- Haskell-Cafe - Haskell.org

cabal and conditional build-depends
by Tristan Ravitch 09 Jan '12

09 Jan '12

Hi Cafe, I have a package that depends on several other Haskell libraries. One of these libraries depends on some native libraries (and associated headers) to build. I would like to make this dependency optional in my package if the libraries don't exist. To do this, I tried to switch my build-type from Simple to Configure in my .cabal file. Then I made a configure script that generates a <pkg>.buildinfo file as suggested in the cabal guide. The buildinfo file is generated and looks as I would expect. If the library is found on the system, it has a "build-info: ..." line. Unfortunately, when Cabal processes it, it says: Warning: archive-inspection.buildinfo: Unknown fields: build-depends (line 2) Fields allowed in this section: buildable, build-tools, cpp-options, cc-options, ld-options, pkgconfig-depends, frameworks, c-sources, default-language, other-languages, default-extensions, other-extensions, extensions, extra-libraries, extra-lib-dirs, includes, install-includes, include-dirs, hs-source-dirs, other-modules, ghc-prof-options, ghc-shared-options, ghc-options, hugs-options, nhc98-options, jhc-options It really doesn't seem to like conditional build-depends entries. Is this expected behavior? And is there a better way to go about having conditional build-time dependencies on Haskell libraries using Cabal? I guess I could start playing with a custom Setup.hs, but I always hate doing that unless absolutely necessary. Thanks

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Questions on the Haskell 2010 report
by Silvio Frischknecht 09 Jan '12

09 Jan '12

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 I am trying to write a haskell compiler and i have stumbled upon 2 issues that i don't understand in the Haskell report 2010. Btw. these issues are also present in the 98 report. 1) first is this in section 5.1 Module Structure [1]. A module is defined like this. module → module modid [exports] where body | body body → { impdecls ; topdecls } | { impdecls } | { topdecls } You can't see it in this mail because there is no font but the curly braces { } are meant to match the tokens { } and are not meant as repetition. However, as I understand it, the layout parser would modify this code: module Foo where import Bar baz=baz to this code (which doesn't match): module Foo where { import Bar ; baz=baz } and not to this code (which would be required to match): module Foo where { { import Bar } ; { baz=baz } } So as i see the definition should state this instead: module → module modid [exports] where body | body body → { impdecls ; topdecls } | impdecls | topdecls 2) In the same section what is it supposed to mean if "module" consists of only a "body" and not "module modid [exports] where body". 3) In section 10.3 Layout [2] it is written. If a let, where, do, or of keyword is not followed by the lexeme {, the token {n} is inserted after the keyword, where n is the indentation of the next lexeme if there is one, or 0 if the end of file has been reached. Together with this rule L [] (m : ms) = } : L [] ms if m≠0 (Note 6) This results in an error if the program ends in a "where", ... Wouldn't it make more sense to put a {1} in case of EOF or just insert the tokens '{' and '}'. On the other hand if you really won't accept that why not simply say that it is an error. btw. GHC doesn't give an error. [1] http://www.haskell.org/onlinereport/haskell2010/haskellch5.html#x11-990005.1 [2] http://www.haskell.org/onlinereport/haskell2010/haskellch10.html#x17-178000… -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iQIcBAEBAgAGBQJPCdgeAAoJEDLsP+zrbatWIjgP/RLISOIz6xZRDso/mVn+xbwh eMPdeqmzJJYpVm+sDdjmoEIAsrwXtYKc9r8LrlUOugbtXFhYYPcSox7Te4DO+Cm+ X+b8b80UQu1nKNoUofDqAXSQb/n7f5zgmaIoF2uvFieuJTE709oZCmBdTgupVdyJ D16VqmKmqpskNepnQuh9rV7vwSPs4PjnsUQDpxjXDvh0tSdp9byBZPcMwEgQb172 FJAAryCuKFBE8FRG+ANlSw2h8fH7rkMLmkjabje5NKtLa2UMKvBlXYa2p0EZwcd2 /bj/2GTksWdsDmqFp3lQJgPk2uxp5reosTiTk5JQz56GcPOTK3wmL62qDeH3+tdS pX5ZD8HeX8RdkLjuFi0fjiJq3L4HEy+OqHbLWoStPPqfY9clueSUJ0g0Dfc4OukU 0naJlASxKr4ovHBiTinrLI6bTTeeMj9QCDGh5hU0x1hJ5f80iQQaKYpI8cq1DxQv CICBFibFnbJ0Zfzfuk0ZJZ8Db1dJUdEGSYZo/QCtpxXwTyKr4zEU6FYHprScRRX8 H6ZDnVE6ZbzDbaUqeQVBXvUGHF+2vTmDo1EZ80BFhDVHjifvV9eHslbF0XD+NjYY iRPsgDzACYsMxvYaBsRlXWwmwWD+EfNerdHZL6h9dBZICwSr0pu4SCp616BR2BpK IuO4MG/B5vAoCs9cb0lG =O6Wd -----END PGP SIGNATURE-----

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Re: [Haskell-cafe] [web-devel] [ANNOUNCE] First release of crypto-conduit
by Aristid Breitkreuz 09 Jan '12

09 Jan '12

Yeah and that's annoying IMHO. :) It's not really important though. Aristid Am 07.01.2012 15:39 schrieb "Felipe Almeida Lessa" <felipe.lessa(a)gmail.com>:

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RoseTree + Data.Typeable.Zipper
by Sergey Mironov 08 Jan '12

08 Jan '12

Hi list! Could you please give me a quick example of navigating throw Data.Typeable.Zipper built on top of a Rose Tree? eg. (See ??? in the last line - is my question) {-#LANGUAGE TemplateHaskell, DeriveDataTypeable, TypeOperators #-} import Data.Typeable.Zipper data Tree k a = Tree { _rules :: [(k,Tree k a)] } deriving(Show, Typeable) $(mkLabelsNoTypes [''Tree]) atree = Tree [(1, Tree []), (2, Tree []), (3, Tree [(11, Tree [])])] moveToLeftmostChild :: (Typeable k, Typeable a) => Zipper1 (Tree k a) -> Zipper1 (Tree k a) moveToLeftmostChild z = moveTo ??? z Thanks, Sergey

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All the random packages
by Eugene Kirpichov 08 Jan '12

08 Jan '12

Hi, I came across the beautiful algorithm for O(1) generation of rational discrete distributions http://www.keithschwarz.com/darts-dice-coins/ and though it'd be fun to implement it in Haskell and put on Hackage, but then it turned out that there's about a dozen random number packages, so I'm not sure to which one to contribute, or better to roll out my own package and encourage authors of the other packages to reference it and fit under their interface. What do you think? Which random number packages are considered to be most mature or perhaps promising - i.e., contributing to which ones will bring the community the most benefit? Is there any effort on unifying them going on? -- Eugene Kirpichov Principal Engineer, Mirantis Inc. http://www.mirantis.com/ Editor, http://fprog.ru/

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OpenAL bindings?
by Jason Dagit 08 Jan '12

08 Jan '12

Hello, Looks like the repo [1] for the OpenAL bindings that Sven Panne created [2] is no longer available. I assume this is a result of The Great Server Outage of 2011 [3]. Do other bindings exist (I didn't see any on hackage, google, or the wiki [4])? I can import the source that is available on hackage into a github repo and hack from there, but I wanted to ask first: Is the source of this repo gone for good? As a side note, I have plenty of other repos and things on my plate so I'm not really interested in becoming the maintainer of this binding. Any OpenAL experts interested in taking it over? I know from experience that Sven appears to be MIA in the Haskell community these days. Thanks, Jason -- [1] http://darcs.haskell.org/packages/OpenAL/ [2] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/OpenAL [3] http://www.haskell.org/pipermail/haskell-cafe/2011-February/088829.html [4] http://www.haskell.org/haskellwiki/OpenAL

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ANN: leapseconds-announced-2012
by Bjorn Buckwalter 08 Jan '12

08 Jan '12

Dear all, The International Earth Rotation and Reference Systems Service (IERS) recently announced[1] that a positive leap second will be introduced at the end of June 2012. Consequently I have updated the leapseconds-announced library[2]. The original announcement of leapseconds-announced can be found below. Best regards, Bjorn Buckwalter [1] http://hpiers.obspm.fr/eoppc/bul/bulc/bulletinc.dat [2] http://hackage.haskell.org/package/leapseconds-announced ---------- Forwarded message ---------- From: Bjorn Buckwalter <bjorn.buckwalter(a)gmail.com> Date: Sat, Jan 17, 2009 at 13:23 Subject: ANN: leapseconds-announced-2009 To: Haskell(a)haskell.org, haskell-cafe(a)haskell.org Dear all, I'm pleased to announce the upload of the leapseconds-announced package[1] to Hackage. leapseconds-announced contains a single module and a single function implementing the Data.Time.Clock.TAI.LeapSecondTable interface (type). The documentation[2] for Data.Time.Clock.TAI.LeapSecondTable says "No table is provided, as any program compiled with it would become out of date in six months" and with that I have no objections. However, I frequently find myself needing a LeapSecondTable for a quick-and-dirty one-off analysis or simulation of the present or past. In these cases I've lazily used "(const 33)" (or more recently: "(const 34)") as my LeapSecondTable. leapseconds-announced is a pragmatic, if imperfect, improvement over my past practices. It provides a LeapSecondTable with all leap seconds announced to date (hence the name). Once the IERS announces[3] another leap second the package will need an update and all code using it a recompile. While this precludes its use in long-running production applications it is eminently adequate for my one-off uses or for applications that can afford to recompile infrequently. While, in the words of the Data.Time.Clock.TAI documentation, "most people won't need this module" I hope it can be of utility to someone. Thanks, Bjorn Buckwalter [1] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/leapseconds-anno… [2] http://www.haskell.org/ghc/docs/latest/html/libraries/time/Data-Time-Clock-… [3] http://hpiers.obspm.fr/eoppc/bul/bulc/bulletinc.dat

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Re: [Haskell-cafe] Problems with libgmp on Amazon Linux
by Nicu Ionita 08 Jan '12

08 Jan '12

Am 07.01.2012 20:01, schrieb Nabil Alsharif: > Ahh your main issue is that --prefix should be /usr not /usr/lib.... > It would be best to reinstall libgmp with the correct prefix. Oh, thanks, I will try this.

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[ANNOUNCE] First release of crypto-conduit
by Felipe Almeida Lessa 07 Jan '12

07 Jan '12

Hello! I'm pleased to announce the first release of crypto-conduit [1]! The crypto-api [2] package provides APIs for many cryptographic operations, such as cryptographic hashes and block ciphers. This new crypto-conduit package allows you to use many of these operations with conduits [3], giving you safe I/O using constant memory and no leaks. As an example, here's how you could get the SHA1 hash a file: import Crypto.Conduit -- from crypto-conduit import Crypto.Hash.SHA1 (SHA1) -- from cryptohash import Data.Conduit -- from conduit import Data.Conduit.Binary (sourceFile) -- from conduit main = do hash <- runResourceT $ sourceFile "my-file" $$ sinkHash print (hash :: SHA1) The code snippet above, despite having only "sourceFile ... $$ sinkHash" on its core, guarantees that the file handle is not kept open and uses a constant amount of memory. Sweet! Please break this package! Although it comes with a test suite, it has just seen the light of the day. Cheers, =) [1] http://hackage.haskell.org/package/crypto-conduit [2] http://hackage.haskell.org/package/crypto-api [3] http://hackage.haskell.org/package/conduit -- Felipe.

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ANNOUNCE: DHD >>= UHac, April 20 - 22, Utrecht
by Sean Leather 07 Jan '12

07 Jan '12

Calling all Haskellers! To open 2012 and in celebration of the group's 3rd year of existence, the Dutch Haskell Users Group is happy to announce a new event that combines an informal conference and a hackathon. >>= >> >> >> >> >> >> >>= >>= >>= >>= *DHD >>= UHac* >>= >>= >>= >>= *April 20 - 22* >>= >>= >>= >>= *Utrecht* >>= >>= >>= >>= >> >> >> >> >> >> >>= >>= DHD >>= The Dutch HUG Day, or DHD, will be a half day of talks on anything Haskell-y or FP-ish. It will be held on Friday, April 20. >>= UHac >>= The Utrecht Hackathon, or UHac, will be a gathering of the community of enthusiastic Haskell hackers from around the world. It will start immediately following the DHD and continue to Sunday, April 22. >>= Call for Speakers >>= We are looking for speakers for the Dutch HUG Day. If you have something interesting to share, please email Sean Leather (leather(a)cs.uu.nl) See the website for more. >>= Website >>= For more information that will be continuously updated, see the event wiki page: *http://www.haskell.org/haskellwiki/DHD_UHac* Join us for a Haskell-y time in the Netherlands. We look forward to seeing you there! Sean Leather and Jurriën Stutterheim Organizers

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