- Haskell-Cafe - Haskell.org

ANN: hledger-1.10
by Simon Michael 03 Jul '18

03 Jul '18

hledger (http://hledger.org) is a friendly, robust, cross-platform program for tracking money, time or other commodities, using double-entry accounting, simple plain text file formats, and command-line, curses or web UIs. I'm very pleased to announce hledger 1.10, including work by release contributors: Alex Chen, Everett Hildenbrandt, Jakub Zárybnický, Nolan Darilek, Dmitry Astapov, Jacob Weisz, Peter Simons, Stephen Morgan, Pavlo Kerestey, Trevor Riles, Léo Gaspard, Mykola Orliuk, Wad, Nana Amfo. You'll note this is not 2.0 as previously planned - we will spend a bit more time on that. The next major release is expected to be on 2018/09/30. Please see http://hledger.org/release-notes#hledger-1.10 for the changes (as soon as I can get to those; until then, the package changelogs): http://hackage.haskell.org/package/hledger-1.10/changelog http://hackage.haskell.org/package/hledger-ui-1.10/changelog http://hackage.haskell.org/package/hledger-web-1.10/changelog http://hackage.haskell.org/package/hledger-api-1.10/changelog http://hackage.haskell.org/package/hledger-lib-1.10/changelog How to get started: ------------------- See http://hledger.org/download for all install methods. One of the easiest is the hledger-install script, which requires only bash and will build and install the hledger tools in $HOME/.local/bin/: $ curl -O https://raw.githubusercontent.com/simonmichael/hledger/master/hledger-insta… $ less hledger-install.sh # (do security review) $ bash hledger-install.sh # (add -v for more detail; use bash -x to show commands being run) or (insecure): $ curl https://raw.githubusercontent.com/simonmichael/hledger/master/hledger-insta… | bash After installation, ensure $HOME/.local/bin is in your $PATH, and try some commands: $ hledger -h # quick help $ hledger help # list built-in manuals $ hledger add # record some transactions $ hledger # list available commands Next, I encourage you to at least skim the tutorials and docs at http://hledger.org. Say hello and ask questions in the #hledger IRC channel on Freenode: http://irc.hledger.org. New users and contributors are always welcome! Give feedback, report bugs, send pull requests, write, evangelise, donate. Best! -Simon

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2nd Call for Talks -- Haskell Implementors' Workshop
by Joachim Breitner 03 Jul '18

03 Jul '18

Call for Contributions ACM SIGPLAN Haskell Implementors’ Workshop https://icfp18.sigplan.org/track/hiw-2018-papers Co-located with ICFP 2018 St. Louis, Missouri, US https://conf.researchr.org/home/icfp-2018 Important dates --------------- Proposal Deadline: Friday, 20 July, 2018 Notification: Friday, 3 August, 2018 Workshop: Sunday, 23 September, 2018 Keynote speaker --------------- This year, the Haskell Implementors’ Workshop is proud to present Rahul Muttineni as the keynote speaker. Rahul brough the joys of Haskell to the realm of Java by creating the Eta programming language. Title: Let's Go Mainstream with Eta! Eta is a fork of GHC that focuses on three core principles: user experience, performance, and safety. We'll discuss how we used these principles to guide the re-implementation of the GHC runtime and code generator on the JVM. Moreover, will also cover the inner workings of the FFI and the typechecker support we added for subtyping to make it smooth to interact with Java libraries. Finally, we'll round out with a look at where Eta is headed and how Eta and GHC can collaborate in the future. About the Haskell Implementors’ Workshop ---------------------------------------- The 10th Haskell Implementors’ Workshop is to be held alongside ICFP 2018 this year in St. Louis. It is a forum for people involved in the design and development of Haskell implementations, tools, libraries, and supporting infrastructure, to share their work and discuss future directions and collaborations with others. Talks and/or demos are proposed by submitting an abstract, and selected by a small program committee. There will be no published proceedings. The workshop will be informal and interactive, with open spaces in the timetable and room for ad-hoc discussion, demos and lightning talks. Scope and Target Audience ------------------------- It is important to distinguish the Haskell Implementors’ Workshop from the Haskell Symposium which is also co-located with ICFP 2018. The Haskell Symposium is for the publication of Haskell-related research. In contrast, the Haskell Implementors’ Workshop will have no proceedings – although we will aim to make talk videos, slides and presented data available with the consent of the speakers. The Implementors’ Workshop is an ideal place to describe a Haskell extension, describe works-in-progress, demo a new Haskell-related tool, or even propose future lines of Haskell development. Members of the wider Haskell community encouraged to attend the workshop – we need your feedback to keep the Haskell ecosystem thriving. Students working with Haskell are specially encouraged to share their work. The scope covers any of the following topics. There may be some topics that people feel we’ve missed, so by all means submit a proposal even if it doesn’t fit exactly into one of these buckets: * Compilation techniques * Language features and extensions * Type system implementation * Concurrency and parallelism: language design and implementation * Performance, optimisation and benchmarking * Virtual machines and run-time systems * Libraries and tools for development or deployment Talks ----- We invite proposals from potential speakers for talks and demonstrations. We are aiming for 20-minute talks with 5 minutes for questions and changeovers. We want to hear from people writing compilers, tools, or libraries, people with cool ideas for directions in which we should take the platform, proposals for new features to be implemented, and half-baked crazy ideas. Please submit a talk title and abstract of no more than 300 words. Submissions can be made via HotCRP at https://icfp-hiw18.hotcrp.com/ until July 20th (anywhere on earth). We will also have lightning talks session. These have been very well received in recent years, and we aim to increase the time available to them. Lightning talks be ~7mins and are scheduled on the day of the workshop. Suggested topics for lightning talks are to present a single idea, a work-in-progress project, a problem to intrigue and perplex Haskell implementors, or simply to ask for feedback and collaborators. Program Committee ----------------- * Edwin Brady (University of St. Andrews, UK) * Joachim Breitner – chair (University of Pennsylvania) * Ben Gamari (Well-Typed LLP) * Michael Hanus (Kiel University) * Roman Leshchinsky (Facebook) * Niki Vazou (University of Maryland) Contact ------- * Joachim Breitner <joachim(a)cis.upenn.edu> -- Joachim Breitner Post-Doctoral researcher http://cis.upenn.edu/~joachim

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Re: [Haskell-cafe] [ANNOUNCE] GHC 8.6.1-alpha1 available
by Ben Gamari 03 Jul '18

03 Jul '18

George Colpitts <george.colpitts(a)gmail.com> writes: > I don't see an apple/darwin binary. Not sure if that is an oversight or was > planned. > Yikes! Thank you for mentioning this. This is indeed a mistake. I'm uploading the Darwin distribution right now; it will be done within 20 minutes. Cheers, - Ben

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[ANNOUNCE] GHC 8.6.1-alpha1 available
by Ben Gamari 01 Jul '18

01 Jul '18

The GHC development team is pleased to announce the first alpha release leading up to GHC 8.6.1. The usual release artifacts are available from https://downloads.haskell.org/~ghc/8.6.1-alpha1 This is the first release (partially) generated using our new CI infrastructure. One known issue is that the haddock documentation is currently unavailable. This will be fixed in the next alpha release. Do let us know if you spot anything else amiss. As always, do let us know if you encounter any trouble in the course of testing. Thanks for your help! Cheers, - Ben

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need help understanding how to specify constraints on monads
by Dennis Raddle 30 Jun '18

30 Jun '18

I'm writing a program with several functions, some of which depend on certain fields in a state monad, others of which depend on others, but no routine needs all the fields. So I thought I would declare a two classes, one for each type of data need that a function has: -- as an aside, here's an example of data which is parameterized by two types. data ReportData t1 t2 = ... -- this is rolling my own state monad with a random generator class Monad m => RandMonad m where getGen :: m StdGen putGen :: StdGen -> () -- this is a class of state monad which logs ReportData: class Monad m => LogMonad m where putReport :: ReportData t1 t2 -> m () For a particular use case, I declare a type of State monad: data MyStateData t1 t2 = MyStateData t1 t2 { theGen :: StdGen , theReports :: [StepReport t1 t2] } type MyState t1 t2 = State (MyStateData t1 t2) And I try to define my instances: instance RandMonad (MyState t1 t2) where getGen = gets theGen putGen g = modify (\s -> s { theGen = g}) instance LogMonad (MyState t1 t2) where putReport r = modify (\s -> s { theReports = r : theReports s}) I get an error on the LogMonad instance, saying that there's no instance for (MonadState (MyState t1 t2) (StateT (MyState t1 t2) Identity)) I guess I don't really understand typeclasses once you start using higher kinded types, so please enlighten me. Any reading on this subject would be helpful, too.

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(New to Conduits) mixing lazy lists and Conduits?
by Jon Fairbairn 29 Jun '18

29 Jun '18

Suppose I’m writing some code using Conduits, but need to use some old function f::[a]->[b] (defined in a library somewhere) that transforms a lazy list. Is there a way of turning f into a Conduit without ending up with all of the list being in memory? ie something that looks like toConduit:: ([a]->[b]) -> ConduitT a b m () I’ve got nowhere with Hoogle or Hayoo -- Jón Fairbairn Jon.Fairbairn(a)cl.cam.ac.uk

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Re: [Haskell-cafe] Lattice and calculation of Least Upper Bounds
by Olaf Klinke 29 Jun '18

29 Jun '18

Aaron, the lattices package provides some modules to extend a given lattice by some elements, e.g. new top and bottoms. There are also derived typeclass instances for combinations like tuples, endomorphisms and so forth. But the way of choice really depends on what you know about your multiple inheritance hierarchy. In universal algebra one powerful method of constructing (semi-)lattices is by generators and relations. That means you define the lattice as a quotient of a free lattice. The quotient itself is defined as a set of ineqalities on the generators. I don't know how one would implement that without dependent types, though, as the type would be another type together with a function. To make things worse, the word problem is undecidable in general. Looking at Algebra.Lattice.Free I'm surprised that the free (semi-)lattice types don't have a Monad instance. Does anyone know why they are not implemented? Under the hood the free lattice types are identical to the continuation monad. Olaf >Hi, > >I am trying to work out how to use the Algebra.Lattice family of Lattice >data structures. > >Firstly how do I construct a lattice ? > >What I am wanting to do is to be able to construct a lattice to represent a >multiple inheritance hierarchy. Then I to be able to find the Least Upper >Bound of a set of classes/types. This is in order to find the type of a >multiple case expression. > >I am not sure if the Haskell classes are actually applicable ? but if they >are how do I apply them to the following problem please ?

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Deadline extension for FARM 2018 (now July 8) - Workshop on Functional Art, Music, Modelling, and Design
by Brent Yorgey 29 Jun '18

29 Jun '18

The FARM submission deadline for papers and demo proposals has been extended to July 8 (the same as the performance submission deadline). 6th ACM SIGPLAN International Workshop on Functional Art, Music, Modelling and Design St. Louis, Missouri, USA, September 29th 2018 Call for Papers and Performances Key Dates ========= Paper submission deadline (extended) July 8 Performance submission deadline July 8 Author Notification July 21 Camera Ready August 5 Workshop September 29 About FARM ========== The ACM SIGPLAN International Workshop on Functional Art, Music, Modelling and Design (FARM) gathers together people who are harnessing functional techniques in the pursuit of creativity and expression. It is co-located with ICFP 2018, the 23rd ACM SIGPLAN International Conference on Functional Programming, and with Strange Loop, in St. Louis, Missouri, USA. Functional Programming has emerged as a mainstream software development paradigm, and its artistic and creative use is booming. A growing number of software toolkits, frameworks and environments for art, music and design now employ functional programming languages and techniques. FARM is a forum for exploration and critical evaluation of these developments, for example to consider potential benefits of greater consistency, tersity, and closer mapping to a problem domain. FARM encourages submissions from across art, craft and design, including textiles, visual art, music, 3D sculpture, animation, GUIs, video games, 3D printing and architectural models, choreography, poetry, and even VLSI layouts, GPU configurations, or mechanical engineering designs. Theoretical foundations, language design, implementation issues, and applications in industry or the arts are all within the scope of the workshop. The language used need not be purely functional (“mostly functional” is fine), and may be manifested as a domain specific language or tool. Moreover, submissions focusing on questions or issues about the use of functional programming are within the scope. FARM 2018 website : http://functional-art.org/2018/ Call for Performances ===================== Submission deadline: July 8, 2018. Submission URL: https://easychair.org/conferences/?conf=farm2018 . FARM also hosts a traditional evening of performances. For this year’s event, FARM 2018 is seeking proposals for live performances which employ functional programming techniques, in whole or in part. We would like to support a diverse range of performing arts, including music, dance, video animation, and performance art. We encourage both risk-taking proposals which push forward the state of the art and refined presentations of highly-developed practice. In either case, please support your submission with a clear description of your performance including how your performance employs functional programming and a discussion of influences and prior art as appropriate. Call for Papers and Demos ========================= Submission deadline (extended): July 8 Submission URL: https://easychair.org/conferences/?conf=farm2018 . We welcome submissions from academic, professional, and independent programmers and artists. Submissions are invited in three categories: 1) Original papers We solicit original papers in the following categories: - Original research - Overview / state of the art - Technology tutorial All submissions must propose an original contribution to the FARM theme. FARM is an interdisciplinary conference, so a wide range of approaches are encouraged. An original paper should have 5 to 12 pages, be in portable document format (PDF), using the ACM SIGPLAN style guidelines and the ACM SIGPLAN template. [ http://www.sigplan.org/Resources/Author/ -- use the 'sigplan' sub-format. ] Accepted papers will be published in the ACM Digital Library as part of the FARM 2018 proceedings. See http://authors.acm.org/main.cfm for information on the options available to authors. Authors are encouraged to submit auxiliary material for publication along with their paper (source code, data, videos, images, etc.); authors retain all rights to the auxiliary material. 2) Demo proposals Demo proposals should describe a demonstration to be given at the FARM workshop and its context, connecting it with the themes of FARM. A demo could be in the form of a short (10-20 minute) tutorial, presentation of work-in-progress, an exhibition of some work, or even a performance. Demo proposals should be in plain text, HTML or Markdown format, and not exceed 2000 words. A demo proposal should be clearly marked as such, by prepending Demo Proposal: to the title. Demo proposals will be published on the FARM website. A summary of the demo performances will also be published as part of the conference proceedings, to be prepared by the program chair. 3) Calls for collaboration Calls for collaboration should describe a need for technology or expertise related to the FARM theme. Examples may include but are not restricted to: - art projects in need of realization - existing software or hardware that may benefit from functional programming - unfinished projects in need of inspiration Calls for collaboration should be in plain text, HTML or Markdown format, and not exceed 5000 words. A call for collaboration should be clearly marked as such, by prepending Call for Collaboration: to the title. Calls for collaboration will be published on the FARM website. Authors take note ================= The official publication date is the date the proceedings are made available in the ACM Digital Library. This date may be up to two weeks prior to the first day of your conference. The official publication date affects the deadline for any patent filings related to published work. All presentations at FARM 2018 will be recorded. Permission to publish the resulting video (in all probability on YouTube, along with the videos of ICFP itself and the other ICFP-colocated events) will be requested on-site. Questions ========= If you have any questions about what type of contributions that might be suitable, or anything else regarding submission or the workshop itself, please contact the organisers at: farm-2018(a)functional-art.org Workshop Organization ==================== Brent Yorgey (general chair) Donya Quick (program chair) Tom Murphy (performance chair) Program Committee ================= Heinrich Apfelmus (self-employed) Chuck Jee Chau (Hong Kong University of Science and Technology, Hong Kong) Brian Heim (Yale, USA) Can Ince (ince.io) Chris Martens (NC State University, USA) Eduardo Miranda (University of Plymouth, UK) Ivan Perez Dominguez (University of Nottingham, UK) Iris Ren (Utrecht University, Netherlands) Henning Thielemann (self-employed) Didier Verna (EPITA, France) Dan Winograd-Cort (Target, USA) Halley Young (University of Pennsylvania, USA) Code of Conduct =============== FARM adheres to ICFP 2018's Code of Conduct: http://icfp18.sigplan.org/attending/code-of-conduct

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Alternative Preludes
by Hilco Wijbenga 28 Jun '18

28 Jun '18

Hi all, I've been looking for a different Prelude to, at minimum, default to Text instead of String but I'm sure there are other things that would be helpful. E.g., less focus on lists. I had a look at [1] and protolude, classy-prelude, basic-prelude, foundation, safe-prelude, and rio all seem interesting. Maybe even base-noprelude? I'm an advanced beginner (I don't think I qualify as intermediate yet). Going by [1], classy-prelude might not be such a good idea because of "scary error messages". And, I'm guessing, I would need to know Haskell better to take advantage of base-noprelude? I would like to know your thoughts/suggestions/opinions/ideas. Also, if there are other preludes that might be of interest, do tell! Cheers, Hilco [1] https://guide.aelve.com/haskell/alternative-preludes-zr69k1hc

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Call for Presentations and Demonstrations: Workshop on Functional High-Performance Computing 2018 at ICFP
by Kei Davis 26 Jun '18

26 Jun '18

7th ACM SIGPLAN Workshop on Functional High-Performance Computing September 29, 2018, St. Louis, Missouri, USA https://icfp18.sigplan.org/track/FHPC-2018-papers The 7th ACM SIGPLAN Workshop on Functional High-Performance Computing (FHPC 2018) is being held as in previous years in conjunction with the International Conference on Functional Programming (ICFP 2018) together with numerous other workshops/symposia, and as a first, colocated with Strange Loop, in St. Louis, MO, USA. Workshop Objectives The FHPC 2018 workshop seeks to bring together researchers and practitioners exploring uses of functional (or more generally, declarative or high-level) programming systems or concepts in application domains where high performance is essential. The aim of the meeting is to enable sharing of results, experiences, and novel ideas about how high-level, declarative specifications of computationally challenging problems can serve as maintainable and portable code that approaches (or even exceeds) the performance of machine-oriented (low-level) imperative implementations. All aspects of performance-critical programming and parallel programming are in scope for the workshop, irrespective of hardware target. This includes both traditional large-scale distributed-memory scientific computing (HPC), as well as work targeting single node systems with SMPs, GPUs, FPGAs, or embedded processors. FHPC 2018 seeks to encourage a range of submissions, focusing on work in progress and facilitating early exchange of ideas and open discussion on innovative and/or emerging results. Original research, experience reports, case studies, and evaluations of programming systems are all welcome. Work on incorporation of functional programming concepts into more traditional (imperative) HPC applications is explicitly solicited. Papers, Presentations, and Demonstrations The refereed paper deadline has passed. In the workshop spirit, the refereed paper presentation program is being augmented to include less formally reviewed presentations in the form of talks not based on accepted papers, and software demonstrations. Topic areas of interest include research or development in progress, experience reports, and position/white paper statements. Proposals will be subject to a mild reviewing process to insure relevance and general interest to FHPC. We expect time slots to be between one-half and one hour. Prospective presenters are requested to submit an abstract describing their proposed contribution via the paper submission site. The deadline is July 29, 2018, midnight anywhere on Earth, but the PC reserves the right to accept proposals at any time after submission. As such, early submission is strongly encouraged. Important Dates - Submission Deadline: Midnight July 29, 2018 Anywhere on Earth. - Notification: early-mid August (TBD) - FHPC 2018: Saturday Sept. 29, 2018. Official website, submissions, registration details https://icfp18.sigplan.org/track/FHPC-2018-papers Previous FHPC websites https://icfp17.sigplan.org/track/FHPC-2017-papers https://sites.google.com/site/fhpcworkshops/ ICFP and related workshops https://conf.researchr.org/home/icfp-2018 https://icfp18.sigplan.org Strange Loop https://www.thestrangeloop.com/ Questions or comments? fhpc18(a)gmail.com

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