July 2011 - Glasgow-haskell-users

partially applied type synonyms
by Arie Peterson 05 Mar '12

05 Mar '12

Dear list, Is there a good reason that partially applied type synonyms cannot be made instances of classes? - A simple example would be making the identity type 'Id' ("type Id x = x") instance of 'Monad'. This would eliminate the need for some silly occurrences of 'runIdentity', and perhaps narrow the gap between monads and monad transformers. - The reason I complain about this now is a more involved example, where introducing a newtype to work around the restriction is not an option. Well, not as far as I can see now, anyway. Partially applied type synonyms are, in a sense, the anonymous functions at the type level, and one might argue that they deserve the same 'first-class member status' as the lambda at the value level. Kind regards, Arie Peterson

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ANNOUNCE: GHC 7.2.1 Release Candidate 1
by Ian Lynagh 11 Feb '12

11 Feb '12

We are pleased to announce the first release candidate for GHC 7.2.1: http://www.haskell.org/ghc/dist/7.2.1-rc1/ This includes the source and testsuite tarballs, installers for OS X and Windows, and bindists for amd64/Linux, i386/Linux, amd64/FreeBSD and i386/FreeBSD. Please test as much as possible; bugs are much cheaper if we find them before the release! Thanks Ian, on behalf of the GHC team

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Proposal to incorporate Haskell.org
by Don Stewart 16 Dec '11

16 Dec '11

Hello everyone. The haskell.org committee[1], in the interest of the long-term stability of the open source Haskell community infrastructure, has decided to incorporate haskell.org as a legal entity. This email outlines our recommendation, and seeks input from the community on this decision. The committee's proposal is that haskell.org incorporate as an entity under the Software Freedom Conservancy umbrella organization (the same group that Darcs joined recently): http://sfconservancy.org/ If we proceed with this move, haskell.org will be a legal entity, and registered as a non-profit, allowing us to more directly accept (US tax-deductible) donations, and to invest in assets that benefit the Haskell open source community. We welcome your feedback on the proposal attached below. -- Don Stewart (on behalf of the Haskell.org committee) ------------------------------------------------------------------------ = A proposal for the incorporation of Haskell.org = In recent years, haskell.org has started to receive assets, e.g. money from Google Summer Of Code, donations for Hackathons, and a Sparc machine for use in GHC development. We have also started spending this money: in particular, on hosting haskell.org itself. There is also interest in running fundraising drives for specific things such as Hackathon sponsorship and hosting fees. However, haskell.org doesn't currently exist as a legal entity, meaning that these assets have had to be held on our behalf by other entities, such as Galois and various universities. This leads to tricky situations, with no-one being sure who should decide how the haskell.org assets can be used. To solve these problems, we propose that haskell.org applies to become a member project of the Software Freedom Conservancy (SFC) <http://conservancy.softwarefreedom.org/>. The SFC is a non-profit organization that provides free financial and administrative services to open source projects. Additionally, it has 501(c)(3) status, meaning donations from the US are tax-deductible. The SFC would hold haskell.org's money and other assets, and would be able to accept donations on behalf of haskell.org. The haskell.org committee, as described here [2], will make decisions on spending assets and other decisions related to governing the non-profit. Before proceeding, we are inviting input from the community in the form of specific objections or queries regarding the plan. We've tried to answer some of the most likely questions: Q: Does this mean that my Haskell project must now be covered by a copyleft licence such as GPL? A: No, but Haskell projects using haskell.org resource should use an Open Source licence <http://www.opensource.org/licenses/alphabetical>. Q: Will it still be possible to use community.h.o to host non-open-source material, such as academic papers? A: An overall minority of such content, as is the current situation, is not a problem. Q: Will it still be possible to have job ads on the haskell.org mailing lists and website? A: Yes. Q: Will this affect our ability to host the Haskell Symposium <http://www.haskell.org/haskell-symposium/> and Industrial Haskell Group<http://industry.haskell.org/> webpages within haskell.org? A: No. Q: What will be the relationship between haskell.org and other organizations such as the Haskell Symposium and Industrial Haskell Group? A: Those organisations will continue to exist as separate entities. Q: If an umbrella non-profit organisation "The Haskell Foundation" was created, would haskell.org be able to join it? A: Yes. It's likely that in such a scenario, the Haskell Foundation would become the owner of the haskell.org domain name, with the cost divided between the members. The entity that is part of the SFC would be renamed "community.haskell.org" in order to avoid confusion. [1]: http://www.haskell.org/haskellwiki/Haskell.org_committee [2]: http://www.haskell.org/haskellwiki/Haskell.org_committee#Operation

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hsc2hs and #include
by Evan Laforge 09 Aug '11

09 Aug '11

So when I upgrade from 6.10 to 6.12 a LONG time ago, there was a bug where hsc2hs would emit INCLUDE pragmas and ghc didn't like that. So I hacked around it with an extra grep -v step in the Makefile. I always meant to go fix it for real in hsc2hs and finally I came back to that TODO item. I took a look at the hsc2hs source, and discovered it's surrounding the INCLUDE line with #elif __GLASGOW_HASKELL__ < 610 However, that macro is never defined for me, so it always emits the bogus INCLUDE line. I can't find anywhere that defines that macro, but there is a lot of "__GLASGOW_HASKELL && ...". So I modified utils/hsc2hs/C.hs from ... "#elif __GLASGOW_HASKELL__ < 610\n"++ " printf (\"{-# INCLUDE %s #-}\\n\", \""++ showCString s++"\");\n"++ "#endif\n" to "#elif __GLASGOW_HASKELL__ && __GLASGOW_HASKELL__ < 610\n"++ " printf (\"{-# INCLUDE %s #-}\\n\", \""++ showCString s++"\");\n"++ "#endif\n" And my problem is solved. Is this the correct solution? Where is that macro defined? I don't know how to mail patches with git, but anyway it's trivial so I don't think it's needed :)

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Why no stack overflow in ghci?
by Roman Cheplyaka 02 Aug '11

02 Aug '11

The code main = print $ foldl (+) 0 [1..1000000] when compiled (without optimizations) results in a stack overflow, which is expected. However, when run from ghci it succeeds. Why is it so? (Tested with GHC 6.12.something and 7.0.4) Is it related to "stack-squeezing"? I couldn't find any description of it, apart from a few bug reports. A related question: how can I control the stack size in evaluations inside ghci? Is it (roughly) the same as setting the ghci's own stack size by passing -K to it in the command line? -- Roman I. Cheplyaka :: http://ro-che.info/

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haskell-platform configures failed on Ubuntu 11.04
by David Smith 01 Aug '11

01 Aug '11

I tried to build the newest haskell-platform-2011.2.01 from source on Ubuntu 11.04, following the instructions http://www.vex.net/~trebla/haskell/haskell-platform.xhtml. But there was still an configure error. $ ./configure ************************************************** * * Haskell Platform Source Installer * * For the Haskell Platform 2011.2.0.1 and GHC 7.0.3 * ************************************************** checking build system type... i686-pc-linux-gnu checking host system type... i686-pc-linux-gnu checking target system type... i686-pc-linux-gnu checking for ghc... /usr/local/bin/ghc checking for ghc-pkg... /usr/local/bin/ghc-pkg checking for hsc2hs... /usr/local/bin/hsc2hs checking version of ghc... 7.0.3 checking version of ghc-pkg matches... yes checking ghc actually works... [1 of 1] Compiling Main ( conftest.hs, conftest.o ) yes checking the ghc core packages are all installed... yes checking for perl... /usr/bin/perl checking for gcc... gcc checking whether the C compiler works... yes checking for C compiler default output file name... a.out checking for suffix of executables... checking whether we are cross compiling... no checking for suffix of object files... o checking whether we are using the GNU C compiler... yes checking whether gcc accepts -g... yes checking for gcc option to accept ISO C89... none needed checking how to run the C preprocessor... gcc -E checking for grep that handles long lines and -e... /bin/grep checking for egrep... /bin/grep -E checking for ANSI C header files... yes checking for sys/types.h... yes checking for sys/stat.h... yes checking for stdlib.h... yes checking for string.h... yes checking for memory.h... yes checking for strings.h... yes checking for inttypes.h... yes checking for stdint.h... yes checking for unistd.h... yes checking zlib.h usability... yes checking zlib.h presence... yes checking for zlib.h... yes checking for zlibVersion in -lz... yes checking GL/gl.h usability... yes checking GL/gl.h presence... yes checking for GL/gl.h... yes checking for library containing glEnd... no configure: error: The OpenGL C library is required In fact, glEnd function did exist in /usr/include/GL/gl.h I googled this issue, only found this one is similar to mine, but my system is Ubuntu not Opensus http://haskell.1045720.n5.nabble.com/Haskell-Platform-can-t-use-OpenGL-on-O… The following are the libraries I already installed sudo apt-get install libgl1-mesa-dev sudo apt-get install libglc-dev sudo apt-get install freeglut3-dev sudo apt-get install libedit-dev sudo apt-get install libglw1-mesa libglw1-mesa-dev Can anyone suggest the libraries my OS missing ?

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integer-simple
by Chris Dornan 31 Jul '11

31 Jul '11

Hi All, I am still having difficulty getting a plain GHC build with INTEGER_LIBRARY = integer-simple. (I outlined my problem here yesterday <http://www.haskell.org/pipermail/glasgow-haskell-users/2011-July/020631.htm l> .) I suspected my failure to get a vanilla build (with GMP) was a minor issue with RHEL 5 and indeed a vanilla build of the the compiler goes through no problem on RHEL 6, producing a working 6.12.3 GHC installation. But when I repeat with INTEGER_LIBRARY = integer-simple (on quick test) I get (the now familiar): GHCi, version 6.12.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. ghc: /usr/local/ghc/6.12.3-si/lib/ghc-6.12.3/integer-simple-0.1.0.0/HSinteger-sim ple-0.1.0.0.o: unknown symbol `base_ControlziExceptionziBase_patError_info' Loading package integer-simple ... linking ... ghc: unable to load package `integer-simple' RHEL 5 and 6 are very different development environments yet all my attempts to build with a variety of source trees from 6.12.1 to 7.0.4 with INTEGER_LIBRARY = integer-simple has ended here. There is clearly something I am doing wrong! (Though it is difficult to see what.) Does anybody have any idea what could be causing this? Is anybody else doing integer-simple builds? It would be nice to get some info on the configurations that are working. Thanks in advance! Chris

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possible strictness bug in profiled version of a program
by Peter Hercek 30 Jul '11

30 Jul '11

Here is a test program (file name prgSrc.hs): import Data.Array.Unboxed main = do let l1 = [1..10] :: [Int] let l2 = [ map (i+) l1 | i <- [1..5000000] ] let l3 = map (\l -> listArray (1,length l) l) l2 :: [UArray Int Int] print $ accumulate l3 0 accumulate [] rv = rv accumulate (h:t) rv = let nextRv = (rv + sum (elems h)) in accumulate t $! nextRv I used ghc 7.0.3-2 on archlinux, 64 bit version. I created it only to check how much memory short unboxed arrays consume. Thanks to the "$!" call at the last line of the "accumulate" function there should not be any stack overflow. When I compile with these options: --make prgSrc.hs -O2 --make prgSrc.hs -prof -auto-all -caf-all --make prgSrc.hs then there is no problem. But when I compile with these options: -O2 -prof -auto-all -caf-all --make prgSrc.hs then program runs out of stack. This indicates that there is a bug while compiling "$!" in an optimized profiling version of this program. Is it a bug? Should it be reported to the ghc trac database? Peter.

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Superclass Cycle via Associated Type
by Ryan Trinkle 30 Jul '11

30 Jul '11

The following code doesn't compile, but it seems sensible enough to me. Is this a limitation of GHC or is there something I'm missing? class C (A x) => C x where type A x :: * instance C Int where type A Int = String instance C String where type A String = Int The error I get is: SuperclassCycle.hs:1:1: Cycle in class declarations (via superclasses): SuperclassCycle.hs:(1,1)-(2,15): class C (A x) => C x where { type family A x :: *; } Ryan

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GHC API output files options problem
by Marianna Rapoport 29 Jul '11

29 Jul '11

Hi all, we are working on a Haskell support plugin for IntelliJ IDEA, and need to provide correct compilation of Haskell programs. We compile the latter using GHC API, with options specifying .hi and .o paths. For some reason, unlike a standalone GHC compilation, GHC API ignores the values of the outputFile and outputHi flags. Please find attached a minimal example where "err_test.hs" uses GHC API to compile "src/A.hs". Thus, "test_ghc.sh" and "test_my.sh" should do the same, but the first works correctly while the latter puts "use.o" and "use.hi" to the "src" folder. To launch "test_my.sh", please change the value of lib in "err_test.hs" according to your GHC installation path. Thank you very much in advance! Marianna Rapoport, amaurremi(a)gmail.com Oleg Sobolev, sobolev_ov(a)mail.ru

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