take place again on Tuesday, June 27 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 nuudel so we can reserve enough seats! It is OK to add yourself to the nuudel anonymously or pseudonymously. https://nuudel.digitalcourage.de/sPH3fnJ1Jrx61Iky Everybody is welcome! cu, -- Leah Neukirchen <leah(a)vuxu.org> https://leahneukirchen.org/

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wiki-account-request
by Val Saven 23 Jun '23

23 Jun '23

Hi! I would like to create an account for https://wiki.haskell.org with the username ValSaven. Thanks in advance.

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