February 2007 - 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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ghci and ghc -threaded broken with pipes & forking
by John Goerzen 29 Dec '08

29 Dec '08

Hi, I've been hitting my head against a wall for the past couple of days trying to figure out why my shell-like pipeline code kept hanging. I found fd leakage (file descriptors not being closed), which disrupts EOF detection and can lead to deadlocks. I just couldn't find the problem. I finally tried compiling my test with ghc instead of running it in ghci. And poof, it worked fine the first time. I tried asking on #haskell, and got the suggestion that ghci uses -threaded. I tried compiling my test program with ghc -threaded, and again, same deadlock. My program never calls forkIO or forkOS or any other threading code. You can see my test case with: darcs get '--tag=glasgow ml' http://darcs.complete.org/hsh ghc -fglasgow-exts --make -o test2 test2.hs That'll run fine. If you add -threaded, it will hang. Ideas? Thanks, -- John

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hasktags - small patch
by Marc Weber 14 Mar '07

14 Mar '07

While starting to learn more about webfunctions I have noticed that hasktags doesn't recognize rwUserName and rwPasswd in the following code: data LogInController = LogInController {rLoggedIn::R Bool, rwUserName::RWE String, rwPasswd::RWE String} When using spaces it does LogInController {rLoggedIn :: R Bool, rwUserName :: RWE String, rwPasswd :: RWE String} This small patch introduces a now mywords function which recognizes a::b as words a,::,b which is what we need here (?) It does work in the above example. Here is the diff. Is it worth applying? 154c154 < let wordlines = map words aslines --- > let wordlines = map mywords aslines 161a162,174 > -- my words is mainly copied from Data.List. > -- difference abc::def is split into three words instead of one. > mywords :: String -> [String] > mywords (':':':':xs) = "::" : mywords xs > mywords s = case dropWhile {-partain:Char.-}isSpace s of > "" -> [] > s' -> w : mywords s'' > where (w, s'') = myBreak s' > myBreak [] = ([],[]) > myBreak (':':':':xs) = ([], "::"++xs) > myBreak (' ':xs) = ([],xs); > myBreak (x:xs) = let (a,b) = myBreak xs > in (x:a,b) Marc Weber

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Problem compiling GHC
by Cristian Perfumo 02 Mar '07

02 Mar '07

Hi all, I'm having a problem when I try to compile GHC. I did it several times before without any problem but I don't know exactly from which moment it started giving me errors. Anyway, I have some clues: 1) I was modifying some STM stuff and I was receiving errors with (I think) out of date information. Then I did "make clean" in "compiler" and in "libraries/base". 2) I don't know if this has to do but some time ago I installed FilePath library and I hadn't executed "make clean" from this moment on. I insist, these two items are only more information but I'm not sure they're related with the error. So, what I did, to be sure that the error had nothing to do with my modification, was to download GHC again and try to build the original version. But I still get the same error (that I paste below this message). Thank you very much in advance for any help. Regards. Cristian Perfumo ------------------------------------------------------------------------ == make boot -r; in /home/cperfumo/ghc/ghc-6.6-original/ghc-6.6/includes ------------------------------------------------------------------------ ../utils/mkdependC/mkdependC -f .depend -- -O -I. -I../rts -- mkDerivedConstants.c ------------------------------------------------------------------------ == make boot -r; in /home/cperfumo/ghc/ghc-6.6-original/ghc-6.6/compat ------------------------------------------------------------------------ ../utils/mkdependC/mkdependC -f .depend -I. -Iinclude -I../includes -- -O -I. -Iinclude -D__GHC_PATCHLEVEL__=0 -I../libraries/base/cbits -I../libraries/base/include -- cbits/directory.c cbits/rawSystem.c cbits/unicode.c /usr/local/bin/ghc -M -optdep-f -optdep.depend -osuf o -optdep--exclude-module=System.Directory.Internals -H16m -O -I. -Iinclude -Rghc-timing -ignore-package Cabal -I../libraries -fglasgow-exts -no-recomp Compat/Directory.hs Compat/RawSystem.hs Compat/Unicode.hs Distribution/Compat/FilePath.hs Distribution/Compat/ReadP.hs Distribution/Compiler.hs Distribution/GetOpt.hs Distribution/InstalledPackageInfo.hs Distribution/License.hs Distribution/Package.hs Distribution/ParseUtils.hs Distribution/Version.hs Language/Haskell/Extension.hs Compat/Directory.hs:42:7: Could not find module `System.Directory': Use -v to see a list of the files searched for. <<ghc: 8676376 bytes, 5 GCs, 84456/84456 avg/max bytes residency (1 samples), 17M in use, 0.00 INIT (0.00 elapsed), 0.01 MUT (0.12 elapsed), 0.00 GC (0.01 elapsed) :ghc>> make[1]: *** [depend] Error 1 make: *** [stage1] Error 1

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Problems with -caf-all
by R Hayes 02 Mar '07

02 Mar '07

I get the following error message when I try to compile with -caf-all. /tmp/ghc583_0/ghc583_0.s:6482:0: FATAL:Symbol _Mainmain_CAF_cc_ccs already defined. My command line looks like this: ghc --make PriceHisto.hs -ljudy -prof -auto-all -caf-all I also tried the following command line and got the same error: ghc --make PriceHisto.hs -ljudy -prof -caf-all Any ideas as to what I'm doing wrong? R Hayes rfhayes<>@</>reillyhayes.com

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How to debug a segfault.
by David Brown 01 Mar '07

01 Mar '07

I'm developing a program with GHC-6.6. I've been on amd64, and haven't had problems, but now when I run the program on on x86 (after cleaning and recompiling), I'm getting a segfault. gdb isn't very helpful at all: Program received signal SIGSEGV, Segmentation fault. [Switching to Thread -1212873040 (LWP 26946)] 0x080b45b8 in s2EI_info () (gdb) bt #0 0x080b45b8 in s2EI_info () #1 0x081757a8 in ?? () #2 0x00000004 in ?? () #3 0xb7875278 in ?? () I am using some various bindings to some C libraries, some I have written and some written by others. But, I'm not able to figure out where to even begin looking for the problem. Any advice on how I might be able to better debug this? Would compiling unregistered help (I'll have to figure out how to build libraries for that)? Thanks, David Brown

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TFP 2007: Last Call for Participation
by TFP 2007 28 Feb '07

28 Feb '07

Dear Colleagues, The deadline to register for TFP 2007 is quickly approaching. You may register at: http://cs.shu.edu/tfp2007/registration.html . Also, please be advised that the deadline to make hotel reservations at the guaranteed rate for TFP 2007 participants is also quickly approaching. Hotel information can be found at: http://cs.shu.edu/tfp2007/accomodations.html . You may browse the program and schedule for TFP 2007 at: http://cs.shu.edu/tfp2007/schedule.html . We look forward to seeing you in NYC!!! Cheers, Marco ************************************************************************************ Dr. Marco T. Morazan TFP 2007 Program Committee Chair http://cs.shu.edu/tfp2007/

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using a stage1 as a compiler for a later ghc?
by Isaac Dupree 28 Feb '07

28 Feb '07

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 I'm on a system with main ghc = 6.4.2. I've built a ghc 6.6 stage1. Is there any problem using that ghc-inplace as a compiler for GHC HEAD? (which is done e.g. by ./configure - --with-ghc=/home/isaac/hardly-mine-at-all/build/ghc-6.6/compiler/stage1/ghc-inplace ?) (which I want to do because, theoretically 6.6 should be faster here, since it supports -fasm unlike the ubuntu-edgy-powerpc-ghc-6.4.2, and also considering how my gcc likes to crash randomly a few times during anything as extensive as compiling ghc...) Isaac -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.3 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFF5LXeHgcxvIWYTTURAoo2AKDHUAo+7759LwBbXh5cP7zklMfKkgCdGoK9 ZQvjhkVTVUt512kpMPquDzc= =zn7+ -----END PGP SIGNATURE-----

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Re: GHC on Cray XMT?
by Peter Tanski 27 Feb '07

27 Feb '07

Chad Scherrer wrote: > The new Cray XMT seems to target exactly the same kind of analytic > problems where Haskell excels: > > http://www.cray.com/products/xmt/ > > I'm not a hardware guy, but this seems like a natural fit with the > recent advances in SMP Haskell. I know some compiler experts, but none > of them have experience with Haskell. > > Can anyone tell me how big an undertaking it would this be to get GHC > going on one of these? It seems to me like the fact that the absence > of cache on XMT processors should simplify things, since there are > less issues reasoning about locality. Porting GHC to a new architecture may be easy or very involved. See http://hackage.haskell.org/trac/ghc/wiki/Building/Porting. Porting to the Cray XMT would appear to be very difficult but a real Plum!. I am not sure how close its UNICOS operating system is to BSD (GHC has ports to FreeBSD and OpenBSD)--that is just the main programming environment; working with the processors may require a smaller microkernel environment. According to the XMT Datasheet the main programming is done on Linux-based nodes. Linux is GHC's "home" OS, so that would seem to make it a little easier. For an experience porting Glasgow Parallel Haskell (GPH) to an MPP, you might want look at the work of Kei Davis (http://www.c3.lanl.gov/ ~kei/), who ported an older version of GHC to the Thinking Machines CM-5 SPMD (http://www.c3.lanl.gov/~kei/lanlwork.html and especially, "MPP Parallel Haskell (Preliminary Draft)", 1996, at http:// www.c3.lanl.gov/~kei/ifl96.ps) Kei Davis's work is also referenced on the Glasgow Parallel Haskell site, under "PORTS" (http:// www.macs.hw.ac.uk/~dsg/gph/) I mention his work in particular because the CM-5 port involved a slightly new (Solaris-like) OS and a specialised message passing system, CMMD, instead of PVM used by Glasgow Parallel Haskell. That would be quit a lot of work since you would have to modify the RTS--the old GUM (Parallel Haskell support) stuff is still in there but it is somewhat bit-rotted. The amount of work required might get worse or better as GHC's future is native assembly output--worse, because you would have to work through the assembly code and efficient C-code generation would require more work with a nasty Perl script called the Mangler; better, depending on whether someone essentially rewrites the ugly spider-web of code in GHC's Native Code Generator (NCG). But all this stuff is for a "native" port: if you have access to an XMT, you might want to simply follow the directions on Porting GHC to a new platform (http://hackage.haskell.org/trac/ghc/wiki/Building/ Porting#PortingGHCtoanewplatform) and see what problems you run into. Cheers, Peter Tanski

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Re: status of GreenCard support
by Peter Tanski 27 Feb '07

27 Feb '07

> Jefferson Heard wrote: >> some simple fix that would make code generated by GreenCard work, >> or is there >> some alternative tool that will make it work? What's the status >> of C2HS? Marc Weber wrote: > When using cabal and GreenCard it might be the case that you have to > tweak setup.hs to add --libdir parameters. Probably it would be better > to update cabal. Maybe I've missed a point to configure it correctly? > If I can save you some minutes by dropping you me quick setup.hs hack > let me know it. I should have answered this in before, sorry. GHC has not supported GreenCard since version 6.2. See http://www.haskell.org/haskellwiki/ Libraries_and_tools/Interfacing_other_languages and http://www.mail-archive.com/haskell@haskell.org/msg14004.html I ran into that problem while attempting to get gcjni-1.2 to work with GHC 6.4 awhile ago, got annoyed, and appended the warning to the Haskell Wiki page lest others ran into the same problem. The Alastair Reid's successor to GreenCard, based on Template Haskell, hasn't been finished yet (or perhaps it is dead?). For more automatic configuration, you might consider Template Haskell: see Ian Lynagh's "Template Haskell: A Report From the Field", at http:// web.comlab.ox.ac.uk/oucl/work/ian.lynagh/papers/ . There are still configuration parameters in the GHC build system for GreenCard but from what I have seen of the rest it seems that you would have to write your own support for the old _casm_ ffi bindings back into the source code practically from scratch (perhaps grabbing an archive of 6.1 would give you a better start). Cheers, Peter Tanski

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