- Haskell-Cafe - Haskell.org

Pointwise Monoid with DerivingVia on n-tuples
by Georgi Lyubenov 07 Feb '19

07 Feb '19

Hi! I would like to use `DerivingVia` to do something like this: ``` import Data.Semigroup data Four = Four Bool (Maybe Int) Bool Bool deriving (Semigroup, Monoid) via (Any, Option (First Int), Any, Any) ``` This, however, doesn't work, because `(Any, Option (First Int), Any, Any)` is not coercible to `Four`. Even if I do ``` data Four a b c d = Four a b c d type Concrete = Four Bool (Maybe Int) Bool Bool ``` `Concrete` is still not coercible to `(Any, Option (First Int), Any, Any)`. This seems like a very common thing you would want to do (for me at least it pops up often, to want to have a `Monoid` instance that is just a pointwise Monoid over it's arguments (exactly the way an n-tuple is a `Monoid`). But I don't seem to be finding an easy way to do this. I am aware of `generic-deriving` but `DerivingVia` seems like it should be able to handle something like this, with only `Coercible` holding it back (?). Thanks in advance, ======= Georgi

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ANN: network 3.0.1.0
by Evan Borden 07 Feb '19

07 Feb '19

Announcing the release of network 3.0.1.0 http://hackage.haskell.org/package/network-3.0.1.0 Changelog - Added getSocketType :: Socket -> IO SocketType. #372 <https://github.com/haskell/network/pull/372> - Correcting manual and brushing up test cases #375 <https://github.com/haskell/network/pull/375> - Fixed long standing bug in getContents on mac #375 <https://github.com/haskell/network/pull/375> - Fixing regression: set correct sockaddr length for abstract addresses for Linux. #374 <https://github.com/haskell/network/pull/374> Thanks to network's contributors for bringing expertise to some hairy platform specific issues. -- Evan Borden

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[TFP'19] first call for papers: Trends in Functional Programming 2019, 12-14 June 2019, Vancouver, BC, CA
by Peter Achten 05 Feb '19

05 Feb '19

------------------------------- C A L L F O R P A P E R S ------------------------------- ====== TFP 2019 ====== 20th Symposium on Trends in Functional Programming 12-14 June, 2019 Vancouver, BC, CA https://www.tfp2019.org/index.html == Important Dates == Submission Deadline Thursday, March 28, 2019 Paper Notification Thursday, May 2, 2019 TFPIE Tuesday, June 11, 2019 Symposium Wednesday, June 12, 2019 – Friday, June 14, 2019 Student Paper Feedback Friday June 21, 2019 Submission for Formal Review Thursday, August 1, 2019 Notification of Acceptance Thursday, October 24, 2019 Camera Ready Friday, November 29, 2019 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 (see below at scope). Please be aware that TFP uses two distinct rounds of submissions (see below at submission details). TFP 2019 will be the main event of a pair of functional programming events. TFP 2019 will be accompanied by the International Workshop on Trends in Functional Programming in Education (TFPIE), which will take place on June 11. == Scope == The symposium recognizes that new trends may arise through various routes. As part of the Symposium's focus on trends we therefore identify the following five article categories. High-quality articles are solicited in any of these categories: Research Articles: Leading-edge, previously unpublished research work Position Articles: On what new trends should or should not be Project Articles: Descriptions of recently started new projects Evaluation Articles: What lessons can be drawn from a finished project Overview Articles: Summarizing work with respect to a trendy subject Articles must be original and not simultaneously submitted for publication to any other forum. They may consider any aspect of functional programming: theoretical, implementation-oriented, or experience-oriented. Applications of functional programming techniques to other languages are also within the scope of the symposium. Topics suitable for the symposium include, but are not limited to: Functional programming and multicore/manycore computing Functional programming in the cloud High performance functional computing Extra-functional (behavioural) properties of functional programs Dependently typed functional programming Validation and verification of functional programs Debugging and profiling for functional languages Functional programming in different application areas: security, mobility, telecommunications applications, embedded systems, global computing, grids, etc. Interoperability with imperative programming languages Novel memory management techniques Program analysis and transformation techniques Empirical performance studies Abstract/virtual machines and compilers for functional languages (Embedded) domain specific languages New implementation strategies Any new emerging trend in the functional programming area If you are in doubt on whether your article is within the scope of TFP, please contact the TFP 2019 program chairs, William J. Bowman and Ron Garcia. == Best Paper Awards == To reward excellent contributions, TFP awards a prize for the best paper accepted for the formal proceedings. TFP traditionally pays special attention to research students, acknowledging that students are almost by definition part of new subject trends. A student paper is one for which the authors state that the paper is mainly the work of students, the students are listed as first authors, and a student would present the paper. A prize for the best student paper is awarded each year. In both cases, it is the PC of TFP that awards the prize. In case the best paper happens to be a student paper, that paper will then receive both prizes. == Instructions to Author == Papers must be submitted at: https://easychair.org/conferences/?conf=tfp2019 Authors of papers have the choice of having their contributions formally reviewed either before or after the Symposium. == Pre-symposium formal review == Papers to be formally reviewed before the symposium should be submitted before an early deadline and receive their reviews and notification of acceptance for both presentation and publication before the symposium. A paper that has been rejected in this process may still be accepted for presentation at the symposium, but will not be considered for the post-symposium formal review. == Post-symposium formal review == Draft papers will receive minimal reviews and notification of acceptance for presentation at the symposium. Authors of draft papers will be invited to submit revised papers based on the feedback receive at the symposium. A post-symposium refereeing process will then select a subset of these articles for formal publication. == Paper categories == Draft papers and papers submitted for formal review are submitted as extended abstracts (4 to 10 pages in length) or full papers (20 pages). The submission must clearly indicate which category it belongs to: research, position, project, evaluation, or overview paper. It should also indicate which authors are research students, and whether the main author(s) are students. A draft paper for which all authors are students will receive additional feedback by one of the PC members shortly after the symposium has taken place. == Format == Papers must be written in English, and written using the LNCS style. For more information about formatting please consult the Springer LNCS web site. == Program Committee == Program Co-chairs William J. Bowman University of British Columbia Ronald Garcia University of British Columbia Matteo Cimini University of Massachusetts Lowell Ryan Culpepper Czech Technical Institute Joshua Dunfield Queen's University Sam Lindley University of Edinburgh Assia Mahboubi INRI Nantes Christine Rizkallah University of New South Wales Satnam Singh Marco T. Morazán Seton Hall University John Hughes Chalmers University and Quviq Nicolas Wu University of Bristol Tom Schrijvers KU Leuven Scott Smith Johns Hopkins University Stephanie Balzer Carnegie Mellon University Viktória Zsók Eötvös Loránd University

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Call for Participation: Midlands Graduate School, 14-18 April, Birmingham UK
by Graham Hutton 05 Feb '19

05 Feb '19

Dear all, Midlands Graduate School (MGS) registration is now open! Eight courses on property based testing, category theory, univalent type theory, lambda calculus, and more. 14-18 April 2019, Birmingham, UK. Spaces are limited, so register early. Please share! http://events.cs.bham.ac.uk/mgs2019/ Best wishes, Graham Hutton ============================================================ Midlands Graduate School 2019 14-18 April 2019, Birmingham, UK http://events.cs.bham.ac.uk/mgs2019/ BACKGROUND: The Midlands Graduate School (MGS) in the Foundations of Computing Science provides an intensive course of lectures on the mathematical foundations of computing. The MGS has been running since 1999, and is aimed at PhD students in their first or second year of study, but the school is open to everyone, and has increasingly seen participation from industry. We welcome participants from all over the world! COURSES: Eight courses will be given. Participants usually take all the introductory courses and choose additional options from the advanced courses depending on their interests. Invited course - Adventures in Property Based Testing, John Hughes Introductory courses - Lambda Calculus, Venanzio Capretta - Category Theory, Thorsten Altenkirch - Univalent Type Theory in Agda, Martn Escard Advanced courses - Calculating programs, Jennifer Hackett - Type Refinement Systems, Noam Zeilberger - Synthesis of Reactive Systems, Rayna Dimitrova - Monoidal Categories, Higher Categories, Jamie Vicary REGISTRATION: Registration is 220 for student, academic and independent participants, and 420 for industry participants. Accommodation is not included; please see the conference webpage for advice. The registration deadline is ** Sunday, 31 March **. Spaces are limited, so please register early to secure your place. SPONSORSHIP: We offer a range of sponsorship opportunities for industry (bronze, silver, gold and platinum), each with specific benefits. Please see the website for further details. ============================================================ This message and any attachment are intended solely for the addressee and may contain confidential information. If you have received this message in error, please contact the sender and delete the email and attachment. Any views or opinions expressed by the author of this email do not necessarily reflect the views of the University of Nottingham. Email communications with the University of Nottingham may be monitored where permitted by law.

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Let's plan BayHac 2019!
by Dan Burton 04 Feb '19

04 Feb '19

It's time to start thinking about the next BayHac! I am assembling a group of organizers for next year's event. Anyone who has been involved in organizing past BayHac events will be automatically accepted. (I have BCCed a number of past organizers; please reach out to any you know in case I missed anyone.) Anyone else who is interested in helping to plan BayHac, please contact me. Depending on how many past organizers rejoin, we will discuss the applicants and accept 1 to 3 new organizers. BayHac is a weekend of learning, sharing, and hacking on a variety of projects for the Haskell community. BayHac usually occurs in San Francisco, California, Mountain View, California, or thereabouts. I'd like to aim for April/May 2019, though that is, of course, subject to change. A rough outline, in rough chronological order, of what the BayHac organizers will be doing: 0. Assemble the organizers. 1. Select date and venue for BayHac 2019. 2. Secure corporate sponsors to cover costs (mainly, food). 3. Invite talk proposals and select speakers. 4. Open online registration and publicize the event. 5. Plan details like catering, registration desk, recording, and make it happen! If any of that sounds like fun to you, then I'd love to hear from you! -- Dan Burton

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ANN: libtelnet-0.1.0.0
by Jack Kelly 03 Feb '19

03 Feb '19

I've just made an initial release of libtelnet[1], a close binding of the C libtelnet[2]. It allows you to write telnet clients/servers in Haskell, if for some bizarre reason that's something you still want to do in 2019. [1]: https://hackage.haskell.org/package/libtelnet-0.1.0.0 [2]: https://github.com/seanmiddleditch/libtelnet Best, -- Jack

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Implementing `MonadBaseControl IO` for application type
by Magnus Therning 02 Feb '19

02 Feb '19

Hi, I'm getting stuck on implementing `MonadBaseControl IO` for my application context type. What I have so far (in a minimized example) is ``` data Env = Env {envBalance :: !(TVar Int)} newtype AppM a = AppM { unAppM :: ReaderT Env IO a } deriving (Functor, Applicative, Monad, MonadIO, MonadReader Env) instance MonadBase IO AppM where liftBase = liftIO instance MonadBaseControl IO AppM where type StM AppM a = a liftBaseWith f = undefined restoreM = return ``` I'm so utterly stuck on the definition of `liftBaseWith`... but I'm not 100% sure on the other bits either, though it "feels right". Any tips on how I should go about it? /M

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ANN: hledger-1.13
by Simon Michael 02 Feb '19

02 Feb '19

I'm pleased to announce the release of hledger 1.13, the first hledger release of 2019! Thank you release contributors Jakob Schöttl and Dmitry Astapov. hledger is a robust, cross-platform plain text accounting tool, for tracking money, time, stocks, cryptocurrencies or any other commodity, using double-entry accounting, private or shared plain text files, revision control, and command-line, curses or web UIs. Find out more at http://hledger.org and http://plaintextaccounting.org. Release notes (condensed, see http://hledger.org/release-notes) ------------- project-wide changes for 1.13 - packaging: A docker image providing the main hledger tools is now linked on the download page. This is another way to get up-to-date hledger tools without building them yourself (and, a way to run hledger-ui on windows ?) (Dmitry Astapov, Simon Michael) - doc: fixed pandoc typography conversion in web manuals. Eg -- was being rendered as en-dash. (#954). hledger 1.13 - cli: reorganised commands list. Addons now have a + prefix. - cli: the command line help and manual section for all hledger’s commands are now consistent, and generated from the same source. - cli: comprehensive bash completion support is now provided (in shell-completion/). See how-to in the Cookbook. (Jakob Schöttl) - balance –budget: budget amounts now aggregate hierarchically, like account balances. Unbudgeted accounts can be shown with -E/–empty (along with zero-balance accounts), and the –show-budgeted flag has been dropped. (Dmitry Astapov) - balance: new –transpose flag switches the rows and columns of tabular balance reports (in txt and csv output formats). (Dmitry Astapov) - close: generated balance assertions now have exact amounts with all decimal digits, ignoring display precision. Also, balance assertion amounts will no longer contain prices. (#941, #824, #958) - files: now shows up in the commands list - import: be silent when there’s nothing to import - roi: percentages smaller than 0.01% are displayed as zero (Dmitry Astapov) - stats, ui: correct file order is preserved when using –auto (#949) - journal: account directive: the account name can now be followed by a comment on the same line - journal: account directive: account types for the bs/bse/cf/is commands can now be set with a type: tag, whose value is Asset, Liability, Equity, Revenue, Expense, A, L, E, R or X (case-insensitive). The previous syntax (account assets A) is now deprecated. - journal: account directive: account sort codes like account 1000 (introduced in 1.9, deprecated in 1.11) are no longer supported. - journal: transaction modifiers (auto postings) can affect periodic transactions (–auto can add postings to transactions generated with –forecast). (Dmitry Astapov) - journal: balance assertion errors now show exact amounts with all decimal digits. Previously it was possible, in case of a commodity directive limiting the display precision, to have a balance assertion error with asserted and actual amounts looking the same. (#941) - journal: fixed a periodic transaction parsing failure (#942) (Dmitry Astapov) hledger-ui 1.13 - on posix systems, control-z suspends the program - control-l now works everywhere and redraws more reliably - the top status info is clearer Getting started: ---------------- All install methods are described at http://hledger.org/download : windows binaries, system packages, docker, nix, cabal, stack, hledger installer, etc. Some of these might take a few days to become up to date. On systems with bash installed, the hledger installer is a reliable way to get the latest release of hledger: $ curl -s https://raw.githubusercontent.com/simonmichael/hledger/master/hledger-insta… > hledger-install.sh $ less hledger-install.sh # satisfy yourself that the script is safe $ bash hledger-install.sh Then try: $ hledger # list available commands $ hledger help # list built-in manuals Tutorials and all other docs: http://hledger.org Chat: #hledger on Freenode or Matrix - http://irc.hledger.org or http://riot.hledger.org . New and old users, contributors, all feedback, always welcome! Best, -Simon

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Patents on Maybe and Tuple
by Henk-Jan van Tuyl 01 Feb '19

01 Feb '19

L.S., I just read the article "Apple Patents Swift".[0] It says that Apple has two patents regarding Swift: [1][2]; these patents state, amongst others, that there are new types of variables: "Additionally, an embodiment of the new language introduces advanced types not found in Objective-C. These types include Tuples and Optionals. Tuples enable a developer to create and pass groupings of values. Tuples group multiple values into a single compound value." and "In one embodiment, an optional type is provided that handles the absence of a value. Optionals are a way to say either “there is a value, and it equals x” or “there isn't a value at all.”" I hope we don't get arrested for using the Maybe monad or tuples in Haskell. Regards, Henk-Jan van Tuyl [0] https://www.i-programmer.info/news/98-languages/12495-apple-patents-swift.h… [1] https://patents.google.com/patent/US9952841B2 [2] https://patents.google.com/patent/US9329844B2 -- Message from Stanford University: Folding@home What if you could share your unused computer power to help find a cure? In just 5 minutes you can join the world's biggest networked computer and get us closer sooner. Watch the video. http://foldingathome.stanford.edu/ -- http://members.chello.nl/hjgtuyl/tourdemonad.html Haskell programming --

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Library for common AST transformations based on haskell-src-exts
by Sandra Dylus 31 Jan '19

31 Jan '19

Hi, in the last couple of years we had a number of projects that used haskell-src-exts [1]. In most of these cases we wanted to do some common AST transformations, e.g., translating function definitions via several rules into one rule using case expressions. So, after needing these transformations a couple of times, I was wondering if there is a library that works on top of haskell-src-exts and implements common transformations like the one mentioned. I took a look at the reverse dependencies of haskell-src-exts, but only found projects implementing these transformations as part of a bigger project. In a nutshell, I am asking if I did miss such a library or if there does not exist such a library yet. If the latter is the case, we will definitely implement such a library as part of the next student project that builds upon haskell-src-exts. Cheers Sandra [1] http://hackage.haskell.org/package/haskell-src-exts <http://hackage.haskell.org/package/haskell-src-exts>

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