December 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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GHC 6.8.1 on Mac OS X 10.5 (Leopard)
by Manuel M T Chakravarty 11 Jan '08

11 Jan '08

A full binary distribution of GHC 6.8.1 for Mac OS X 10.5 (Leopard) is available from http://www.cse.unsw.edu.au/~chak/haskell/ghc-6.8.1-i386-apple-darwin.tar.bz2 To use it, you need two other pieces of software installed: Xcode 3.0 -- as available from the Leopard upgrade/install DVD or developer.apple.com readline 5.2 -- preferably installed via macports in /opt/local Moreover, if you have the GMP.framework installed (a leftover from 10.4), remove it first. To install, follow the instructions at http://www.haskell.org/ghc/docs/latest/html/users_guide/installing-bin-dist… Happy Haskell Hacking! Manuel -=- GHC on Mac OS X 10.5 mini FAQ: * When trying to compile GHC, I get a segv on Float.lhs (of the base package is compiled). Why? AFAIK this only happens if the GHC you try to bootstrap with is too old (eg, 6.6). * With the binary distribution why do I get a link error complaining about "_environ"? You still have the GMP framework installed. It was linked against an old libc, which causes the error. Remove the GMP framework. * What GMP library is used? GHC 6.8.1 includes an embedded GMP library (ie, it's bundled with the source). It is compiled as a static library and placed into the GHC install tree.

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Rank-2 polymorphism and pattern matching
by Jim Apple 07 Jan '08

07 Jan '08

The following won't compile for me isnull :: (forall a . [a]) -> Bool isnull ([] :: forall b . [b]) = True Couldn't match expected type `forall b. [b]' against inferred type `[a]' In the pattern: [] Wrapping it in a constructor doesn't help, though I can define a "null": data NullList = NullList (forall a . [a]) null = NullList [] isnull2 :: NullList -> Bool isnull2 (NullList []) = True Why? Jim

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binary-dists for ghc-6.8.2
by Christian Maeder 07 Jan '08

07 Jan '08

Dear all, I've built binary distributions for Mac OS 10.4 (Tiger) based on (better supported) GMP and GNUreadline frameworks and for Solaris 10. http://www.dfki.de/sks/hets/mac/versions/ghc-6.8.2-powerpc-apple-darwin.tar… http://www.dfki.de/sks/hets/intel-mac/versions/ghc-6.8.2-i386-apple-darwin.… The frameworks under http://www.haskell.org/ghc/dist/mac_frameworks/mac_e.htm should do. The Mac binaries have been built using gcc version 4.0.1 (Apple Computer, Inc. build 5367) and a patched Linker.lhs from http://hackage.haskell.org/trac/ghc/ticket/1798 (also the files compiler/main/DriverPipeline.hs and utils/hsc2hs/Main.hs are patched according to http://hackage.haskell.org/trac/ghc/ticket/1395) The PPC binary still features: http://hackage.haskell.org/trac/ghc/ticket/1845 The PPC ghc can be used on Intel Macs with the additional options: -optc-arch -optcppc -opta-arch -optappc -optl-arch -optlppc (but that's slower than an i386 binary). The Intel-Mac binary has also a patched file rts/Exception.cmm for http://hackage.haskell.org/trac/ghc/ticket/1980 (although I don't know if it is a Mac problem at all.) The Solaris 10 binaries have been built using gcc-4.2.2 http://www.dfki.de/sks/hets/pc-solaris/versions/ghc-6.8.2-i386-unknown-sola… http://www.dfki.de/sks/hets/solaris/versions/ghc-6.8.2-sparc-sun-solaris2.t… The sparc binary was built on a "sun4u sparc SUNW,Sun-Fire-280R" using: SRC_HC_OPTS += -optc-mcpu=ultrasparc -opta-mcpu=ultrasparc Maybe these binary-dists are somehow useful. Christian

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GHC 6.8.1 port on FreeBSD-amd64?
by Wilhelm B. Kloke 07 Jan '08

07 Jan '08

As I have got an amd64 machine again, I am returning to my previous porting effort. When I try to build to .hc files on i386 system, I get the following error: > ... > gmake[2]: Entering directory `/usr/home/wb/ghc-6.8.1/libraries/unix' > ../../compiler/stage1/ghc-inplace -package-name unix-2.2.0.0 -hide-all-packages -i -idist/build/autogen -idist/build -i. -Idist/build -Iinclude -#include "HsUnix.h" -#include "execvpe.h" -odir dist/build -hidir dist/build -stubdir dist/build -package base-3.0.0.0 -package directory-1.0.0.0 -O -XCPP -XForeignFunctionInterface -idist/build -H32m -O0 -fasm -Rghc-timing -keep-hc-files -O -c dist/build/System/Posix/Process.hs -o dist/build/System/Posix/Process.o -ohi dist/build/System/Posix/Process.hi > Prologue junk?: .type s32x_ret, @function > s32x_ret: > pushl %ebp > movl %esp, %ebp > > <<ghc: 114363808 bytes, 9 GCs, 2951168/5799936 avg/max bytes residency (2 samples), 33M in use, 0.00 INIT (0.00 elapsed), 0.78 MUT (2.33 elapsed), 0.20 GC (0.23 elapsed) :ghc>> > gmake[2]: *** [dist/build/System/Posix/Process.o] Fehler 255 > gmake[2]: Leaving directory `/usr/home/wb/ghc-6.8.1/libraries/unix' > gmake[1]: *** [make.library.unix] Fehler 2 > gmake[1]: Leaving directory `/usr/home/wb/ghc-6.8.1/libraries' > gmake: *** [stage1] Fehler 2 which I don't understand at all. The build of ghc-6.8.1 for native use on a FreeBSD-6.2 i386 did not cause any problems. Perhaps someone else has done the porting work already. Please give me a note, if anybody is able to provide me a set of files to get the bootstrap further. -- Dipl.-Math. Wilhelm Bernhard Kloke Institut fuer Arbeitsphysiologie an der Universitaet Dortmund Ardeystrasse 67, D-44139 Dortmund, Tel. 0231-1084-257 PGP: http://vestein.arb-phys.uni-dortmund.de/~wb/mypublic.key

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Haddocumentation of 6.8.1
by Daniel Fischer 06 Jan '08

06 Jan '08

Yesterday, doing runghc ./Setup.hs haddock in zlib.0.4.0.1, I noticed that no Haddock docs have been built for my 6.8.1. I followed the usual building steps, which worked with previous GHCs, set XMLDocWays=html, then ./configure make make install make install-docs No library docs (users guide and Cabal manual are fine). I looked around in a couple of Makefiles, tried 'make doc' in libraries, that built docs, but Haddock couldn't make any cross-package links and libraries/index.html links to package/Package-Name.html, which doesn't exist, because it's package/dist/doc/html/package/Package-Name.html. Question 1: How do I get proper library documentation? Question 2: When I build a package via Cabal, is there a way to merge the documentation into the installed library docs (and if yes, how do I do it)? Feature request: Could the README in future please contain information on how to build library documentation properly? Thanks, Daniel

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Redefining built in syntax
by Neil Mitchell 05 Jan '08

05 Jan '08

Hi, I'm getting errors such as: C:/Documents/Uni/packages/base/GHC/Base.lhs:270:12: Illegal binding of built-in syntax: [] When I try and compile GHC/Base.lhs using the GHC API. Is there some flag I can pass to allow the rebinding of built in syntax? Thanks Neil

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<.> defined in GHC and System.FilePath
by Neil Mitchell 03 Jan '08

03 Jan '08

Hi The GHC API uses the <.> operator, which clashes with System.FilePath. Possibly this might want renaming to something else - I have absolutely no idea what it does! Prelude> :m GHC Prelude GHC> :i <.> (<.>) :: HsWrapper -> HsWrapper -> HsWrapper -- Defined in HsBinds Thanks Neil

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Readline for Windows in the FAQ
by Walt Rorie-Baety 03 Jan '08

03 Jan '08

Maybe I'm just too new at this, but the GCH FAQ entry for readline in GHCi is confusing for me. Especially since it ends with the sentence "Instructions for GHC 6.2.2. are here." However, as the quote goes, "there's no 'here' here." - the location of the instructions are missing. Could someone please clue me in to what I'm missing? That way, I could edit the Wiki page, to clue in others better. -- This signature intentionally left blank

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