- Haskell-Cafe - Haskell.org

cabal problem with Digits
by Roelof Wobben 22 May '15

22 May '15

Hello, When I want to install digits I see this output: cabal install digits Resolving dependencies.. [1 of 1] Compiling Main ( /tmp/digits-0.2-415/digits-0.2/Setup.lhs, /tmp/digits-0.2-415/digits-0.2/dist/setup/Main.o ) /tmp/digits-0.2-415/digits-0.2/Setup.lhs:3:3: Warning: Module ‘System.Cmd’ is deprecated: Use "System.Process" instead /tmp/digits-0.2-415/digits-0.2/Setup.lhs:5:49: Warning: In the use of ‘runTests’ (imported from Distribution.Simple, but defined in Distribution.Simple.UserHooks): Deprecated: "Please use the new testing interface instead!" Linking /tmp/digits-0.2-415/digits-0.2/dist/setup/setup ... Warning: digits.cabal: A package using 'cabal-version: >=1.2' must use section syntax. See the Cabal user guide for details. Configuring digits-0.2... Building digits-0.2... Preprocessing library digits-0.2... [1 of 1] Compiling Data.Digits ( src/Data/Digits.hs, dist/build/Data/Digits.o ) ****/usr/bin/ld: cannot find -lHSQuickCheck-2.8.1-ghc7.8.3 /usr/bin/ld: cannot find -lHStf-random-0.5-ghc7.8.3 /usr/bin/ld: cannot find -lHSprimitive-0.6-ghc7.8.3 /usr/bin/ld: cannot find -lHSrandom-1.1-ghc7.8.3**** How to soilve this one ? Roelof --- Dit e-mailbericht is gecontroleerd op virussen met Avast antivirussoftware. http://www.avast.com

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Haskell Weekly News: Issue 322
by Semen Trygubenko / Семен Тригубен ко 22 May '15

22 May '15

New Releases 99 Haskell: A web service by Bram Hoskin Solve live Haskell coding problems based on H-99 in the browser to strengthen your understanding of the language. http://www.99haskell.org/ https://github.com/bramgg/99haskell/ Magic Cookies A commercial Android game is released that is written in Haskell using SDL2 for multimedia and the Arrowized Functional Reactive Programming DSL Yampa. The authors had to "escape their functional comfort zones and come up with smarter abstractions that mutable reality and performance demand". The game consists of 2K lines of code, of which 1K is game specific and 400 are Yampa code. The most complex parts were certain Yampa constructs (arrow-based, with lots of tupling/untupling). http://keera.co.uk/blog/2015/03/19/magic-cookies-released-google-play/ https://play.google.com/store/apps/details?id=uk.co.keera.games.magiccookies https://github.com/keera-studios/keera-hails https://github.com/ivanperez-keera/Yampa Discussion Finding a GHC bug by Neil Mitchell A write up of the hunt for bug #10176 http://neilmitchell.blogspot.it/2015/03/finding-ghc-bug.html https://ghc.haskell.org/trac/ghc/ticket/10176 What are your most persuasive examples of using Quickcheck? Quickcheck helped many people in a number of areas — compiler optimisations, date/time validation, regular expressions, encoding/decoding, topological sort, fuzzing HTTP APIs and even exhibiting classical voting paradox! Apart from the obvious benefit of helping to find big juicy bugs as well as valid but potentially harmless tiny bugs in edge cases that no-one cares about, Quickcheck can help attain enlightenment in the sense that spelling out Quickcheck properties in itself can be rewarding because this can reveal assumptions that have been made without realizing it. Roman Cheplyaka reminds us about SmallCheck and that it should be used instead of Quickcheck when one has a good idea about what depth is needed and when exhaustive search at that depth is affordable. https://www.reddit.com/r/haskell/comments/308ps6/what_are_your_most_persuas… http://stackoverflow.com/questions/20092191/how-much-should-one-control-the… What is the difference between free monads and free monoids? A comment by Edward Kmett. https://www.reddit.com/r/haskell/comments/2znhjk/what_is_the_difference_bet… Type-Checked Pseudo-Code Tom Ashworth argues that Haskell is an excellent tool for fleshing out ideas and prototyping solutions, and that it makes one generalize and shake out many conceptual bugs before concepts become code. https://phuu.net/2015/03/24/type-checked-pseudo-code.html Where does GHC spend most of it's time during compilation? Optimisation and codegen, it seems. Also, GHC compilation times went up substantially from version 7.6 to 7.8. https://www.reddit.com/r/haskell/comments/309430/where_does_ghc_spend_most_… Quotes of the Week "Haskell doesn't feel like code. It feels like a language for thinking in: it's expressive, terse and simple, especially as type-checked pseudo-code." (Tom Ashworth) https://phuu.net/2015/03/24/type-checked-pseudo-code.html "Well that's not in the spec. If you want to change the requirements you have to renegotiate the contract =P" (sccrstud92) https://www.reddit.com/r/haskell/comments/2zxekg/while_learning_haskell_i_m… "Unit tests are double entry bookkeeping" (EvanDaniel) https://www.reddit.com/r/haskell/comments/308ps6/what_are_your_most_persuas… augustss> "Well, type checking is worst case exponential…" barsoap> "Yep. That's also the reason why I don't really get the insistence of dependently-typed languages to have to be total at the type level: I don't care whether type-checking takes ten or infinitely many years, both figures are too large." https://www.reddit.com/r/haskell/comments/309430/where_does_ghc_spend_most_… "Our prophet Djistra said that a testing shows the presence, not the absence of bugs … <snip> … Today Djistra would have been stoned under a myriad of inutile unit tests that people perform for a sense of false security, in a sort of superstitious sacrificial ritual, a waste of time to convince himself and others that his software is right." (agocorona) https://www.reddit.com/r/haskell/comments/308ps6/what_are_your_most_persuas… "You might also consider these sorts of infelicities as teachable moments" (ericpashman) https://www.reddit.com/r/haskell/comments/2zxekg/while_learning_haskell_i_m… "Nice gradual progression there. Big O notion, smoothly divided into 3 easy parts, then bam, Coyoneda. =) I approve. [Yes, I realize it is a bag of topics, not a course outline, but it still grabbed me.]" (edwardkmett) https://www.reddit.com/r/haskell/comments/2zqyes/we_released_a_video_librar…

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23% of calls to map fuse away
by Joachim Breitner 22 May '15

22 May '15

Hi, I just compiled all¹ of Stackage LTS 2.9 with GHC 7.8.4 with -ddump-rule-firings, and counted the occurrences of the rules. Here is a fun fact: 23% of all (static) occurrences of "map" fuse away². And 50387 lists are fused away in total³ Full data at https://gist.github.com/nomeata/071c1f87450cf668bbeb Greetings, Joachim ¹ but the SDL2 bindings ² 16925 × rule map 12904 × rule mapList, which fires if no fusion happened. ³ 27846 × rule fold/build 11293 × rule foldr/single 11248 × rule augment/build -- Joachim “nomeata” Breitner mail(a)joachim-breitner.de • http://www.joachim-breitner.de/ Jabber: nomeata(a)joachim-breitner.de • GPG-Key: 0xF0FBF51F Debian Developer: nomeata(a)debian.org

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I'm reading #OutOfTheTarPit does ghc have a relational model built in for state?
by KC 21 May '15

21 May '15

I'm reading #OutOfTheTarPit does ghc have a relational model built in for state? "Out of the Tar Pit" talks about FRP - Functional Relational Programming -- -- Sent from an expensive device which will be obsolete in a few months! :D Casey

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Library design around FFI library
by Marco Zocca 21 May '15

21 May '15

I'm implementing the low-level interface to a large C library (using c2hs). The C functions can be broadly classified by: *) the main datastructure they operate on, e.g. returnType AFunction (A* a, ...); *) creation, modification, read access, destruction operations for each of these datastructures, following a common pattern: ACreate(), ASet1(), ASet2(), .., ARead(), ADestroy(), BCreate(), etc. The library rests on top of MPI, so there are e.g. AScatterBegin(), AScatterEnd() function pairs that account for potentially large delays associated with computing and moving data around. On the Haskell side, the C pointer types are represented as e.g. data Ah = Ah (Ptr Ah) deriving instance Storable Ah and e.g. a Create function returns the representation of the fresh pointer along with the usual integer error code: ahCreate :: MPIComm -> IO (Ah, Err) What abstraction may I use to capture logic such as: *) separate read-only functions from the potentially overwriting ones *) guarantee precedence relations (e.g. computation can only occur after initialization) *) collect or even compose error codes, letting computation go through iff Err==0 (e.g. a n-ary Maybe ?) Sequencing in the IO monad causes all effectful functions to run and return their result and/or error code. All feedback is welcome; Thank you in advance

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NoOO languages
by Harry . 21 May '15

21 May '15

Could we mimic the marketing success of NoSQL databases by branding functional languages as NoOO (or even NoIO)?

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[ANN] codex 0.3
by Alois Cochard 20 May '15

20 May '15

Hello Café, I have released a new version of `codex`[1] (a ctags file generator for cabal project and their dependencies). It should be noted that *this version now fully support the windows operating system*, thanks to a great contribution from Ben James. This new version include: - Tagging of the current project can be turned-off - Fix/Enhance the `emacs` and `sublime` default format - Tags file name is now configurable - Replace `curl` with `wrep` - Misc fixes and portability enhancement Thanks to the contributors (Ben James, Tal Walter, Eyal Lotem). [1] https://github.com/aloiscochard/codex -- *Λ\ois* http://twitter.com/aloiscochard http://github.com/aloiscochard

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glfw demos ?
by briand＠aracnet.com 20 May '15

20 May '15

Hi, Looks like the demos, including the one on the wiki page, and the glfw-b-demo package, are suffering from bit-rot. I was hoping somebody could point me to a small get-started demo. Meanwhile I am working on trying to get the wiki demo running. Thanks, Brian

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text-icu (and FFI in general) on Windows 64 bits
by Yitzchak Gale 20 May '15

20 May '15

I was finally successful in getting text-icu to work on Windows 64 bits. This is probably an indication of what to expect in general for packages requiring FFI on Windows 64 bits. In the past, on 32 bits, the standard Windows binary distribution from the ICU site could be used together with msys/mingw, even though it was officially only for MSVC. This no longer seems to be the case for 64 bits. When I build text-icu in that way with a 64 bit GHC and the Windows 64-bit binary ICU distribution for MSVC, the resulting EXEs segfault as soon as any function from text-icu is called. There is no official ICU download for mingw-w64 binaries. But happily, the MSYS2 project does provide a pre-built ICU binary distribution for mingw-w64. It tends to be quite up-to-date; the current version is ICU 55.1. Note, however, that I was *not* able to use the partial MSYS2 that comes with MinGHC, because pacman seems to be missing. So the solution is: 1. Download and install 64-bit MSYS2, following the instructions on the site: http://msys2.github.io 2. In the MSYS2 shell window, get the ICU package for mingw-w64: pacman -S mingw64/mingw-w64-x86_64-icu 3. Now you can build the Haskell text-icu library using this command: cabal install --extra-lib-dirs="c:\path\to\msys64\mingw64\lib" --extra-include-dirs="c:\path\to\msys64\mingw64\include" text-icu 4. Provide the following DLLs with your EXE that uses text-icu: libicudt55.dll libicuin55.dll libicuuc55.dll libgcc_s_seh-1.dll libstdc++-6.dll Get them from: c:\path\to\msys64\mingw64\bin This not only compiles, but EXEs produced using this library actually run without segfaulting. You can even compile native Windows EXEs from C using ICU this way, with the gcc that is put on your path by the Haskell Platform installer (and probably also MinGHC, but I didn't try that). Just include -L and -I options to gcc with the same paths as above, and make sure to specify -licuuc -licudt etc. as needed. -Yitz

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Automated Differentiation of Matrices (again)
by Florian Hofmann 20 May '15

20 May '15

In [1](this) email thread Edward Kmett and Dominic Steinitz discuss the state of interoperability of `ad` and `hmatric` (or `repa`) with Edward hinting that the 4.0 line of `ad` might improve on the situation. Could someone elaborate on the state of affairs two years later? Florian [1]: https://mail.haskell.org/pipermail/haskell-cafe/2013-April/107561.html

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