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Sam Staton giving this year's LMS/BCS-FACS Evening Seminar (online) -- registration open until this Wednesday at 5PM, UTC
by Andrei Popescu 14 Nov '22

14 Nov '22

EVENT: Annual LMS/BCS-FACS Evening Seminar SPEAKER: Sam Staton, University of Oxford TITLE: Programming-based foundations for statistics DATE: Thursday, 17 November 2022, Starting time: 18:00 UTC VENUE: Online via Zoom EVENT PAGE: https://www.lms.ac.uk/events/lectures/lms-bcs-facs-evening-seminars REGISTRATION LINK: https://www.lms.ac.uk/civicrm/event/register?id=88&reset=1 Prior registration is required for attendance -- the registration site will close on Wednesday, 16 November, at 17:00 SYNOPSIS Probabilistic programming is a popular tool for statistics and machine learning. The idea is to describe a statistical model as a program with random choices. The program might be a simulation of a system, such as a physics model, a model of viral spread, or a model of electoral behaviour. We can now carry out statistical inference over the system, for example, by running a Monte Carlo simulation – running the simulation 100,000’s of times. As I will discuss in this talk, the idea of treating statistical models as computer programs also has a foundational appeal. If we can understand statistical models as programs, then the foundations of probability and statistics can be discussed in terms of program semantics. There is a chance of new foundational perspectives on statistics, in terms of programming languages and their formal methods. As I will explain, this programming-based foundation for statistics is attractive because there are some intuitively simple scenarios, such as inference over function spaces, which have an easy programming implementation, but for which the traditional mathematical interpretation is complicated. SPEAKER BIOGRAPHY Sam Staton is a Professor of Computer Science and Royal Society University Research Fellow at the University of Oxford. There he currently runs an ERC grant "Better Languages for Statistics". Before arriving in Oxford in 2015, Sam spent time in Nijmegen, Paris, and Cambridge. His PhD was in Cambridge with Marcelo Fiore (2007). Sam's main research is in programming language theory, but he is also interested in logic and category theory. He has recent contributions in probabilistic programming languages, and quantum computing and programming languages. Webpage: https://www.cs.ox.ac.uk/people/samuel.staton/main.html

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[ANN] updated vim's cabal syntax file
by coot＠coot.me 13 Nov '22

13 Nov '22

vim-9.0.0849 comes with an updated cabal syntax file which supports a few more fields. If you want to see the changes, check out the few recent commits: https://github.com/coot/haskell-vim-scripts/commits/master/syntax/cabal.vim… Cheers, Marcin

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Numerical Recipes in Haskell?
by Jonathan Drews 12 Nov '22

12 Nov '22

Hi: New member here. I am looking for a book similar to "Numerical Recioes in C" but for Haskell. https://www.amazon.com/Numerical-Recipes-Scientific-Computing-Second/dp/052… Does such a book exist? I've looked and can't seem to find one. I am new to Haskell and don't have much programming experience. I am using the No Starch press book "Learn Physics with Functional Programming: A Hands-on Guide to Exploring Physics with Haskell". It's very well written. -- Kind regards, Jonathan

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[CFP] FOSDEM Haskell Devroom, Sun 2023-02-05, Brussels
by Fraser Tweedale 12 Nov '22

12 Nov '22

I am thrilled to announce that Europe's largest free software conference, FOSDEM, will in 2023 and for the first time feature a Haskell devroom (specialist track). The Call for Participation is open now, until 2022-11-28. Read on for more info! FOSDEM 2023 will be held on 4 & 5 February 2023, in Brussels. For more information see the official site: https://fosdem.org/2023/. The Haskell devroom will take place on Sunday 5 February, from 13:10 to 17:00 UTC+1. Presentations will be also be streamed live and published afterwards. ## Key Dates 2022-11-28: Submission Deadline 2022-12-12: Announcement of selected talks 2023-02-04..2023-02-05: FOSDEM conference 2023-02-05: Haskell Devroom ## About the Haskell devroom Haskell is a statically typed functional programming language. Its vibrant community spans industry, academia and the hobbyist realm. The Haskell devroom welcomes people new to Haskell or functional programming, as well as intermediate or experienced Haskellers. The Haskell devroom will: - Advocate the Haskell programming language, and its community, to a wide audience of free software developers and users. - Promote and support participation in free software projects that use Haskell. - Teach Haskell (more broadly, functional) programming techniques, and introduce important libraries, frameworks or developer tools. ## Call for Participation We invite proposals for talks, tutorials and demos on topics including: - Introductory talks teaching functional programming concepts and Haskell programming - Practical advice for Haskell programming: developer tools, package ecosystem, Haskell in production. - "Show and tell" session for people to introduce Haskell projects they are involved with, and invite contributions. - Experience reports: share about problems you tackled using Haskell, and the outcomes. - What is going on in the Haskell community? Where and how you can get involved? Sessions will have a maximum duration of 30 minutes, including questions. You are welcome to propose shorter sessions (for example a demo, short talk or Q&A). This is an in-person event. Presenters must be able to attend to deliver their presentation. ## Code of conduct Speakers and attendees must abide by the FOSDEM Code of Conduct[1]. Also, because this is a Haskell community event we expect participants to follow the Haskell Foundation Guidelines for Respectful Communication[2]. [1] https://fosdem.org/2023/practical/conduct/ [2] https://haskell.foundation/guidelines-for-respectful-communication/ If you submit a proposal and it is accepted, you will be required to confirm that you accept the FOSDEM Code of Conduct. If you have any questions about the Code of Conduct or wish to have one of the devroom organizers review your presentation slides or any other content for compliance, please email us and we will do our best to assist you. ## How to submit Submit proposals through the FOSDEM Pentabarf submission tool[3]. If you do not already have an account, you need to create one. [3] https://penta.fosdem.org/submission/FOSDEM23 Go to "Create Event" and select the "Haskell devroom" track. Ensure you fill the following fields: - Event title - Track ("Haskell devroom") - Duration (including questions; <= 30 minutes) - Event type - Short abstract - Full abstract - Submission notes (if any) You can use the Submission notes to mention: - Any special requirements - Anything else you want the organisers/reviewers to know In the "Person" profile section please provide your: - Name, nickname (optional), image - Short Biography - Email address - Phone number (in case we need to contact you during the conference) Presentations will be live-streamed and recordings published under the CC-BY licence. By submitting you consent to having your presentation recorded and broadcast/published under the CC-BY licence. ## People and contacts The Haskell devroom organisers are: - Fraser Tweedale - Troels Henriksen Thanks to David Christiansen and the Haskell Foundation for supporting this event. If you need to reach the Haskell devroom organisers or program committee, email <haskell-devroom-manager(a)fosdem.org>.

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Re: [Haskell-cafe] [ANN] faster-megaparsec
by Olaf Klinke 11 Nov '22

11 Nov '22

Emily wrote: > Do you provide reproducible benchmarks for these claims? I'd love to > see the outcome for various types of projects to make the choice for > myself. > > Unsubstantiated claims of "This is Faster™️" are the path to shame > and treachery. Version 0.1.2 now includes a CSV Benchmark. The benchmark generates random table layouts of up to 50 columns and decodes two named columns in 100000 lines. Speed-up on my machine is roughly 0.7x over ParsecT and 0.6x over Cassava when decoding only few columns of a broad table. In particular, a Text-based ParsecT is faster than (ByteString-based) Cassava in this scenario. This was also the initial reason why I got interested in improving performance of megaparsec parsers in the first place. Cheers, Olaf

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Re: [Haskell-cafe] [ANN] faster-megaparsec
by Olaf Klinke 11 Nov '22

11 Nov '22

> Do you provide reproducible benchmarks for these claims? I'd love to > see the outcome for various types of projects to make the choice for > myself. > > Unsubstantiated claims of "This is Faster™️" are the path to shame > and treachery. > Dear Emily, version 0.1.1 [1] now contains a benchmark suite, where words of randomly generated languages are parsed with both parsers (ParsecT and StateT Text Maybe). For tiny to moderately sized languages, the speed- up is not huge but noticeable. (I need to work on improving test case generation.) I've been using this trick for a long time but only now decided to spin off a dedicated package. My experience with parsing large amounts of tabular data files shows there is a more substantial difference, although that might be due to my lack of understanding how to write optimized megaparsec parsers. Still your point is valid that this is merely anecdotal evidence. If time permits, I shall add a more realistic benchmark with randomly generated CSV data or Finn Bender's haskell-parsing-benchmarks [2]. Cheers, Olaf [1] https://hackage.haskell.org/package/faster-megaparsec-0.1.1.0 [2] https://gitlab.com/FinnBender/haskell-parsing-benchmarks > On Tue, Nov 08, 2022 at 1:31 PM, Olaf Klinke < olf at aatal- > apotheke.de > wrote: > > > > > > > > > Dear Haskellers, > > > > > > > > megaparsec [1] is a parsing library with excellent error reporting. > Being > > able to emit decent parse error messages is traded off against > speed, > > however. Wouldn't it be nice to have a faster parser for your daily > > parsing needs, but obtain megaparsec's informative error messages > for the > > rare cases when things go wrong? > > > > > > > > Thanks to megaparsec's parser type class, MonadParsec, you can have > both: > > I wrote a MonadParsec instance for StateT s Maybe (s being the > input > > stream type such as Text or ByteString) which does not do all the > > bookkeeping ParsecT needs to do. If you manage to write your parser > only > > using the type class primitives, then you can specialize your > parser to > > StateT s Maybe. Only if that returns Nothing specialize again to > ParsecT > > Void s and parse the input again, thus obtaining a decent error > message. > > The package faster-megaparsec [1,2] provides a convenient function > to do > > just that. > > > > > > > > Of course StateT s Maybe can not provide all the features ParsecT > has: > > * StateT s Maybe is always backtracking. > > * It does not know the offset in the stream. > > * It must hold the entire input stream in memory for a second pass, > so no > > garbage collecting the consumed input while parsing. So if your > parsing > > relies on non-backtracking choice, stream offset or garbage- > collecting > > input while parsing, you can not use faster- megaparsec as a drop- > in > > replacement. > > > > > > > > Happy parsing! > > Olaf > > > > > > > > [1] https:/ / hackage. haskell. org/ package/ megaparsec ( > > https://hackage.haskell.org/package/megaparsec ) > > [2] https:/ / hackage. haskell. org/ package/ faster-megaparsec ( > > https://hackage.haskell.org/package/faster-megaparsec ) > > [3] https://hub.darcs.net/olf/faster-megaparsec >

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[ANNOUNCE] GHC 9.4.3 is now available
by Ben Gamari 08 Nov '22

08 Nov '22

The GHC developers are happy to announce the availability of GHC 9.4.3. Binary distributions, source distributions, and documentation are available at downloads.haskell.org: https://downloads.haskell.org/ghc/9.4.3 This release is primarily a bugfix release addressing a few issues found in 9.4.2. These include: * An issue where recursively calls could be speculatively evaluated, resulting in non-termination (#20836) * A code generation issue in the AArch64 native code generator backend resulting in incorrect runtime results in some circumstances (#22282) * A crash on Darwin when running executables compiled with IPE support (#22080) * A long-standing interface-file determinism issue where full paths would leak into the interface file (#22162) * A bug in the `process` library where file handles specified as `NoStream` would still be usable in the child (process#251) Note that, as GHC 9.4 is the first release series where the release artifacts are all generated by our new Hadrian build system, it is possible that there will be packaging issues. If you enounter trouble while using a binary distribution, please open a [ticket]. Likewise, if you are a downstream packager, do consider migrating to [Hadrian] to run your build; the Hadrian build system can be built using `cabal-install`, `stack`, or the in-tree [bootstrap script]. See the accompanying [blog post] for details on migrating packaging to Hadrian. We would also like to emphasize that GHC 9.4 must be used in conjunction with Cabal-3.8 or later. This is particularly important for Windows users due to changes in GHC's Windows toolchain. We would like to thank Microsoft Azure, GitHub, IOG, the Zw3rk stake pool, Well-Typed, Tweag I/O, Serokell, Equinix, SimSpace, Haskell Foundation, and other anonymous contributors whose on-going financial and in-kind support has facilitated GHC maintenance and release management over the years. Finally, this release would not have been possible without the hundreds of open-source contributors whose work comprise this release. As always, do give this release a try and open a ticket if you see anything amiss. Happy Haskelling, - Ben [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new [bootstrap script]: https://gitlab.haskell.org/ghc/ghc/-/blob/e2520df3fffa0cf22fb19c5fb872832d1… [Hadrian]: https://gitlab.haskell.org/ghc/ghc/-/blob/e2520df3fffa0cf22fb19c5fb872832d1… [blog post]: https://www.haskell.org/ghc/blog/20220805-make-to-hadrian.html

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CIS 194 not compiling under new GHC
by Borys Kopeć 07 Nov '22

07 Nov '22

Hi all, I've been working through the CIS 194 <https://www.cis.upenn.edu/~cis1940/spring13/lectures.html> course recently and unfortunately from lecture 7 onwards the code is not compliant with current compiler. I can still follow the lectures but I'd like to do every homework exercise. Unfortunately most homework exercises provide you with a code framework to work with and this code does not compile. Do any of you know about updated versions or corrections to this course? I believe there could be a repo where someone is keeping the course's homework up to date because this course is still quite popular. Regards Borys

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[Haskell] [ANNOUNCE] GHC 9.2.5 released
by Zubin Duggal 07 Nov '22

07 Nov '22

The GHC developers are very happy to at announce the availability of GHC 9.2.5. Binary distributions, source distributions, and documentation are available at [`downloads.haskell.org`](https://downloads.haskell.org/ghc/9.2.5). Download Page: https://www.haskell.org/ghc/download_ghc_9_2_5.html Blog Post: https://www.haskell.org/ghc/blog/20221107-ghc-9.2.5-released.html This release is primarily a bugfix release addressing a few issues found in 9.2.4. These include: * Code generation issues in the AArch64 native code generator backend resulting in incorrect runtime results in some circumstances (#22282, #21964) * Fixes for a number of issues with the simplifier leading to core lint errors and suboptimal performance (#21694, #21755, #22114) * A long-standing interface-file determinism issue where full paths would leak into the interface file (#22162) * A runtime system bug where creating empty mutable arrays resulted in a crash (#21962) - ... and a few more. See the [release notes] for a full accounting. As some of the fixed issues do affect correctness users are encouraged to upgrade promptly. We would like to thank Microsoft Azure, GitHub, IOG, the Zw3rk stake pool, Well-Typed, Tweag I/O, Serokell, Equinix, SimSpace, Haskell Foundation, and other anonymous contributors whose on-going financial and in-kind support has facilitated GHC maintenance and release management over the years. Finally, this release would not have been possible without the hundreds of open-source contributors whose work comprise this release. As always, do give this release a try and open a [ticket][] if you see anything amiss. Happy compiling, - Zubin [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new [release notes]: https://downloads.haskell.org/~ghc/9.2.5/docs/html/users_guide/9.2.5-notes.…

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Help with TH trick
by David Feuer 06 Nov '22

06 Nov '22

I remember seeing a package that offered a function used something like this: $(deriveThingy [d| instance Foo a => Thingy a |]) to allow the user to specify the constraint(s) for a generated instance. I'd love to borrow the code for that, but I can't remember what package it was in, what class it derived, etc. Can anyone help?

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