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megaparsec 6 migration
by ☂Josh Chia (謝任中) 01 Sep '17

01 Sep '17

I'm trying to migrate my codebase from megaparsec 5 to megaparsec 6. There appears to be major changes. For example, Text.Megaparsec.String.Parser & Text.Megaparsec.Error.Dec have both disappeared. I'm sure I could slowly plod through the new documentation, figure out the types and figure out how to migrate the code on my own, but examples & tutorials would be more time-efficient. Are there examples or tutorials compatible with megaparsec 6? For a start, what should I do with the above two things that have 'disappeared'? What do I replace them with? Josh

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Crossreferenced codebase for Stackage LTS 9.2 available
by Robin Palotai 01 Sep '17

01 Sep '17

To find out who else uses your favorite functions and how: http://stuff.codereview.me/lts/9.2 . For example, click 'async' at http://stuff.codereview.me/lts/9.2/#async-2.1.1.1/Control/Concurrent/Async.… to get all the callsites of that method. There are additional files available at http://stuff.codereview.me/ if you want to serve the xrefs locally, or merge your own packages into the index (assuming you use the same stackage lts version). A request: the crossreferencing is pretty usable, but far from complete. If you find any issues (missing crossreferences or bad ones), please have a look at the buglist at https://github.com/google/haskell-indexer/issues, and thumbs-up any that you find hurting, or open new ones! Thank you & happy code browsing, Robin

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ThEdu'17 Post-Proceedings: Call for Papers
by Achim D. Brucker 31 Aug '17

31 Aug '17

(Apologies for duplicates) Call for Papers - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Post-Proceedings --- ThEdu'17 - Electronic Proceedings in Theoretical Computer Science ThEdu'17 --- Theorem proving components for Educational software 6 August 2017, Gothenburg, Sweden, at CADE26 http://www.uc.pt/en/congressos/thedu/thedu17 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Post-Proceedings THedu'17 Scope: Computer Theorem Proving is becoming a paradigm as well as a technological base for a new generation of educational software in science, technology, engineering and mathematics. The workshop brought together experts in automated deduction with experts in education in order to further clarify the shape of the new software generation and to discuss existing systems. This call is open for everyone, also those who did not participate in the workshop. Important Dates (EPTCS Post-Proceedings) * Call for papers: 08 Sep 2017 * Submission (full papers): 17 Nov 2017 * Notification of acceptance: 15 Dec 2017 * Revised papers due: 19 Jan 2018 Topics of interest include: - methods of automated deduction applied to checking students' input; - methods of automated deduction applied to prove post-conditions for particular problem solutions; - combinations of deduction and computation enabling systems to propose next steps; - automated provers specific for dynamic geometry systems; - proof and proving in mathematics education. Submission We welcome submission of papers presenting original unpublished work which is not been submitted for publication elsewhere. The authors should comply with the "instructions for authors", LaTeX style files and accept the "Non-exclusive license to distribute" of EPTCS: Instructions for authors (http://info.eptcs.org/) LaTeX style file and formatting instructions (http://style.eptcs.org/) Copyright (http://copyright.eptcs.org/) Papers should be submitted via easychair, https://easychair.org/conferences/?conf=thedu17 . Program Committee Francisco Botana, University of Vigo at Pontevedra, Spain Achim Brucker, University of Sheffield, United Kingdom Roman Hašek, University of South Bohemia, Czech Republic Filip Maric, University of Belgrade, Serbia Walther Neuper, Graz University of Technology, Austria (co-chair) Pavel Pech, University of South Bohemia, Czech Republic Pedro Quaresma, University of Coimbra, Portugal (co-chair) Vanda Santos, CISUC, Portugal Wolfgang Schreiner, Johannes Kepler University, Austria Burkhart Wolff, University Paris-Sud, France -- Dr. Achim D. Brucker | Software Assurance & Security | University of Sheffield https://www.brucker.ch | https://logicalhacking.com/blog @adbrucker | @logicalhacking

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cabal file build-depends list sensitive to ordering
by Olaf Klinke 30 Aug '17

30 Aug '17

Dear cafe, I discovered that stack/cabal is sensitive to permutations in the dependencies list. Is that desired behaviour and documented anywhere? #File stack.yaml resolver: lts-9.2 packages: - '.' extra-deps: [iCalendar-0.4.0.3,mime-0.4.0.2,wx-0.92.3.0,wxcore-0.92.3.0,wxc-0.92.3.0,wxdirect-0.92.3.0] flags: {} extra-package-dbs: [] system-ghc: false # In file myproject.cabal build-depends: base >= 4.7 && < 5 , HaXml >= 1.13.3 , iCalendar >= 0.3.7.3 , containers , time >= 1.6.0.1 , text , case-insensitive , xslx , xlsx-tabular , wx "stack build" generates the rather uninformative error message In the dependencies for myproject-0.2.1.0: xslx must match -any, but the stack configuration has no specified version # In file myproject.cabal build-depends: base >= 4.7 && < 5 , xlsx , xlsx-tabular , HaXml >= 1.13.3 , iCalendar >= 0.3.7.3 , containers , time >= 1.6.0.1 , text , case-insensitive , wx This version builds just fine. -- Olaf

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profiling of functions generated by LLVM
by Henning Thielemann 30 Aug '17

30 Aug '17

I use LLVM to create sub-routines for efficient inner loops. I like to profile them. However, it seems that GHC's profiler does not interact well with such generated functions. Say, I have a function that creates an efficient subroutine for filling a block of data. It looks like the following: generateFill :: IO (Word64 -> Ptr Float -> IO ()) generateFill = generateFunction (LLVM code for traversing block) main :: IO () main = do let n = 100*10^6 fill <- generateFill allocaArray n $ \ptr -> {-# SCC fill #-} fill (fromIntegral n) ptr I run this with profiling. The resulting .prof report says, that 'generateFunction' demands all the computation time and 'fill' inherits it. fill Main 1297 1 0.0 0.0 99.9 0.0 generateFill Main 1298 0 0.0 0.0 99.9 0.0 generateFunction Main 1299 0 99.9 0.0 99.9 0.0 I have a rough idea why GHC treats the generated functions the way it does. However, it is pretty counter-intuitive and difficult to understand in more complex programs.

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Munich Haskell Meeting, 2017-08-31 @ 19:30
by Christian Neukirchen 30 Aug '17

30 Aug '17

Dear all, This week, our monthly Munich Haskell Meeting will take place again on Thursday, August 31 at Augustiner-Gaststätte Rumpler (Baumstraße 21) at 19h30. For details see here: http://muenchen.haskell.bayern/dates.html If you plan to join, please add yourself to this dudle so we can reserve enough seats! It is OK to add yourself to the dudle anonymously or pseudonymously. https://dudle.inf.tu-dresden.de/haskell-munich-aug-2017/ Everybody is welcome! cu, -- Christian Neukirchen <chneukirchen(a)gmail.com> http://chneukirchen.org

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Haddock's Hackage page --- Bravo!
by Albert Y. C. Lai 29 Aug '17

29 Aug '17

https://hackage.haskell.org/package/haddock now puts the whole cheatsheet up front. Well done! Bravo! Whoever thought up this is a genius! Thanks!

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Does the streaming package need a new/additional maintainer?
by David Feuer 29 Aug '17

29 Aug '17

The streaming package has a couple old pull requests that have not been commented on. My recently reported issues and pull requests have also met with silence. It appears that the maintainer, Michael Thompson, was last active on GitHub and Reddit in April. I emailed him a few days ago, but have not yet received a response. I hope he is just on a short break, but if not, someone should probably take over the package. David

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Numerical / Data Special Interest Group at ICFP'17
by Marco Zocca 29 Aug '17

29 Aug '17

Dear all, thanks to the ICFP organisers and to D.Steinitz (https://idontgetoutmuch.wordpress.com/) we will have a late-minute workshop on the numerical and data-related Haskell at ICFP'17 (Oxford) on Saturday 9th September in the slot 12:30 - 14:00. Looking forward to meeting you all there; Best, Marco Zocca https://github.com/ocramz

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GHC 8.2's new ghci commands: `:type +d` and `:type +v`
by Takenobu Tani 28 Aug '17

28 Aug '17

Dear cafe, GHC 8.2 supports two new ghci commands. They are `:type +d` and `:type +v` [1]. 0. normal `:type` command: Prelude> :type length length :: Foldable t => t a -> Int Prelude> :type ($) ($) :: (a -> b) -> a -> b 1. new `:type +d` command for newcomers: Prelude> :type +d length length :: [a] -> Int 2. new `:type +v` command for detail information: Prelude> :type +v ($) ($) :: forall (r :: GHC.Types.RuntimeRep) a (b :: TYPE r). (a -> b) -> a -> b That's excellent :) [1]: https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/ghci.html#g… Regards, Takenobu

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