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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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STM rollback?
by amindfv＠mailbox.org 04 Dec '20

04 Dec '20

I'd like to be able to give up on an STM transaction: roll back and don't retry. I've cooked up something with exceptions but it feels a bit icky to use exceptions for something like this - is there a better way?: data Rollback = Rollback deriving (Show) instance Exception Rollback rollback :: STM x rollback = throwSTM Rollback atomicallyWithRollback :: STM x -> IO (Maybe x) atomicallyWithRollback a = (Just <$> atomically a) `catch` (\Rollback -> pure Nothing) The alternative I've found is something like: otherWay :: STM x -> IO (Maybe x) otherWay a = atomically $ (Just <$> a) `orElse` pure Nothing But this turns any "retry" in "a" into a rollback, and I'd like to have the option to do either (retry or rollback). Thanks, Tom

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untyped printf
by Ben Franksen 04 Dec '20

04 Dec '20

I am writing an interpreter for a very simple untyped language and I want to provide a built-in function to format a list of values in a printf like fashion. There is the beautiful Text.Printf module with its multi-variadic printf function, and I would like to use that to do all the heavy lifting. I can easily implement an instance PrintfArg Value for my Value type, but what I need in addition to that is an "untyped" version of printf i.e. something like format :: String -> [Value] -> String with the property that format fmt [] = printf fmt format fmt [x] = printf fmt x format fmt [x,y] = printf fmt x y ... I am pretty sure this is possible using a bit of class hackery and perhaps GADTs or continuation passing thrown in, but I can't seem to get it working. Any hint that helps to untangle the knots in my brain would be appreciated! Cheers Ben

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2020 Haskell.org Call for Nominations
by Jasper Van der Jeugt 03 Dec '20

03 Dec '20

Dear Haskellers, It is time to put out a call for new nominations (typically but not necessarily self-nominations) to the haskell.org committee. Three members of the committee are at the ends of their current terms: Ryan Trinkle, George Wilson and Tikhon Jelvis. The Haskell Foundation has also recently put out a call for nominations. How does Haskell.org differ from the new Haskell Foundation? Why should you nominate yourself for a role? While the Haskell.org committee shares many goals with the Haskell Foundation, it remains an independent organization to operate the haskell.org website, provide resources and infrastructure, and run programs such as GSoC, like it has been doing for years. The Haskell.org committee has voted to affiliate itself with the Haskell Foundation and several of its members were involved in the founding of the Haskell Foundation. We believe that Haskell.org can represent the community as a stakeholder in the Haskell Foundation and help drive it forward. This makes it an exciting time to nominate yourself, as we'll be able to serve the community better, working closely with other groups in the Haskell community. To nominate yourself, please send an email to committee at haskell.org by the 7th of January, 2020. Current members are eligible to re-nominate themselves. Please feel free to include any information about yourself that you think will help us to make a decision. Being a member of the committee does not necessarily require a significant amount of time, but committee members should aim to be responsive during discussions when the committee is called upon to make a decision. Committee members do not need to be deep technical Haskell experts. Instead we look for enthusiasm towards improving the Haskell community. We aim to represent the different facets of the community. We aim to be diverse in terms of industry or research, and in terms of gender, race and location. The role is about setting policy, providing direction/guidance for Haskell.org infrastructure, planning for the long term, and being fiscally responsible with the Haskell.org funds and donations. As overseers for policy regarding the open source side of Haskell, committee members must also be able to set aside personal or business related bias and make decisions with the good of the open source Haskell community in mind. More details about the committee's roles and responsibilities are on https://www.haskell.org/haskell-org-committee/ If you have any questions about the process, please feel free to e-mail us at committee at haskell.org, or contact one of us individually. Warm regards Jasper

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