June 2008 - 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 6.8.3 Release Candidate
by Ian Lynagh 22 Sep '09

22 Sep '09

We are pleased to announce the Release Candidate phase for GHC 6.8.3. Snapshots beginning with 6.8.2.20080527 are release candidates for 6.8.3 You can download snapshots from here: http://www.haskell.org/ghc/dist/stable/dist/ Right now we have the source bundles: http://www.haskell.org/ghc/dist/stable/dist/ghc-6.8.2.20080527-src.tar.bz2 http://www.haskell.org/ghc/dist/stable/dist/ghc-6.8.2.20080527-src-extralib… Only the first of these is necessary. The "extralibs" package contains various extra packages that are often supplied with GHC - unpack the extralibs tarball on top of the source tree to add them, and they will be included in the build automatically. There is also currently an installer for i386/Windows and binary distributions for x86_64/Linux and i386/Linux. More may appear later. Please test as much as possible; bugs are much cheaper if we find them before the release! We expect to release in a few days, assuming no major issues are discovered. Thanks Ian, on behalf of the GHC team

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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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Arrow without `>>>'
by Valery V. Vorotyntsev 03 Sep '08

03 Sep '08

Hi, friends, I've built GHC from darcs, and... Could anybody tell me, what's the purpose of Arrow[1] not having `>>>' method? 1. http://darcs.haskell.org/packages/base/Control/Arrow.hs $ ghci GHCi, version 6.9.20080104: http://www.haskell.org/ghc/ :? for help Loading package base ... linking ... done. Prelude> :m + Control.Arrow Prelude Control.Arrow> :i Arrow class (Control.Category.Category a) => Arrow a where arr :: (b -> c) -> a b c pure :: (b -> c) -> a b c first :: a b c -> a (b, d) (c, d) second :: a b c -> a (d, b) (d, c) (***) :: a b c -> a b' c' -> a (b, b') (c, c') (&&&) :: a b c -> a b c' -> a b (c, c') -- Defined in Control.Arrow instance Arrow (->) -- Defined in Control.Arrow instance (Monad m) => Arrow (Kleisli m) -- Defined in Control.Arrow Prelude Control.Arrow> Leaving GHCi. I can't build[2] arrows-0.3 package without `>>>' in Arrow. 2. vvv@fun:~/src/arrows$ darcs w { hunk ./Control/Arrow/Operations.hs 36 +import Control.Category ((>>>)) hunk ./Control/Arrow/Transformer/CoState.hs 23 +import Control.Category ((>>>)) } vvv@fun:~/src/arrows$ runhaskell Setup build Preprocessing library arrows-0.3... Building arrows-0.3... [ 3 of 12] Compiling Control.Arrow.Transformer.CoState ( Control/Arrow/Transformer/CoState.hs, dist/build/Control/Arrow/Transformer/CoState.o ) Control/Arrow/Transformer/CoState.hs:29:7: `>>>' is not a (visible) method of class `Arrow' The question arises "should I?", but this is one of lambdabot's[3] depencies. 3. http://code.haskell.org/lambdabot/ Thanks a lot! -- vvv

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Generalized phase control for GHC
by Max Bolingbroke 07 Jul '08

07 Jul '08

Hi, As some of you may know, I'm working on adding support for dynamically loaded plugins to GHC this summer. As part of this we need a way to specify ordering on the compiler phases installed, so e.g. you can say that a phase you install should run after strictness analysis does. This problem begs for a more modular and principled solution than just reusing the current system where we use the natural numbers to impose an ordering on INLINE/RULE activations. I have proposed a system at http://hackage.haskell.org/trac/ghc/wiki/Plugins/Phases that replaces this with one of named compiler phases not only for plugins but for all activation control in the compiler. The proposal mostly remains backwards compatible with the most common uses of the numeric format, with an exception noted on the page and below. I would be interested in feedback on the design before the implementation is complete and in the wild. I'm especially interested in hearing if you believe that loss of support for numeric phase numbers > 2 is a problem, as this is the only breaking change that I'm proposing. Cheers, Max

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Takusen build error
by Benjamin Franksen 02 Jul '08

02 Jul '08

I get a strange error building Takusen (more precisely: the module Foreign/C/UTF8.hs) with ghc-6.8.3. It says aragon: .../ghc-6.8.3/Takusen-0.8.1 > ./Setup build -v Reading parameters from /srv/projects/ctl/franksen/haskell/ghc-6.8.3/Takusen-0.8.1/takusen.buildinfo Creating dist/build (and its parents) Creating dist/build/autogen (and its parents) Preprocessing library Takusen-0.8.1... Building Takusen-0.8.1... Building library... Creating dist/build (and its parents) Creating dist/build (and its parents) /projects/ctl/franksen/usr/bin/ghc -package-name Takusen-0.8.1 --make -hide-all-packages -i -idist/build/autogen -idist/build -i. -Idist/build -I/opt/oracle/product/client/rdbms/demo -odir dist/build -hidir dist/build -stubdir dist/build -package base-3.0.2.0 -package mtl-1.1.0.1 -package time-1.1.2.1 -package old-time-1.0.0.0 -O -XCPP Database.Enumerator Database.Util Database.Oracle.Enumerator Database.Oracle.OCIConstants Database.Oracle.OCIFunctions Database.Stub.Enumerator Control.Exception.MonadIO Foreign.C.UTF8 Database.InternalEnumerator [1 of 9] Compiling Foreign.C.UTF8 ( Foreign/C/UTF8.hs, dist/build/Foreign/C/UTF8.o ) /tmp/ghc18936_0/ghc18936_0.s: Assembler messages: /tmp/ghc18936_0/ghc18936_0.s:1257:0: Error: symbol `base_GHCziBase_Z0T_closure' is already defined I compiled ghc-6.8.3 from source, using ghc-6.8.2 to bootstrap. Any ideas? Cheers Ben

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ANNOUNCE: GHC version 6.8.3
by Ian Lynagh 02 Jul '08

02 Jul '08

============================================================= The (Interactive) Glasgow Haskell Compiler -- version 6.8.3 ============================================================= The GHC Team is pleased to announce a new patchlevel release of GHC. This release contains a number of bugfixes relative to 6.8.2, so we recommend upgrading. Release notes are here: http://haskell.org/ghc/docs/6.8.3/html/users_guide/release-6-8-3.html How to get it ~~~~~~~~~~~~~ The easy way is to go to the web page, which should be self-explanatory: http://www.haskell.org/ghc/ We supply binary builds in the native package format for many platforms, and the source distribution is available from the same place. Packages will appear as they are built - if the package for your system isn't available yet, please try again later. Background ~~~~~~~~~~ Haskell is a standard lazy functional programming language; the current language version is Haskell 98, agreed in December 1998 and revised December 2002. GHC is a state-of-the-art programming suite for Haskell. Included is an optimising compiler generating good code for a variety of platforms, together with an interactive system for convenient, quick development. The distribution includes space and time profiling facilities, a large collection of libraries, and support for various language extensions, including concurrency, exceptions, and foreign language interfaces (C, whatever). GHC is distributed under a BSD-style open source license. A wide variety of Haskell related resources (tutorials, libraries, specifications, documentation, compilers, interpreters, references, contact information, links to research groups) are available from the Haskell home page (see below). On-line GHC-related resources ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Relevant URLs on the World-Wide Web: GHC home page http://www.haskell.org/ghc/ GHC developers' home page http://hackage.haskell.org/trac/ghc/ Haskell home page http://www.haskell.org/ Supported Platforms ~~~~~~~~~~~~~~~~~~~ The list of platforms we support, and the people responsible for them, is here: http://hackage.haskell.org/trac/ghc/wiki/Contributors Ports to other platforms are possible with varying degrees of difficulty. The Building Guide describes how to go about porting to a new platform: http://hackage.haskell.org/trac/ghc/wiki/Building Developers ~~~~~~~~~~ We welcome new contributors. Instructions on accessing our source code repository, and getting started with hacking on GHC, are available from the GHC's developer's site run by Trac: http://hackage.haskell.org/trac/ghc/ Mailing lists ~~~~~~~~~~~~~ We run mailing lists for GHC users and bug reports; to subscribe, use the web interfaces at http://www.haskell.org/mailman/listinfo/glasgow-haskell-users http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs There are several other haskell and ghc-related mailing lists on www.haskell.org; for the full list, see http://www.haskell.org/mailman/listinfo/ Some GHC developers hang out on #haskell on IRC, too: http://www.haskell.org/haskellwiki/IRC_channel Please report bugs using our bug tracking system. Instructions on reporting bugs can be found here: http://www.haskell.org/ghc/reportabug

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Error building GHC 6.8.3 with MinGW 4.2.1-2 dw2
by leledumbo 30 Jun '08

30 Jun '08

I try to build a lite version (e.g. no extra libs) of GHC 6.8.3, I'm using MinGW GCC 4.2.1-2 with dwarf-2 exception and pre-compiled GHC 6.8.3. Here's my configure: sh configure --prefix=/c/ghc-new CFLAGS='-s -O2' LDFLAGS='-s -O2' --with-gmp-includes=/usr/local/gmp/include --with-gmp-libraries=/usr/local/gmp/lib And my make: make bootstrap3 But in the middle, I got this: Preprocessing library hpc-0.5.0.1... In file included from D:/Sources/ghc/ghc-6.8.3-lite/includes/Stg.h:183, from D:/Sources/ghc/ghc-6.8.3-lite/includes/Rts.h:19, from Trace\Hpc\Reflect.hsc:18: D:/Sources/ghc/ghc-6.8.3-lite/includes/Regs.h:28:17: error: gmp.h: No such file or directory In file included from D:/Sources/ghc/ghc-6.8.3-lite/includes/Stg.h:183, from D:/Sources/ghc/ghc-6.8.3-lite/includes/Rts.h:19, from Trace\Hpc\Reflect.hsc:18: D:/Sources/ghc/ghc-6.8.3-lite/includes/Regs.h:121: error: expected specifier-qua lifier-list before 'MP_INT' In file included from Trace\Hpc\Reflect.hsc:18: D:/Sources/ghc/ghc-6.8.3-lite/includes/Rts.h:203: error: expected ')' before '*' token D:/Sources/ghc/ghc-6.8.3-lite/includes/Rts.h:204: error: expected ')' before '*' token compiling dist\build\Trace\Hpc\Reflect_hsc_make.c failed command was: gcc -c -mno-cygwin -D__GLASGOW_HASKELL__=608 -ID:/Sources/ghc/ghc-6 .8.3-lite/includes -ID:/Sources/ghc/ghc-6.8.3-lite/gmp/gmpbuild -I/usr/local/gmp /include -D__GLASGOW_HASKELL__=608 dist\build\Trace\Hpc\Reflect_hsc_make.c -o di st\build\Trace\Hpc\Reflect_hsc_make.o make[2]: Entering directory `/d/Sources/ghc/ghc-6.8.3-lite/libraries/hpc' make[2]: *** No targets specified and no makefile found. Stop. make[2]: Leaving directory `/d/Sources/ghc/ghc-6.8.3-lite/libraries/hpc' make[1]: *** [make.library.hpc] Error 2 make[1]: Leaving directory `/d/Sources/ghc/ghc-6.8.3-lite/libraries' make: *** [stage1] Error 2 As you can see above, I have gmp installed under /usr/local/gmp. However, this is not the gmp that comes with GHC (version 4.2.1, mine is 4.2.2). PS: I must comment these two lines in IOManager.h: 12: extern void* GetCurrentFiber ( void ); 13: extern void* GetFiberData ( void ); or an error about "static declaration follows non-static declaration" will come up. -- View this message in context: http://www.nabble.com/Error-building-GHC-6.8.3-with-MinGW-4.2.1-2-dw2-tp181… Sent from the Haskell - Glasgow-haskell-users mailing list archive at Nabble.com.

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Implicit Function Arguments
by Tyson Whitehead 30 Jun '08

30 Jun '08

What do people think about implicit function argument? That is, named function arguments, possibly tagged with something special like a tilde, whereby scoped variables of the same name are automatically passed. The idea is to avoid the pain of a lots of pass through parameters while make it easy to modify one or two of them. For example, in f1 :: ~state::State -> Input -> Output f1 input = f2 input f2 :: ~state::State -> Input -> Output f2 input = <whatever> we don't have to specify ~state for f2 because it picks it up automatically from ~state being in scope from f1. To change it, however, we just do f1 :: ~state::State -> Input -> Output f1 input = f2 input where ~state = <whatever> The advantage over wrapping it in a monad being: 1) it is evident what is being passed around behind the scenes from the type signatures, and 2) we avoiding the lifting issue (to compose multiple implicit arguments we just specifying them -- assuming their are no name clashes). Cheers! -Tyson

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Illegal instruction with ghc-6.8.3 distribution (OS X Tiger)
by Judah Jacobson 27 Jun '08

27 Jun '08

Hi, I recently installed ghc-6.8.3 on an iBook running OS X 10.4.11 (PowerPC G4), using the following distribution: http://www.haskell.org/ghc/dist/6.8.3/maeder/ghc-6.8.3-powerpc-apple-darwin… Running the following program, compiled with -O, causes an illegal instruction error: =========== module Main where main = print foo foo :: Integer foo = gcd 400 85 ================== Running through gdb produced the following output: Program received signal EXC_BAD_INSTRUCTION, Illegal instruction/operand. 0x00046b50 in __gmpn_gcd_1 () (gdb) where #0 0x00046b50 in __gmpn_gcd_1 () #1 0x00028cb0 in gcdIntzh_fast () #2 0x0002be34 in scheduleWaitThread () #3 0x0001fdb8 in real_main () #4 0x0001fec0 in main () (gdb) quit Christian, did you compile this distribution on a G5 PowerPC? GMP is statically linked into this distribution, so if it's using any processor-specific instructions I could see that tripping up my G4. If you or someone else can confirm that this works on a G5, then we should probably just update the downloads page with that requirement. Thanks, -Judah

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