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Re: [Haskell-cafe] Haskell-Cafe Digest, Vol 191, Issue 3
by Information The FLOSS 08 Jul '19

08 Jul '19

Bu ileti The FLOSS Information'a gönderdiğiniz ileti sonucunda otomatik olarak oluşturuldu. Bu iletiye yanıt vermenize gerek yoktur. Bu iletiyi gönderdiğiniz için teşekkür ederiz. 4 gün içerisinde yanıtlamaya çalışacağız. Eğer 4 gün içinde yanıt gelmezse tekrar ileti gönderebilirsiniz. Sık Sorulabilecek Sorular: https://theflossinformation.gitlab.io/sik-sorulabilecek-sorular.html Hakkımızda: https://theflossinformation.gitlab.io/hakkimizda.html Bize Ulaşın: https://theflossinformation.gitlab.io/bize-ulasin.html Saygılarımızla, The FLOSS Information https://theflossinformation.gitlab.io/

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Call for Participation: Summer BOB 2019 (August 21, Berlin)
by Stefan Wehr 08 Jul '19

08 Jul '19

======================================================================== Summer BOB 2019 Conference “What happens if we simply use what’s best?” August 21, 2019, Berlin co-located with ICFP 2019 http://bobkonf.de/2019-summer/ Program: http://bobkonf.de/2019-summer/program.html Registration: http://bobkonf.de/2019-summer/registration.html ======================================================================== Are you interested in technologies beyond the mainstream, that are a pleasure to use, and effective at getting the job done? BOB is the forum for developers, architects and builders to explore and discover the best tools available today for building software. Our goal is for all participants to leave the conference with new ideas to improve development back at the ranch. Summer BOB is a one-time-only event, in the spirit of the spectacular Winter BOB. The International Conference on Functional Programming is coming to town, and Summer BOB will be right in the middle of it, on the last day of ICFP proper, prior to all the workshops. Summer BOB will feature two tracks: one from practitioners, and one from researchers, and foster communication and cross-pollination between these communities. BOB features two tracks of seven talk each: One research track with invited talks, and one track by practitioners, designed to cross-pollinate and inspire. http://bobkonf.de/2019-summer/program.html Topics include distributed programming, testing, linear algebra, functional design patterns, type systems, formal methods, and interactive development. We are committed to diversity: We aim at exploring a wide range of tools in a welcoming and friendly crowd of diverse people. To that end, a number of support options for participants from groups under-represented in tech are available. http://bobkonf.de/2019-summer/registration.html NOTE: The early-bird rates expire on July 18, 2019!

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Help wanted getting old GADT code to compile
by nr＠cs.tufts.edu 05 Jul '19

05 Jul '19

Here is a legacy file that does not compile with GHC 8.0.1: {-# LANGUAGE RankNTypes, GADTs, KindSignatures #-} module Bookgadt where data TExp :: * -> * where TLit :: (forall a . (a -> (TExp a))) TLit' :: (a -> (TExp a)) The compiler rejects value constructor TLit with this error message: • Data constructor ‘TLit’ returns type ‘forall a. a -> TExp a’ instead of an instance of its parent type ‘TExp a’ I really want to keep the explicit "forall," as I'm trying to make a point for readers not familiar with Haskell. Does anyone know if there is some option or other incantation that would enable this code to compile? Norman

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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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