- Haskell-Cafe - Haskell.org

The future of the SPARC NCG backend
by Ben Gamari 01 Jul '19

01 Jul '19

Hello everyone, If you use (or think you might use in the future) GHC's SPARC NCG backend please do leave a note on #16882 [1]. My impression is that it has no users and no plausible means of testing. Consequently I am suggesting that we remove it in GHC 8.12. Cheers, - Ben [1] https://gitlab.haskell.org/ghc/ghc/issues/16882

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NB: DO NOT USE `pure = return`
by Johannes Waldmann 01 Jul '19

01 Jul '19

Dear Cafe, the migration guide (for AMP) https://gitlab.haskell.org/ghc/ghc/wikis/migration/7.10#ghc-says-no-instanc… contains this advice: instance Applicative Foo where -- NB: DO NOT USE `pure = return` Why not? Because it would require another refactoring once "monad of no return" comes true? So defining `return` in the Monad instance should work fine until then? Which is when exactly? I can't quite make it out from https://gitlab.haskell.org/ghc/ghc/wikis/proposal/monad-of-no-return/discus… - J.W.

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Call For Papers: Workshop in OCL and Textual Modeling (OCL 2019)
by Achim D. Brucker 29 Jun '19

29 Jun '19

CALL FOR PAPERS 19th International Workshop on OCL and Textual Modeling Co-located with MODELS 2019 ACM/IEEE 22nd International Conference on Model Driven Engineering Languages and System, September 15-20, 2019, Munich, Germany http://oclworkshop.github.io The goal of this workshop is to create a forum where researchers and practitioners interested in building models using OCL or other kinds of textual languages (e.g., OCL, textual MOF, Epsilon, or Alloy) can directly interact, report advances, share results, identify tools for language development, and discuss appropriate standards. In particular, the workshop will encourage discussions for achieving synergy from different modeling language concepts and modeling language use. The close interaction will enable researchers and practitioners to identify common interests and options for potential cooperation. ## Topics of interest Topics of interest include (but are not limited to): - Mappings between textual modeling languages and other languages/formalisms - Mathematical models and/or formal semantics for textual modeling languages - Algorithms, evaluation strategies and optimizations in the context of textual modeling languages for: - validation, verification, and testing, - model transformation and code generation, - meta-modeling and DSLs, and - query and constraint specifications - Alternative graphical/textual notations for textual modeling languages - Evolution, transformation and simplification of textual modeling expressions - Libraries, templates and patterns for textual modeling languages - Tools that support textual modeling languages (e.g., verification of OCL formulae, runtime monitoring of invariants) - Model-driven security using textual modeling languages - Complexity results for textual modeling languages - Quality models and benchmarks for comparing and evaluating textual modeling tools and algorithms - Successful applications of textual modeling languages - Case studies on industrial applications of textual modeling languages - Experience reports: - usage of textual modeling languages and tools in complex domains, - usability of textual modeling languages and tools for end-users - Empirical studies about the benefits and drawbacks of textual modeling languages - Innovative textual modeling tools - Comparison, evaluation and integration of modeling languages - Correlation between modeling languages and modeling tasks We particularly encourage submissions describing applications and case studies of textual modeling as well as test suites and benchmark collections for evaluating textual modeling tools. ## Submissions Four types of submissions will be considered: * Presentation only submission (not included in the workshop proceedings), e.g., for already published work. Authors should submit a short (1 page) abstract of their presentation. * Short papers (between 5 and 7 pages) describing new ideas or position papers. * Tool papers (between 5 and 7 pages) describing tools supporting textual modeling tools * Full papers (between 10 and 14 pages). All submissions should follow the LNCS format guidelines and should be uploaded to [EasyChair](https://easychair.org/conferences/?conf=ocl2019). Accepted papers will be published online in [CEUR](http://www.ceur-ws.org). ## Important Dates - Submission of papers: 14 Jul 2019 - Notification: 25 Aug 2019 - Pre-Workshop CRC: 9 Sep 2019 - Post-Workshop CRC: 5 Oct 2019 -- Prof. Achim Brucker | Chair in Cybersecurity & Head of Group | University of Exeter https://www.brucker.ch | https://logicalhacking.com/blog @adbrucker | @logicalhacking

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Intention to take over package "quipper"
by selinger＠mathstat.dal.ca 27 Jun '19

27 Jun '19

I am writing, as recommended at https://wiki.haskell.org/Taking_over_a_package, to announce my intention to take over the "quipper" package on Hackage. I have contacted the author (miniBill, aka Leonardo Taglialegne) in February 2019, and again this Tuesday, with no response. I am one of the authors of Quipper, and the code in miniBill's "quipper" package was actually written by me and my coauthors. Since the package is both outdated and incomplete, and he is not maintaining it, we would like to assume ownership of the package. Thanks, -- Peter

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Reshaping arrays in accelerate
by Lana Black 27 Jun '19

27 Jun '19

Hello cafe, Is there a generic way to reshape an array in accelerate[1] assuming the number of dimensions remains constant? For example, given a matrix, is there a way to add or, more importantly, remove several rows or columns? It seems to me that the API is lacking in this case, but I hope I'm wrong. Thank you. [1]: https://hackage.haskell.org/package/accelerate-1.2.0.1/

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Re: [Haskell-cafe] extra semi-colons
by Johannes Waldmann 26 Jun '19

26 Jun '19

> The rule "alt" allows "(empty alternative)" Ah, yes. But no? The standard says > A case expression must have at least one alternative > and each alternative must have at least one body. Should this be "each non-empty alternative must have ..."? I think the intention is to allow case () of () | False -> () | True -> () (one alternative, two bodies) but to disallow case () of () (one alternative, no body) - J.

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Unexpected result from Data.Compact.inCompact?
by Viktor Dukhovni 26 Jun '19

26 Jun '19

I am seeing surprising results from 'inCompact' after 'compact'. It seems there are additional limitations on what can be compacted, with 'compact' not throwing a 'CompactionFailed' exception in some cases, and yet not compacting the value. Is this expected? When the below is compiled and run: {-# LANGUAGE OverloadedStrings #-} module Main (main) where import Data.Compact import qualified Data.ByteString.Short as S import qualified Data.Map.Strict as M fib :: [Int] fib = 0:1:zipWith (+) fib (tail fib) u = if M.lookup 3 m == Just 2 then () else undefined f3 = head $ drop 3 fib m = M.fromList $ zip [0..9] fib main :: IO () main = do test "explicit ()" () test "computed ()" u test "explicit Int" (42 :: Int) test "computed Int" f3 test "empty string" ("" :: String) test "non-empty string" ("some string" :: String) test "empty short bytestring" S.empty test "non-empty short bytestring" (S.toShort "some bytestring") test "explict empty map" (M.empty :: M.Map Int Int) test "computed fib table" m where test :: String -> a -> IO () test msg val = do putStr (msg ++ ": ") c <- compact val inCompact c (getCompact c) >>= print it outputs: explicit (): False computed (): False explicit Int: False computed Int: True empty string: False non-empty string: True empty short bytestring: True non-empty short bytestring: True explict empty map: False computed fib table: True but the documentation promises: getCompact :: Compact a -> a # Retrieve a direct pointer to the value pointed at by a Compact reference. If you have used compactAdd, there may be multiple Compact references into the same compact region. Upholds the property: inCompact c (getCompact c) == True so when 'compact' does not bottom, I'd expect 'True'. -- Viktor.

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OT: CLR and JVM
by trent shipley 26 Jun '19

26 Jun '19

Is there a typed, functional language with mature versions on Microsoft's CLR and the JVM? A JVM OCaml to go with F# would be ideal. Trent

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(Extended deadline) Formal Methods 2019 - 1st Workshop on Formal Methods for Blockchains, CFP
by Bruno Bernardo 25 Jun '19

25 Jun '19

[ Please distribute, apologies for multiple postings. ] ========================================================== 1st Workshop on Formal Methods for Blockchains (FMBC) 2019 https://sites.google.com/view/fmbc/home Porto, Portugal, October 11 Part of the 3rd World Congress on Formal Methods http://formalmethods2019.inesctec.pt/ ------------------------------------------------------------- IMPORTANT DATES -------------------------------- Abstract submission: June 30, 2019 (extended) Full paper submission: July 7, 2019 (extended) Notification: July 31, 2019 Camera-ready: September 2, 2019 Conference: October 11, 2019 -------------------------------- -------------------------------- 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 so ware. 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: * Design and implementation of Smart Contract languages * Formal models of blockchain applications or concepts * Formal methods for consensus protocols * Formal methods for blockchain-specific cryptographic primitives or protocols Formal languages for Smart * Verification of Smart Contracts -------------------------------- -------------------------------- SUBMISSION -------------------------------- Submit original manuscripts (not published or considered elsewhere) with a maximum of twelve pages (regular 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 of up to 15 minutes. At least one author of an accepted paper is expected to present the paper at the workshop as a registered participant. All accepted contributions will be reviewed once more by the program committee after the workshop and before being included in the post-proceedings. submission link https://easychair.org/conferences/?conf=fmbc19 -------------------------------- -------------------------------- 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 FM workshop post-proceedings, published as a volume of the Lecture Notes in Computer Science (LNCS) by Springer. -------------------------------- -------------------------------- INVITED SPEAKER --------------------------------------------------------------------------------------------------------- Ilya Sergey - Associate Professor at Yale-NUS College and NUS School of Computing, (Singapore). --------------------------------------------------------------------------------------------------------- -------------------------------- -------------------------------- PROGRAM committee -------------------------------- Program Chairs Bruno Bernardo (bruno(a)nomadic-labs.com <mailto:bruno@nomadic-labs.com>) Néstor Cataño (nestor.catano(a)gmail.com <mailto:nestor.catano@gmail.com>) Diego Marmsoler (diego.marmsoler(a)tum.de <mailto:diego.marmsoler@tum.de>) Program Committee Pietro Abate (Nomadic Labs, France) Ijaz Ahmed (University of Madeira, Portuga) Jonathan Aldrich (Carnegie Mellon University, USA) Bernhard Beckert (Karlsruhe Institute of Technology, Germany) Bruno Bernardo (Nomadic Labs, France) Sukriti Bhattacharya (LIST, Luxembourg) Néstor Cataño (Universidad del Norte, Colombia) Maria Christakis (MPI-SWS, Germany) Léa-Zaynah Dargaye (CEA LIST, France) Georges Gonthier (Inria, France) Neville Grech (University of Athens, Greece / University of Malta, Malta) Davide Grossi (University of Groningen, Netherlands) Sorren Hanvey (Liverpool John Moores University, UK) Andreas Lochbihler (Digital Asset, Swiss) Diego Marmsoler (Technische Universitat Munchen, Germany) Anastasia Mavridou (NASA Ames, USA) Simão Melo de Sousa (Universidade da Beira Interior, Portugal) Fabio Mogavero (Università degli Studi di Napoli, Italy) Peter Csaba Ölveczky (University of Oslo, Norway) Karl Palmskog (University of Texas at Austin, USA) Vincent Rahli (University of Luxembourg, Luxembourg) Steve Reeves (University of Waikato, New Zealand) Camilo Rueda (Pontificia Universidad Javeriana, Colombia) Claudio Russo (Dfinity Foundation, USA) Jorge Sousa Pinto (Universidade do Minho, Portugal) Bas Spitters (Aarhus University, Denmark) Christoph Sprenger (ETH, Zürich) Mark Staples (Data61, Australia) Philip Wadler (University of Edinburgh / IOHK, UK) Xi Wu (The University of Queensland, Australia) Santiago Zanella-Beguelin (Microsoft Research Cambridge, UK) --------------------------------

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extra semi-colons
by Johannes Waldmann 25 Jun '19

25 Jun '19

Dear Cafe, why does ghc accept the extra semi-colon in case () of { () -> (); } or even case () of { ;;; () -> () ;;; } Yes I understand that semicolons like this are introduce by the layout rule L (<n> : ts) (m : ms) = ; : (L ts (m : ms)) if m = n https://www.haskell.org/onlinereport/haskell2010/haskellch10.html#x17-17800… and it's convenient to ignore extra ones. But it's not in the grammar? alts → alt1 ; … ; altn (n ≥ 1) https://www.haskell.org/onlinereport/haskell2010/haskellch3.html#x8-460003.… - J.

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