- Haskell-Cafe - Haskell.org

Cabal builds file at top level incorrectly
by Tom Ellis 10 Dec '14

10 Dec '14

Cabal's behaviour is strange to me. My example cabal file is as follows: name: break version: 0.1 cabal-version: >= 1.2 build-type: Simple library hs-source-dirs: src build-depends: base >= 4 && < 5 exposed-modules: Break and I have a module `src/Break.hs` that I want it to compile. That would work fine. But if I have another file at the top-level caled `Break.hs` it compiles that one instead. It also seems to want it to be an executable. What's going on? Full reproduction below. You can see it is trying to compile `Break.hs` not `src/Break.hs`. % git clone https://github.com/tomjaguarpaw/break.git Cloning into 'break'... [...] % cd break % cabal configure && cabal test Resolving dependencies... Configuring break-0.1... Re-configuring with test suites enabled. If this fails, please run configure manually. Resolving dependencies... Configuring break-0.1... Building break-0.1... Preprocessing library break-0.1... [1 of 1] Compiling Main ( Break.hs, dist/build/Main.o ) Break.hs:1:1: The function `main' is not defined in module `main:Main'

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Why doesn't text-icu work on 64 bit Windows?
by Yitzchak Gale 10 Dec '14

10 Dec '14

The text-icu library works fine with a 32 bit build of GHC on Windows. But with a 64 bit build of GHC, any use of a function from this library causes a segfault. See the issue on github for simple instructions for how to reproduce the problem: https://github.com/bos/text-icu/issues/12 As far as we know now, this could be caused by any of the following: 1. Some difference in the way ICU builds their DLLs for 64 bit Windows. 2. Some difference in the FFI bindings that is needed specifically for 64 bit Windows. 3. A problem with GHC's linking on 64 bit Windows. 4. A problem with Cabal, e.g., some option or flag that needs to be passed by default on 64 bit Windows. This is an important (and extremely high quality, thanks to Bryan O'Sullivan) library for the community, and very important for us, so I'm posting about the issue here to raise visibility. Any ideas about possible approaches to investigate or eliminate any of the above possibilities would be highly appreciated. Thanks, Yitz

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[ANN] servant 0.2 - trying to rethink webservices and APIs
by Alp Mestanogullari 10 Dec '14

10 Dec '14

Hello -cafe, These past few weeks, with Sönke Hahn and Julian Arni, we've been working on a complete rewrite of servant, a library whose aim is to assist as much as possible in writing webservices. We came up with a (type-level) "API combinator" based design, that lets us declare webservice APIs, implement handlers that serve those APIs, derive client functions in Haskell and Javascript to query those endpoints and generate documentation. This is all very composable, you can write your own combinators or write your own interpretation of an API's type, or just use the "standard" ones already provided by the core library. Here's an announcement post with an example: http://alpmestan.com/posts/2014-12-09-rethinking-webservices-apis-haskell.h… Getting started guide: http://haskell-servant.github.io/getting-started/ The reddit discussion (in case you prefer reddit to here for such discussions): http://www.reddit.com/r/haskell/comments/2orb8t/rethinking_webservice_and_a… All 4 libraries are installable with a simple 'cabal install', have a decent amount of documentation and accompanying examples. We would be glad to hear any kind of feedback or ideas -- we're already deploying servant webservices in our respective companies so it suits our use cases, but we would gladly discuss new combinators and what not. -- Alp Mestanogullari

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Cabal 1.8 ignores bounds in test-suite sections?
by Tom Ellis 09 Dec '14

09 Dec '14

I have a cabal file with two test suites https://github.com/tomjaguarpaw/haskell-opaleye/blob/master/opaleye.cabal If I change the dependency in "test-suite tutorial", say, from `profunctors` to `profunctors >= 0.6` then the bound is completely ignored and cabal will attempt to compile and run the test suite even without a suitable version present. Is this expected behaviour? Tom

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Typed communications in (Safe) Haskell
by Giacomo Tesio 09 Dec '14

09 Dec '14

Hi, I'm Giacomo and I'm new to this list. I'm looking for advices to develop an haskell p2p system where the nodes comunicate over an untrusted channel (the internet). I'd like to use TLS to authenticate each node with each other. I'm wondering if exists any library/framework that already suits my needs: 1. Enable typed communications (make it easy to go from ByteString to our ADT for messages) 2. Support TLS 3. Is written in plain (possibly Safe) Haskell, because I plan to make it runnable on HaLVM/HaLNS (in the long run) 4. Acceptably easy to use since most of nodes will simply receive messages, run a simple (often pure) function on them and return a response to the caller I've seen a lot of interesting libraries on hackage (courier, daemons and more...) but AFAIK none support TLS. Any suggestion? Thanks, Giacomo

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External representation of GHC bytecode
by Sean Seefried 09 Dec '14

09 Dec '14

Friends, I'd like to ask a possible quite ignorant question. Can GHC produce an external representation of GHC byte code, and load that byte code back up? If it's just an internal representation is there any good reason for this? It seems to me that this would be useful for at least a few reasons: 1. This could solve the Template Haskell on cross compiler's dilemma. Currently, the problem is that a cross compiler will produce object code for the target machine which cannot be run on the host machine. But if this were bytecode the problem would be trivial to solve. 2. You could transmit Haskell programs over the network to run on arbitrary machines. 3. As it stands GHC sometimes has long standing bugs where it produces incorrect machine code on some architectures for various (fairly boring) reasons. Interpreting bytecode might be less efficient but would at least ensure that you could, in principle, run GHC on a variety of different platforms until these bugs are finally squashed. Sean

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Music made with Haskell
by Anton Kholomiov 08 Dec '14

08 Dec '14

I wrote two tracks completely with Haskell. You can listen to them on the soundcloud: https://soundcloud.com/anton-kho/celtic https://soundcloud.com/anton-kho/invisible-ocean The music is based on samples but a single track uses no more than 6 samples. The code is under 100 lines of code. I'm using my libs csound-sampler and csound-expression. You can check out the source code at: http://ge.tt/3MjwF852/v/0 Please turn off the AdBlock for this page to download the code. Happy haskelling! Anton

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New Functional Programming Job Opportunities
by Functional Jobs 08 Dec '14

08 Dec '14

Here are some functional programming job opportunities that were posted recently: Senior Software Engineer at McGraw-Hill Education http://functionaljobs.com/jobs/8771-senior-software-engineer-at-mcgraw-hill… Cheers, Sean Murphy FunctionalJobs.com

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[Haskell] ANNOUNCE: Applied Functional Programming (AFP) Summerschool 6-17 July 2015, Utrecht, Netherlands
by Atze Dijkstra 08 Dec '14

08 Dec '14

=========== AFP Summerschool 2015 =========== Applied Functional Programming (AFP) Summerschool July 6-17, 2015 Utrecht University, Department of Information and Computing Sciences Utrecht, The Netherlands Summerschool & registration website: http://www.utrechtsummerschool.nl/courses/science/applied-functional-progra… AFP website : http://www.cs.uu.nl/wiki/USCS contact : Uscs-afp(a)lists.science.uu.nl *** The 2015 edition of the Applied Functional Programming (AFP) Summerschool in Utrecht, Netherlands will be held from 6-17 July 2015. The summerschool teaches Haskell on both beginners and advanced levels via lectures and lab exercises. More info can be found via the references above, included here is a summary from the summerschool info: ``Typed functional programming in Haskell allows for the development of compact programs in minimal time and with maximal guarantees about robustness and correctness. The course introduces Haskell as well as its theoretical underpinnings such as typed lambda calculus, and Damas-Milner type inference. There is ample opportunity to put this all in practice during lab sessions. Typed functional programming languages allow for the development of robust, concise programs in a short amount of time. The key advantages are higher-order functions as an abstraction mechanism, and an advanced type system for safety and reusability. This course introduces Haskell, a state-of-the-art functional programming language, together with some of its theoretical background, such as typed lambda calculi, referential transparency, Damas-Milner type inference, type level programming, and functional design patterns. We will combine this with applications of functional programming, concentrating on topics such as language processing, building graphical user interfaces, networking, databases, and programming for the web. The goal of the course is not just to teach the programming language and underlying theory, but also to learn about the Haskell community and to get hands-on experience by doing lab exercises or a Haskell project of your own.'' *** This year is somewhat special in that the Tour de France starts in Utrecht the weekend before the start of the summerschool. It is an opportunity for enjoying the related festivities. It also implies that housing may be more difficult the weekend before the summerschool, something to keep in mind when you wait with registration until the latest. regards, - Atze - Atze Dijkstra, Department of Information and Computing Sciences. /|\ Utrecht University, PO Box 80089, 3508 TB Utrecht, Netherlands. / | \ Tel.: +31-30-2534118/1454 | WWW : http://www.cs.uu.nl/~atze . /--| \ Fax : +31-30-2513971 .... | Email: atze(a)uu.nl ............... / |___\ _______________________________________________ Haskell mailing list Haskell(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell

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Announce: Leksah 0.14.3
by Hamish Mackenzie 08 Dec '14

08 Dec '14

Download it here https://github.com/leksah/leksah/wiki/download If you have not tried Leksah recently here are some things that are new(ish). If you have GHCJS installed you can build and run your applications in Leksah's output pane. https://www.youtube.com/watch?v=zQnExdDL63c There is also a WebKit "Web Inspect" pane built in (Right click in the Output pane and select Inspect Element). Windows and OS X binaries now use Gtk 3.14. Windows installer includes all the Gtk+-3.0 files you need to build Gtk2Hs applications (including Leksah).

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