November 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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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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suggestion: add a .ehs file type
by Alex Jacobson 13 Dec '07

13 Dec '07

.ehs stands for extended haskell and encapsulates the 90% case of people just wanting -fglasgow-exts with a minimum of fuss. Having a filetype seesm better than the alternatives of either adding boilerplate language/options pragmas to the top of your source files or putting them in a cabal file. -Alex-

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HUnit 1.2.0.0 on 6.8.1 vs 1.1.1 on 6.6.1
by Greg Fitzgerald 07 Dec '07

07 Dec '07

On Windows, HUnit's assertions are not working - trace below in ghci 6.8.1and 6.6.1. Can others reproduce? Is this the right place to report bugs? Should I confirm a bug here and then create a ticket, create a ticket and that's it, or just mention it here and someone else creates a ticket? GHCi, version 6.8.1: http://www.haskell.org/ghc/ :? for help Loading package base ... linking ... done. > :m Test.HUnit > "abc" @=? "efg" Loading package HUnit-1.2.0.0 ... linking ... done. *** Exception: (unknown) ___ ___ _ / _ \ /\ /\/ __(_) / /_\// /_/ / / | | GHC Interactive, version 6.6.1, for Haskell 98. / /_\\/ __ / /___| | http://www.haskell.org/ghc/ \____/\/ /_/\____/|_| Type :? for help. Loading package base ... linking ... done. > :m Test.HUnit > "abc" @=? "efg" Loading package HUnit-1.1.1 ... linking ... done. *** Exception: user error (HUnit:expected: "abc" but got: "efg") Thanks, Greg

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GHC generated dll makes Excel crash on exit.
by Olivier Boudry 04 Dec '07

04 Dec '07

Hi all, I need to call an Haskell module from Excel and as an exercise I started to play with the example given in GHC documentation: http://www.haskell.org/ghc/dist/current/docs/users_guide/win32-dlls.html I could build the DLL without problem but encountered a problem when using it. I created an Excel document using the dll. If I open the Excel document, do something that will trigger a function call in the DLL, then Excel will crash on Exit. On the opposite if I open the same document and changes cells not related to the function the program closes properly. I does not crash directly on the function call but later, just when I close Excel. As it crashes when closing Excel I suspect something is wrong when unloading the dll. I modified the dllMain.c code to handle the DLL_PROCESS_DETACH event but it doesn't solve the problem. } else if (reason == DLL_PROCESS_DETACH) { shutdownHaskell(); return TRUE; } I attached the code to this e-mail. I built the dll this way: ghc -fglasgow-exts -c adder.hs ghc -c dllMain.c ghc -shared -o adder.dll adder.o adder_stub.o dllMain.o Any idea on what could go wrong? Another event to handle? Thanks, Olivier.

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ghc vs ghci: why can't ghci do everything ghc can do?
by Claus Reinke 04 Dec '07

04 Dec '07

1) is there a single place/wiki/ticket that collects all the deficiencies of ghci, compared to ghc? things like: a) which platforms have ghc, but not ghci b) which features are available in ghc, but not in ghci c) does ghci encounter bugs where ghc would succeed d) which of these deficiencies are temporary, which are likely to stay 2) given that ghci is ghc --interactive, why are there any cases of b/c above at all? wouldn't it be possible for ghci to try its stuff, but to fall back to ghc only for those modules which it can't handle from source itself (yet)? - we can do ghc --make; ghci, to get around issues - we can do ghci -fforce-recomp, to get to sources but those two are rather coarse-grained, and require too much manual tweaking to get the effect of creating a ghci session with as many modules from source as possible, and all others from object files. 3) suggestions: a) could we have a :make command in ghci that does a 'ghc --make' while reusing the information from the current session? b) could we have a --prefer-source option for ghci, so that 'ghc --make; ghci --prefer-source' will try to load all modules from source, but will fall back to the existing object files if necessary (instead of failing, as -fforce-recomp does)? c) allow selective switching between source and object files loaded into ghci (:prefer source M,N,..; :prefer object O,P,Q,..). the application i have in mind is trying to use ghci on non-trivial projects, such as darcs, or even ghc itself: - it isn't possible to load all sources into ghci - loading all object files is possible, but prevents use of ghci features such as ':m *Module', ':browse *Module', breakpoints, tags, .. - ghci -fforce-recomp fails because it applies to all modules - there is substantial setup to do before one can call ghc or ghci, so dropping out of a session and trying to figure out dependencies and flags for compiling individual modules by hand isn't practical - there is often a configurable makefile, so that one can use the same setup for calling either 'ghc --make' or 'ghc --interactive'; but, within the latter, one cannot simply switch to full :make or to selective --prefer-source, without losing the setup ideally, ghci would simply work whereever ghc works, and would provide its additional features for as many modules as it can. but in the interim, having 3a and especially 3b would help me a lot. 3c would also be nice, too, but not as urgent as 3b. i find it sad that, currently, there is this gap that doesn't allow me to make full use of ghci's features for larger projects such as darcs or ghc. is hoping for 3b realistic? claus

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Leopard: ghc 6.8.1 and the case of the missing _environ
by Joel Reymont 04 Dec '07

04 Dec '07

Symptoms: You build 6.8.1 from source on Leopard (x86 in my case) and then junior:ghc-6.8.1 joelr$ ghci GHCi, version 6.8.1: http://www.haskell.org/ghc/ :? for help ghc-6.8.1: /usr/local/lib/ghc-6.8.1/lib/base-3.0.0.0/HSbase-3.0.0.0.o: unknown symbol `_environ' Loading package base ... linking ... ghc-6.8.1: unable to load package `base' Problem: ghc binaries are being stripped upon installation which eliminates _environ, e.g. junior:tmp joelr$ nm x|grep environ 00002ff0 T ___hscore_environ 0004d004 D _environ junior:tmp joelr$ strip x junior:tmp joelr$ nm x|grep environ Solution: Need to make sure install-sh does _not_ use the -s option. Haven't found out where this needs to be done yet. A temporary workaround is to ask Manuel for the pre-built binaries. Thanks, Joel -- http://wagerlabs.com

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