- Haskell-Cafe - Haskell.org

ANN: NASA's ogma
by Ivan Perez 03 Dec '21

03 Dec '21

Dear café We are thrilled to announce the release of Ogma, a new open-source NASA tool, written in Haskell, to generate hard-realtime C runtime monitoring applications from high-level specifications. Ogma takes the output of existing tools, like NASA's requirements elicitation tool FRET [2], and produces monitors in Copilot [3], a runtime verification language that can be compiled to hard-realtime C99. Ogma is also able to produce monitoring applications for NASA's Core Flight System (cFS), which can be compiled alongside existing applications to flag requirement violations. On the website you will see several videos, including one with a FRET requirement being monitored inside the XPlane flight simulator by taking the code generated by Ogma and making it accessible to the simualtor via a custom on-screen plugin. This is research-only software (Class E) and it has not been certified for use in aircraft or UAVs. We are currently using it for upcoming experiments at NASA Langley. We'd like to also take this opportunity to publicly thank the team that creates BNFC, for their tool, their response to technical questions during the development of ogma, and for accommodations made to help us speed up our release process. If you have any issues, feel free to open a ticket in the github repo directly. Happy haskelling, [1] https://github.com/NASA/ogma [2] https://github.com/NASA-SW-VnV/fret [3] https://github.com/Copilot-Language/copilot

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Why and How the External STG Interpreter is Useful (Online presentation, Dec 2, Thursday, 17:00 UTC)
by Csaba Hruska 03 Dec '21

03 Dec '21

Hello, Today I'll do a presentation about the external stg interpreter. If you are interested please join and ask questions. https://skillsmatter.com/meetups/13654-haskell-stg-interp Regards, Csaba Hruska Abstract: Haskell: Why and How the External STG Interpreter is Useful The external STG interpreter is a from scratch implementation of the STG machine in Haskell. Currently it supports almost all GHC primops and RTS features. It can run real world Haskell programs that were compiled with GHC Whole Program Compiler (GHC-WPC). GHC-WPC is a GHC fork that exports the whole program STG IR. The external STG interpreter is an excellent tool to study the runtime behaviour of Haskell programs, i.e. it can run/interpret GHC or Pandoc. The implementation of the interpreter is in plain simple Haskell, so it makes compiler backend and tooling development approachable for everyone. It already has a programmable debugger which supports step-by-step evaluation, breakpoints and execution region based inspection. It also can export the whole program memory state and call-graphs to files for further investigation. These features make it easy to find a memory leak or to identify a performance bottleneck in a large real world Haskell application. https://github.com/grin-compiler/ghc-whole-program-compiler-project

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Re: [Haskell-cafe] Breaking change to Eq accepted by Core Libraries Committee
by Olaf Klinke 03 Dec '21

03 Dec '21

For what it's worth, one of the examples listed in the issue where (/=) is not simply the negation of (==) is violating the laws. It is the one in https://hackage.haskell.org/package/numbers-3000.2.0.2/docs/Data-Number-Int… That module defines two intervals to be equal if their bounds are equal, but to be unequal only if they are disjoint. In my eyes this speaks for the proposal, because the library author would have been unable to write the broken instance. (And I did look at the proposal some time ago, whence I feel it was indeed discussed or at least mentioned on this list before.) Olaf

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Trends in Functional Programming in Education 2022 2nd call for submissions
by Elena Machkasova 02 Dec '21

02 Dec '21

TFPIE 2022 Call for papers https://wiki.tfpie.science.ru.nl/TFPIE2022 (February 11th 2022, Krakow, Poland co-located with TFP 2022 and Lambda Days) TFPIE 2022 welcomes submissions describing techniques used in the classroom, tools used in and/or developed for the classroom and any creative use of functional programming (FP) to aid education in or outside Computer Science. Topics of interest include, but are not limited to: FP and beginning CS students FP and Computational Thinking FP and Artificial Intelligence FP in Robotics FP and Music Advanced FP for undergraduates FP in graduate education Engaging students in research using FP FP in Programming Languages FP in the high school curriculum FP as a stepping stone to other CS topics FP and Philosophy The pedagogy of teaching FP FP and e-learning: MOOCs, automated assessment etc. Best Lectures - more details below In addition to papers, we are requesting best lecture presentations. What's your best lecture topic in an FP related course? Do you have a fun way to present FP concepts to novices or perhaps an especially interesting presentation of a difficult topic? In either case, please consider sharing it. Best lecture topics will be selected for presentation based on a short abstract describing the lecture and its interest to TFPIE attendees. The length of the presentation should be comparable to that of a paper. In addition, the speaker can provide commentary on effectiveness or student feedback. Submissions Potential presenters are invited to submit an extended abstract (4-6 pages) or a draft paper (up to 20 pages) in EPTCS style. The authors of accepted presentations will have their preprints and their slides made available on the workshop's website. Papers and abstracts can be submitted via easychair at the following link: https://easychair.org/conferences/?conf=tfpie2022 After the workshop, presenters are invited to submit (a revised version of) their article for the formal review. The PC will select the best articles for publication in the Electronic Proceedings in Theoretical Computer Science (EPTCS). Articles rejected for presentation and extended abstracts will not be formally reviewed by the PC. Important Dates Submission deadline: January 5th 2022, Anywhere on Earth. Notification: January 10th 2022 (Note: earlier submissions will receive earlier response) TFPIE Registration Deadline: TBA Workshop: February 11th 2022 Submission for formal review: April 15th 2022, Anywhere on Earth. Notification of full article: June 1st 2022 Camera ready: July 1st 2022 Program Committee Peter Achten, Radboud University, Netherlands Stephen Chang, University of Massachusetts Boston, USA John Hughes, Chalmers University of Technology, Sweden Elena Machkasova (Chair) - University of Minnesota Morris, USA Kristina Sojakova - INRIA, Paris, France Melinda Tóth, Eötvös Loránd University, Budapest, Hungary Keynote speaker Our keynote talk is "The perfect Functional Programming course" by Peter Achten. Registration information This year TFPIE takes place on the second day of the Lambda Days, concurrent with TFP. Participants will need to register for the Lambda Days. Please note that TFP and TFPIE have in-person attendance only. For registration fee, the deadlines, and the link to register see the Lambda Days web site: https://www.lambdadays.org/lambdadays2022 Registration and attendance are mandatory for at least one author of every paper that is presented at the workshop. Presenters will have their registration fee waived. Only papers that have been presented at TFPIE may be submitted to the post-reviewing process. Best regards, Elena Machkasova -- Dr. Elena Machkasova Associate Professor of Computer Science Division of Science and Mathematics University of Minnesota, Morris Office: Sci 2325 (320) 589-6308 http://cda.morris.umn.edu/~elenam/ Pronouns: she/her/hers or any other

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Call for Haskell.org Committee Nominations
by Ida Bzowska 02 Dec '21

02 Dec '21

Hey, The Haskell.org Committee is looking for members. Maybe this is you or someone from your friends? Please read this post https://discourse.haskell.org/t/call-for-haskell-org-committee-nominations/… and drop us a line. λCheers Ida Bzowska

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10 PhD studentships in Nottingham
by Graham Hutton 02 Dec '21

02 Dec '21

Dear all, The School of Computer Science at the University of Nottingham in the UK is seeking applications for 10 fully-funded PhD studentships: https://tinyurl.com/ten-phd-2021 Applicants in the area of the Functional Programming Lab (tinyurl.com/fp-notts) are strongly encouraged! If you are interested in applying, please contact a potential supervisor as soon as possible; the application deadline is 13th Feb: Thorsten Altenkirch - constructive logic, proof assistants, homotopy type theory, category theory, lambda calculus. Graham Hutton - functional programming, haskell, category theory, program verification, program calculation. Nicolai Kraus - homotopy type theory, higher category theory, constructive mathematics, and related topics. The studentships are open to applicants of any nationality. Best wishes, Graham Hutton +-----------------------------------------------------------+ 10 Fully-Funded PhD Studentships School of Computer Science University of Nottingham, UK tinyurl.com/ten-phd-2021 Applications are invited from international and home students for 10 fully-funded PhD studentships offered by the School of Computer Science, starting on 1st October 2022. The topics for the studentships are open, but should relate to interests of one of the School's research groups: Computational Optimisation and Learning; Computer Vision; Cyber Security; Functional Programming; Intelligent Modelling and Analysis; Mixed Reality; Uncertainty in Data and Decision Making. The studentships are fully-funded for 3.5 years and include a stipend of £15,009 per year and tuition fees. Applicants are normally expected to have a first class bachelors or masters degree in Computer Science or another relevant area, and must obtain the support of a potential supervisor in the School prior to submitting their application. If you are interested in applying, please contact a potential supervisor as soon as possible, and at least two weeks prior to the closing date. If the supervisor wishes to support your application, they will direct you to make an official application through the MyNottingham system. Closing date for applications: Sunday 13th February 2022. +-----------------------------------------------------------+ This message and any attachment are intended solely for the addressee and may contain confidential information. If you have received this message in error, please contact the sender and delete the email and attachment. Any views or opinions expressed by the author of this email do not necessarily reflect the views of the University of Nottingham. Email communications with the University of Nottingham may be monitored where permitted by law.

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ANN: hledger 1.24
by Simon Michael 02 Dec '21

02 Dec '21

I am pleased to announce hledger 1.24! https://hledger.org/release-notes.html#hledger-1-24 Highlights include new report layout options with less eliding, hledger-ui mouse support, and many fixes and improvements. Thank you to release contributors Stephen Morgan, toonn, Pranesh Prakash, Dmitry Astapov, ShrykeWindgrace, Joaquin Azcarate, and Lawrence Wu. hledger (https://hledger.org) is a dependable, cross-platform "plain text accounting" tool, with command-line, terminal and web interfaces. It is an actively maintained, largely compatible reimplementation of Ledger CLI with many improvements. You can use it to track money, time, investments, cryptocurrencies, inventory and more. See also the Plain Text Accounting site (https://plaintextaccounting.org) https://hledger.org/download shows all the ways to install hledger on mac, windows or unix (stack, cabal, brew, nix, CI binaries, your package manager..). Or, run this bash script to install or upgrade to the latest release: $ curl -sO https://raw.githubusercontent.com/simonmichael/hledger/master/hledger-insta… $ less hledger-install.sh # security review $ bash hledger-install.sh New users, check out https://hledger.org/quickstart or the tutorials (with pictures) at hledger.org -> FIRST STEPS or the https://hledger.org/videos.html. To get help, see https://hledger.org#help, and join our chat via Matrix: - #hledger:matrix.org (http://matrix.hledger.org) or Libera (they are bridged): - #hledger:libera.chat (http://irc.hledger.org) Beginners and experts, contributors, sponsors, and all feedback are most welcome. Wishing you health and prosperity, -Simon

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What is Data.Vec.DataFamily.SpineStrict.Pigeonhole and why is it following me?
by Galaxy Being 01 Dec '21

01 Dec '21

Spam detection software, running on the system "mail.haskell.org", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see @@CONTACT_ADDRESS@@ for details. Content preview: This <https://hackage.haskell.org/package/vec-0.4/docs/Data-Vec-DataFamily-SpineS…> in Hackage is something a rank amateur like me can't fathom. I just hit a chapter in a book that dives into the Pigeonhole Principle. Is this the "accompanying Haskell Wundercode" for the math world's PHP? I know PHP is a big deal in math. I don't see an "author," and I see no documentation. Anyone know how I can figure this mystery out, like at least find the author or someone that knows something about this? [...] Content analysis details: (5.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (borgauf[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record -0.0 BAYES_40 BODY: Bayes spam probability is 20 to 40% [score: 0.3039] 5.0 UNWANTED_LANGUAGE_BODY BODY: Message written in an undesired language 0.0 HTML_MESSAGE BODY: HTML included in message 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid The original message was not completely plain text, and may be unsafe to open with some email clients; in particular, it may contain a virus, or confirm that your address can receive spam. If you wish to view it, it may be safer to save it to a file and open it with an editor.

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MonadFail with type parameter for error message
by Daneel Yaitskov 30 Nov '21

30 Nov '21

Dear Cafe, MonadFail.fail takes String. I wasn't able to find MonadFail for custom error type. Is there any proposals to base? Let's say Data.Text, which gains popularity with OverloadedStrings extensions. class MonadFail m where fail :: String -> m a Why not ? class MonadFail m where fail :: (forall s. IsString s => s) -> m a class MonadFailWith m s where fail :: s -> m a -- Best regards, Daniil Iaitskov

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Re: [Haskell-cafe] methods/tools for reading/presenting (time/allocation) profiling information?
by Olaf Klinke 26 Nov '21

26 Nov '21

> Dear Cafe, > > with +RTS -p -RTS, the resulting .prof file > shows (in the second part) what the expensive functions are. > (counting sections as GHC docs do - > first part gives program name and options) > > Often, that's useful, but sometimes, this info does not surprise me - > some things just don't have an easy implementation. > For those, I want to find out who calls them - > to possibly replace some of these calls > with a cheaper implementation (that is only valid > because the caller knows something that the callee does not) > > Is there some automation for getting this information? > I am not even sure how to formalize what I want. > Perhaps, for the first N heavy cost centers (SCCs), > a suitably ordered list of their callers (that inherit the cost)? > > The data is in the third (long, detailed) part of the .prof file > but I find it hard to process (in that form). It represents > the call hiearchy by indentation (first column) and adjacency (of rows) > but this goes out the window as soon as I grep or sort the rows. > > The JSON output format seems the way to go > https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/profiling.h… > . > Yeah, I should probably just aeson it and then walk the tree. > I still wanted to ask for advice first, or references > to existing work. Any pointers appreciated. > > - J. > Profiteur has served me well in this regard. It shows me what top-level functions eat most of the execution times, and which sub-functions have the biggest share thereof, etc. All in a nice interactive browser interface. https://hackage.haskell.org/package/profiteur Olaf

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