May 2022 - Haskell-Cafe

Call for Reviewers APLAS 2022 Artifact Evaluation Committee
by Arpita Dutta 12 May '22

12 May '22

Dear all; The /20th Asian Symposium on Programming Languages and Systems/ (APLAS'22) is going to be holding its first /Artifact Evaluation Committee/ (AEC). The artifact evaluation process aims to promote, share, and catalogue the research artifacts of papers accepted to the APLAS research track. We are looking for motivated researchers at all academic stages (PhD Students, Researchers, Lecturers, & Professors) to join us on the inaugural APLAS'22 AEC. The self-nomination form is available at: https://forms.gle/rJREG9DiFQHegZmD9 To nominate other people please use the following form: https://forms.gle/KFiQYLjELMsEjGLp8 As a committee member your primary responsibility will be to review artifacts submitted by authors of accepted papers and ensure that the artifact is a faithful representation of the accepted paper's results. This will involve interacting with some tooling provided by the authors, check if the results of the main paper are consistent with the claims in the paper and are also reproducible for researchers to come. APLAS will use a three-phase artifact review process: Kick-The-Tyres; Review the Artifact; and Iron-out-the-Wrinkles. Reviewing guidance for committee members will be made available once the committee has been formed. We will close nominations on: Friday 08 July 2022 (AOE) and notify the selected committee members on: Friday 15 July 2022 (AOE) We expect most of the reviewing process to be performed between 22nd August 2022 and 19th September 2022. We expect each artifact to take around eight hours to review and we will look to assign each reviewer three to four reviews. For each artifact we will assign a Lead Reviewer to lead the reviewing process. Salient information about the reviewing process can be found online: https://2022.splashcon.org/track/aplas-2022-aec#Reviewer-Information<https://2022.splashcon.org/track/aplas-2022-aec#Reviewer-Information> Come join us to improve the quality of research in our field! Thanks Arpita Dutta and Jan de Muijnck-Hughes APLAS'22 AEC Co-Chairs. This call was adapted from the PLDI'22 AEC Call for Nominations.

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BX 2022 - Call for papers (deadline 14 May)
by Li-yao Xia 10 May '22

10 May '22

# Tenth International Workshop on Bidirectional Transformations (BX 2022) 8 July 2022, Nantes, France Part of STAF 2022 (5-8 July): https://staf2022.univ-nantes.io/ BX 2022 homepage: http://bx-community.wikidot.com/bx2022:home ## Overview Bidirectional transformations (BX) are a mechanism for maintaining the consistency between two or more related (and heterogeneous) sources of information (e.g., relational databases, software models and code, or any other artefacts following standard or domain-specific formats). The strongest argument in favour of BX is its ability to provide a synchronization mechanism that is guaranteed to be correct by construction. BX has been attracting a wide range of research areas and communities, with prominent presence at top conferences in several different fields (namely databases, programming languages, software engineering, and graph transformation). Nowadays, the fast-growing complexity of software- or data-intensive systems has forced industry and academia to use and investigate different development techniques to manage the many different aspects of the systems. Researchers are actively investigating the use of bidirectional approaches to tackle a diverse set of challenges with various applications including model-driven software development, visualization with direct manipulation, big data, databases, domain-specific languages, serializers, and data transformation, integration and exchange. BX 2022 is a dedicated venue for BX in all relevant fields and is part of a workshop series that was created in order to promote cross-disciplinary research and awareness in the area. As such, since its beginning in 2012, the workshop has rotated between venues in different fields. Papers for BX 2022 can be submitted on EasyChair: https://www.easychair.org/conferences/?conf=bx2022 ## Important Dates - Paper submission: 14 May, 2022 - Author notification: 28 May, 2022 - Workshop: 8 July, 2022 ## Topics The aim of the workshop is to bring together researchers and practitioners, established and new, interested in bx from different perspectives, including but not limited to: - bidirectional programming languages and frameworks - software development with BX - data and model synchronization - view updating - inter-model consistency analysis and repair - data/schema (or model/metamodel) co-evolution - coupled software/model transformations - inversion of transformations and data exchange mappings - domain-specific languages for BX - analysis and classification of requirements for BX - bridging the gap between formal concepts and application scenarios - analysis of efficiency of transformation algorithms and benchmarks - model-driven and model-based approaches - survey and comparison of BX technologies - case studies and tool support - applications and experiences of adopting BX in the real world ## Categories of Submissions Five categories of submissions are considered: 1. Full Research Papers (13-15 pages) - in-depth presentations of novel concepts and results - applications of bx to new domains - survey papers providing novel comparisons between existing bx technologies and approaches, case studies 2. Tool Papers (7-8 pages) - guideline papers presenting best practices for employing a specific bx approach (with a specific tool) - presentation of new tools or substantial improvements to existing ones - qualitative and/or quantitative comparisons of applying different bx approaches and tools 3. Experience Report (7-8 pages) - sharing experiences and lessons learned with bx tools/frameworks/languages - how bx is used in (research/industrial/educational) projects 4. Short Papers (5 pages) - work in progress - small focused contributions - position papers and research perspectives - critical questions and challenges for bx 5. Talk Proposals (2 pages) - proposed lectures about topics of interest for bx - existing work representing relevant contributions for bx - promising contributions that are not mature enough to be proposed as papers of the other categories ## Submission guidelines Papers should use the new CEUR-ART style, single column, available as an Overleaf page or as a zip archive: https://www.overleaf.com/read/gwhxnqcghhdt http://ceur-ws.org/Vol-XXX/CEURART.zip and must be submitted via EasyChair: https://www.easychair.org/conferences/?conf=bx2022 If your submission is not a Full Research Paper, please include the intended submission category in the Title field of EasyChair’s submission form. Tool papers, experience reports and short papers will be mapped to the short paper category in CEUR (having between 5-9 standard pages, 1 standard page = 2500 characters), whereas full research papers will be mapped to the regular paper category in CEUR (having at least 10 standard pages). The bibliography is excluded from the page limits. All papers are expected to be self-contained and well-written. Tool papers are not expected to present novel scientific results, but to document artifacts of interest and share bx experience/best practices with the community. Experience papers are expected to report on lessons learnt from applying bx approaches, languages, tools, and theories to practical application case studies. Extended abstracts should primarily provoke interesting discussion at the workshop and will not be held to the same standard of maturity as regular papers; short papers contain focused results, positions or perspectives that can be presented in full in just a few pages, and that correspondingly contain fewer results and that therefore might not be competitive in the full paper category. Talk proposals are expected to present work that is of particular interest to the community and worth a talk slot at the workshop. We strongly encourage authors to ensure that any (variants of) examples are present in the bx example repository at the time of submission, and, for tool papers, to allow for reproducibility with minimal effort, either via a virtual machine (e.g., via Share) or a dedicated website with relevant artifacts and tool access. All papers will be peer-reviewed by at least three members of the program committee. If a submission is accepted, at least one author is expected to participate in the workshop to present it. Authors of accepted tool paper submissions are also expected to be available to demonstrate their tool at the event. ## Proceedings The workshop proceedings (in a STAF 2022 joint volume for workshops), including all accepted papers (except talk proposals), shall be submitted after the conference to CEUR-WS.org for online publication. Pre-prints of all papers will be available via the workshop website at the beginning of the conference. In case of questions, please contact the PC chairs at bx2022(a)easychair.org. Best regards, Li-yao Xia, Vadim Zaytsev, Xiao He

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Full professorships at Utrecht University
by Swierstra, W.S. (Wouter) 10 May '22

10 May '22

Utrecht University is currently recruiting four full professors in Computing Science. The exact research areas are not fixed -- but I'd love to see applications from the functional programming community: https://www.uu.nl/en/organisation/working-at-utrecht-university/jobs/4-full… # Job description The Department of Information and Computing Sciences (ICS) is nationally and internationally renowned for its fundamental and applied research in computer science and information science. In our constantly changing (digital) society, we are continually looking for new, realistic ways to push the boundaries of both science and societal application. We contribute to innovative information technologies through the development and application of new concepts, theories, algorithms, and software methods. With our expertise, we nourish a wide range of interdisciplinary and societal collaboration initiatives. The Department has grown significantly in the past years. Due to this growth and the upcoming retirement of some of our professors we envisage having appointed eight new full professors by the end of 2024 in the following fields of expertise: software systems (preferably in software production, and software and information security), artificial intelligence and data science (preferably in machine learning, responsible AI, and natural Language processing) and interaction (preferably in data-driven interaction). We are now actively searching to fill four positions. Since we aim to continue to increase the participation of women in Information and Computing Sciences (both students and staff), we wish to appoint at least two female full professors. Additionally, we have one position open that is not tied to any specific area, exclusively reserved for female candidates, a Westerdijk chair*. In Software Systems, we have research groups on Software Technology, Software Technology for Teaching and Learning, Software Production, and Business Process Management and Analytics. We lead the research masters on Computing Science and Business Informatics, and co-lead the bachelors Informatics and Information Science. We engage closely with industry and public sector partners to study the development and adoption of software technology and software production methods. In Artificial Intelligence & Data Science, we have research groups on Intelligent Systems, Data Intensive Systems, Data Mining, and Natural Language Processing. We lead the multidisciplinary research master in Artificial Intelligence and Data Science, and co-lead the Applied Data Science master and Artificial Intelligence bachelor. We closely collaborate with the public sector and companies, for example in our National Police Lab AI and AI & Mobility Lab. We also work closely with other disciplines, for example in the university's Human Centered AI and Applied Data Science focus areas. In Interaction Technology, we have research groups on Human Centered Computing, Game and Media Technology, Social and Affective Computing, and Visualisation and Graphics. We lead the Research Masters on Game & Media Technology and Human-Computer Interaction, and co-lead the Bachelor Information Science. Our state-of-the-art facilities include a Human-Centered Computing lab for prototyping interactive systems and conducting user studies and a Motion Capture and Virtual Reality Lab with full body motion capture equipment. We co-lead the multidisciplinary AI & Media and AI & Healthy Living labs and the Center for Game Research. As a full professor you are a committed, internationally acknowledged and leading scientist with expertise in one of the areas of Information and Computing Science. Your ambition is to lead the further development of research, the quality of education (both in teaching and curriculum development) and the achievement of societal impact in the field of information and computing sciences. You seek internal and external (interdisciplinary) collaboration and acquire funding for research, developing new research collaborations and new application areas. You are an inspiring educator with enthusiasm for teaching. Alongside you will take a leading role in your field of expertise, you also play an important role in creating a workplace that is supportive, socially safe and inclusive, further enhancing scientific integrity and working together towards open science. You have a clear view of how to achieve this as a leading staff member. The Department provides a dynamic, informal and international work environment. Our approach is characterized by a connected, open, and can-do spirit that stimulates personal initiative and curiosity. You are a team player who encourages taking ownership and create value while sharing your knowledge both internally and across the wider (global) community. If you are excited to actively participate and collaborate in shaping our developing department, we invite you to apply. It is important that when you apply, you make clear where and how you see that your expertise fits the overall research and education portfolio of the department, including the relationship with (future) external stakeholders. *A Westerdijk chair is a position especially installed to be occupied by a female professor. It is named after Johanna Westerdijk, appointed at Utrecht University in 1917 as the first female full professor in the Netherlands. # Qualifications We are looking for new colleagues to complement our team at an academic as well as a personal level, who fit well with the following qualifications: a PhD in Computer Science, Information Science or another relevant discipline; an internationally acknowledged research line with a strong publication track record on original research of high impact; an active player in international scientific communities; experience in and a personal view on how to lead a group of scientists and create and sustain a supportive, collaborative and inclusive work environment; demonstrated ability to acquire external funding for research and innovation; driven to explore and forge new collaborations in- and outside academia; enthusiasm for education and experience with student supervision, ability to teach in BSc and MSc programmes; experience in and aspiration for further development of courses and programmes. # Offer a tenured position as full professor; a full-time gross salary ranging from €5,864 to €8,539 in scale H2 at full professor level; benefits including an 8% holiday bonus and an 8.3% end-of-year bonus; a pension scheme, partially paid parental leave, and flexible employment conditions based on the Collective Labour Agreement (cao) Dutch Universities; a starting package that is negotiable and depends on what is necessary to give you a running start in the department; assistance in finding housing and, if applicable, help with finding employment for a partner and schools for children; in addition to the employment conditions laid down in the CAO for Dutch Universities, Utrecht University has a number of its own arrangements. For example, there are agreements on professional development, leave arrangements and sports. We also give you the opportunity to expand your terms of employment via the Employment Conditions Selection Model. This is how we like to encourage you to continue to grow. # About the organisation At the Faculty of Science, there are 6 departments to make a fundamental connection with: Biology, Chemistry, Information and Computing Sciences, Mathematics, Pharmaceutical Sciences, and Physics. Each of these is made up of distinct institutes that work together to focus on answering some of humanity’s most pressing problems. More fundamental still are the individual research groups – the building blocks of our ambitious scientific projects. Utrecht University is a friendly and ambitious university at the heart of an ancient city. We love to welcome new scientists to our city – a thriving cultural hub that is consistently rated as one of the world’s happiest cities. We are renowned for our innovative interdisciplinary research and our emphasis on inspirational research and excellent education. We are equally well-known for our informal atmosphere and the can-do mentality of our people. This lively and inspiring academic environment attracts professors, researchers and PhD candidates from all over the globe, making both the University and the Faculty of Science a vibrant international and wonderfully diverse community. # Additional information If you have specific questions regarding the positions or the department, please email them to Professor Johan Jeuring (Head of Department) or Professor Judith Masthoff (Director of Research) at j.t.jeuring(a)uu.nl/ j.f.m.masthoff(a)uu.nl. If you are interested in reading more about the development of our department, we can provide you with a copy of our summarized organizational development plan. You can send your request to a.bonsma(a)uu.nl. Do you have a question about the application procedure? Please send an email to science.recruitment(a)uu.nl # Apply https://ssl1.peoplexs.com/Peoplexs22/CandidatesPortalNoLogin/ApplicationFor… Everyone deserves to feel at home at our university. We welcome employees with a wide variety of backgrounds and perspectives. Please enclose: your motivation letter; your full academic curriculum vitae, including a list of publications; your vision on research and education. If this specific opportunity isn’t for you, but you know others who may be interested, please forward this vacancy to them. The application deadline is 1 July 2022.

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[direct-sqlite] Package takeover
by ☂Josh Chia (謝任中) 09 May '22

09 May '22

Hi all, I tried to contact the author of https://hackage.haskell.org/package/direct-sqlite via github issues and direct email 27 days ago about taking over the package but have not received a response. I would like to take over as maintainer for the package and would also welcome co-maintainers. Josh Chia

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cabal v2 global install status
by amindfv＠mailbox.org 09 May '22

09 May '22

I'm very comfortable using cabal's `v2-` nix-style local builds at home and at work, but on a personal machine at home I've clung to `v1-install` because I _really_ like the ability to choose which packages are available in a simple `ghci` session. For a long time that's been impossible or painful with the `v2-` commands. What's the status these days? I'm particularly interested in how it works for packages that only exist locally without a Hackage server. (Please note that while I'm open to hearing that it's impossible or only possible with workarounds/hacks, I'm not particularly looking for a discussion on whether it's "wrong" to want this feature.) Thanks! Tom

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Coverage icon on hackage
by Ivan Perez 07 May '22

07 May '22

Hi all, What analysis does the hackage server run to determine the coverage level of, or rating given to, a particular package? For example, for one package it is showing this icon: https://img.shields.io/static/v1?label=Coverage&message=32%&color=red What does that actually mean? The build log states: Code Coverage expressions 32% (224/684) booleanguards 100% (0/0) conditions 20% (1/5) qualifiers 100% (0/0) alternatives 27% (5/18) local declarations 40% (6/15) top-level declarations 32% (29/90) Is it possible to see details of how hackage is arriving to these conclusion, and to replicate these results locally? Thanks, Ivan

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[ANN] mtl-2.3
by Emily Pillmore 07 May '22

07 May '22

Hello Everyone, mtl-2.3 has been released. This release marks the first major version for the library in a long time, and addresses some longstanding issues that have taken years to fix. As a result, this will be a *breaking update* for many. Please review the following changelog notes: * Added instances for Control.Monad.Trans.Writer.CPS and Control.Monad.Trans.RWS.CPS from transformers 0.5.6 and add Control.Monad.Writer.CPS and Control.Monad.RWS.CPS. * Control.Monad.Cont now re-exports evalCont and evalContT. * Add tryError , withError , handleError , and mapError to Control.Monad.Error.Class , and re-export from Control.Monad.Except. * Remove Control.Monad.List and Control.Monad.Error. * Remove instances of deprecated ListT and ErrorT. * Remove re-exports of Error. * Add instances for Control.Monad.Trans.Accum and Control.Monad.Trans.Select ( http://control.monad.trans.select/ ). * Require GHC 8.6 or higher, and cabal-install 3.0 or higher. * Require transformers-0.5.6 or higher. * Add Control.Monad.Accum for the MonadAccum type class, as well as the LiftingAccum deriving helper. * Add Control.Monad.Select ( http://control.monad.select/ ) for the MonadSelect type class, as well as the LiftingSelect deriving helper. A big thank you to all contributors and commentators, and a special thanks to Koz for picking up maintenance so swiftly. Happy hacking, Emily

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Re: [Haskell-cafe] data/newtype examples
by Olaf Klinke 06 May '22

06 May '22

> Dear Cafe - > > > I wanted a quick example (for teaching) > that shows a difference between data and newtype. > > What examples do you use? > I'm interested both in simple ones, > and confusing/obfuscated ones. Perhaps on the obscure side: I like to play with different implementations of Void. Let the students demonstrate that newtype Void = Void Void contains only one element whereas data Void = Void Void contains infinitely many elements that can be distinguished by pattern matching. Also consider data Void = Void !Void. Is this observably different from the Void newtype? Since you will have to explain lifting, you can also demonstrate that(,) is not the categorical product. Olaf

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GHC proposal for ImplicitQualifiedImport
by Tristan Cacqueray 06 May '22

06 May '22

Dear Café, I've proposed a new language extensions to enable implicit imports, so that a qualified name can be used without adding an import declaration: https://github.com/ghc-proposals/ghc-proposals/pull/500 Would such an extension makes your life better? I value your feedback, so let me know what you think! Kind Regards, -Tristan

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Was simplified subsumption worth it for industry Haskell programmers?
by pareto optimal 06 May '22

06 May '22

I originally posted on Reddit and the thread contains much debate and discussion. I'm concerned the views of the mailing list and likely ghc devs might not be as represented there or discourse, so i'm also copying it here. Copy-paste of post: Warning: Long post tl;dr - simplified subsumption seems to make common code I write in industry clunky for no good reason in lots of places - Are others concerned with motivating what seem like "pointless lambdas" to new hires or students for simple tasks? - Are there more real world advantages that make these frequent annoyances worth it? - How is quicklook impredicativity useful in industry? The biggest advantage seems to be that laziness is more predictable. However looking at [commits fixing simplified subsumption errors on github](https://github.com/search?q=simplified+subsumption+language%3Ahaske… I see very common patterns in industry Haskell now need an explicit lambda for "reasons" such as: readFreqSumFile :: (MonadSafe m) => FilePath -> m (FreqSumHeader, Producer FreqSumEntry m ()) - readFreqSumFile file = readFreqSumProd $ withFile file ReadMode PB.fromHandle + readFreqSumFile file = readFreqSumProd $ withFile file ReadMode (\h -> PB.fromHandle h) and: - toOrders <- asks _pdfConfToOrder + toOrders <- asks (\r -> _pdfConfToOrder r) And this typical use of id is no longer valid: instance MonadOrvilleControl IO where - liftWithConnection = id - liftFinally = id + liftWithConnection ioWithConn = ioWithConn + liftFinally ioFinally = ioFinally On my $work codebase that means hundreds of changes that make our code worse with seemingly no benefit. This case is addressed in the proposal, but seems to handwave this as: > The benefit, in terms of programming convenience, is small. >From my perspective while updating my codebase, it certainly doesn't feel that way. >From the persective of onboarding new Haskell hires, it doesn't feel simpler. I envision a future teaching session like: > student: This code looks correct but I get an error that means nothing to me of error: • Couldn't match type: b0 -> b0 with: forall q. q -> q Expected: p -> forall q. q -> q Actual: p -> b0 -> b0 • In the first argument of ‘g’, namely ‘f’ In the expression: g f In an equation for ‘h’: h = g f | | h = g f | ^ > me: Ah, that's because of something called simplified subsumption which we'll cover much later. > me: For now, just know putting it in an explicit lambda fixes it when you notice a compile error like that. > me: Now lets try to move past that and get back to basic file reading and writing > student: oookkkay? (feeling unsure, disillusioned about Haskell requiring pointless ceremony and being overly complex for no seeming benefit) Being a fan of and proponent of Haskell I think: If this complication is being added, surely something is made possible in return that gives more value. This led me to [the proposal](https://github.com/ghc-proposals/ghc-proposals/blob/master/propos… and I found with simplified subsumption: - Laziness characteristics and semantics of programs will be changed less, which I infer will lead to more predictable performance - I assume that simplifying a compiler step like this will speed up compile times and reduce space usage - Quick look impredicativity seems to be the real driving reason behind simplified subsumption and somehow makes dealing with very polymorphic code easier At this point my thought is: > Making highly polymorphic code simpler to write that isn't as typical in industry Haskell code in ways I can't determine without great effort was valued over "small incoveniences" that I'll run into daily But, still wanting to give the benefit of the doubt I dive face first into [The proposal for Quicklook impredicativity](https://github.com/ghc-proposals/ghc-proposals/blob/master…. Reading the whole thing, I still cannot ground this concept in real world terms that may effect me or that I could take advantage of. So, I go to the paper [A quick look at impredicativity](https://www.microsoft.com/en-us/research/publication/a-qui… and start reading many things I don't fully understand. Running out of energy, I start skimming and finally find some examples in section 10 APPLICATIONS. I see an example with gZipWithM that I still don't understand. Further down I see reference to pieces of code updated in Streamly that take advantage of quick look polymorphism and wonder why the real world example wasn't included and explained. So, i'm left frustrated with "simplified" subsumption and posting here for help answering: - Are others in the same boat? - Are there advantages i'm not seeing? - Can we use my reflection to improve industry/academic communication? And finally, any revant commentary surrounding this I may be oblivious to. Thanks!

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