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Cabal config file - default install flags?
by Lucas Paul 02 Feb '15

02 Feb '15

I'd like to have cabal automatically use -j8 when I cabal install something. Is there something I can put into the .cabal/config file that will accomplish this? More generally, where can I find documentation on that config file? - Lucas Paul

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Template Haskell attempts to load mingw32.dll during build
by Darren Grant 02 Feb '15

02 Feb '15

Hi all, Windows GHC 7.8.4 build issue here: I've noticed that GHC will attempt to link mingw32 if a related dependency (in my case sdl2) is required in a TH pass. Unsurprisingly, the OS fails to find the imaginary mingw32.dll file. Are there any known resolutions to this quirk? Cheers, Darren

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What could be the possible reason of linking errors on "_info" and "_closure"?
by Magicloud Magiclouds 02 Feb '15

02 Feb '15

Hi, I am making a cabal project including a library and a executable using the library. Building the library is fine. But when linking src/main, I got "undefined reference to someFunction1_info" and "someFunction1_closure". -- 竹密岂妨流水过山高哪阻野云飞 And for G+, please use magiclouds#gmail.com.

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ANNOUNCE: monad-levels
by Ivan Lazar Miljenovic 02 Feb '15

02 Feb '15

I'm pleased to announce the first release of my new monad-levels library (aka Yet Another Monad Transformer Library ;-) http://hackage.haskell.org/package/monad-levels I've written more about the motivations of the library here: https://ivanmiljenovic.wordpress.com/2015/02/02/monadic-yak-shaving/ -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com http://IvanMiljenovic.wordpress.com

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parallelism and purity
by Kazu Yamamoto 02 Feb '15

02 Feb '15

Hi cafe, I received questions about parallelism in Haskell. I'm familiar with concurrency but not with parallelism. So, let me ask: Q1) Are there any *applications* using Haskell parallelism? Q2) What kind of parallelism is used in the application? - Task parallel - Data parallel - Data-flow paralle? - etc Q3) Does Haskell purity contribute for the application in the parallelism point of view? I'm one of the translators of "Parallel and Concurrent Programming in Haskell" into Japanese. So, please don't say read the book. :-) --Kazu

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cpp question
by S. Doaitse Swierstra 01 Feb '15

01 Feb '15

With the new version of GHC (7.8.3) I am running into problems with cpp. The header of one of the files of my uu-parsinglib library reads as follows: {-# LANGUAGE NoMonomorphismRestriction, RankNTypes, FlexibleContexts, CPP #-} #define DEMO(p,i) demo "p" i p #define DEMOG(p,i) demo "p" i (mkP (p)) module Text.ParserCombinators.UU.Demo.MergeAndPermute where ... However when I try to compile this file I get error messages like: Text/ParserCombinators/UU/Demo/Demo.hs:88:17: Not in scope: data constructor ‘DEMOG’ So it seems that the cpp is no longer called at all. Any hints? I am running: MacBook-Doaitse:src doaitse$ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.8.3 MacBook-Doaitse:src doaitse$ gcc --version Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1 Apple LLVM version 6.0 (clang-600.0.56) (based on LLVM 3.5svn) Target: x86_64-apple-darwin14.1.0 Thread model: posix MacBook-Doaitse:src doaitse$ Any help is appreciated, Doaitse Swierstra

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Side conditions on Data.Profunctor.Choice?
by David Turner 31 Jan '15

31 Jan '15

Hi, I was expecting to see coherence conditions for instances of Data.Profunctor.Choice along the lines of: dimap (either (Left . f) Right) id . right' === dimap id (either (Left . f) Right) . right' and similarly for left', but there's nothing like that in the docs. Does anyone know whether (a) those conditions aren't true in general, or (b) they are true but provable from other theorems so not worth mentioning? Many thanks, David

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ANN: processor-creative-kit
by Takenobu Tani 31 Jan '15

31 Jan '15

Dear Haskellers, I am pleased to announce the first release of processor-creative-kit package for playing processors. You can create your processors with your own instruction set. It simulates a simple microprocessor(cpu) with some development tools. https://hackage.haskell.org/package/processor-creative-kit https://github.com/takenobu-hs/processor-creative-kit feature: * easy try, easy modify * a purely functional CPU core (without IO) * including a very simple prototype assembler * including a very simple prototype profiler * including a very simple prototype debugger Thank you, Takenobu

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Using m4 as a preprocessor
by Francesco Ariis 30 Jan '15

30 Jan '15

Hello, today I tried to compile a Haskell program using m4 as preprocessor, with the {-# OPTIONS_GHC -F -pgmF m4 #-} pragma on top of a .hs file. I didn't add anything else, there are no ''' or '`' in the source. Upon compiling, ghc (7.8.3) complains: m4: cannot open `/tmp/ghc10655_0/ghc10655_1.hspp': No such file or directory I searched the net for a solution, but no dice (apparently there are no Haskell programs using -F -pgmF m4?), so I am writing here. Any ideas on what is wrong?

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Creating a list with do notation
by Cody Goodman 30 Jan '15

30 Jan '15

List is a monad, does that mean i can create a list with do notation? My intuition led me to believe this would work: main = do x <- return $ do 1 2 3 print (x :: [Int]) However it didn't. Is this possible?

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