- Haskell-Cafe - Haskell.org

Re: [Haskell-cafe] Controlling how test data is generated in, QuickCheck 2
by Li-yao Xia 03 May '16

03 May '16

Hi Michael, > What I noticed was the answer suggested that one should write a `newtype`, > wrapping a `[Int]` and making a new `Arbitrary` instance. However, I also > noticed that the answer is from 2012, and `QuickCheck 2` has an `Args` > `datatype` that appears to be able to do what I need. So, can I create a > new `Args` to limit the range of tests, (just want the first 1000 Fibonacci > numbers), and also to limit the number of tests run? If not is the solution > from the above link the approach I would have to take? The module Test.Hspec.QuickCheck has functions to modify the number of tests to be run (modifyMaxSuccess) and the maximum size passed to the generators (modifyMaxSize) (and indeed internally they modify the Args passed to QuickCheck's driver). I believe their purpose is to modify values coming from outside the program, via the command line options --qc-max-success and --qc-max-size. You can certainly set them to constants: modifyMaxSuccess (const 1000) $ prop ... But to specify the domains of your properties from within the program, the approaches mentioned in the answer you linked to are still current. Defining a newtype wrapper with an Arbitrary instance is a somewhat heavyweight solution. Some already exist for common preconditions, for example you can use Positive instead of the first check in modfiz: modfiz :: Positive Int -> Bool modfiz (Positive int) = ... The answer also mentions forAll and standalone generators, which I find to be most straightforward to set the domain of testfib: testfib :: Property testfib = forAll (choose (1, 1000)) $ \n -> ... Li-yao

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Controlling how test data is generated in QuickCheck 2
by Michael Litchard 03 May '16

03 May '16

I have a problem similar to this question < http://stackoverflow.com/questions/9977734/controlling-how-test-data-is-gen…>. Below I will articulate my specifics, the code I am using, and the particular question I have. I have written a fizz-buzz program that uses a Fibonacci sequence as input. I would like to test two things. (1) Does my program emit the correct string given an Int that meets a particular condition. (2) Is my Fibonacci generator generating Fibonacci numbers? The problem I am having is similar to the link above. The range of `Int`s is too large. How do I constrain my tests to say, the first 1000 Fibonacci numbers? Here is code that I think is both adequate and minimal. Please let me know if I need to elaborate. import Data.Numbers.Primes (isPrime) import Test.Hspec (Spec,hspec,describe,it,shouldBe) import Test.Hspec.QuickCheck (prop) qcheck :: Spec qcheck = do describe "QuickCheck test fiz" $ prop "QuickCheck test" $ modfiz describe "QuickCheck test fib" $ prop "QuickCheck test fib" $ testfib modfiz int | int <= 0 = True -- code smell, should never generate number less than or equal to zero. | int == 3 = test3 | int == 5 = test5 | int `mod` 15 == 0 = testMod35 | int `mod` 3 == 0 = testMod3 | int `mod` 5 == 0 = testMod5 | isPrime int == True = testPrime | otherwise = testRest where test3 = Right "Buzz BuzzFizz" == fizzbuzz 3 test5 = Right "Fizz BuzzFizz" == fizzbuzz 5 testMod3 = Right "Buzz " == fizzbuzz int testMod5 = Right "Fizz " == fizzbuzz int testMod35 = Right "Buzz Fizz " == fizzbuzz int testPrime = Right "BuzzFizz" == fizzbuzz int testRest = Right (show int) == fizzbuzz int testfib :: Integer -> Bool testfib n = case (fibb n) of Left _ -> False Right n' -> isFib n' `fibb` takes an `Int` and finds that nth Fibonacci. So `fibb 6` would return `Right 8`. The `Left` value is not relevant to this problem. What I noticed was the answer suggested that one should write a `newtype`, wrapping a `[Int]` and making a new `Arbitrary` instance. However, I also noticed that the answer is from 2012, and `QuickCheck 2` has an `Args` `datatype` that appears to be able to do what I need. So, can I create a new `Args` to limit the range of tests, (just want the first 1000 Fibonacci numbers), and also to limit the number of tests run? If not is the solution from the above link the approach I would have to take? the entire project here <https://github.com/mlitchard/swiftfizz>

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Applications using generalized monads?
by Jan Bracker 03 May '16

03 May '16

Hello, I am currently looking into applications of generalized monads. I am aware of the following generalized monad concepts (and libraries implementing them): * Indexed/Parameterized/Hoare Monads [1] * indexed [8] * simple-sessions [9][4] * monad-param [10][3][6] * Effect Monads [2] * effect-monad [11][5] * monad-param [12][3] * Constrained Monads * rmonad [13] Question 1: Do you know of other libraries that implement generalized monad concepts? Most of the libraries I listed above are in working condition, but still outdated. Question 2: Do you know of (open source) software and applications that use these concepts/libraries to implement something? This mail is a copy of my post on Reddit [7]. I am sorry for reposting it here, but I dod not get a response on that post for almost 2 weeks now. Best, Jan [1]: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.104.3020 [2]: http://dl.acm.org/citation.cfm?doid=2578855.2535846 [3]: http://comonad.com/reader/2007/parameterized-monads-in-haskell/ [4]: http://www.ccs.neu.edu/home/tov/pubs/haskell-session-types/session08.pdf [5]: https://www.cl.cam.ac.uk/~dao29/publ/haskell14-effects.pdf [6]: http://www.researchgate.net/profile/Dominique_Devriese/publication/22128235… [7]: https://www.reddit.com/r/haskellquestions/comments/4fs80x/ [8]: http://hackage.haskell.org/package/indexed [9]: http://hackage.haskell.org/package/simple-sessions [10]: http://hackage.haskell.org/package/monad-param [11]: http://hackage.haskell.org/package/effect-monad [12]: http://hackage.haskell.org/package/monad-param [13]: http://hackage.haskell.org/package/rmonad

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cannot perform arithmetic with GHC.TypeLits?
by Baojun Wang 03 May '16

03 May '16

Hi List, When I try to build below program, the compiler complains Couldn't match type ‘n’ with ‘1 + (n - 1)’ … Why GHC (7.10.3) cannot do type level natural number arithmetic? `` n /= 1 + (n-1)`` at type level? -- | main.hs {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE KindSignatures #-} {-# LANGUAGE TypeOperators #-} {-# LANGUAGE DataKinds #-} {-# LANGUAGE OverloadedStrings #-} {-# LANGUAGE DeriveGeneric #-} module Main where import qualified Data.ByteString as B import Data.ByteString(ByteString) import Data.Serialize -- require cereal import GHC.TypeLits data Scalar :: Nat -> * -> * where Nil :: Scalar 0 a Cons :: a -> Scalar m a -> Scalar (1+m) a instance (Serialize a) => Serialize (Scalar 0 a) where get = return Nil put _ = return $ mempty instance (Serialize a) => Serialize (Scalar n a) where get = do x <- get :: Get a xs <- get :: Get (Scalar (n-1) a) return $! Cons x xs put (Cons x xs) = do put (x :: a) put xs -- /tmp/vect1/app/Main.hs:31:15: Couldn't match type ‘n’ with ‘1 + (n - 1)’ … ‘n’ is a rigid type variable bound by the instance declaration at /tmp/vect1/app/Main.hs:27:10 Expected type: Scalar n a Actual type: Scalar (1 + (n - 1)) a Relevant bindings include xs :: Scalar (n - 1) a (bound at /tmp/vect1/app/Main.hs:30:5) get :: Get (Scalar n a) (bound at /tmp/vect1/app/Main.hs:28:3) In the second argument of ‘($!)’, namely ‘Cons x xs’ In a stmt of a 'do' block: return $! Cons x xs Compilation failed. - baojun

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Hackage package upload error: Invalid package
by Kostiantyn Rybnikov 03 May '16

03 May '16

Hi! Wanted to upload the 0.8.1 version of hedis, did what I usually did, but getting an error. Running "stack -v upload ." seems to show some tls-related details. ``` ➜ hedis git:(master) stack -v upload . Version 1.0.4.3 x86_64 2016-05-01 15:29:31.034044: [debug] Checking for project config at: /Users/kb/workspace/hedis/stack.yaml @(stack_2rXRdr1j02iFXWAif5re4K:Stack.Config src/Stack/Config.hs:761:9) 2016-05-01 15:29:31.037100: [debug] Loading project config file stack.yaml @(stack_2rXRdr1j02iFXWAif5re4K:Stack.Config src/Stack/Config.hs:779:13) 2016-05-01 15:29:31.110561: [debug] Checking for project config at: /Users/kb/workspace/hedis/stack.yaml @(stack_2rXRdr1j02iFXWAif5re4K:Stack.Config src/Stack/Config.hs:761:9) 2016-05-01 15:29:31.110690: [debug] Loading project config file stack.yaml @(stack_2rXRdr1j02iFXWAif5re4K:Stack.Config src/Stack/Config.hs:779:13) 2016-05-01 15:29:31.111459: [debug] Trying to decode /Users/kb/.stack/build-plan-cache/x86_64-osx/lts-5.3.cache @(stack_2rXRdr1j02iFXWAif5re4K:Data.Binary.VersionTagged src/Data/Binary/VersionTagged.hs:55:5) 2016-05-01 15:29:31.124939: [debug] Success decoding /Users/kb/.stack/build-plan-cache/x86_64-osx/lts-5.3.cache @(stack_2rXRdr1j02iFXWAif5re4K:Data.Binary.VersionTagged src/Data/Binary/VersionTagged.hs:64:13) 2016-05-01 15:29:31.132890: [debug] Trying to decode /Users/kb/.stack/indices/Hackage/00-index.cache @(stack_2rXRdr1j02iFXWAif5re4K:Data.Binary.VersionTagged src/Data/Binary/VersionTagged.hs:55:5) 2016-05-01 15:29:31.421690: [debug] Success decoding /Users/kb/.stack/indices/Hackage/00-index.cache @(stack_2rXRdr1j02iFXWAif5re4K:Data.Binary.VersionTagged src/Data/Binary/VersionTagged.hs:64:13) 2016-05-01 15:29:31.434522: [debug] Run process: ghc --info @(stack_2rXRdr1j02iFXWAif5re4K:System.Process.Read src/System/Process/Read.hs:269:3) 2016-05-01 15:29:31.498337: [debug] Run process: ghc --numeric-version @(stack_2rXRdr1j02iFXWAif5re4K:System.Process.Read src/System/Process/Read.hs:269:3) 2016-05-01 15:29:31.543696: [debug] Run process: ghc-pkg --no-user-package-db field --simple-output Cabal version @(stack_2rXRdr1j02iFXWAif5re4K:System.Process.Read src/System/Process/Read.hs:269:3) 2016-05-01 15:29:31.576011: [debug] Run process: ghc-pkg --no-user-package-db list --global @(stack_2rXRdr1j02iFXWAif5re4K:System.Process.Read src/System/Process/Read.hs:269:3) 2016-05-01 15:29:31.625682: [info] Getting file list for /Users/kb/workspace/hedis/ @(stack_2rXRdr1j02iFXWAif5re4K:Stack.SDist src/Stack/SDist.hs:96:5) 2016-05-01 15:29:31.628599: [debug] Checking resolver: lts-5.3 @(stack_2rXRdr1j02iFXWAif5re4K:Stack.Build.Source src/Stack/Build/Source.hs:164:17) 2016-05-01 15:29:31.628777: [debug] Trying to decode /Users/kb/.stack/build-plan-cache/x86_64-osx/lts-5.3.cache @(stack_2rXRdr1j02iFXWAif5re4K:Data.Binary.VersionTagged src/Data/Binary/VersionTagged.hs:55:5) 2016-05-01 15:29:31.636259: [debug] Success decoding /Users/kb/.stack/build-plan-cache/x86_64-osx/lts-5.3.cache @(stack_2rXRdr1j02iFXWAif5re4K:Data.Binary.VersionTagged src/Data/Binary/VersionTagged.hs:64:13) 2016-05-01 15:29:31.650120: [debug] Run process: ghc-pkg --no-user-package-db list --global @(stack_2rXRdr1j02iFXWAif5re4K:System.Process.Read src/System/Process/Read.hs:269:3) 2016-05-01 15:29:31.679601: [debug] Run process: /Users/kb/.stack/setup-exe-cache/x86_64-osx/setup-Simple-Cabal-1.22.5.0-ghc-7.10.3 --builddir=.stack-work/dist/x86_64-osx/Cabal-1.22.5.0 sdist --list-sources /private/var/folders/7l/3ys9j0lx20j6z69lm6s_9r780000gn/T/stack-sdist56408/source-files-list @(stack_2rXRdr1j02iFXWAif5re4K:System.Process.Read src/System/Process/Read.hs:287:3) 2016-05-01 15:29:31.728919: [info] Building sdist tarball for /Users/kb/workspace/hedis/ @(stack_2rXRdr1j02iFXWAif5re4K:Stack.SDist src/Stack/SDist.hs:98:5) 2016-05-01 15:29:31.756558: [info] Checking package 'hedis' for common mistakes @(stack_2rXRdr1j02iFXWAif5re4K:Stack.SDist src/Stack/SDist.hs:274:5) 2016-05-01 15:29:31.758110: [warn] Package check reported the following warnings: 'ghc-options: -Wall -Werror' makes the package very easy to break with future GHC versions because new GHC versions often add new warnings. Use just 'ghc-options: -Wall' instead. 'ghc-prof-options: -auto-all' is fine during development, but not recommended in a distributed package. @(stack_2rXRdr1j02iFXWAif5re4K:Stack.SDist src/Stack/SDist.hs:285:9) Uploading hedis-0.8.1.tar.gz... TlsExceptionHostPort (HandshakeFailed (Error_Packet_unexpected "Alert [(AlertLevel_Fatal,BadRecordMac)]" " expected: change cipher")) "hackage.haskell.org" 443 ➜ hedis git:(master) stack upload . Getting file list for /Users/kb/workspace/hedis/ Building sdist tarball for /Users/kb/workspace/hedis/ Checking package 'hedis' for common mistakes Package check reported the following warnings: 'ghc-options: -Wall -Werror' makes the package very easy to break with future GHC versions because new GHC versions often add new warnings. Use just 'ghc-options: -Wall' instead. 'ghc-prof-options: -auto-all' is fine during development, but not recommended in a distributed package. Uploading hedis-0.8.1.tar.gz... unhandled status code: 400 Error: Invalid package 'ghc-options: -Wall -Werror' makes the package very easy to break with future GHC versions because new GHC versions often add new warnings. Use just 'ghc-options: -Wall' instead. Upload failed on hedis-0.8.1.tar.gz ``` Hope somebody can take a look. Thank you.

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[TFP'16] call for participation
by Peter Achten 02 May '16

02 May '16

----------------------------- C A L L F O R P A R T I C I P A T I O N ----------------------------- ======== TFP 2016 =========== 17th Symposium on Trends in Functional Programming June 8-10, 2016 University of Maryland, College Park Near Washington, DC http://tfp2016.org/ The symposium on Trends in Functional Programming (TFP) is an international forum for researchers with interests in all aspects of functional programming, taking a broad view of current and future trends in the area. It aspires to be a lively environment for presenting the latest research results, and other contributions (see below). Authors of draft papers will be invited to submit revised papers based on the feedback receive at the symposium. A post-symposium refereeing process will then select a subset of these articles for formal publication. TFP 2016 will be the main event of a pair of functional programming events. TFP 2016 will be accompanied by the International Workshop on Trends in Functional Programming in Education (TFPIE), which will take place on June 7nd. == INVITED SPEAKERS == TFP 2016 is pleased to announce keynote talks by the following two invited speakers: * Ronald Garcia, University of British Columbia: "Static and Dynamic Type Checking: A Synopsis" * Steve Zdancewic, University of Pennsylvania: "Type- and Example-Driven Program Synthesis" == HISTORY == The TFP symposium is the heir of the successful series of Scottish Functional Programming Workshops. Previous TFP symposia were held in * Edinburgh (Scotland) in 2003; * Munich (Germany) in 2004; * Tallinn (Estonia) in 2005; * Nottingham (UK) in 2006; * New York (USA) in 2007; * Nijmegen (The Netherlands) in 2008; * Komarno (Slovakia) in 2009; * Oklahoma (USA) in 2010; * Madrid (Spain) in 2011; * St. Andrews (UK) in 2012; * Provo (Utah, USA) in 2013; * Soesterberg (The Netherlands) in 2014; * and Inria Sophia-Antipolis (France) in 2015. For further general information about TFP please see the TFP homepage. (http://www.tifp.org/) == SCOPE == The symposium recognizes that new trends may arise through various routes. As part of the Symposium's focus on trends we therefore identify the following five article categories. High-quality articles are solicited in any of these categories: Research Articles: leading-edge, previously unpublished research work Position Articles: on what new trends should or should not be Project Articles: descriptions of recently started new projects Evaluation Articles: what lessons can be drawn from a finished project Overview Articles: summarizing work with respect to a trendy subject Articles must be original and not simultaneously submitted for publication to any other forum. They may consider any aspect of functional programming: theoretical, implementation-oriented, or experience-oriented. Applications of functional programming techniques to other languages are also within the scope of the symposium. Topics suitable for the symposium include, but are not limited to: Functional programming and multicore/manycore computing Functional programming in the cloud High performance functional computing Extra-functional (behavioural) properties of functional programs Dependently typed functional programming Validation and verification of functional programs Debugging and profiling for functional languages Functional programming in different application areas: security, mobility, telecommunications applications, embedded systems, global computing, grids, etc. Interoperability with imperative programming languages Novel memory management techniques Program analysis and transformation techniques Empirical performance studies Abstract/virtual machines and compilers for functional languages (Embedded) domain specific languages New implementation strategies Any new emerging trend in the functional programming area If you are in doubt on whether your article is within the scope of TFP, please contact the TFP 2016 program chair, David Van Horn. == BEST PAPER AWARDS == To reward excellent contributions, TFP awards a prize for the best paper accepted for the formal proceedings. TFP traditionally pays special attention to research students, acknowledging that students are almost by definition part of new subject trends. A student paper is one for which the authors state that the paper is mainly the work of students, the students are listed as first authors, and a student would present the paper. A prize for the best student paper is awarded each year. In both cases, it is the PC of TFP that awards the prize. In case the best paper happens to be a student paper, that paper will then receive both prizes. == SPONSORS == TFP is financially supported by CyberPoint, Galois, Trail of Bits, and the University of Maryland Computer Science Department. == PAPER SUBMISSIONS == Acceptance of articles for presentation at the symposium is based on a lightweight peer review process of extended abstracts (4 to 10 pages in length) or full papers (20 pages). The submission must clearly indicate which category it belongs to: research, position, project, evaluation, or overview paper. It should also indicate which authors are research students, and whether the main author(s) are students. A draft paper for which ALL authors are students will receive additional feedback by one of the PC members shortly after the symposium has taken place. We use EasyChair for the refereeing process. Papers must be submitted at: https://easychair.org/conferences/?conf=tfp2016 Papers must be written in English, and written using the LNCS style. For more information about formatting please consult the Springer LNCS web site: http://www.springer.com/computer/lncs?SGWID=0-164-6-793341-0 == IMPORTANT DATES == Submission of draft papers: April 25, 2016 Notification: May 2, 2016 Registration: May 13, 2016 TFP Symposium: June 8-10, 2016 Student papers feedback: June 14, 2016 Submission for formal review: July 14, 2016 Notification of acceptance: September 14, 2016 Camera ready paper: October 14, 2016 == PROGRAM COMMITTEE == Amal Ahmed Northeastern University (US) Nada Amin École Polytechnique Fédérale de Lausanne (CH) Kenichi Asai Ochanomizu University (JP) Małgorzata Biernacka University of Wroclaw (PL) Laura Castro University of A Coruña (ES) Ravi Chugh University of Chicago (US) Silvia Ghilezan University of Novi Sad (SR) Clemens Grelck University of Amsterdam (NL) John Hughes Chalmers University of Technology (SE) Suresh Jagannathan Purdue University (US) Pieter Koopman Radboud University Nijmegen (NL) Geoffrey Mainland Drexel University (US) Chris Martens University of California, Santa Cruz (US) Jay McCarthy University of Massachusetts, Lowell (US) Heather Miller École Polytechnique Fédérale de Lausanne (CH) Manuel Serrano INRIA, Sophia-Antipolis (FR) Scott Smith Johns Hopkins University (US) Éric Tanter University of Chile (CL) David Van Horn (Chair) University of Maryland (US) Niki Vazou University of California, San Diego (US) Stephanie Weirich University of Pennsylvania (US)

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Transforming graphs with loops with Hoopl
by Anakreontas 02 May '16

02 May '16

I am trying to implement a program transformation with Hoopl. The transformation replaces a particular statement with variable declarations provided that the variables have not been previously declared. A map keeps track of declared variables where the map keys store variable names. The transformation works only for programs without loops. In the program below, it should replace line 2 rec #3 INxt B37H00G with 1 Global Field B37H00G 2 Global Array B37HO3R 3 rec #3 INxt B37H00G but it doesn't. === Example graph == 0 goto L4 1 L4: 2 rec #3 INxt B37H00G 3 while #3 goto L5 goto L2 4 L5: 5 Global Field VSTF01a 6 goto L4 7 L2: I think the reason it fails is because there are two paths leading to L4, one from the program start (line 0) and a second when the loop repeats from line 6. In the first case the transformation produces the substitution graph since the two variables are not in the map. In the analysis of the second path however, the variables are in the name space so the rewrite function returns Nothing. In the end, the second transformation result is preserved (i.e. Nothing) and the graph is not transformed. Do I understand correctly why the transformation fails for loops? How would you suggest to solve this problem? Regards

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Call for Contributions - Haskell Communities and Activities Report, May 2016 edition (30th edition)
by Mihai Maruseac 01 May '16

01 May '16

Dear all, It's that time of the year again (https://ro-che.info/ccc/16) :) We would like to collect contributions for the 30th edition of the ============================================================ Haskell Communities & Activities Report http://www.haskell.org/haskellwiki/Haskell_Communities_and_Activities_Report Submission deadline: 30 April 2016 ============================================================ The short story follows: * If you are working on _any_ project that is in some way related to Haskell, please write a short entry and submit it. Even if the project is small, unfinished or used only by yourself or you think it is not important enough, please reconsider and submit an entry anyway! * The submission file can be in _any_ format you like. Although the final report uses LaTeX, if it is easier for you to submit a Markdown file, text file, Doc file or anything else, please do so. We'll be happy to do the translation and get a new entry in the HCAR :) * If you are interested in an existing project related to Haskell that has not previously been mentioned in the HCAR, please tell me or contact a project leader to get them to submit an entry. We have received feedback in the past that some projects were missing from the edition, but, sadly, that was too late at the time, but those projects will be contacted for this edition. * Feel free to pass on this call for contribution to others that might be interested. More detailed information: The Haskell Communities & Activities Report is a bi-annual overview of the state of Haskell as well as Haskell-related projects over the last, and possibly the upcoming six months. If you have only recently been exposed to Haskell, it might be a good idea to browse the previous edition --- you will find interesting projects described as well as several starting points and links that may provide answers to many questions. Contributions will be collected until the submission deadline. They will then be compiled into a coherent report that is published online as soon as it is ready. As always, this is a great opportunity to update your webpages, make new releases, announce or even start new projects, or to talk about developments you want every Haskeller to know about! Looking forward to your contributions, Mihai FAQ: Q: What format should I write in? A: The recommeneded format is a LaTeX source file, adhering to the template that is available at: http://haskell.org/communities/05-2016/template.tex There is also a LaTeX style file at http://haskell.org/communities/06-2016/hcar.sty that you can use to preview your entry. If you modify an old entry that you have written for an earlier edition of the report, you should soon receive your old entry as a template (provided we have your valid email address). Please modify that template, rather than using your own version of the old entry as a template. _However_, if you don't want/have time to format the entry for LaTeX, you can submit it in any other format possible and we will be happy to convert it for the final report. Q: Can I include Haskell code? A: Yes. Please use lhs2tex syntax (http://www.andres-loeh.de/lhs2tex/) The report is compiled in mode polycode.fmt. Q: Can I include images? A: Yes, you are even encouraged to do so. Please use .jpg or .png format, then, PNG being preferred for simplicity. Q: How much should I write? A: Authors are asked to limit entries to about one column of text. A general introduction is helpful. Apart from that, you should focus on recent or upcoming developments. Pointers to online content can be given for more comprehensive or "historic" overviews of a project. Images do not count towards the length limit, so you may want to use this opportunity to pep up entries. There is no minimum length of an entry! The report aims for being as complete as possible, so please consider writing an entry, even if it is only a few lines long. Q: Which topics are relevant? A: All topics which are related to Haskell in some way are relevant. We usually had reports from users of Haskell (private, academic, or commercial), from authors or contributors to projects related to Haskell, from people working on the Haskell language, libraries, on language extensions or variants. We also like reports about distributions of Haskell software, Haskell infrastructure, books and tutorials on Haskell. Reports on past and upcoming events related to Haskell are also relevant. Finally, there might be new topics we do not even think about. As a rule of thumb: if in doubt, then it probably is relevant and has a place in the HCAR. You can also simply ask us. Q: Is unfinished work relevant? Are ideas for projects relevant? A: Yes! You can use the HCAR to talk about projects you are currently working on. You can use it to look for other developers that might help you. You can use HCAR to ask for more contributors to your project, it is a good way to gain visibility and traction. Q: If I do not update my entry, but want to keep it in the report, what should I do? A: Tell us that there are no changes. The old entry will typically be reused in this case, but it might be dropped if it is older than a year, to give more room and more attention to projects that change a lot. Do not resend complete entries if you have not changed them. Q: Will I get confirmation if I send an entry? How do I know whether my email has even reached its destination, and not ended up in a spam folder? A: Prior to publication of the final report, we will send a draft to all contributors, for possible corrections. So if you do not hear from us within two weeks after the deadline, it is safer to send another mail and check whether your first one was received. -- Mihai Maruseac (MM) "If you can't solve a problem, then there's an easier problem you can solve: find it." -- George Polya

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[ANN] Pre-announcing ZuriHac 2016
by Alexander Bernauer 30 Apr '16

30 Apr '16

Hello fellow Haskellers, it's my pleasure to announce that this year's ZuriHac, the Zurich Haskell hackathon, will happen from July 22nd to 24th. The registration will open this Saturday at 12pm (UTC+2). More information will follow. Greetings, Alex on behalf of the orga team

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[ANN] Darcs 2.12.0 release
by Guillaume Hoffmann 29 Apr '16

29 Apr '16

Hi all, The Darcs team is pleased to announce the release of Darcs 2.12.0. # Downloading # One way of installing Darcs 2.12.0 is with stack: $ stack install darcs-2.12.0 Or first install the Haskell Platform (http://www.haskell.org/platform) and install Darcs with cabal-install: $ cabal update $ cabal install darcs-2.12.0 You can also download the tarball from http://darcs.net/releases/darcs-2.12.0.tar.gz and build it by hand. The 2.12 branch is also available as a darcs repository from http://darcs.net/releases/branch-2.12 # What's new since Darcs 2.10.3 # ## New features ## * `darcs show dependencies`: export patch dependency graph as dot file (Ale Gadea) ## User Interface ## * improvements in `darcs record` output with irrelevant files (Ben Franksen) * `darcs log -v --machine-readable`: show internal representation of patches (including explicit dependencies). Remove patch viewing via the "darcs annotate" command. (Guillaume Hoffmann) * `whatsnew -s` (and `status`) show conflicting files (Guillaume Hoffmann) * honor "quiet" flag in command outputs (Ben Franksen) * a single `show patch-index` command (Guillaume Hoffmann) * remove deprecated aliases of show (Guillaume Hoffmann) * remove hack to enable arbitrary protocols via env variables (Guillaume Hoffmann) ## Performance ## * handle file moves natively when importing from git (Owen Stephens) ## Developer-related ## * require GHC 7.6 (base > 4.6) and support GHC 8 (Ganesh Sittampalam) * switch to sandi from dataenc (Daniil Frumin) * refactoring to prepare stash (Ganesh Sittampalam) * change argument order of type witness RL (Ben Franksen) * Darcs.Repository / repository cloning refactoring (Ben Franksen) * use of async when cloning with packs (Ben Franksen) * SSH code refactoring (Ben Franksen) * Patch and RealPatch renamed to RepoPatchV1 and RepoPatchV2 (Guillaume Hoffmann) * merged hashed-storage into libdarcs and hashed-storage tests into darcs-test (Guillaume Hoffmann) * reorganize Darcs.Repository.* modules (Guillaume Hoffmann) ## Issues resolved in Darcs 2.12 ## * issue1807: clarify help of PAGER, DARCS_PAGER (Guillaume Hoffmann) * issue2258: improve patch index error message with suggestion (Guillaume Hoffmann) * issue2269: push hijack test to suspend time (Eric Kow) * issue2276: Keep track of patch hijack decisions (Eric Kow) * issue2138: report conflicting files in whatsnew -s (Guillaume Hoffmann) * issue2393: remove whatsnew functionality from annotate (Guillaume Hoffmann) * issue2400: use async package to keep track of unpack threads (Ben Franksen) * issue2459: fall back to writing the file if createLink fails (Ben Franksen) * issue2479: root dir most not be among the sources of a move (Ben Franksen) * issue2481: expose API for 'darcs diff' command (Ganesh Sittampalam) * issue2486: obliterate --not-in-remote -q should be more quiet (Ben Franksen) * issue2489: dequote filepaths while importing from git (Guillaume Hoffmann) * issue2494: output of darcs record with file arguments (Ben Franksen) Thanks! Guillaume

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