- Haskell-Cafe - Haskell.org

How to make a Hashable instance for (Finite n)?
by David Banas 31 Mar '20

31 Mar '20

What is the most expedient way to get around this error? Could not deduce (Hashable (Finite n)) Thanks, -db

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Research Assistant/Associate Position (Postdoc) at Imperial College London
by David Castro 30 Mar '20

30 Mar '20

Hello, We are looking for candidates for this position at Imperial College London. The official text of the advertisement follows: Department of Computing, Imperial College London Research Assistant/Associate Position (Full Time) 35,477 GBP to 47,579 GBP per annum Reference: ENG01270 Fixed-term: 2 years (with a possible 24 month extension) Starting date: as soon as possible (no later than 1st October 2020) Closing Date: 26th April 2020 The Research Assistant will work under the EPSRC Established Career Fellowship Project, POST: Protocols, Observabilities and Session Types. Imperial College London provides a flexible arrangement to be able to start and work remotely until we re-open the campus (this depends on your nationality and current living address). Please contact with Nobuko Yoshida (n.yoshida(a)imperial.ac.uk) Imperial College London if you would like to apply to the position to have informal discussions. The application deadline is also extendable. ------------------------------------------------------------ The project has particular emphasis on putting theory into practice, by embedding session types in a range of programming languages and applying them to case studies; or developing the links between session types and other areas of theoretical computer science. The research programme includes collaboration with several companies and organisations. Candidates for the post-doc position will need to have expertise in either: 1. programming language design and implementation; or 2. formal semantics, type theory and concurrency theory Different positions will be suitable for different points on the theory/practice spectrum. We are especially interested in candidates with a combination of theoretical and practical skills. For more details, see http://mrg.doc.ic.ac.uk. The focus of Imperial College London Group is theories and applications of (Multiparty) Session Types (JACM,POPL'08) which include: -- Go (POPL'19,ICSE'18,POPL'17,CC'16), Scala (PLDI'19,ECOOP'17,ECOOP'16), F# (CC'18), Erlang (CC'17), Haskell (CC'20,POPL'16), OCaml (SOC), Java (FASE'16,FASE'17), MPI-C (FPL'16,OOPSLA'15,CC'15) and Python (FOAC,LMCS,FMSD); -- session types theories (ESOP'20,POPL'19,ESOP'19,ESOP'16,CONCUR'15), automata theories (CAV'19,CONCUR'19,FoSSaCs'17,TACAS'16,CONCUR'15,POPL'15), game semantics (POPL'19,FoSSaCs'19), Implicit Complexity (LICS'18) and linear logic (ESOP'18,FoSSaCs'18,CONCUR'15); or -- mechanisation of session types meta-theory (Coq, Isabelle, Agda, etc) (TACAS 20) -- other applications such as blockchains (FSE'19) and robotics (ECOOP'19) The contact person is Professor Nobuko Yoshida, Imperial College London (n.yoshida(a)imperial.ac.uk) The candidate is welcome to contact her. Details: https://www.imperial.ac.uk/jobs/description/ENG01270/research-assistant-res…

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[ANN] esqueleto-3.3.3.0: Support for UNION, safer joins, and subquery joins!
by Christian Charukiewicz 29 Mar '20

29 Mar '20

Hi all, My friend Ben Levy and I spent a while writing and documenting Database.Esqueleto.Experimental, a new module in the esqueleto package which adds support for UNION, subqueries, and improves the safety of outer JOINs. We've done a lot of use/testing of this implementation, but it is currently in the Experimental module in order to allow for gathering feedback. It is now live on Hackage as esqueleto-3.3.3.0. The module docs give examples of the new functionality. Feel free to take a take a look here: https://hackage.haskell.org/package/esqueleto-3.3.3.0/docs/Database-Esquele… Thanks, Christian

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gitlab.haskell.org down?
by Ivan Perez 29 Mar '20

29 Mar '20

Hi, Is the Haskell gitlab down or has anything changed? https://downforeveryoneorjustme.com/gitlab.haskell.org Cheers, Ivan

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Re: [Haskell-cafe] Strange error when cabal installing.
by David Banas 28 Mar '20

28 Mar '20

Okay, I was able to get the _Haskell Platform_ approach to work, by doing the following: - Uninstall Haskell Platform. - Reinstall Haskell Platform, overriding the default suggested installation path with something _not containing spaces_. - Change my `~\AppData\Roaming\cabal\config` file from this: ``` extra-prog-path: C:\HaskellPlatform\8.6.5\msys\usr\bin, C:\Users\capnf\AppData\Roaming\cabal\bin ``` to this: ``` extra-prog-path: C:\HaskellPlatform\8.6.5\msys\usr\bin extra-prog-path: C:\Users\capnf\AppData\Roaming\cabal\bin ``` -db

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Why does the Haskell Platform Windows installer suggest a path with spaces?!
by David Banas 28 Mar '20

28 Mar '20

Why does the Haskell Platform Windows installer suggest a default installation path that contains spaces?! This breaks builds: configure:2365: checking build system type configure:2379: result: x86_64-pc-msys configure:2399: checking host system type configure:2412: result: x86_64-pc-msys configure:2487: checking for gcc configure:2514: result: C:\PROGRA~1\Haskell Platform\8.6.5\lib\../mingw/bin\gcc.exe configure:2743: checking for C compiler version configure:2752: C:\PROGRA~1\Haskell Platform\8.6.5\lib\../mingw/bin\gcc.exe --version >&5 C:\/Users/capnf/Documents/GitHub/gitit/network-3.1.1.1/configure: line 2754: C:\PROGRA~1\Haskell: No such file or directory configure:2763: $? = 127 configure:2752: C:\PROGRA~1\Haskell Platform\8.6.5\lib\../mingw/bin\gcc.exe -v >&5 C:\/Users/capnf/Documents/GitHub/gitit/network-3.1.1.1/configure: line 2754: C:\PROGRA~1\Haskell: No such file or directory -db

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Which option causes 'cabal install' to leave temp. build dirs. in place?
by David Banas 28 Mar '20

28 Mar '20

Hi all, Which option to a 'cabal install' command will cause the temporary build directories to be left in place, so that I can inspect, for instance, the 'config.log' file of a failed dependency build? Thanks, -db

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ANN: latex-svg
by Oleg Grenrus 27 Mar '20

27 Mar '20

I occasionally write blog posts with some math. So far I have been using latex-formulae family of packages. This week Andres Löh asked whether LaTeX can be rendered as SVGs. The answer turns out to be yes, it wasn't few years ago. The preview CTAN package, and the dvisvgm tool make it very easy. I forked latex-formulae into latex-svg to use above mentioned tools. There are three packages on Hackage now: - latex-svg-image: render LaTeX formulae to SVG images - latex-svg-pandoc: render LaTeX formulae in pandoc documents - latex-svg-hakyll: render LaTeX formulae in hakyll pages To mention some differences between latex-formulae and latex-svg: - latex-svg-image uses only latex and dvisvgm, ImageMagick is not required. You don't need to tweak policy.xml to allow rasterization of PostScript. (See this StackOverflow question). - latex-svg-image supports global cache (off by default), which speedups hakyll site builds. My blog builds in 20 seconds instead of three minutes with empty cache. I wouldn't worry about space usage too much, the cache contents take 15M after building my blog. which is way less than the size of site executable. - latex-svg-hakyll has initFormulaCompilerSVGPure variant, which doesn't need IO to be created. You don't need to thread renderFormulae function through. Together with global cache, the perfomance penalty is small. - One drawback is that result pages become bigger (and slower). For example a formula-heavy https://oleg.fi/gists/posts/2018-12-12-find-correct-laws.html is - 576k in size with latex-formulae - 2819k in size with latex-svg (almost 5 times larger). Rendering SVG images is also more CPU expensive. Otherwise the API and module names are the same. If you are already a user of latex-formulae you can easily migrate to latex-svg. See the announcement blog post how some examples look like: https://oleg.fi/gists/posts/2020-03-06-latex-svg.html <http://oleg.fi/gists/posts/2020-03-06-latex-svg.html> <http://oleg.fi/gists/posts/2020-03-06-latex-svg.html> Crisp math-blogging to everyone - Oleg Grenrus <http://oleg.fi/gists/posts/2020-03-06-latex-svg.html>

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2nd Workshop on Formal Methods for Blockchains (FMBC) 2020 - First Call
by Bruno Bernardo 26 Mar '20

26 Mar '20

[ Please distribute, apologies for multiple postings. ] ======================================================================== 2nd Workshop on Formal Methods for Blockchains (FMBC) 2020 - First Call https://fmbc.gitlab.io/2020 July 19, 2020, Los Angeles, USA Co-located with the 32nd International Conference on Computer-Aided Verification (CAV 2020) http://i-cav.org/2020/ ------------------------------------------------------------- IMPORTANT DATES -------------------------------- Abstract submission: April 21, 2020 Full paper submission: April 28, 2020 Notification: June 9, 2020 Camera-ready: July 7, 2020 Conference: July 19, 2020 -------------------------------- -------------------------------- 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 maximum of twelve pages (full papers), six pages (short papers), and two pages (extended abstract) describing new and emerging ideas or summarizing existing work). Each paper should include a title and the name and affiliation of each author. Authors of selected extended-abstracts are invited to give a short lightning talk. At least one author of an accepted paper is expected to present the paper at the workshop as a registered participant. Submission link: https://easychair.org/conferences/?conf=fmbc2020 -------------------------------- -------------------------------- 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. -------------------------------- -------------------------------- INVITED SPEAKER -------------------------------- Grigore Rosu, Professor at University of Illinois at Urbana-Champaign, USA and Founder of Runtime Verification http://fsl.cs.illinois.edu/index.php/Grigore_Rosu https://runtimeverification.com/ -------------------------------- -------------------------------- 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) * Bernhard Beckert (Karlsruhe Institute of Technology, Germany) * Achim Brucker (University of Exeter, UK) * Silvia Crafa (Universita di Padova, Italy) * Zaynah Dargaye (Nomadic Labs, France) * Jérémie Decouchant (University of Luxembourg, Luxembourg) * Ansgar Fehnker (University of Twente, Netherlands) * Georges Gonthier (Inria, France) * Florian Kammueller (Middlesex University London, UK) * Maurice Herlihy (Brown University, USA) * Igor Konnov (Informal, Austria) * Andreas Lochbihler (Digital Asset, Switzerland) * Anastasia Mavridou (NASA Ames, USA) * Simão Melo de Sousa (Universidade da Beira Interior, Portugal) * Karl Palmskog (KTH, Sweden) * Vincent Rahli (University of Birmingham, UK) * Andreas Rossberg (Dfinity Foundation, Germany) * Claudio Russo (Dfinity Foundation, USA) * César Sanchez (Imdea, Spain) * Clara Schneidewind (TU Wien, Austria) * Ilya Sergey (Yale-NUS College/NUS, Singapore) * Bas Spitters (Aarhus University/Concordium, Denmark) * Mark Staples (CSIRO Data61, Australia) * Meng Sun (Peking University, China) * Simon Thompson (University of Kent, UK) * Philip Wadler (University of Edinburgh / IOHK, UK) (Note: Additional PC members may be added in the coming weeks.)

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GSoC 2020
by Guillem Bartrina Moreno 25 Mar '20

25 Mar '20

Hello everybody! My name is Guillem and I'm a 3rd year computer science student from Spain. This semester I'm taking Functional Programming, where we use Haskell as base language, and Compilers courses. I really love Haskell and the functional programming paradigm in general, so when I saw it in the GSoC list I got really excited. The idea that caught my attention, that is related to both Haskell and Compilers, is: - Update stylish-haskell to use ghc-lib-parser I have a medium understanding of Haskell and I would like to know if this idea is suitable for me. I've tried to start reading the source code and I have understood the most part. I will proceed to write my proposal in the next few days if all goes well. All thoughts are welcome! Thanks for your attention, -- Guillem Bartrina Moreno

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