December 2020 - Haskell-Cafe

Re: [Haskell-cafe] Teaching High-School one-semester FP (using Haskell)
by Andrew Butterfield 11 Dec '20

11 Dec '20

Dear all > On 11 Dec 2020, at 00:07, Henning Thielemann <lemming(a)henning-thielemann.de> wrote: .... stuff elided > So recursion looks to me as funtional programming's GOTO, and if it is tail recursive, it actually is one. Yes, but it's "GOTO considered beneficial" ;-) Thanks to Zachi for asking the original question - I've already seen lots more ideas for me to chase up for my course! Regards, and Happy Holidays, Andrew > _______________________________________________ > 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. -------------------------------------------------------------------- Andrew Butterfield Tel: +353-1-896-2517 Fax: +353-1-677-2204 Lero@TCD, Head of Software Foundations & Verification Research Group School of Computer Science and Statistics, Room G.39, O'Reilly Institute, Trinity College, University of Dublin http://www.scss.tcd.ie/Andrew.Butterfield/ --------------------------------------------------------------------

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Re: [Haskell-cafe] What features should an (fictitious) IDE for Haskell have?
by Olaf Klinke 08 Dec '20

08 Dec '20

On 20-12-07 18:22, André Popovitch wrote: > One feature I've always wanted would be able to "manually inline" a > function. For example, if I have > > foo a = a + a > bar = foo 3 > > I'd like to be able to right-click on the invocation of `foo` and > select > some option to inline it, rewriting the file to read > > foo a = a + a > bar = 3 + 3 > > I think this would make it simple to dive into an abstraction to see > what's > really going on. For example, imagine a new user is confused by this > expression: > > Just 3 >> Just 4 > > They could right-click on `>>` to see that it is identical to: > > case Just 3 of > Just _ -> Just 4 > Nothing -> Nothing > > > Which would allow them to easily see that this expression will always > evaluate to "Just 4" (and hopefully simplify it). Enlightened, they > could > then hit ctrl-z to revert the code to its original state. > > Haskell's purity and laziness makes it one of the only mainstream > languages > where equational reasoning is really possible, so this feature would > play > on Haskell's strengths and provide a feature that couldn't be > replicated in > other languages' IDEs. It would also allow new users to more easily > dive in > and understand certain abstractions (although how it would work in > many > cases would be hard to determine). +1 for this. It is like a step-by-step evaluation/debugger but limited to function calls at the syntactic level. I can image so many past situations where this would have prevented lots of head-scratching. This hypothetical IDE feature might go well with a tree view where inlining a function application is equivalent to expanding a level in a tree (within the same source line number), like so: Folded: [+] button appears on mouse over "foo". bar = foo[+] 3 Expanded: One code line now occupies two lines in the IDE window. [-] button reverts code to previous state. bar = foo 3 [-] 3 + 3 I've seen similar things in action in a demo implementation of [1,2]. Also great for teaching, I guess. Olaf [1] https://www.cs.bham.ac.uk/~pbl/papers/functionalexplainsupp.pdf [2] https://dl.acm.org/doi/10.1145/3110258

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[TFP'21] second call for papers: Trends in Functional Programming 2021, 18-19 February (online event with Lambda Days 2021 & TFPIE 2021)
by Peter Achten 08 Dec '20

08 Dec '20

------------------------------------------------------------------------- Second call for papers 22nd Symposium on Trends in Functional Programming tfp2021.org ------------------------------------------------------------------------- Did you miss the deadline to submit a paper to Trends in Functional Programming http://tfp2021.org/? No worries -- it's not too late! Submission is open until January 15th 2021, for a presentation slot at the event and post-symposium reviewing. The symposium on Trends in Functional Programming (TFP) is an international forum for researchers with interests in all aspects of functional programming, taking a broad view of current and future trends in the area. It aspires to be a lively environment for presenting the latest research results, and other contributions. * TFP offers a supportive reviewing process designed to help less experienced authors succeed, with two rounds of review, both before and after the symposium itself. Authors have an opportunity to address reviewers' concerns before final decisions on publication in the proceedings. * TFP offers two "best paper" awards, the John McCarthy award for best paper, and the David Turner award for best student paper. * TFP is co-located with Lambda Days in beautiful Krakow. Lambda Days is a vibrant developer conference with hundreds of attendees and a lively programme of talks on functional programming in practice. Due to the covid pandemic, the event is online with a lot of attention to interaction and getting to socialize with the community. Important Dates --------------- Submission deadline for pre-symposium review: 20th November, 2020 -- passed -- Submission deadline for draft papers: 15th January, 2021 Symposium dates: 18-19th February, 2021 Visit http://tfp2021.org/ for more information.

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What features should an (fictitious) IDE for Haskell have?
by Gueven Bay 08 Dec '20

08 Dec '20

Greetings, Imagine that you can decide what functionality and features an Integrated Development Environment for Haskell should get. You can make this IDE with your wishlist similar in power as other IDEs for Java for example. Now list as many features as you can, what would make the life of a Haskell developer as comfortable as possible!? I am dying to know how this list of features at the end (of this thread) will look like.

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Call for Participation: BOB 2021 (February 26, online, early-bird until Dec 31)
by Stefan Wehr 08 Dec '20

08 Dec '20

“What happens if we simply use what’s best?” BOB Conference 2021 February 26, 2021, online (0100+UTC) http://bobkonf.de/2021/ Program: http://bobkonf.de/2021/program.html Registration: http://bobkonf.de/2021/registration.html Keynote: Jeremy Gibbons BOB conference is a place for developers, architects and decision-makers to explore technologies beyond the mainstream in software development, and to find the best tools available to software developers today. Our goal is for all participants of BOB to return home with new insights that enable them to improve their own software development experience. The program features 14 talks and 8 tutorials on current topics: http://bobkonf.de/2021/program.html The subject range includes functional programming, logic programming, revision control, formal methods, mindfulness, event sourcing, front-end development, and more. Jeremy Gibbons will give the keynote talk. BOB 2021 will take place online. We are working towards fostering lively exchange of exciting ideas and enable meaningful social interactions. Registration is open online: http://bobkonf.de/2021/registration.html The early-bird registration is €10 for a regular ticket, €5 for a student ticket. (If you need financial aid, let us know.) We intend to make this the most diverse, colorful, fun BOB ever! NOTE: The early-bird rates expire on December 31, 2020!

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Help lead Haskell: Executive Director sought for Haskell Foundation
by Richard Eisenberg 08 Dec '20

08 Dec '20

Posting on behalf of the Haskell Foundation Working Group. Please forward widely! -------- The Haskell Foundation is seeking an Executive Director. Please find the job description here: https://haskell.foundation/ <https://haskell.foundation/executive-director>ed-job-description <https://haskell.foundation/ed-job-description/> The Haskell Foundation (HF) is an independent, non-profit organization dedicated to driving Haskell adoption and open-source development. HF seeks a full-time Executive Director (ED) to lead and develop the organization going forward. The ED is responsible for furthering the HF’s mission and vision, ensuring that resources are in place to accomplish its goals. The HF is supported by an active group of volunteers, and the ED will be a key focal point for that community, in addition to hiring support staff. This is a salaried position. Salary will be commensurate with the experience, qualities, and location of the individual, and will also reflect the Foundation’s status as a non-profit organisation funded by donations.

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ANN: hledger-1.20
by Simon Michael 07 Dec '20

07 Dec '20

I'm pleased to announce hledger 1.20 ! Changes include: - Strict mode - check command - rendering, speed, and valuation fixes. https://hledger.org/release-notes has the full details. Thanks to release contributors Stephen Morgan, Dmitry Astapov, TANIGUCHI Kohei, and legrostdg. hledger (http://hledger.org) is a robust, cross-platform, plain text accounting tool, with command-line, terminal and web UIs. 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 (http://plaintextaccounting.org) http://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. To get help, see http://hledger.org#help-feedback, and join our chat channel via Freenode (#hledger, http://irc.hledger.org) or Matrix (#freenode_#hledger:matrix.org, http://riot.hledger.org) Beginners and experts, contributors, sponsors, and all feedback are most welcome! Be safe and well, -Simon

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Re: [Haskell-cafe] What features should an (fictitious) IDE for Haskell have?
by Johannes Waldmann 07 Dec '20

07 Dec '20

> very cool feature would be if I could select a program phrase > and let it find /similar/ phrases, where a similarity metric > could be edit-distance with respect to language tokens ... I often wanted a tool that finds (nearly) duplicate AST sub-trees in a large code base, and suggests refactorings. Of course, in an IDE, it could alert me on-the-fly that I'm typing some code that's already present elsewhere. How might one go about implementing this? Actual (approximate) sub-tree matching seems the easy part; but I have no clear idea about whether this should just use syntax, or needs types as well (my guess is: yes) what libraries are there to provide the (annotated) ASTs, etc. - J.W.

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Haskell on windows 7 without chocolatey?
by Jim Blorg 06 Dec '20

06 Dec '20

Is there a way to install haskell on windows 7 manually via zip without all the requirements for scripting?

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Re: [Haskell-cafe] [Ann] group-theory
by Emily Pillmore 05 Dec '20

05 Dec '20

Hi Marcin, > > Nice work; I also implemented free groups in the free-algebra package > > Wonderful - I'll take a look. Those were a bit rough, and it'd be good to see how you encoded them in `free-algebra`. Maybe we can collaborate on expanding the knowledgebase and utility of free group calculations in our respective packages :) > > However 'FG' is the free group in the class of all groups. > > I'm glad you noted this as well! The `DList` encoding is interesting - I'll need to study that a bit :) Someone has also linked me to Sjoerd's `free-functors` library, which seems is also very interesting: https://github.com/sjoerdvisscher/free-functors/blob/master/src/Data/Functo… > > There's an interesting difference between 'FreeGroup' (using notation of > your package) and 'FG'. First one is not a free group in the class of all > groups, but only free in the class of groups for which multiplication is > strict in the left argument > > Correct. Regarding motivation, I provided both because I know some people do like to operate in the fast-and-loose strict subset of Haskell. It's no skin off my back. But I was very unsatisfied with strict (vis. "moral") Free constructions with respect to bottoms, and, inspired by Dan Doel's article ( http://comonad.com/reader/2015/free-monoids-in-haskell/ ), attempted to find a free construction for groups that was more in line with Haskell's domain-like types. I note this article in the documentation for FG. Maybe this deserves a broader blog post? > > I identified that `Foldable` can only be defined for algebraic structures > for which `Endo b` has the same algebra type; this fails for groups: only > automorphisms form a group. Having a seprate `GroupFoldable` class makes > sense. > > That class ended up being good for two things: * Great puns. * Very convenient word evaluation If you'd like to add to it, I'd be stoked. Cheers, Emily On Sat, Dec 05, 2020 at 2:53 PM, < coot(a)coot.me > wrote: > > Hi Emily, > > Nice work; I also implemented free groups in the free-algebra package. > > > There's an interesting difference between 'FreeGroup' (using notation of > your package) and 'FG'. First one is not a free group in the class of all > groups, but only free in the class of groups for which multiplication is > strict in the left argument, i.e. ones that satisfy the equation `⊥ <> a > == ⊥`. That's because `++` is strict in the left argument. For the same > reason `[]` is free monoid in the class of left strict monoids. > > > > However 'FG' is the free group in the class of all groups. Another > isomorphic construction of a free group (in the class of all groups) can > be based on `DList` - the free monoid. You might want to check out https:/ > / hackage. haskell. org/ package/ free-algebras-0. 1. 0. 0/ docs/ Data-Algebra-Free. > html ( > https://hackage.haskell.org/package/free-algebras-0.1.0.0/docs/Data-Algebra… > ) which gives a uniform interface for all free algebras (not just groups). > You'll recover there `Monad` instance of `FG` (and `FreeGroup`), and a bit > more. > > > I identified that `Foldable` can only be defined for algebraic structures > for which `Endo b` has the same algebra type; this fails for groups: only > automorphisms form a group. Having a seprate `GroupFoldable` class makes > sense. > > > > Cheers, > > Marcin Szamotulski > > > > > > > > ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ > > On Saturday, December 5th, 2020 at 19:52, Emily Pillmore < emilypi@ cohomolo. > gy ( emilypi(a)cohomolo.gy ) > wrote: > > > > >> Hello all, >> >> >> >> I am pleased to announce the release of the group-theory ( >> https://hackage.haskell.org/package/group-theory ) package: a package aimed >> at implementing the theory of finite groups in a reasonably ergonomic, >> well-documented, and featureful way. It's hardly finished, but my >> co-maintainer, Reed Mullanix (@totbwf) and I thought this was a good mvp >> with which we could announce. >> >> >> >> Contributions are very welcome, and I hope everyone enjoys. >> >> >> >> Cheers, >> >> Emily Pillmore >> >> > >

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