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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 28 Jun '18

28 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 25 Jun '18

25 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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ANN: network-2.7.0.1
by evan＠evan-borden.com 24 Jun '18

24 Jun '18

Announcing network-2.7.0.1 * A new API: socketPortSafe. [#319](https://github.com/haskell/network/pull/319) * Fixing a drain bug of sendAll. [#320](https://github.com/haskell/network/pull/320) * Porting the new CALLCONV convention from master. [#313](https://github.com/haskell/network/pull/313) * Withdrawing the deprecations of packFamily and unpackFamily. [#324](https://github.com/haskell/network/pull/324) Thank you to network contributors for bug reports in the push to 3.0.0.0. As well as the continued effort to increase windows reliability and support. -- Evan Borden

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Munich Haskell Meeting, 2018-06-26 @ 19:30
by Leah Neukirchen 23 Jun '18

23 Jun '18

Dear all, Next week, our monthly Munich Haskell Meeting will take place again on Tuesday, June 26 at Cafe Puck at 19h30. For details see here: http://muenchen.haskell.bayern/dates.html If you plan to join, please add yourself to this dudle so we can reserve enough seats! It is OK to add yourself to the dudle anonymously or pseudonymously. https://dudle.inf.tu-dresden.de/haskell-munich-jun-2018/ Everybody is welcome! cu, -- Leah Neukirchen <leah(a)vuxu.org> http://leah.zone

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Colored Haskell Listings in LaTeX
by Artem Pelenitsyn 23 Jun '18

23 Jun '18

Dear Cafe, In his recent Stitch manuscript, https://cs.brynmawr.edu/~rae/papers/2018/stitch/stitch.pdf Richard Eisenberg mentions that he uses lhs2TeX to typeset Haskell listings, but I'm not aware of the support for colors in lhs2TeX. Can anyone suggest how to get such a nice code highlighting (presumably with lhs2TeX). -- Best wishes, Artem

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Type level seq
by Benjamin Franksen 23 Jun '18

23 Jun '18

I have observed that type functions seem to be lazy. A type function that is partial does not give me a type error when it is called with an argument for which it is not defined. Is there a 'seq' at the type level? Here is my use case, simplified of course. Suppose we want to statically track the state of a switch with a phantom type parameter: > {-# LANGUAGE DataKinds, TypeFamilies #-} > > data State (s :: Bool) = State Bool deriving Show > > off :: State False > off = State False We want user code to be able to call the function 'turnOff' only if the switch is currently on: > turnOff :: State True -> State False > turnOff (State True) = State False This works fine: *Main> turnOff off <interactive>:1:9: error: ? Couldn't match type ?'False? with ?'True? Expected type: State 'True Actual type: State 'False But now I want to abstract this pattern and write a (closed) type function > type family TurnOff s where > TurnOff True = False > turnOff' :: State x -> State (TurnOff x) > turnOff' (State True) = State False > bad = turnOff' off *Main> :t bad bad :: State (TurnOff 'False) *Main> bad *** Exception: TypeLevelSeq.lhs:37:3-37: Non-exhaustive patterns in function turnOff'

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Call for a maintainer of protocol-buffers
by Kostiantyn Rybnikov 22 Jun '18

22 Jun '18

Hey everyone, I'm looking for a person who would become the major maintainer of the protocol-buffers package. Details here: https://github.com/k-bx/protocol-buffers/issues/64 Please comment on the issue or send me an email if you'd like to apply. Thank you

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dfinity-radix-tree: A Merkleized key–value data store.
by Enzo 21 Jun '18

21 Jun '18

I am pleased to announce the first release of dfinity-radix-tree: A Merkleized key–value data store. The library provides a simple and easy to use data integrity layer for LevelDB. For more information, please see: [1] https://github.com/dfinity-lab/hs-radix-tree [2] https://hackage.haskell.org/package/dfinity-radix-tree Warm regards, Enzo Haussecker DFINITY Stiftung *We're hiring Haskell developers in Palo Alto and Zürich. Apply now:* [3] https://dfinity.org/openings

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