March 2014 - Haskell-Cafe

RFC: GSoC proposal: Improve the Hackage login system
by Chris Wong 21 Mar '14

21 Mar '14

Hello Cafe, Like Matthew and Mateusz, I'm submitting a GSoC proposal as well! The initial draft is here: https://docs.google.com/document/d/1bcDiudULtaz3NFCqTHXD2WU6Ighsm199D7ojfS8… It's not a long read, so please do. Any comments, suggestions, &c would be appreciated greatly. If all is well, I will submit this in 48 hours. As an aside: would anyone like to mentor this project? Again, apologies for the late response. Thanks Chris

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Last call for Google Summer of Code 2014 applications
by Shachaf Ben-Kiki 21 Mar '14

21 Mar '14

Haskell.org is participating in Google Summer of Code again this year, and the student application deadline is nigh. Edward Kmett and I are the administrators this year. The deadline is 2014-03-21 at 19:00 UTC (noon PDT), or roughly 11 hours from now, so make sure to get your applications in before then. For a full timeline see <http://www.google-melange.com/gsoc/events/google/gsoc2014>. If you have any questions, feel free to ask on IRC (#haskell-gsoc on Freenode), or to contact me or Edward directly! Shachaf

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Re: [Haskell-cafe] Regular Expression Simplification
by Niklas Haas 21 Mar '14

21 Mar '14

On Thu, 20 Mar 2014 12:17:58 +0000, "Berg, Matias Juho" <m.berg.10(a)aberdeen.ac.uk> wrote: > ?Hi all, > > I am a final year undergraduate student at a university and I am doing my final honours project on natural language generation from regular expressions. For this to work efficiently I need to simplify the regular expressions before I translate them. It seems that there is some previous work done on this in Haskell but I have only been able to find this code (http://hackage.haskell.org/package/HaLeX-1.1/docs/src/Language-HaLex-RegExp…) which does some elementary simplification. > > Does anyone have any suggestions on where to look for more examples so I can see what kinds of attempts people have used to try and solve this problem? Also if someone has worked on this kind of problem was Kleene algebra a good starting point? > > Best regards, > > Matias My first thought was: Maybe it would be possible to convert the regular expression to something like an NFA, and then use one of the existing known algorithms to generate a minimal NFA from that, and then turn that back into a regular expression somehow? Although I'm slightly worried that the overhead of converting to an NFA is far too great for complicated regular expressions (finite doesn't mean reasonable), and that the conversion from NFA to regular expression will generate very suboptimal regular expressions despite the NFA being minimal. Maybe a similar analog could be used for another type of regular machine? Or a regular grammar, perhaps? Those are also fairly easy to bring into a normalized form and then convert back to a regex.

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GSOC and "scripting the inference process" .Was: Re: Haskell compilation errors break the complexity encapsulation on DSLs
by Alberto G. Corona 20 Mar '14

20 Mar '14

Now that GSOC comes again, I call you into attention one of the biggest problems that Haskell has to solve before being fully accepted in the IT industry: The (unnecessary) complexity of the DSL error messages. There is some work being done: http://dl.acm.org/citation.cfm?id=944707 The idea was to implement it in GHC after refining and testing it if I remember well. If some of this work can be carried out in a GSOC project, IMHO it should be given priority. In case that this work is not going to be available in the short-medium term, there is a ticket with some suggestions that can be carried out in a GSOC project, just in case any of you are interested into mentoring/carrying out this or any other solution to overcome this problem: http://hackage.haskell.org/trac/ghc/ticket/7870 2013-04-27 22:14 GMT+02:00 Ozgur Akgun <ozgurakgun(a)gmail.com>: > Hi, > > On 27 April 2013 10:07, Alberto G. Corona <agocorona(a)gmail.com> wrote: > >> I created a ticket for the feature request: >> >> Ticket #7870 >> >> Teachers, newbies and people working in Industry: Please push it! >> > > A link to the ticket may be helpful for the lazy. > > http://hackage.haskell.org/trac/ghc/ticket/7870 > > I quite like this idea, and I think this is one thing people use TH for > now instead. > (Using quasi-quotes, you can produce any compilation error you like...) > It would be great if we didn't have to pull in the full power of TH (or > QQ) for this. > > > Cheers, > Ozgur > > -- Alberto.

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Well-Typed Haskell courses now include a "Type System" course
by Andres Löh 20 Mar '14

20 Mar '14

Hi Haskell-Cafe. As you might already know, Well-Typed LLP are offering regular (commercial) Haskell courses in collaboration with Skills Matter in London for about 1.5 years now. The next courses will take place in the week from April 28 to May 2, 2014, and will for the first time include an all-new 1-day course on all the magic you can do with Haskell's (or more precisely GHC's) type system (taught by me, if that makes a difference). I hope this might be interesting to some on this list, and would certainly like to see many of you there. There's more info available here: http://www.well-typed.com/blog/88/ Here are direct links to the Skills Matter pages for each course. If you'd like to register, go to these: https://skillsmatter.com/courses/504-well-typed-s-guide-to-the-haskell-type… https://skillsmatter.com/courses/464-well-typed-fast-track-to-haskell https://skillsmatter.com/courses/465-well-typed-advanced-haskell Cheers, Andres -- Andres Löh, Haskell Consultant Well-Typed LLP, http://www.well-typed.com

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ANN: timezone-olson V0.1.4
by Yitzchak Gale 19 Mar '14

19 Mar '14

Version 0.1.4 of timezone-olson has been released on Hackage. This version adds support for version 3 olson timezone files, which are now beginning to appear in the wild. Thanks to Renzo Carbonara and Oliver Charles for providing this update. The timezone-olson package provides a parser and renderer for binary Olson timezone files whose format is specified by the tzfile(5) man page on Unix-like systems. For more information about this format, see: http://www.twinsun.com/tz/tz-link.htm Functions are provided for converting the parsed data into 'TimeZoneSeries' objects from the timezone-series package [1]. On many platforms, binary Olson timezone files suitable for use with this package are available in the directory /usr/share/zoneinfo and its subdirectories on your computer. Hackage: http://hackage.haskell.org/package/timezone-olson Home page: http://projects.haskell.org/time-ng/ Note that support for tzfile versions 2 and 3 is not complete. We parse all of the explicit clock transitions, but we do not yet support the textual POSIX-style time zone specifications that can be included; currently, those only affect clock transitions that are predicted to occur far in the future. We also do not yet support parsing the leap second tables that are now provided in olson files; see the function Data.Time.Clock.TAI.parseTAIUTCDATFile in Ashely Yakeley's time library [2] for an alternative. Regards, Yitz [1] http://hackage.haskell.org/package/timezone-series [2] http://hackage.haskell.org/package/time

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Re: [Haskell-cafe] Listing native package requirements based on cabal information
by Tobias Dammers 18 Mar '14

18 Mar '14

On Wed, Mar 19, 2014 at 10:15:08AM +1300, Chris Wong wrote: > On Wed, Mar 19, 2014 at 9:47 AM, Tobias Dammers <tdammers(a)gmail.com> wrote: > > Hmm, but then, not all package managers/repositories use the same names > > for packages. So even if there were a way to extract the required > > libraries from cabal, feeding that information to the package manager > > isn't going to be trivial at all. > > It's not trivial, but I don't think it's difficult. > > For example, Debian Haskell packages all take the form > libghc-NAME-dev. Fedora uses haskell-NAME. Sure, there's a bit of hard > coding involved, but the set of prominent distributions is finite. I think installing *haskell* packages is not the problem; cabal already does a decent job at that. The problem we're facing is that cabal can *only* install haskell packages, but not any of the native libraries they depend on (usually through FFI, but other examples exist, such as the pg_config tool from PostgreSQL). Besides naming convention issues (which could be compensated for with lookup dictionaries; a brute-force solution, sure, but better than nothing), a bigger problem is that sometimes packages don't match 1:1 between distros, so one distro might just provide one monolithic foobar-dev package, while another might split it up into foobar-client-dev and foobar-server-dev, while yet another might provide more than one alternative. TL;DR: I think if we could just get a list of required native packages, we'd be a long way. > > One problem, though, would be versions. I know we often ask for the > latest and greatest packages, which may conflict with what the > distribution supplies. So the benefits may not be as high as they > seem. > > By the way -- has anyone looked into 0install? It hashes things, > similarly to Nix, but also tries to integrate with the existing > package manager. For example, if the user wishes to install GHC 7.6, > but the Debian repositories already supply it, it will invoke apt-get > instead of installing on its own. > > > (And frankly, looking at build systems > > for other languages, I've never seen anything that does this - even > > autotools doesn't really do a lot more than check whether a library is > > available). > > > > That said, even if we could just get a list of required libraries out of > > cabal, in a somewhat human and machine readable format, that would be a > > huge win in itself. > > > > On Tue, Mar 18, 2014 at 11:48:33AM -0700, David Thomas wrote: > >> One option that just occurred to me would be to allow passing a script to > >> cabal that could be passed the extra-libraries (if any), and could install > >> if it knew the relevant OS packages (or NIX packages), or abort with a > >> cleaner error message. > >> > >> Actually, wrapping ghc might be sufficient (though not ideal). > >> > >> > >> > >> On Tue, Mar 18, 2014 at 11:29 AM, Michal Antkiewicz < > >> mantkiew(a)gsd.uwaterloo.ca> wrote: > >> > >> > This is not an immediate solution but I can imagine listing NIX packages > >> > as dependencies inside a cabal file, then NIX would create a sandbox with > >> > these dependencies and cabal would build in that sandbox. The advantages > >> > are that you're not messing around with the underlying operating system's > >> > packages, NIX handles all dependencies transitively, and everything is > >> > specified declaratively. Sounds like a nice GSoC project :-) You could > >> > also do cross GHC version's builds as GHC itself can be sandboxed. Quite > >> > intriguing. > >> > > >> > Michal > >> > > >> > > >> > > >> > On Tue, Mar 18, 2014 at 2:16 PM, Michal Antkiewicz < > >> > mantkiew(a)gsd.uwaterloo.ca> wrote: > >> > > >> >> Certainly NIX is an interesting approach. It already comes with a large > >> >> base of dependencies, a format for specifying them. NIX can be installed in > >> >> any Linux distro and serve as an environment for building packages. That > >> >> might provide a cross-distribution solution to the native dependency > >> >> problem. > >> >> > >> >> See, a nice post by Oliver Charles > >> >> > >> >> http://ocharles.org.uk/blog/posts/2014-02-04-how-i-develop-with-nixos.html > >> >> > >> >> Michal > >> >> > >> >> > >> >> > >> >> On Tue, Mar 18, 2014 at 1:59 PM, David Thomas <davidleothomas(a)gmail.com>wrote: > >> >> > >> >>> Ok, well, if that's the case I'd like to see about remedying that. > >> >>> Anyone have any thoughts as to how to best go about this? I'm not clear on > >> >>> exactly what info lives where, especially across systems. Entirely manual > >> >>> population would be a (barely) acceptable fallback. > >> >>> > >> >>> > >> >>> On Tue, Mar 18, 2014 at 9:36 AM, Dan Burton <danburton.email(a)gmail.com>wrote: > >> >>> > >> >>>> I have wished for this on multiple occasions. I don't believe such a > >> >>>> thing exists as of yet. > >> >>>> > >> >>>> -- Dan Burton > >> >>>> > >> >>>> > >> >>>> On Tue, Mar 18, 2014 at 9:26 AM, David Thomas <davidleothomas(a)gmail.com > >> >>>> > wrote: > >> >>>> > >> >>>>> Is there a way to extract this? I'm looking to make it easier for > >> >>>>> newcomers to my project to get things building across different linux > >> >>>>> distros. > >> >>>>> > >> >>>>> _______________________________________________ > >> >>>>> Haskell-Cafe mailing list > >> >>>>> Haskell-Cafe(a)haskell.org > >> >>>>> http://www.haskell.org/mailman/listinfo/haskell-cafe > >> >>>>> > >> >>>>> > >> >>>> > >> >>> > >> >>> _______________________________________________ > >> >>> Haskell-Cafe mailing list > >> >>> Haskell-Cafe(a)haskell.org > >> >>> http://www.haskell.org/mailman/listinfo/haskell-cafe > >> >>> > >> >>> > >> >> > >> >> <mantkiew(a)gsd.uwaterloo.ca> > >> >> > >> > > >> > > >> > > > > >> _______________________________________________ > >> Haskell-Cafe mailing list > >> Haskell-Cafe(a)haskell.org > >> http://www.haskell.org/mailman/listinfo/haskell-cafe > > > > _______________________________________________ > > Haskell-Cafe mailing list > > Haskell-Cafe(a)haskell.org > > http://www.haskell.org/mailman/listinfo/haskell-cafe

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[ANN] cabal-cargs: A command line program for extracting compiler arguments from a cabal file.
by Daniel Trstenjak 18 Mar '14

18 Mar '14

Hi cafe, for further details please consult 'https://github.com/dan-t/cabal-cargs'. A little teaser, you can use cabal-cargs to make your default, non modified hdevtools aware of the settings in the cabal file and of a present cabal sandbox. Greetings, Daniel

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[GSoC] A proposal for GSoC regarding computational algebra
by Hiromi ISHII 18 Mar '14

18 Mar '14

Hello, cafe I am a currently an undergraduate student and will enter the graduate school on April. As a student, I have a project to propose for the GSoC: purely functional computer algebra library. I've been working on computational-algebra library [1], but this library needs more improvements. Especially, it needs much more performance improvements for Groebner bases computation. I want to implement efficient algorithms called F4 and F5 [2, 3] as the GSoC project. These algorithms require efficient linear algebra algorithms, so this project also involves the development of efficient symbolic linear algebra library. This project is not on any ideas list as far as I know, and I want to directly propose to the GSoC and I'm looking for a mentor. Is there anyone interested in my proposal? [1]: http://github.com/konn/computational-algebra [2]: http://www-polsys.lip6.fr/~jcf/Papers/F99a.pdf [3]: http://www.risc.jku.at/Groebner-Bases-Bibliography/gbbib_files/publication_… -- Hiromi ISHII konn.jinro(a)gmail.com

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Re: [Haskell-cafe] linking warnings when using regex-posix
by Rouan van Dalen 18 Mar '14

18 Mar '14

Thanks Kyra, I appreciate the feedback. Good to know it is in the process of being fixed. Regards --Rouan

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