- Haskell-Cafe - Haskell.org

ANNOUNCE: fgl-5.5.0.0
by Ivan Lazar Miljenovic 27 Apr '14

27 Apr '14

I'm pleased to announce a new version of the functional graph library: http://hackage.haskell.org/package/fgl-5.5.0.0 The main change in this version: proper Show, Read and Eq instances for both graph implementations. Previously, Data.Graph.Inductive.Tree had a pretty-printed Show output; now both it and PatriciaTree have Show and Read instances via the mkGraph function, and Eq via deriving (I'm not sure how well this will work because as I write this I realise it may not deal with multiple edges that well... I guess I'll be doing an updated version tomorrow after getting some sleep ;p). The previous Show behaviour of Tree is now available as a pretty-printing function for all DynGraph instances. The PatriciaTree implementation is now exported and used by default, because as far as I'm aware it will always perform better. Finally, the Data.Graph.Inductive.Graphviz module has been removed; if you want to visualise your fgl graph, please see my graphviz package on Hackage (cheap plug? moi?). -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com http://IvanMiljenovic.wordpress.com

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Packing Haskell values into a C array
by Michael Baker 27 Apr '14

27 Apr '14

I'm working on a game in Haskell and I'm at a point where I have to do some optimization so I'm looking for advice or resources from people who may have already solved my problem. Specifically, I have a grid of 10,000 circles and I need to get them rendered. This involves translating the 10,000 circles into a single C array (of CFloats in my case) so that I can ship that array off to OpenGL for rendering. This is something I can't change, that's just the way OpenGL works. What I can change is the way I create and maintain the array. Currently I'm doing the most naive thing I can, which is to convert the list of circles into a list of floats, and then convert that list into a C array every frame. This is obviously very expensive. I've thought of several things to try including: * Only allocate an array when the number of circles changes. * Convert a circles into a C struct and "poke" them directly into an existing array instead of going through the intermediate form of a list. * Do some manual memory management and index each circle into a preallocated array, only updating the values of the array that correspond to circles which have changed. I'm wondering if there are already common solutions to this sort of problem (packing a lot of Haskell values that might change each frame into an array efficiently). Any resources that are tangential to this sort of thing would also be nice. For instance, how I can use the type system to ensure that the resulting array has the shape I want.

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[ANN] codex - generate tags file from dependencies
by Alois Cochard 27 Apr '14

27 Apr '14

Hi, Just to let you know that I released a tool which allow to generate a tags[1] file for a given cabal project using the sources of all the dependencies of that project. `cabal install codex` You can simply run `codex update` in one of your cabal project directory and you'll get a 'codex.tags' file to feed in your favorite text editors. It store the source code in the hackage local cache, and it store there as well the tags file per module (so the tool just aggregate per project). I hope it will be useful to other hackers, it's a joy for me in vim when using unknown libraries. Note: This tool actually use `ctags` but that could be easily made configurable if someone need it, integrating native haskell tagger is an option too. I personally like using ctags, it's very fast. *[1]Those tags file basically contain references to functions/types definition in source code and allow "jump to definition" like functionality in text editors.* source: http://github.com/aloiscochard/codex hackage: http://hackage.haskell.org/package/codex -- *Alois Cochard* http://twitter.com/aloiscochard

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Building foreign shared libraries with Cabal
by Nikolay Amiantov 26 Apr '14

26 Apr '14

Hello, I want to use cabal to build and install shared library, which will be called from C. I've already found necessary combination of flags and options to successfully build it, but now I have two main issues: 1) The library is installed into "bin". 2) The generated "stub" C headers are not installed at all. How can I resolve this? My current options is as follows: executable libtest.so hs-source-dirs: src main-is: Test.hs default-language: Haskell2010 default-extensions: ForeignFunctionInterface build-depends: base >= 4.7 c-sources: cbits/library_init.c ghc-options: -no-hs-main -shared -dynamic cc-options: -DMODULE=Test -fPIC Thanks for any help and have a nice day, Nikolay.

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Job: Automatic Exploit Generation developer
by David Brumley 26 Apr '14

26 Apr '14

Hi, ForAllSecure is a small startup bent on checking the world's software for exploitable bugs. We have two open positions, posted at http://jobs.forallsecure.com/ 1) Performing program analysis on binary (x86) code. Our current code base is in OCaml. The product automatically finds vulnerabilities, and generate exploits to prove which ones are exploitable. 2) Automatically harden binary (x86) code against vulnerabilities. As a side project, we've ran our tools on 33,000 Debian programs, and found about 11,000 new unique crashing bugs (150 give us a shell). Please consider applying if this sounds exciting. http://jobs.forallsecure.com/ Take care, -David PS. ForAllSecure is a Carnegie Mellon University spinoff. The job is in Pittsburgh, but we will also consider highly qualified remote candidates.

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How to extract current bindings from GHCi ?
by ducis 26 Apr '14

26 Apr '14

Currently I need to manually find the last binding of a value if I want to copy-paste it into an editor. With ':show bindings' I get the result of computation. Say, if I had input 'let a = 1' and 'let b = a+2' I would only get either 'b = _' or 'b = 3' with ':show bindings', while I actually need 'b = a+2'. Are there any externel tools that can help? At 2014-04-26 20:00:04,haskell-cafe-request@haskell.org wrote: >Send Haskell-Cafe mailing list submissions to > haskell-cafe(a)haskell.org > >To subscribe or unsubscribe via the World Wide Web, visit > http://www.haskell.org/mailman/listinfo/haskell-cafe >or, via email, send a message with subject or body 'help' to > haskell-cafe-request(a)haskell.org > >You can reach the person managing the list at > haskell-cafe-owner(a)haskell.org > >When replying, please edit your Subject line so it is more specific >than "Re: Contents of Haskell-Cafe digest..." > > >Today's Topics: > > 1. Re: Unicode Haskell source -- Yippie! (Chris Warburton) > 2. Re: Unicode Haskell source -- Yippie! (Rustom Mody) > 3. Haddock CSS (Sylvain Henry) > 4. Re: [ANN] codex - generate tags file from dependencies > (Luke Taylor) > 5. Re: Haddock CSS (satvik chauhan) > 6. Re: Haddock CSS (Sylvain Henry) > 7. Re: [ANN] codex - generate tags file from dependencies > (Alois Cochard) > 8. Re: [ANN] codex - generate tags file from dependencies > (Alois Cochard) > 9. ANN: Cryptol, a DSL for cryptography (Iavor Diatchki) > > >---------------------------------------------------------------------- > >Message: 1 >Date: Fri, 25 Apr 2014 14:02:38 +0100 >From: Chris Warburton <chriswarbo(a)googlemail.com> >To: Rustom Mody <rustompmody(a)gmail.com> >Cc: Haskell Cafe <haskell-cafe(a)haskell.org> >Subject: Re: [Haskell-cafe] Unicode Haskell source -- Yippie! >Message-ID: <86wqedmuj5.fsf(a)gmail.com> >Content-Type: text/plain > >Rustom Mody <rustompmody(a)gmail.com> writes: > >> As for APL, it failed for various reasons eg >> - mixing up assembly language (straight line code with gotos) with >> functional idioms >> - the character set was a major hurdle in the 60s. Thats not an issue today >> when most OSes/editors are unicode compliant > >I know it's bikeshedding, but I think Agda and Idris are more relevant >to Haskell than APL, since their semantics are closer (and they're both >implemented in Haskell). > >Agda makes extensive (ab)use of Unicode identifiers, >eg. https://github.com/agda/agda-stdlib/blob/master/src/Algebra.agda > >Idris specifically avoids Unicode identifiers, for reasons outlined at >https://github.com/idris-lang/Idris-dev/wiki/Unofficial-FAQ > >Personally I prefer working in Idris to Agda, since the Unicode puts me >off. I usually resort to copy/pasting symbols, which is tedious compared >to typing names. > >Cheers, >Chris > > >------------------------------ > >Message: 2 >Date: Fri, 25 Apr 2014 19:00:34 +0530 >From: Rustom Mody <rustompmody(a)gmail.com> >To: Chris Warburton <chriswarbo(a)googlemail.com> >Cc: Haskell Cafe <haskell-cafe(a)haskell.org> >Subject: Re: [Haskell-cafe] Unicode Haskell source -- Yippie! >Message-ID: > <CAJ%2BTeocfycOCW7BOymd%2B%3DO5qCgeOx_iX2Wgz6wB5k_vGapKEuQ(a)mail.gmail.com> >Content-Type: text/plain; charset="utf-8" > >On Fri, Apr 25, 2014 at 6:32 PM, Chris Warburton ><chriswarbo(a)googlemail.com>wrote: > >> Rustom Mody <rustompmody(a)gmail.com> writes: >> >> > As for APL, it failed for various reasons eg >> > - mixing up assembly language (straight line code with gotos) with >> > functional idioms >> > - the character set was a major hurdle in the 60s. Thats not an issue >> today >> > when most OSes/editors are unicode compliant >> >> I know it's bikeshedding, but I think Agda and Idris are more relevant >> to Haskell than APL, since their semantics are closer (and they're both >> implemented in Haskell). >> >> Agda makes extensive (ab)use of Unicode identifiers, >> eg. https://github.com/agda/agda-stdlib/blob/master/src/Algebra.agda >> >> Idris specifically avoids Unicode identifiers, for reasons outlined at >> https://github.com/idris-lang/Idris-dev/wiki/Unofficial-FAQ >> >> Personally I prefer working in Idris to Agda, since the Unicode puts me >> off. I usually resort to copy/pasting symbols, which is tedious compared >> to typing names. >> >> Cheers, >> Chris >> > >Thanks Chris for that evaluation. Not bike-shedding as far as I can see. > >Yes input-ing things by some GUI-picker or copy-pasting etc would quickly >become a major pain. >I believe that there are roughly these 5 levels to this with >per-char cost decreasing and fixed cost increasing as we go down > >1. GUI-picker (IBUS etc) copy-pasting from the web etc -- ok for arm-chair >discussions; ridiculous for serious development >2. Editor based input methods eg tex input-method in emacs >3. Window-system (X/MS etc) input methods >4. OS-based input methods >5. Special purpose hardware-keyboards > >I believe 3 makes for a particularly good fixed/variable cost balance point > >eg in X-windows if you run this command >$ setxkbmap -layout "us,gr" -option "grp:switch" >then typing >abcdefg >with right-alt depressed, gives: >??????? > >For those who prefer a more moded approach (vi-users?) here is >$ setxkbmap -option "grp:switch,grp:alt_shift_toggle,grp_led:scroll" >-layout "us,gr" > >This makes the Shift-Alt chord switch in and out (ie toggle) greek keyboard >with the scroll-lock light as indicator > >All this is clearly just an analogy; what we need is not a greek keyboard >but a keyboard mapping analogous to gr(eek). Try s/gr/apl in the commands >above for apl which, while distant from haskell gives a taste for what a >*programmer* can use/make. > >regards >Rusi >

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ANN: Cryptol, a DSL for cryptography
by Iavor Diatchki 25 Apr '14

25 Apr '14

Hello, Galois is happy to announce the first open source release of Cryptol! Please visit Cryptol's website for documentation, source code, and information on how to contribute: http://www.cryptol.net/ Cryptol is a domain-specific language for specifying cryptographic algorithms. A Cryptol implementation of an algorithm resembles its mathematical specification more closely than an implementation in a general purpose language. Furthermore, Cryptol shares lots of similarities with Haskell so, hopefully, Haskell programmers should be able to start writing Cryptol programs fairly quickly. Last, but not least, we are always interested in contributors! So, if you think of a cool new feature, or discover an annoying bug, please don't be afraid to have a look at the source code. At present, we think that the easiest way to manage contributions is by using github's fork model, so just sand us a pull request. Also, if you have questions about the source code or the Cryptol language, please feel free to drop me an e-mail or a message on git-hub (I am user "yav"). Happy hacking, -Iavor and the Cryptol team

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Haddock CSS
by Sylvain Henry 25 Apr '14

25 Apr '14

Hi, I have quickly hacked a new CSS for haddock based on ocean.css (see attached file). It has a fixed maximal width and is a little bit lighter. To try it with cabal, use: > cabal haddock --css=ocean2.css [--hyperlink-source] Feel free to improve it, I am not that good at web design. -Sylvain

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Munich Haskell Meeting
by Heinrich Hördegen 25 Apr '14

25 Apr '14

Dear all, next week, our monthly Munich Haskell Meeting is scheduled for the 29th of April, 19h30 Cafe Puck. If you plan to join, please go to http://www.haskell-munich.de/dates and hit the button. Everybody is welcome! Heinrich

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Thoughts on Hakyll vs. Octopress for an experienced Haskeller but HTML newbie
by Joey Eremondi 25 Apr '14

25 Apr '14

Disclaimer: Cross-posted at http://www.reddit.com/r/haskell/comments/23xgzf/thoughts_on_hakyll_vs_octop… I'm starting a personal website/blog, just the typical thing you see a lot of programmers keeping. I'm looking at using Github Pages, but as I don't want to hand-code everything, I'll be using a static site generator. I'm choosing between Hakyll and Octopress, but I wanted to get some opinions before I put in the effort of learning and installing one. I'll start by saying that I'm comfortable with Monads, EDSLs, and Haskell in general. Conversely, I have next to no HTML/CSS skill. What I'm really wondering is, how much hand-HTML does Hakyll require you to do? In particular: 1. Does Hakyll have any support for visual "themes"? If not, are there libraries/examples of visual layouts I could choose from? 2. Does Hakyll integrate well with Github pages? 3. How hard is it to get things like a Facebook like button, twitter sidebar, comments, etc. working in Hakyll? Is there anything equivalent to Octopress's plugins <http://octopress.org/docs/blogging/plugins/>? 4. Octopress advertises itself as dealing well with code snippets. Does Hakyll deal well with code within pages? I realize that many of these things will not be built into Hakyll, so cases where it's not built in but there are lots of easy examples to take from are welcome. Reccomendations of one over the other are welcome, but I'm more looking for feedback and knowledge from people who have used Hakyll (and Octopress, though that's more tangential to this subreddit). Thanks! EDIT: Generalized to "comments" instead of just "disqus comments"

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