- Haskell-Cafe - Haskell.org

[ANNOUNCE] Experimental Windows GHC 8.10.5 binary release. Supports Haskell DLLs.
by kyra 29 Apr '21

29 Apr '21

An experimental Windows GHC 8.10.5 64-bit Visual C/Native Windows SDK binary compatible distribution is released. Features: Supports Haskell DLLs. Both static and dynamic compilers are shipped. Uses LLVM tools exclusively, hence linking is blazing fast compared to the stock distro. Is position-independent (can be loaded to any address, not only the lower 2GBs) and generates position-independent code. Based on and targets Microsoft Visual C runtime and native Windows SDK. The "full" variant of distro contains 438 extra prebuilt packages and a set utilities, including not only the mandatory cabal, stack, Happy and Alex, but also linters, formatters, preprocessors, and even beasts like pandoc, haskell-language-server and even Agda compiler. Distribution site: https://awson.github.io/ghc-nw/. Cheers, K. Briantsev (aka awson)

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Munich Virtual Haskell Meeting, 2021-04-29 @ 19:30
by Leah Neukirchen 28 Apr '21

28 Apr '21

Dear all, This week, our monthly Munich Haskell Meeting will take place again tomorrow(!) Thursday, April 29 on Google Meet at 19:30 CEST. **Due to meetup limitations in Bavaria, this meeting will take place online!** For details see here: https://muenchen.haskell.bayern/dates.html A Google Meet link to join the room is provided on the page. Everybody is welcome, especially the Haskellers from Bavaria that do not usually come to our Munich meetings due to travel distance! cu, -- Leah Neukirchen <leah(a)vuxu.org> https://leahneukirchen.org/

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Template Haskell question
by Kai-Oliver Prott 28 Apr '21

28 Apr '21

Dear Cafe, what is the reasoning behind the behavior of the following two Haskell expressions: ghci> :set -XTemplateHaskell ghci> let f x ($([p| x |])) = x in f 1 2 2 ghci> let f ($([p| x |])) x = x in f 1 2 2 I'd have guessed that they should both fail compilation with "Conflicting definitions for ‘x’" like the following expression. ghci> let f x x = x in f 1 2 error: ... Moreover, it seems odd that the "x" on the right side always refers to the rightmost pattern variable "x" (regardless if quoted or not). Cheers, Kai

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Haskell translation and transformation
by Dušan Kolář 27 Apr '21

27 Apr '21

Dear Café, I've tried to make my code more compact and faster in runtime and I tried to use primitive types, e.g. Int#. To omit all influences, I ended with Ackermann function: acker :: Int# -> Int# -> Int# acker 0# n = n +# 1# acker m 0# = acker (m -# 1#) 1# acker m n = acker (m -# 1#) (acker m (n -# 1#)) I was quite surprised, that the result was the same as for function without primitive types when it was compiled with -XStrict option. Both memory and time consumption was the same (small difference under 0.5%). Of course, -O2 option was used. :-) I compared with the same C implementation: int acker(int m, int n) { if (m==0) return n+1; if (n==0) return acker(m-1, 1); return acker(m-1, acker(m,n-1)); } with -O2 option used for gcc, the C code is 7 times faster, for no -O options provided both for ghc and gcc, the C code is also 7 times faster. Thus, no difference. My question is: does the ghc use primitive types automatically when possible? Otherwise, I cannot explain the same times... Or, to my big surprise, using primitives does not save memory and computation time, really? And the other question is about reasoning during translation and code generation, what is the reason the code is so slow? I would guess that forcing primitive types and strict evaluation would produce a code with comparable time to C code... The difference seems to be like the one between compiled code to executable and to low level virtual machine code, which is interpreted then. Versions I used: ghc: 8.10.3 gcc: 10.2.0 Dušan P.S. I definitely don't want to make someone upset with the content, I'm simply wondering... D.

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FMBC 2021 - 3rd Call for Papers (Deadline extensions)
by Bruno Bernardo 27 Apr '21

27 Apr '21

[ Please distribute, apologies for multiple postings. ] ======================================================================== 3rd International Workshop on Formal Methods for Blockchains (FMBC) - Third Call https://fmbc.gitlab.io/2021 July 18 or 19 (TBA), 2021, *online* Co-located with the 33nd International Conference on Computer-Aided Verification (CAV 2021) http://i-cav.org/2021/ ------------------------------------------------------------- IMPORTANT DATES -------------------------------- Abstract submission: May 6, 2021 (extended) Paper submission: May 13, 2021 (extended) Notification: June 24, 2021 (extended) Camera-ready: July 8, 2021 Workshop: July 18 or 19 (TBA), 2021 Deadlines are Anywhere on Earth: https://en.wikipedia.org/wiki/Anywhere_on_Earth -------------------------------- -------------------------------- TOPICS OF INTEREST -------------------------------- Blockchains are decentralized transactional ledgers that rely on cryptographic hash functions for guaranteeing the integrity of the stored data. Participants on the network reach agreement on what valid transactions are through consensus algorithms. Blockchains may also provide support for Smart Contracts. Smart Contracts are scripts of an ad-hoc programming language that are stored in the Blockchain and that run on the network. They can interact with the ledger’s data and update its state. These scripts can express the logic of possibly complex contracts between users of the Blockchain. Thus, Smart Contracts can facilitate the economic activity of Blockchain participants. With the emergence and increasing popularity of cryptocurrencies such as Bitcoin and Ethereum, it is now of utmost importance to have strong guarantees of the behavior of Blockchain software. These guarantees can be brought by using Formal Methods. Indeed, Blockchain software encompasses many topics of computer science where using Formal Methods techniques and tools are relevant: consensus algorithms to ensure the liveness and the security of the data on the chain, programming languages specifically designed to write Smart Contracts, cryptographic protocols, such as zero-knowledge proofs, used to ensure privacy, etc. This workshop is a forum to identify theoretical and practical approaches of formal methods for Blockchain technology. Topics include, but are not limited to: * Formal models of Blockchain applications or concepts * Formal methods for consensus protocols * Formal methods for Blockchain-specific cryptographic primitives or protocols * Design and implementation of Smart Contract languages * Verification of Smart Contracts -------------------------------- -------------------------------- SUBMISSION -------------------------------- Submit original manuscripts (not published or considered elsewhere) with a page limit of 12 pages for full papers and 6 pages for short papers (excluding bibliography and short appendix of up to 5 additional pages). Alternatively you may also submit an extended abstract of up to 3 pages (including bibliography) summarizing your ongoing work in the area of formal methods and blockchain. Authors of selected extended-abstracts are invited to give a short lightning talk. Submission link: https://easychair.org/conferences/?conf=fmbc2021 Authors are encouraged to use LaTeX and prepare their submissions according to the instructions and styling guides for OASIcs provided by Dagstuhl. Instructions for authors: https://submission.dagstuhl.de/documentation/authors#oasics At least one author of an accepted paper is expected to present the paper at the workshop as a registered participant. -------------------------------- -------------------------------- PROCEEDINGS -------------------------------- All submissions will be peer-reviewed by at least three members of the program committee for quality and relevance. Accepted regular papers (full and short papers) will be included in the workshop proceedings, published as a volume of the OpenAccess Series in Informatics (OASIcs) by Dagstuhl. -------------------------------- -------------------------------- INVITED SPEAKER -------------------------------- David Dill, Lead Researcher, Blockchain, Novi/Facebook, USA https://research.fb.com/people/dill-david/ -------------------------------- -------------------------------- PROGRAM COMMITTEE -------------------------------- PC CO-CHAIRS * Bruno Bernardo (Nomadic Labs, France) (bruno(a)nomadic-labs.com) * Diego Marmsoler (University of Exeter, UK) (D.Marmsoler(a)exeter.ac.uk) PC MEMBERS * Wolfgang Ahrendt (Chalmers University of Technology, Sweden) * Lacramioara Astefanoei (Nomadic Labs, France) * Massimo Bartoletti (University of Cagliari, Italy) * Joachim Breitner (Dfinity Foundation, Germany) * Achim Brucker (University of Exeter, UK) * Zaynah Dargaye (Nomadic Labs, France) * Jérémie Decouchant (TU Delft, Netherlands) * Dana Drachsler Cohen (Technion, Israel) * Ansgar Fehnker (University of Twente, Netherlands) * Maurice Herlihy (Brown University, USA) * Lars Hupel (INNOQ, Germany) * Florian Kammueller (Middlesex University London, UK) * Igor Konnov (Informal Systems, Austria) * Andreas Lochbihler (Digital Asset, Switzerland) * Simão Melo de Sousa (Universidade da Beira Interior, Portugal) * Karl Palmskog (KTH, Sweden) * Maria Potop-Butucaru (Sorbonne Université, France) * Andreas Rossberg (Dfinity Foundation, Germany) * Albert Rubio (Complutense University of Madrid, Spain) * César Sanchez (Imdea, Spain) * Clara Schneidewind (TU Wien, Austria) * Ilya Sergey (Yale-NUS College/NUS, Singapore) * Mark Staples (CSIRO Data61, Australia) * Meng Sun (Peking University, China) * Simon Thompson (University of Kent, UK) * Josef Widder (Informal Systems, Austria)

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Re: [Haskell-cafe] [Haskell] [ANNOUNCE] GHC 9.2.1-alpha2 released
by Henning Thielemann 26 Apr '21

26 Apr '21

On Thu, 22 Apr 2021, Ben Gamari wrote: > The GHC developers are very happy to announce the availability of the > second alpha release in the 9.2.1 series. Binary distributions, source > distributions, and documentation are available at > > https://downloads.haskell.org/ghc/9.2.1-alpha2 When I try a GHC installed from the Debian tarball I get a permission error on the package.cache because of $ ll /usr/local/ghc-9.2.0.20210422/lib/ghc-9.2.0.20210422/package.conf.d/package.cache -rw------- 1 root root 188641 23. Apr 16:56 /usr/local/ghc-9.2.0.20210422/lib/ghc-9.2.0.20210422/package.conf.d/package.cache I can solve the problem with $ sudo chmod a+r /usr/local/ghc-9.2.0.20210422/lib/ghc-9.2.0.20210422/package.conf.d/package.cache

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Smooth developer experience with Cloud IDE for modern Haskell now
by YueCompl 26 Apr '21

26 Apr '21

Dear Cafe, I'd like to share that I find that, we can have rather smooth developer experience for Haskell, on cloud, now. Gitpod (https://gitpod.io <https://gitpod.io/>) recently supported VSCode in addition to Eclipse Theia, making the UX much more smoother, with proper Gitpod workspace setup, now it's much easier for Haskell beginners, as well as chromeOS and Windows users to painlessly onboard modern Haskell. Github codespaces (https://github.com/features/codespaces <https://github.com/features/codespaces>) is up coming too, there sure will be industry strength cloud infrastructures for serious Haskell development soon. And the setup can be fully automated, a full fledged Cloud IDE for modern Haskell development, is only a click away, see my demo: https://github.com/complyue/GHCiCode#readme <https://github.com/complyue/GHCiCode#readme> I also expect more beginner-friendly tutorials can be written this way, especially for Windows users, they'll be able to touch & feel the mass without going through painful setup procedures. Sincerely, Compl

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WST 2021: deadline extension (9 May, 2021)
by Samir Genaim 25 Apr '21

25 Apr '21

====================================================================== WST 2021 - Call for Papers 17th International Workshop on Termination http://costa.fdi.ucm.es/wst2021 July 16, 2021, Pittsburgh, PA, United States Co-located with CADE-28 **** The workshop will be virtual **** ====================================================================== *[The submission deadline was extended to May 9, 2021].* The Workshop on Termination (WST) traditionally brings together, in an informal setting, researchers interested in all aspects of termination, whether this interest be practical or theoretical, primary or derived. The workshop also provides a ground for cross-fertilization of ideas from the different communities interested in termination (e.g., working on computational mechanisms, programming languages, software engineering, constraint solving, etc.). The friendly atmosphere enables fruitful exchanges leading to joint research and subsequent publications. IMPORTANT DATES: * * submission deadline: May 9, 2021* (extended) * notification: June 6, 2021 * final version due: June 20, 2021 * workshop: July 16, 2021 INVITED SPEAKERS: TBA TOPICS: The 17th International Workshop on Termination welcomes contributions on all aspects of termination. In particular, papers investigating applications of termination (for example in complexity analysis, program analysis and transformation, theorem proving, program correctness, modeling computational systems, etc.) are very welcome. Topics of interest include (but are not limited to): * abstraction methods in termination analysis * certification of termination and complexity proofs * challenging termination problems * comparison and classification of termination methods * complexity analysis in any domain * implementation of termination methods * non-termination analysis and loop detection * normalization and infinitary normalization * operational termination of logic-based systems * ordinal notation and subrecursive hierarchies * SAT, SMT, and constraint solving for (non-)termination analysis * scalability and modularity of termination methods * termination analysis in any domain (lambda calculus, declarative programming, rewriting, transition systems, etc.) * well-founded relations and well-quasi-orders SUBMISSION GUIDELINES: Submissions are short papers/extended abstracts which should not exceed 5 pages. There will be no formal reviewing. In particular, we welcome short versions of recently published articles and papers submitted elsewhere. The program committee checks relevance and provides additional feedback for each submission. The accepted papers will be made available electronically before the workshop. Papers should be submitted electronically via the submission page: https://easychair.org/conferences/?conf=wst2021 Please, use LaTeX and the LIPIcs style file http://drops.dagstuhl.de/styles/lipics/lipics-authors.tgz to prepare your submission. PROGRAM COMMITTEE: * Martin Avanzini - INRIA Sophia, Antipolis * Carsten Fuhs - Birkbeck, U. of London * Samir Genaim (chair) - U. Complutense de Madrid * Jürgen Giesl - RWTH Aachen * Matthias Heizmann - U. of Freiburg * Cynthia Kop - Radboud U. Nijmegen * Salvador Lucas - U. Politècnica de València * Étienne Payet - U. de La Réunion * Albert Rubio - U. Complutense de Madrid * René Thiemann - U. of Innsbruck

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ANN: first release candidate for stack-2.7
by Emanuel Borsboom 24 Apr '21

24 Apr '21

You can download binaries for this pre-release from here: https://github.com/commercialhaskell/stack/releases/tag/rc%2Fv2.7.0.1<https://github.com/commercialhaskell/stack/releases/tag/rc/v2.7.0.1> **Changes since v2.5.1.1:** Behavior changes: * `stack repl` now always warns about GHCi problems with loading multiple packages. It also sets now proper working directory when invoked with one package. See [#5421](https://github.com/commercialhaskell/stack/issues/5421) * `custom-setup` dependencies are now properly initialized for `stack dist`. This makes `explicit-setup-deps` no longer required and that option was removed. See [#4006](https://github.com/commercialhaskell/stack/issues/4006) Other enhancements: * Nix integration now passes `ghcVersion` (in addition to existing `ghc`) to `shell-file` as an identifier that can be looked up in a compiler attribute set. * Nix integration now allows Nix integration if the user is ready in nix-shell. This gets rid of "In Nix shell but reExecL is False" error. * `stack list` is a new command to list package versions in a snapshot. See [#5431](https://github.com/commercialhaskell/stack/pull/5431) * Consider GHC 9.0 a tested compiler and remove warnings. * `custom-preprocessor-extensions` is a new configuration option for allowing stack to be aware of any custom preprocessors you have added to `Setup.hs`. See [#3491](https://github.com/commercialhaskell/stack/issues/3491) * Added `--candidate` flag to `upload` command to upload a package candidate rather than publishing the package. * Error output using `--no-interleaved-output` no longer prepends indentating whitespace. This allows emacs compilation-mode and vim quickfix to locate and track errors. See [#5523](https://github.com/commercialhaskell/stack/pull/5523) Bug fixes: * `stack new` now suppports branches other than `master` as default for GitHub repositories. See [#5422](https://github.com/commercialhaskell/stack/issues/5422) * Ignore all errors from `hi-file-parser`. See [#5445](https://github.com/commercialhaskell/stack/issues/5445) and [#5486](https://github.com/commercialhaskell/stack/issues/5486). * Support basic auth in package-indices. See [#5509](https://github.com/commercialhaskell/stack/issues/5509). * Add support for parsing `.hi`. files from GHC 8.10 and 9.0. See [hi-file-parser#2](https://github.com/commercialhaskell/hi-file-parser/pull/….

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repeat confusion
by Galaxy Being 23 Apr '21

23 Apr '21

I'm in Bird's *Thinking Functionally with Haskell *and he has this code to transpose a matrix based on a list of row lists transpose :: [[a]] -> [[a]] transpose [xs] = [[x] | x <- xs] transpose (xs:xss) = zipWith (:) xs (transpose xss) then he says transpose can be rewritten with this pattern transpose [] = ... what could be the rest of it? The answer he gives is transpose2 :: [[a]] -> [[a]] transpose2 [] = repeat [] transpose2 (xs:xss) = zipWith (:) xs (transpose2 xss) where repeat [] gives an infinite list of repetitions. And, he says, note that transpose [xs] = zipWith (;) xs (repeat []) = [[x] | x <- xs] I suppose I get this last equation, but I don't understand repeat in transpose2. Can someone explain this to me? LB

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