- Haskell-Cafe - Haskell.org

Post Doc Vacancy at St Andrews
by Christopher Brown 17 Jun '22

17 Jun '22

The Programming Languages Group at the University of St Andrews seeks a post-doctoral research fellow for a fixed 12-month position. Details of the position can be found here: https://www.vacancies.st-andrews.ac.uk/Vacancies/W/4238/0/352367/889/resear… Vacancy Description School of Computer Science Salary: £34,304 per annum Start date: 1 October 2022 or as soon as possible thereafter Fixed-term: 12 months Applications are sought for a committed Post-doctoral Research Fellow to work with Dr Chris Brown conducting research for a EPSRC funded project entitled Energise: Refactorings and Skeletons for Energy-Aware Applications on High-Performance Embedded Systems. The primary duties will be to implementing refactorings for target languages such as C; proving general soundness of the refactorings using e.g. dependent types; developing new programming abstractions (skeletons) for abstracting common energy-reducing programming patterns; running experiments; writing proofs of correctness. The successful applicant will have (or be near to completion of) a PhD in Programming Languages with expertise in formal semantics of programming languages, compilers, program transformation, lightweight formal methods (including, e.g. dependent types) and/or knowledge of parallelism and non-functional properties, including energy. The post is available on a fixed-term basis for 12 months starting 1st October or as soon as possible thereafter. Further details of the project can be found by contacting Dr Christopher Brown (cmb21(a)st-andrews.ac.uk<mailto:cmb21@st-andrews.ac.uk>). Applications are particularly welcome from women, people from the Black, Asian and Minority Ethnic (BAME) community, and other protected characteristics who are under-represented in research posts at the University. Equality, diversity and inclusion are at the heart of the St Andrews experience. We strive to create a fair and inclusive culture demonstrated through our commitment to diversity awards (Athena Swan, Carer Positive, LGBT Charter, Race Charters and Stonewall). We celebrate diversity by promoting profiles of BAME, LGBTIQ+ staff and supporting networks including the Staff BAME Network; Staff with Disabilities Network; Staff LGBTIQ+ Network; and the Staff Parents & Carers Network. Full details available online: https://www.st-andrews.ac.uk/hr/edi/ Closing Date: 29 July 2022 Interview Date: 23 August 2022 Please quote ref:AR2699GB School of Computer Science Salary: £34,304 per annum Start date: 1 October 2022 or as soon as possible thereafter Fixed-term: 12 months

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How to override binary package
by ☂Josh Chia (謝任中) 14 Jun '22

14 Jun '22

Hi, Given that binary is one of the packages that comes with GHC, it seems that it can't be overridden with my own version using the standard ways (e.g. extra-deps in stack.yaml), at least not easily. On GHC 9.2.3, using stack, I would like to use my own version from my github repo. I've tried extra-deps referencing the github repo commit and it did not work; judging by the behavior of some functions, I was still getting the standard binary package instead of my own version. Is there a way to override? Josh

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State Monad Tutorial
by danon 14 Jun '22

14 Jun '22

Saw the discussion on the https://wiki.haskell.org/Talk:State_Monad I don´t have an account on the wiki. If anyone is interested in a small practical example of how to State Monad. I may have 1 or 2. Kind Regards dhj

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CALL FOR PAPERS - IFL22 - The 34th Symposium on Implementation and Application of Functional Languages
by Pieter Koopman 13 Jun '22

13 Jun '22

*CALL FOR PAPERS - The 34th Symposium on Implementation and Application of Functional Languages* *Important dates* Draft paper submission: 7th of August 2022 Draft paper notification: 9th of August 2022 Registration deadline: 12th of August 2022 Symposium: 31th of August to 2nd of September *Scope* The goal of the IFL symposia is to bring together researchers actively engaged in the implementation and application of functional and function-based programming languages. IFL 2022 will be a venue for researchers to present and discuss new ideas and concepts, work in progress, and publication-ripe results related to the implementation and application of functional languages and function-based programming. Topics of interest to IFL include, but are not limited to: * language concepts * type systems, type checking, type inferencing * compilation techniques * staged compilation * run-time function specialization * run-time code generation * partial evaluation * abstract interpretation * metaprogramming * generic programming * automatic program generation * array processing * concurrent/parallel programming * concurrent/parallel program execution * embedded systems * web applications * embedded domain specific languages * security * novel memory management techniques * run-time profiling performance measurements * debugging and tracing * virtual/abstract machine architectures * validation, verification of functional programs * tools and programming techniques * industrial applications *Submissions and peer-review* Following IFL tradition, IFL 2022 will use a post-symposium review process to produce the formal proceedings. Before the symposium authors submit draft papers. These draft papers will be screened by the program chair to make sure that they are within the scope of IFL. The draft papers will be made available to all participants at the symposium. Each draft paper is presented by one of the authors at the symposium. After the symposium, a formal review process will take place, conducted by the program committee. Reviewing is single blind. There will be at least 3 reviews per paper. The reviewers have 6 weeks to write their reviews. For the camera-ready version the authors can make minor revisions which are accepted without further reviewing. *Where* IFL 2022 will be held physically in Copenhagen, Denmark, arranged by DIKU at the University of Copenhagen. See the IFL 2022 website at https://ifl22.github.io/ for more information. [image: beacon]

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pipes Producer combination
by PICCA Frederic-Emmanuel 13 Jun '22

13 Jun '22

Hello, I would like to combine Producers in order to create a Producer of another type whcih combine these values I want a Producer of the 'A' type data A :: A a b by I have a Producer of 'a' values and another on of 'b' values. what is the best way to create from thoses two producers a Producer of 'A' ? Is ther a Generic way to automatically generate these combine Producers. In my programmes, I will have plenty of these combine Producers. thanks for considering. Cheers Frederic

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Phase correction?
by Mario Lang 08 Jun '22

08 Jun '22

Hi. This is more a math question then a Haskell specific thing. However, Haskell fits nicely to write down the problem as executable "pseudo" code, so here I am, knowing that you all can read this and actually grasp the problem at hand (which I obviously dont). I stumbled across this while naively playing with C++ infinite ranges, starting with std::ranges::views::iota. So there I was, happily playing with signal generation, until I went stuck here: Modulating oscillation frequency while trying to stay stateless. But code says more then a foreign language, so: #!/usr/bin/env stack -- stack --resolver lts-19.8 runghc import Data.Ratio n = [0 ..] d = 10 -- EXAMPLE, usually 48000 t = (% d) <$> n sine f = (\x -> sin $ 2*pi * fromRational x * f x) <$> t sine1 = sine $ const 1 -- OK -- Lets devise a method to specify a value changing over time data I = No | Lin | Exp erp No a _ _ = a erp Lin a b mu = (1 - mu) * a + mu * b erp Exp a b mu = a * ((b / a) ** mu) data Curve a = Curve a [(I, Double, a)] at (Curve p1 []) _ = p1 at (Curve p1 ((i, d, p2):xs)) t = go 0 d p1 p2 i d xs where go t1 t2 p1 p2 i d xs | t < t2 = erp i p1 p2 $ (t - t1) / d | null xs = p1 | (i', d', p2') <- head xs = go t2 (t2 + d') p2 p2' i' d' $ tail xs -- Frequency modulation? c = Curve 1 [(Exp, 1.0, 2), (Exp, 1.0, 1)] sine2 = sine $ at c . fromRational -- WRONG!🙅 -- Whenever a change occurs, phase is incorrect -- because current step doesn't know about the past main = do print $ take 10 $ sine1 print $ at c 0.5 == at c 1.5 print $ take 10 $ sine2 -- The naive question of an experimenting non-math coder person is: -- Can a version of `at` be written which compensates for the phase -- differences which runs in O(n) where n is the number of curve points? -- Intuitively this should be possible given `d` (denominator). at' :: Curve a -> Ratio b -> a at' c t = undefined -- CYa, ⡍⠁⠗⠊⠕

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Dashboard
by Anton Pichugin 08 Jun '22

08 Jun '22

Hello everyone in the Haskell cafe! Such a nice place! My name is Anton. A month ago I started learning Haskell. I want to make a dashboard about the language. What data should I analyze and add to it? I see this project as a page where you can see charts and diagrams that change in real time. As of now I only have Google Trends (search Interest over time) + number of commits on GitHub. What else can I visualize? Which one could be helpful to the community? Kind regards, Anton Pichugin

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[ANN] Yampa 0.13.5
by Ivan Perez 08 Jun '22

08 Jun '22

Dear all, I'm happy to announce the release of Yampa 0.13.5! Yampa is a fast, elegant FRP library that enforces a separation between effects (e.g., user input, rendering) and FRP signal function specifications.Yampa prides itself in being a long-standing community project. It's now been around for almost 20 years!!! In all this time, it has enjoyed abundant use in research, in open source, and in industry. * Summary of changes - Tests in the yampa-test library have now been reorganized to follow the same structure of Yampa. This change will make it easier to identify what tests are missing. A summary has been produced as part of an issue [1]. - A less-known feature of Yampa is that applicative style is also supported, and renders programs reminiscent of classic FRP. To make Yampa more inviting to users who prefer such style, the descriptions in the package, README and main module have been adapted so that they do not suggest that arrows syntax or the arrow-based interface is the only available or even preferred style. - Tabs will now produce a compilation error. - Multiple maintenance fixes (fix broken links in documentation, remove unnecessary imports, style fixes, etc.). As always, Yampa and yampa-test are released in sync. The CHANGELOGs are available at: https://github.com/ivanperez-keera/Yampa/blob/develop/yampa/CHANGELOG https://github.com/ivanperez-keera/Yampa/blob/develop/yampa-test/CHANGELOG * Releases You can explore the current versions at: https://hackage.haskell.org/package/Yampa https://hackage.haskell.org/package/yampa-test * Code The github repo is located at: https://github.com/ivanperez-keera/Yampa * Upcoming changes We are discussing an upcoming change that may affect users. We are interested in knowing if/how this would affect you (if at all). - Addition of new constraint to integral/derivative: The VectorSpace implementation we are using imposes the Eq and Floating constraints on vector spaces, but they have turned out not to be necessary. An alternative implementation is being proposed [2], which removes those constraints, and gives default implementations for some functions that meet some type constraints. This change would require adapting the code of integral, derivative and some related functions to impose an additional type constraint. We expect most user code to be compatible, but the change is, technically, API-breaking. This topic is open to discussion, we invite interested users to come forward. * Other notes: We have a plan for the upcoming releases. Check out the project issues or message me if you are interested in participating. https://github.com/ivanperez-keera/Yampa/issues All the best, Ivan [1] https://github.com/ivanperez-keera/Yampa/issues/217 [2] https://github.com/ivanperez-keera/simple-affine-space/tree/develop-no-cons…

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Deadline Extended: 26th Brazilian Symposium on Programming Languages (SBLP 2022)
by Cristiano D. Vasconcellos 07 Jun '22

07 Jun '22

SBLP 2022 is the 26th edition of the Brazilian Symposium on Programming Languages<https://cbsoft2022.facom.ufu.br/sblp.php>. It is promoted by the Brazilian Computer Society (SBC) and constitutes a forum for researchers, students, and professionals to present and discuss ideas and innovations in the design, definition, analysis, implementation, and practical use of programming languages. SBLP's first edition was in 1996. Since 2010, it has been part of CBSoft, the Brazilian Conference on Software: Theory and Practice. The Conference is planned to be held on October 3-7, 2022, fully online. Submission Guidelines Papers can be written in Portuguese or English. Submissions in English are encouraged considering that only accepted papers written in English will appear in the proceedings, usually indexed in the ACM Digital Library (to be confirmed). The acceptance of a paper implies the registration of at least one author in the symposium to present it. Papers must be original and not simultaneously submitted to another journal or conference. No-show of scheduled papers will result in excluding them from the proceedings. SBLP 2022 will use a lightweight double-blind review process. The manuscripts should be submitted for review anonymously (i.e., without listing the author’s names on the paper) and references to own work should be made in the third person. Papers must be submitted electronically (in PDF format) via the EasyChair System.<https://easychair.org/conferences/?conf=sblp2022> The following paper categories are welcome (page limits include figures, references, and appendices): • Full papers: up to 8 pages long in ACM 2-column conference format.<http://www.acm.org/publications/proceedings-template> Full papers can be further specialized, at submission time, as student papers (i.e., as papers describing research conducted mainly by a student at any level). student papers will be subject to the exact same reviewing process and criteria but may be entitled for an award (see below). • Short papers: up to 3 pages in the same format. Short papers can discuss new ideas which are at an early stage of development or can report partial results of on-going dissertations or theses. Each paper can have a maximum of one extra page for references. Active graduate and undergraduate students seeking feedback are invited to submit short papers of their original unpublished and in-progress research work. A set of selected papers, which did not get accepted as full papers, may be accepted as short papers. Awards: Two best paper awards will be attributed, distinguishing full paper submissions of the best: • student paper; • non-student paper. List of Topics (related but not limited to the following): • Programming paradigms and styles, scripting and domain-specific languages and support for real-time, service-oriented, multi-threaded, parallel, distributed, and quantum programming; • Program generation and transformation; • Formal semantics and theoretical foundations: denotational, operational, algebraic, and categorical; • Program analysis and verification, type systems, static analysis, and abstract interpretation; • Programming language design and implementation, programming, language environments, compilation, and interpretation techniques; • Programming languages for the blockchain technology: design and implementation of Smart Contract languages, implementation of consensus protocols, language-based security, and cryptographic primitives. A selection of the best papers appearing in the last editions of SBLP have been invited to be extended and considered for publication in a special issue of the Journal of Computer Languages (COLA), by Elsevier. We will approach COLA for a similar special issue regarding the 2022 edition of SBLP. Important dates: • Abstract submission: 20 June, 2022. • Paper submission: 20 June, 2022. • Author notification: 16 Aug, 2022. • Camera ready deadline: 29 Aug, 2022. Program Committee Program Committee Chair: Cristiano Vasconcellos, UDESC Program Committee Alberto Pardo, Universidad de la República Alcides Fonseca, Universidade de Lisboa Alejandro Díaz-Caro, Universidad Nacional de Quilmes & Universidad de Buenos Aires Alex Kavvos, University of Bristol Anderson Faustino, UEM Andrei Paskevich, Université Paris-Sud, LRI Andre Maidl, Elastic Dalvan Griebler, PUCRS/SETREM Emmanuel Chailloux, University Pierre and Marie Curie Fernando Castor, UFPE & Utrecht University Fernando Pereira, UFMG Francisco Sant'anna, UERJ Karina Roggia, UDESC Leonardo dos Santos, UFJF Liam O'Connor, University of Edinburgh Marcos Viera, Universidad de la República Mário Pereira, Universidade NOVA de Lisboa Mariza Bigonha, UFMG Nuno Macedo, INESC TEC & University of Porto Paul Leger, Universidad Católica del Norte Roberto Bigonha, UFMG Roberto Ierusalimschy PUC-Rio Rodrigo Ribeiro, UFOP Samuel Feitosa, UFFS Sérgio Medeiros, UFRN Simão Sousa, Universidade da Beira Interior Stefania Dumbrava, ENSIIE Paris-Evry Contact: All questions about submissions should be emailed to cristiano.vasconcellos(a)udesc.br

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Re: [Haskell-cafe] Should there be a haskell template for inclusion polymorphism in Haskell?
by Olaf Klinke 05 Jun '22

05 Jun '22

> So my central questions for discussions are: > > - Is inclusion polymorphism something we should use at all in Haskell? > - These boiler plate code maybe better be generated using Haskell template > instead, is there one already, or should > there be one? Maybe one of the authors of a sub-typing library can share a more informed opinion on this. My view as a mathematician: A type being a subtype of another is a relation between types. Relations between types is what multi-parameter type classes is about. Hence it seems that this is how subtypes in Haskell ought to be done. For example, in the attenuation and records-sop package, the latter of which is based on genercis-sop, which depends on Template Haskell. So without having used any of the mentioned packages, I believe your second question can be answered with "yes". Regarding the first question, we should probably ask ourselves how much type-safety we're sacrificing for the convenience we gain. The Num example you gave shows one possible danger: While a subtype relation may hold mathematically, the implementiation details may cause this relation to fail in reality. Example: All floating point numbers are rationals, aren't they? So there should be a subtype relation. But how to convert NaN, -infinity or -0 of type Double to a pair of Integers? Olaf

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