September 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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bug in 6.8.1-candidate
by Serge D. Mechveliani 17 Oct '07

17 Oct '07

Dear GHC developers, this is a bug report on ghc-6.8.1-candidate. The archive http://botik.ru/pub/local/Mechveliani/ghcBugs/bug-6.8.0-sep28.zip contains a project for which `making' under ghc-6.8.0.20070928-src produces a report of kind ---------------------------------------------------- ... <many modules compiled> GBasFld_.hs: ... ghc-6.8.0.20070928: panic! (the 'impossible' happened) (GHC version 6.8.0.20070928 for i386-unknown-linux): initC: srt_lbl Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug ---------------------------------------------------- unzip it, please, and see install.txt. Then, see GBasFld_.hs, it is small, and it looks like ghc cannot compile it. In ghc-6.6.1, this project works all right. The project can easily be reduced to the size of about a single GBasFld_.hs module (see install.txt). Regards, ----------------- Serge Mechveliani mechvel(a)botik.ru

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FFI Bindings to Libraries using GMP
by benedikth 30 Sep '07

30 Sep '07

Hello, I've been struggling using FFI bindings to libraries which rely on the GNU Mp Bignum library (gmp) - this is apparently a well known problem (http://hackage.haskell.org/trac/ghc/ticket/311, http://hackage.haskell.org/trac/ghc/wiki/ReplacingGMPNotes) I do rely on using such libraries, and so started to get it work on MacOsX; no solution was close to being satisfactory however, so I'd like to ask for some advice. Those two options worked to some extend: (1) Create or modify the library in question, so gmp is statically linked and its symbols are hidden. When source code is available, this is relatively easy, altough it requires modification of the build process (which can be a hassle). If a static "ar" archive is available, it is cumbersome (at least on Mac Os X I ran into a lot of troubles using nmedit), but possible. Furthermore, the resulting libraries are bloated, as each of them contains a copy of the GMP; left alone portability issues. (2) As suggested in ticket#311, I tried switching the allocator functions when switching to FFI. It worked, but not in GHCi; also, doing it manually is a lot of work, because, as far as I could figure out, it is neccessary to write a wrapper function for every C-function (indirectly) using the gmp. Furthermore, most of the libraries expose gmp datatypes (mpz_t,mpq_t) in their API. I currently use a little haskell module working on GHC.Exts, but that's propably not a good option from a maintainer's point of view. There are certainly other possibilities, but I couldn't find one which is both maintainable and portable. I would be very grateful for any advice, or some information on plans for resolving ticket #311. There are some great libraries (like the Parma Polyhedral Library, to pick an example) out there using gmp, and it would be nice if writing bindings to those libs could be simplified. Thanks, Benedikt Huber

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runhaskell rather than runghc
by Serge D. Mechveliani 30 Sep '07

30 Sep '07

Dear GHC and Cabal developers and users, I suggest to use `runhaskell' rather than `runghc'. Because it looks to have more sense, and also for political correctness. Cabal is a tool for `making' various Haskell implementations. In 2015, we may have implementations ghc, Hugs, hbc, foo_1, ..., foo_n. Does Cabal need to provide runghc, runhugs, runhbc ... runfoo_n ? Do I mistake? Regards, ----------------- Serge Mechveliani mechvel(a)botik.ru

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bug in 6.8.1-candidate
by Serge D. Mechveliani 30 Sep '07

30 Sep '07

Dear GHC developers, I am preparing a bug report for the compiler of ghc-6.8.0.20070928-src: ------------------ GBasFld_.hs:387:45: Warning: Defined but not used: `t' ghc-6.8.0.20070928: panic! (the 'impossible' happened) (GHC version 6.8.0.20070928 for i386-unknown-linux): initC: srt_lbl Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug ------------------ This happens in the middle of the DoCon-2.11 `make'. Can you wait with ghc-6.8.1 ? Another point: the module Char_ exports several instances, and the module DPrelude has `module Char_' in its export list, and ghc-6.8.0.20070928-src reports that this latter decl "exports nothing". Probably, it must report "exports nothing, besides maybe, some instances" ? Regards, ----------------- Serge Mechveliani mechvel(a)botik.ru

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Data.Map in 6.8.1
by Serge D. Mechveliani 29 Sep '07

29 Sep '07

Dear GHC developers and users, I am trying to port the Dumatel-1.06 application from ghc-6.6.1 to ghc-6.8.0.20070928-src. First, it does not find runhaskell. All right, I replace it with runghc in order to see what happens next. Now, make configure reports runghc Setup.hs configure --ghc --prefix=/home/mechvel/dm/1.06/dm/source/inst Configuring dumatel-1.6... In 6.6.1, the report of runhaskell looked better, it wrote on the screen about ghc found in such and such place, and so on. Where to see this new report in a more detail? (is this a matter of the Cabal version?) Further, make build reports ------------------------------------- runghc Setup.hs build Preprocessing library dumatel-1.6... Building dumatel-1.6... Dumatel/Prelude5.hs:28:17: Could not find module `Data.Map': it is a member of package containers-0.1, which is hidden ------------------------------------ Should I change something in dm.cabal ? For example, it contains the line build-depends: base, haskell98 Where are docs on ghc-6.8.1 (in particular, release notes) ? Thank you in advance for your explanations, ----------------- Serge Mechveliani mechvel(a)botik.ru

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runhaskell in 6.8
by Serge D. Mechveliani 29 Sep '07

29 Sep '07

Dear GHC developers, this is on the future ghc-6.8.1. The DoCon-2.10 distribution uses the command runhaskell in its Makefile. This works in ghc-6.6.1 but does not work in ghc-6.8.0.20070928-src. Because the latter provides only runghc. Can you can put runhaskell next to runghc ? What to you have against runhaskell ? Regards, ----------------- Serge Mechveliani mechvel(a)botik.ru

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6.8.1-toTest
by Serge D. Mechveliani 29 Sep '07

29 Sep '07

Dear GHC developers, in old days I was able to download GHC from CVS. Now, it changed to darcs. I have read how to download via darcs and tried to download ghc-6.8-head. It responded with a hard to undertsand message and was hanging. I pressed Control-c. Immediately after this, there started to come e-mail messages about "returned mail", from various strange addresses. They were about 200 first day, 80 second day, 30 third, and then, they stopped, by and by, to my pleasure. This was the first case in my life of such a massive attack. I fear of this darcs. Maybe, you can put the source, for example, ghc-6.8.1-toTest-September-29.src...., and announce in this list where to download it from ? I care for this because my programs DoCon and Dumatel run (mainly) under GHC, and it is a good idea for them to comply with each new public GHC version, so, it is better to test a pre-release of GHC. Regards, ----------------- Serge Mechveliani mechvel(a)botik.ru

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ANNOUNCE: GHC 6.8.1 Release Candidate
by Ian Lynagh 28 Sep '07

28 Sep '07

We are pleased to announce the Release Candidate phase for GHC 6.8.1. Snapshots beginning with 6.8.20070909 are release candidates for 6.8.1 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-6.8.20070912-src.tar.bz2 http://www.haskell.org/ghc/dist/stable/dist/ghc-6.8.20070912-src-extralibs.… Only the first of these is necessary. The "extralibs" package contains various extra packages that we normally supply 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 hope to release in a couple of weeks, but of course that may slip if problems are uncovered. Thanks Ian, on behalf of the GHC team

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