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inference with implicitparams seems broken
by rowan goemans 28 Mar '22

28 Mar '22

Hello everyone, I wonder why the following taken from an stackoverflow answer doesn't work: https://stackoverflow.com/questions/71184922/is-it-possible-to-infer-a-type…. Code of the answer posted here verbatim: ``` {-# LANGUAGE ImplicitParams #-} {-# LANGUAGE RankNTypes #-} module Temp where withX :: Int -> ((?x :: Int) => r) -> r withX x r = let ?x = x in r somethingThanNeedsX :: (?x :: Int) => Int somethingThanNeedsX = ?x + 2 foo :: Int foo = bar where bar = withX 42 baz baz = somethingThanNeedsX ``` This won't compile with the error message: ``` Orig.hs:19:11: error: • Unbound implicit parameter (?x::Int) arising from a use of ‘somethingThanNeedsX’ • In the expression: somethingThanNeedsX In an equation for ‘baz’: baz = somethingThanNeedsX In an equation for ‘foo’: foo = bar where bar = withX 42 baz baz = somethingThanNeedsX | 19 | baz = somethingThanNeedsX ``` If you give `baz` a type signature which includes the implicit param it compiles. But I think this is a bug. GHC should not require a type signature here. I tried searching for a GHC ticket but I couldn't find one. But that might also be down to me not using the right query. Anyway my question is, is this expected behavior? This really makes implicit params less ergonomic. Best regards, Rowan Goemans

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Munich Haskell Meeting, 2022-03-30 @ 19:30
by Leah Neukirchen 27 Mar '22

27 Mar '22

Dear all, Next week, our monthly Munich Haskell Meeting will take place again on Wednesday, March 30 at **Augustiner-Gaststätte Rumpler** at 19h30 CEST. For details see here: http://muenchen.haskell.bayern/dates.html If you plan to join, please add yourself to this dudle so we can reserve enough seats! It is OK to add yourself to the dudle anonymously or pseudonymously. https://dudle.inf.tu-dresden.de/haskell-munich-mar-2022/ Everybody is welcome! Local COVID rules apply. cu, -- Leah Neukirchen <leah(a)vuxu.org> https://leahneukirchen.org/

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Hatlab: My attempt to make a library inspired by Matlab and NumPy
by TeraTux 27 Mar '22

27 Mar '22

Greetings! I made a library which implements functions similar to those in Matlab or NumPy. The code is not much clean yet, you can see it at https://gitlab.com/Hume2/hatlab . The functions with comments are intended to be used. I want to know if it is a good start or I just wasted time. The matrices can have arbitrary dimensions, starting from 0D matrices, which are basically scalars. Operations like + - * / are element-wise. I also implemented broadcasting of these operations. I also implemented indexing. Some examples: a = matrix2D [[1,2,3],[4,5,6],[7,8,9]] a !# [2,2] -- element at index [2,2] a !$ [At 1, All] -- 1st row a !$ [To (-1), All] -- all rows except the last one a !$ [Where $ a ># 5] -- all elements bigger than 5 (The ># operator returns a matrix of bools, I will come to that later.) It is also possible to update a matrix. These operations do not copy all the elements from the original matrix, they just make another matrix which points to the original matrix at places where it was not changed. Some examples: a = eye 5 b = matrix2D [[1,2,3],[4,5,6],[7,8,9]] a !:[FromTo 1 4, FromTo 1 4]:= b -- replace the middle square by a different matrix a !:[FromTo 1 4, FromTo 1 4]:= 1 -- set all values in the middle square to 1 a !:[FromTo 1 4, FromTo 1 4]:+= 1 -- add one to all values in the middle square a !:[FromTo 1 4, FromTo 1 4]:$= cos -- replace all values in the middle square by their cosine Operators are broadcasted the same way as in Matlab or NumPy. If one operand has size 1 and the other one has size N or vice-versa in given dimension, the operator acts as if the thinner matrix was repeated in the given dimension N times. Example: a = matrix1D [10, 20, 30] -- row vector b = matrix2D [[1], [2], [3]] -- column vector a + b -- returns [[11, 21, 31], [12, 22, 32], [13, 23, 33]] There is a function "scalar" which creates a 0D matrix out of any value, so we can do: a + (scalar 5) -- returns [15, 25, 35] a * (scalar 2) -- returns [20, 40, 60] If a type is in the class Num, Fractional or Floating, the matrix of the given type is also in the given class. Conversions are performed using the function "scalar", so we can write: a + 5 a * 2 because the "5" and "2" are then interpreted as 0D matrices. Operator * is interpreted as element-wise multiplication. To do matrix multiplication, use the × operator. It can be also used to multiply matrices with vectors. Examples: v = matrix1D [1,2,3] m = matrix2D [[1,0,1],[2,-1,1],[0,1,-1]] v × m -- multiply row vector v with matrix m m × v -- multiply matrix m with column vector v m × m -- multiply matrix m by itself There are also functions for element-wise boolean operations. They work similarly and they have the # suffix. Examples: a = matrix2D [[True, True], [False, False]] b = matrix2D [[True, False], [True, False]] a &# b -- element-wise and a |# b -- element-wise or There are also element-wise comparison functions in a similar fashion. Examples: a = eye 3 b = ones [3,3] a ==# b -- returns a matrix of bools saying where the element of matrix a is equal to the corresponding element in matrix b. a <# b -- similar as above except that it tests for being less than instead of equality. a ==# 1 -- Broadcasting works for these operators too, so this syntax is valid also. There are also other functions not described in this mail. I will not describe them here because this mail is already too long. Don't worry asking me if you don't understand the meaning of any function from my comments. I did not implement any algorithms for linear equation solving, not even any other matrix algorithms yet. If this library has any potential, I may do that in the future. Please, let me know if this library has any potential or it was just a waste of time. Hume2

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Haskell Symposium 2022: Call for Papers
by Nadia Polikarpova 26 Mar '22

26 Mar '22

========================================================================= ACM SIGPLAN CALL FOR SUBMISSIONS Haskell Symposium 2022 Ljubljana, Slovenia Thu 15 -- Fri 16 September, 2022 http://www.haskell.org/haskell-symposium/2022/ ========================================================================= The ACM SIGPLAN Haskell Symposium 2022 will be co-located with the 2022 International Conference on Functional Programming (ICFP). Differently from previous years, Haskell'22 will use a single-track submission process (that is, we will only have the regular track and no early track). The Haskell Symposium presents original research on Haskell, discusses practical experience and future development of the language, and promotes other forms of declarative programming. Topics of interest include: * Language design, with a focus on possible extensions and modifications of Haskell as well as critical discussions of the status quo; * Theory, such as formal semantics of the present language or future extensions, type systems, effects, metatheory, and foundations for program analysis and transformation; * Implementations, including program analysis and transformation, static and dynamic compilation for sequential, parallel, and distributed architectures, memory management, as well as foreign function and component interfaces; * Libraries, that demonstrate new ideas or techniques for functional programming in Haskell; * Tools, such as profilers, tracers, debuggers, preprocessors, and testing tools; * Applications, to scientific and symbolic computing, databases, multimedia, telecommunication, the web, and so forth; * Functional Pearls, being elegant and instructive programming examples; * Experience Reports, to document general practice and experience in education, industry, or other contexts; * Tutorials, to document how to use a particular language feature, programming technique, tool or library within the Haskell ecosystem; * System Demonstrations, based on running software rather than novel research results. Regular papers should explain their research contributions in both general and technical terms, identifying what has been accomplished, explaining why it is significant, and relating it to previous work, and to other languages where appropriate. Experience reports and functional pearls need not necessarily report original academic research results. For example, they may instead report reusable programming idioms, elegant ways to approach a problem, or practical experience that will be useful to other users, implementers, or researchers. The key criterion for such a paper is that it makes a contribution from which other Haskellers can benefit. It is not enough simply to describe a standard solution to a standard programming problem, or report on experience where you used Haskell in the standard way and achieved the result you were expecting. Like an experience report and a functional pearl, tutorials should make a contribution from which other Haskellers can benefit. What distinguishes a tutorial is that its focus is on explaining an aspect of the Haskell language and/or ecosystem in a way that is generally useful to a Haskell audience. Tutorials for many such topics can be found online; the distinction here is that by writing it up for formal review it will be vetted by experts and formally published. System demonstrations should summarize the system capabilities that would be demonstrated. The proposals will be judged on whether the ensuing session is likely to be important and interesting to the Haskell community at large, whether on grounds academic or industrial, theoretical or practical, technical, social or artistic. Please contact the program chair with any questions about the relevance of a proposal. If your contribution is not a research paper, please mark the title of your experience report, functional pearl, tutorial or system demonstration as such, by supplying a subtitle (Experience Report, Functional Pearl, Tutorial Paper, System Demonstration). Submission Details ================== Formatting ---------- Submitted papers should be in portable document format (PDF), formatted using the ACM SIGPLAN style guidelines. Authors should use the `acmart` format, with the `sigplan` sub-format for ACM proceedings. For details, see: http://www.sigplan.org/Resources/Author/#acmart-format It is recommended to use the `review` option when submitting a paper; this option enables line numbers for easy reference in reviews. Functional pearls, experience reports, tutorials and demo proposals should be labelled clearly as such. Lightweight Double-blind Reviewing ---------------------------------- Haskell Symposium 2022 will use a lightweight double-blind reviewing process. To facilitate this, submitted papers must adhere to two rules: 1. Author names and institutions must be omitted, and 2. References to authors' own related work should be in the third person (e.g., not "We build on our previous work" but rather "We build on the work of "). The purpose of this process is to help the reviewers come to an initial judgment about the paper without bias, not to make it impossible for them to discover the authors if they were to try. Nothing should be done in the name of anonymity that weakens the submission or makes the job of reviewing the paper more difficult (e.g., important background references should not be omitted or anonymized). In addition, authors should feel free to disseminate their ideas or draft versions of their paper as they normally would. For instance, authors may post drafts of their papers on the web or give talks on their research ideas. A reviewer will learn the identity of the author(s) of a paper after a review is submitted. Page Limits ----------- The length of submissions should not exceed the following limits: Regular paper: 12 pages Functional pearl: 12 pages Tutorial: 12 pages Experience report: 6 pages Demo proposal: 2 pages There is no requirement that all pages are used. For example, a functional pearl may be much shorter than 12 pages. In all cases, the list of references is not counted against these page limits. Deadlines --------- Abstract submission: 27 May 2022 (Fri) Paper submission: 3 June 2022 (Fri) Notification: 1 July 2022 (Fri) Deadlines are anywhere on Earth. Submission ---------- Submissions must adhere to SIGPLAN's republication policy (http://sigplan.org/Resources/Policies/Republication/) and authors should be aware of ACM's policies on plagiarism (https://www.acm.org/publications/policies/plagiarism) Program Committee members are allowed to submit papers, but their papers will be held to a higher standard. The paper submission deadline and length limitations are firm. There will be no extensions, and papers violating the length limitations will be summarily rejected. Papers should be submitted through HotCRP at: https://haskell22.hotcrp.com/ Improved versions of a paper may be submitted at any point before the submission deadline using the same web interface. Supplementary material: Authors have the option to attach supplementary material to a submission, on the understanding that reviewers may choose not to look at it. This supplementary material should not be submitted as part of the main document; instead, it should be uploaded as a separate PDF document or tarball. Supplementary material should be uploaded at submission time, not by providing a URL in the paper that points to an external repository. Authors can distinguish between anonymized and non-anonymized supplementary material. Anonymized supplementary material will be visible to reviewers immediately; non-anonymized supplementary material will be revealed to reviewers only after they have submitted their review of the paper and learned the identity of the author(s). Resubmitted Papers: authors who submit a revised version of a paper that has previously been rejected by another conference have the option to attach an annotated copy of the reviews of their previous submission(s), explaining how they have addressed these previous reviews in the present submission. If a reviewer identifies him/herself as a reviewer of this previous submission and wishes to see how his/her comments have been addressed, the conference chair will communicate to this reviewer the annotated copy of his/her previous review. Otherwise, no reviewer will read the annotated copies of the previous reviews. Proceedings =========== Accepted papers will be included in the ACM Digital Library. Their authors will be required to choose one of the following options: - Author retains copyright of the work and grants ACM a non-exclusive permission-to-publish license (and, optionally, licenses the work with a Creative Commons license); - Author retains copyright of the work and grants ACM an exclusive permission-to-publish license; - Author transfers copyright of the work to ACM. For more information, please see ACM Copyright Policy (http://www.acm.org/publications/policies/copyright-policy) and ACM Author Rights (http://authors.acm.org/main.html) Accepted proposals for system demonstrations will be posted on the symposium website but not formally published in the proceedings. Publication date: The official publication date of accepted papers is the date the proceedings are made available in the ACM Digital Library. This date may be up to two weeks prior to the first day of the conference. The official publication date affects the deadline for any patent filings related to published work. Artifacts ========= Authors of accepted papers are encouraged to make auxiliary material (artifacts like source code, test data, etc.) available with their paper. They can opt to have these artifacts published alongside their paper in the ACM Digital Library (copyright of artifacts remains with the authors). If an accepted paper's artifacts are made permanently available for retrieval in a publicly accessible archival repository like the ACM Digital Library, that paper qualifies for an Artifacts Available badge (https://www.acm.org/publications/policies/artifact-review-badging#available) Applications for such a badge can be made after paper acceptance and will be reviewed by the PC chair. Program Committee ================= Lennart Augustsson Epic Games Jean-Philippe Bernardy University of Gothenburg Iavor Diatchki Galois, Inc Michael Gale Tweag William Hallahan Yale University Makoto Hamana Gumma University John Hughes Chalmers University of Technology Alexis King Tweag James Koppel Massachusets Institute of Technology Rudy Matela Dominic Orchard University of Kent Nadia Polikarpova (chair) University of California, San Diego Eric Seidel Bridgewater Associates Satnam Singh Groq Wouter Swierstra Utrecht University Hiroshi Unno University of Tsukuba Marco Vassena CISPA - Helmholtz-Zentrum Dimitrios Vytiniotis DeepMind If you have questions, please contact the chair at: npolikarpova(a)ucsd.edu =========================================================================

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Accessing a MinGW/MSYS2 shell from Setup.hs
by Hécate 26 Mar '22

26 Mar '22

Hi everyone, I am writing a custom Setup.hs to do an Autotools build for a bundled library. This is easy everywhere with `process` _except_ Windows, because I can't get a shell with the Autotools in them, despite there definitely being one. `process` gives me a cmd.exe shell, which wouldn't know about the Autotools, and on Windows, _any_ GHC installation has to have certain POSIX stuff available, which is why it bundles MinGW. Is the shell I get from that accessible from Setup.hs, via `process` or otherwise? Cheers, Hécate -- Hécate ✨ 🐦: @TechnoEmpress IRC: Hecate WWW:https://glitchbra.in RUN: BSD

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Call for Talks: Haskell Implementors' Workshop 2022
by Alejandro Serrano Mena 23 Mar '22

23 Mar '22

(apologies for multiple copies of this message) ACM SIGPLAN Haskell Implementors' Workshop https://icfp22.sigplan.org/home/hiw-2022 Ljubljana, Slovenia, 11 September 2022 Co-located with ICFP 2022 https://icfp22.sigplan.org/ Important dates --------------- Deadline: 11 July, 2022 (AoE) Notification: 11 August, 2022 Workshop: 11 September, 2022 The 14th Haskell Implementors' Workshop is to be held alongside ICFP 2022 this year in Ljubljana. 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 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 lightning short 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 2022. 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 encouraged to attend the workshop -- we need your feedback to keep the Haskell ecosystem thriving. Students working with Haskell are specially 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://icfphiw22.hotcrp.com until July 11th (anywhere on earth). We will also have lightning talks session. These have been very well received in recent years, and we aim to increase the time available to them. Lightning talks 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 ----------------- * Pepe Iborra (Meta) * Gabrielle Keller (Utrecht University) * Emily Pilmore (Kadena) * Vladislav Zavialov (Serokell) * Alejandro Serrano (Tweag) Contact ------- * Alejandro Serrano <trupill at gmail.com>

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Retro/indie Haskell to appreciate
by Rishiyur Nikhil 21 Mar '22

21 Mar '22

> I’m looking to appreciate “retro” Haskell projects, things from before stabilization/company use. > Such as: > ... > BlueSpec compiler https://github.com/B-Lang-org/bsc Note, the Bluespec compiler, though written in "retro" Haskell, remains in daily production use (as it has been, for 2 decades). Another project, written a few years ago but in totally "retro" style is Forvis, a complete executable spec for the RISC-V instruction set: https://github.com/rsnikhil/Forvis_RISCV-ISA-Spec Covers RV32 and RV64; unprivileged and privileged: unprivileged ISA: I (basic integer) M (integer multiply/divide) A (atomics) F, D (single and double precision floating point) C (compressed) privileged ISA: M (machine), S (supervisor) and U (user modes) Sv32, Sv39 and Sv48 virtual memory and has successfully booted a Linux kernel. Rgds, Nikhil

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[announce] Stackage LTS 19 (ghc-9.0) & Nightly moved to ghc-9.2
by Jens Petersen 20 Mar '22

20 Mar '22

The Stackage Team is happy to announce the first release of the stable LTS 19 series of package sets over GHC 9.0.2: https://www.stackage.org/lts-19.0 We are also excited to announce that Nightly has been updated to use ghc-9.2.2 (thanks to heroic work by Adam Bergmark)! You can find a few more details in the short accompanying post: https://www.stackage.org/blog/2022/03/announce-lts-19-nightly-ghc9.2 Thank you to everyone in the Haskell community who contributed to make these new releases possible!

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Haskell internships with Standard Chartered Bank in the UK
by José Pedro Magalhães 20 Mar '22

20 Mar '22

All details at https://discourse.haskell.org/t/haskell-internships-with-standard-chartered… Cheers, Pedro

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Re: [Haskell-cafe] Retro/indie Haskell to appreciate
by Johannes Waldmann 19 Mar '22

19 Mar '22

> I’m looking to appreciate “retro” Haskell projects, If "retro" = "old", then look at this from 1997 https://github.com/jwaldmann/rx (state at first commit) And, I second what others have suggested: Paul Hudak: Haskore, https://web.archive.org/web/19970206084830/http://haskell.cs.yale.edu:80/ha… Peter Thiemann: Wash, http://www2.informatik.uni-freiburg.de/~thiemann/haskell/WASH/ The pinnacle of Haskell retrocomputing certainly is https://downloads.haskell.org/~ghc/0.29/ > ... things from before stabilization/company use. Haskell(98,2010) does have stability: language and core libraries adhere to the report. It's the companies that are destroying it :-) But you're right, they also spend effort on stabilization. When I cabalized my project in/around 2014, I was pleasantly surprised how little change it needed. Basically, just build-depend: haskell98. Don't read the actual source too closely - it's full of Lists and Ints, because, well .. little did I know at the time. On the other hand: naive means of expression, combined with absence, or ignorance, of libraries - makes future-proof software. Will you tell us the results of your appreciations? Are you "just" collecting sources? (already that is worthwhile) Compiling them? Running? Benchmarking? Writing a paper? I'd love to read that. - J.W.

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