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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 Submission We welcome submission of papers presenting original unpublished work which is not been submitted for publication elsewhere.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 29 Aug '17

29 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 28 Aug '17

28 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 28 Aug '17

28 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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undefined reference to '__gxx_personality_v0'
by Henning Thielemann 28 Aug '17

28 Aug '17

I have trouble to compile my llvm-ffi package containing C++ binding code. I am on Ubuntu 16.04 and I have created a custom llvm.pc file: $ cat /usr/local/lib/pkgconfig/llvm-3.8.pc Name: LLVM Description: Low-level Virtual Machine compiler framework Version: 3.8.0 URL: http://www.llvm.org/ Requires: Conflicts: Libs: -L/usr/lib/llvm-3.8/lib -lLLVM-3.8.0 Cflags: -I/usr/lib/llvm-3.8/include -std=c++0x -std=c++11 /tmp$ cabal unpack llvm-ffi Unpacking to llvm-ffi-3.8.1/ /tmp$ cd llvm-ffi-3.8.1/ /tmp/llvm-ffi-3.8.1$ cabal configure -fbuildExamples --with-ghc=ghc-8.2.1 Resolving dependencies... Configuring llvm-ffi-3.8.1... /tmp/llvm-ffi-3.8.1$ cabal build Preprocessing library for llvm-ffi-3.8.1.. cc1: warning: command line option ‘-std=c++11’ is valid for C++/ObjC++ but not for C cc1: warning: command line option ‘-std=c++11’ is valid for C++/ObjC++ but not for C cc1: warning: command line option ‘-std=c++11’ is valid for C++/ObjC++ but not for C cc1: warning: command line option ‘-std=c++11’ is valid for C++/ObjC++ but not for C cc1: warning: command line option ‘-std=c++11’ is valid for C++/ObjC++ but not for C cc1: warning: command line option ‘-std=c++11’ is valid for C++/ObjC++ but not for C cc1: warning: command line option ‘-std=c++11’ is valid for C++/ObjC++ but not for C cc1: warning: command line option ‘-std=c++11’ is valid for C++/ObjC++ but not for C Building library for llvm-ffi-3.8.1.. [ 1 of 22] Compiling LLVM.FFI.Core ( dist/build/LLVM/FFI/Core.hs, dist/build/LLVM/FFI/Core.o ) [ 2 of 22] Compiling LLVM.FFI.BitWriter ( src/LLVM/FFI/BitWriter.hs, dist/build/LLVM/FFI/BitWriter.o ) [ 3 of 22] Compiling LLVM.FFI.BitReader ( src/LLVM/FFI/BitReader.hs, dist/build/LLVM/FFI/BitReader.o ) [ 4 of 22] Compiling LLVM.FFI.Analysis ( src/LLVM/FFI/Analysis.hs, dist/build/LLVM/FFI/Analysis.o ) ... Preprocessing executable 'llvm-ffi-example' for llvm-ffi-3.8.1.. Building executable 'llvm-ffi-example' for llvm-ffi-3.8.1.. [1 of 1] Compiling Main ( example/JIT.hs, dist/build/llvm-ffi-example/llvm-ffi-example-tmp/Main.o ) Linking dist/build/llvm-ffi-example/llvm-ffi-example ... /tmp/llvm-ffi-3.8.1/dist/build/libHSllvm-ffi-3.8.1-KKUvbYcVYVe5ZjJKumuzkS.a(support.o):support.cpp:function LLVMGetHostFeatures: error: undefined reference to 'operator new(unsigned long)' /tmp/llvm-ffi-3.8.1/dist/build/libHSllvm-ffi-3.8.1-KKUvbYcVYVe5ZjJKumuzkS.a(support.o):support.cpp:function LLVMGetHostFeatures: error: undefined reference to 'operator delete(void*)' /tmp/llvm-ffi-3.8.1/dist/build/libHSllvm-ffi-3.8.1-KKUvbYcVYVe5ZjJKumuzkS.a(support.o):support.cpp:function LLVMCheckFeature(llvm::StringMap<bool, llvm::MallocAllocator>*, llvm::StringMapConstIterator<bool>*): error: undefined reference to 'operator delete(void*)' /tmp/llvm-ffi-3.8.1/dist/build/libHSllvm-ffi-3.8.1-KKUvbYcVYVe5ZjJKumuzkS.a(support.o):support.cpp:function LLVMGetFirstFeature: error: undefined reference to 'operator new(unsigned long)' /tmp/llvm-ffi-3.8.1/dist/build/libHSllvm-ffi-3.8.1-KKUvbYcVYVe5ZjJKumuzkS.a(support.o):support.cpp:function LLVMCreateExecutionEngineKindForModuleCPU: error: undefined reference to 'operator delete(void*)' /tmp/llvm-ffi-3.8.1/dist/build/libHSllvm-ffi-3.8.1-KKUvbYcVYVe5ZjJKumuzkS.a(support.o):support.cpp:function LLVMCreateExecutionEngineKindForModuleCPU: error: undefined reference to 'std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::_M_replace(unsigned long, unsigned long, char const*, unsigned long)' /tmp/llvm-ffi-3.8.1/dist/build/libHSllvm-ffi-3.8.1-KKUvbYcVYVe5ZjJKumuzkS.a(support.o):support.cpp:function LLVMCreateExecutionEngineKindForModuleCPU: error: undefined reference to 'operator delete(void*)' /tmp/llvm-ffi-3.8.1/dist/build/libHSllvm-ffi-3.8.1-KKUvbYcVYVe5ZjJKumuzkS.a(support.o):support.cpp:DW.ref.__gxx_personality_v0: error: undefined reference to '__gxx_personality_v0' collect2: error: ld returned 1 exit status `gcc' failed in phase `Linker'. (Exit code: 1) StackOverflow discussions on those linker errors suggest that it is important to link with g++, not gcc. Can I control how GHC links? How do other packages cope with C++ code? It seems that they most oftenly come with custom Setup modules that cause trouble with different Cabal versions. I hoped that I can prevent those difficulties using pkg-config. Unfortunately, pkg-config seems to be limited to C libraries. Thus the warnings about the -std=c++11 option in the beginning. Maybe it is cleaner to write a separate LLVM C package that interfaces to the C++ code and bind Haskell to C via pkg-config. However, it would mean that I have to maintain a C library for Linux, Mac and Windows with autoconf et.al.

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how would I do this properly in Haskell?
by Dennis Raddle 25 Aug '17

25 Aug '17

I have a problem which I can solve with OO organization, but I want to know how to do it properly in Haskell. I have a search optimization problem in which there are a lot of individual fitness functions which combine scores to give an overall fitness level. Each fitness function will be associated with data, both initial data to configure it, and a cache that it maintains. So I could have something like this: data Fitness = Fit1 SomeData1 | Fit2 SomeData2 | Fit3 SomeData3 -- this function would evaluate the fitness of a particular -- result of type 'S' (in my case, a partially-constructed -- musical composition) evaluate :: Fitness -> S -> (Fitness,Double) -- something like this would have to be written for -- every sub-type of "Fitness" evaluate (Fit1 d) s = (Fit1 d',v) where (d',v) = evaluate1 d s evaluate1 :: SomeData1 -> S -> (SomeData1,Double) Is there a better way to do this? D

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