- Glasgow-haskell-users

Bug or not-yet-supported?
by Niklas Broberg 17 Mar '08

17 Mar '08

I haven't payed much attention to how much of type families is/should be implemented for 6.8.2. What of equality constraints? The following parses alright, but can't be used it seems. ------------------------------------ module Foo where class C a where proof :: a instance (a ~ Int) => C a where proof = 1 ------------------------------------ %> ghci -fglasgow-exts -XUndecidableInstances Foo.hs GHCi, version 6.8.2: http://www.haskell.org/ghc/ :? for help Loading package base ... linking ... done. [1 of 1] Compiling Foo ( Foo.hs, interpreted ) Ok, modules loaded: Foo. *Foo> proof :: Int : panic! (the 'impossible' happened) (GHC version 6.8.2 for i386-unknown-mingw32): nameModule $dC{v aoz} Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug ------------------------------------ I would follow that last advice if I knew this was *supposed* to work. :-) Cheers, /Niklas

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timer_create
by Christian Maeder 16 Mar '08

16 Mar '08

Hi, my binary distribution http://www.haskell.org/ghc/dist/6.8.2/maeder/ghc-6.8.2-i386-unknown-linux.t… creates binaries that fail on some i386 linux boxes with: timer_create: Invalid argument I've built the distribution with gcc version 4.1.2 20061115 (prerelease) (SUSE Linux) and the file lib/ghc-6.8.2/include/ghcautoconf.h contains: #define HAVE_TIMER_CREATE 1 The failing machine uses gcc version 3.3.5 and ./configure within the ghc-6.8.2 sources says: checking for a working timer_create(CLOCK_REALTIME)... no Take this as a warning when using my binary-dist above (or when building your own). Or is there a work around (apart from creating a new binary-dist using ghc-6.6.1)? Cheers Christian

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Making rule application less fragile
by Johan Tibell 14 Mar '08

14 Mar '08

Hi, I'm trying (for the first time ever) to use RULES pragmas to achieve some nice speedups in my bytestring parsing library. The relevant code in my library's module is: -- The module imports Control.Applicative which containes 'many' and 'some'. -- | The parser @satisfy p@ succeeds for any byte for which the -- supplied function @p@ returns 'True'. Returns the byte that is -- actually parsed. satisfy :: (Word8 -> Bool) -> Parser Word8 satisfy p = Parser $ \s@(S bs pos eof) succ fail -> case S.uncons bs of Just (b, bs') -> if p b then succ b (S bs' (pos + 1) eof) else fail s Nothing -> if eof then fail s else IPartial $ \x -> case x of Just bs' -> retry (S bs' pos eof) Nothing -> fail (S bs pos True) where retry s' = unParser (satisfy p) s' succ fail -- | @byte b@ parses a single byte @b@. Returns the parsed byte -- (i.e. @b@). byte :: Word8 -> Parser Word8 byte b = satisfy (== b) -- --------------------------------------------------------------------- -- Rewrite rules satisfyMany :: (Word8 -> Bool) -> Parser S.ByteString satisfyMany p = undefined -- More efficient implementation goes here. satisfySome :: (Word8 -> Bool) -> Parser S.ByteString satisfySome p = undefined -- More efficient implementation goes here. {-# RULES "fmap/pack/many/satisfy" forall p. fmap S.pack (many (satisfy p)) = satisfyMany p "fmap/pack/some/satisfy" forall p. fmap S.pack (some (satisfy p)) = satisfySome p #-} In another module where I use the library I have this code: pHeaders :: Parser [(S.ByteString, S.ByteString)] pHeaders = many header where header = liftA2 (,) fieldName (byte (c2w ':') *> spaces *> contents) fieldName = liftA2 (S.cons) letter fieldChars contents = liftA2 (S.append) (fmap S.pack $ some notEOL <* crlf) (continuation <|> pure S.empty) continuation = liftA2 (S.cons) ((c2w ' ') <$ some (oneOf (map c2w " \t"))) contents -- It's important that all three of these definitions are kept on the -- top level to have RULES fire correctly. fieldChars = fmap S.pack $ many fieldChar -- fieldChar = letter <|> digit <|> oneOf (map c2w "-_") fieldChar = satisfy isFieldChar where isFieldChar b = (isDigit $ chr $ fromIntegral b) || (isAlpha $ chr $ fromIntegral b) || (b `elem` map c2w "-_") I want the fieldChars use of 'fmap S.pack $ many fieldChar' to trigger my rewrite rule "fmap/pack/many/satisfy" which it does in this case. The trouble is that the rule only triggers when I make at least fieldChars and fieldChar top-level definition and isFieldChar either a named local definition in fieldChar or a top-level definition. If I turn the predicate (isFieldChar) into to an anonymous lambda function it doesn't trigger, if I make either fieldChars or fieldChars a local defintion (in a where clause) of pHeaders it doesn't trigger. If I make fieldChar a local definition in fieldChars it doesn't trigger, etc. It would be great if there was a way to make this a bit less fragile and have the rule trigger more often as it is potentially a huge performance win. I understand it's hard to guarantee that the rule always triggers but now it triggers in rare cases. -- Johan

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Re: ANN: ghc 6.8.2 from MacPorts
by Christian Maeder 14 Mar '08

14 Mar '08

Hi Greg, I can't test it myself because I don't have root access to our machines. Maybe someone else can? (Meanwhile I'll try to make a binary-dist that includes the extra-libs.) Cheers Christian Gregory Wright wrote: > > Hi Christian, > > I built a new bootstrapping compiler on Tiger/ppc, incorporating > Thorkil's .text section > patch. I've modified the portfile, but since I don't have a Leopard/ppc > machine I can't > try it. Could you give it a go? > > Do > > $ sudo port selfupdate > $ sudo port clean --all ghc > $ sudo port -dv install ghc > inst.log 2>&1 > > You might want to check after the selfupdate that you have revision 2 of > the ghc portfile. > It may take a few hours for the server to index the port and make it > available by rsync. > > If it fails, you can compress the log and send it to me. The "-dv" > flags dump all of the > MacPorts and build information. > > There may still be a stupid bug or two since I can't test it myself. > > Thanks, > Greg >

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setlocale
by Tristan Allwood 14 Mar '08

14 Mar '08

Hi, I've been playing around with hs-curses and utf8, and have discovered that I need to use an ffi call at the top of my main to setlocale(LC_ALL, "") in order to get the hscurses bindings to display utf8-encoded strings correctly. If I understand correctly, the fact that I need to do this means that the ghc rts is either not setting the default locale, or is forcing it to be a c-style one. With that as my context I'm just wondering: a) if this is a known issue b) if there's a known work-around other than rolling your own ffi wrapped call (a library function that I'm not aware of) c) any side effects this might have elsewhere d) if I'm being stupid and could get this to work by just using env vars Regards, Tristan Allwood 21:23:39 - tora@colorado:~ >locale LANG=en_GB.UTF-8 LC_CTYPE="en_GB.UTF-8" LC_NUMERIC="en_GB.UTF-8" LC_TIME="en_GB.UTF-8" LC_COLLATE="en_GB.UTF-8" LC_MONETARY="en_GB.UTF-8" LC_MESSAGES="en_GB.UTF-8" LC_PAPER="en_GB.UTF-8" LC_NAME="en_GB.UTF-8" LC_ADDRESS="en_GB.UTF-8" LC_TELEPHONE="en_GB.UTF-8" LC_MEASUREMENT="en_GB.UTF-8" LC_IDENTIFICATION="en_GB.UTF-8" LC_ALL= >ghc -v Glasgow Haskell Compiler, Version 6.8.2, for Haskell 98, stage 2 booted by GHC version 6.8.1 >uname -a Linux colorado 2.6.24-1-amd64 #1 SMP Mon Feb 11 13:47:43 UTC 2008 x86_64 GNU/Linux -- Tristan Allwood PhD Student Department of Computing Imperial College London

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ghc's trac is wedged
by Gregory Wright 13 Mar '08

13 Mar '08

Hi, This morning (13 March 2008) the ghc trac wedged reporting Trac detected an internal error: with the python traceback Traceback (most recent call last): File "/var/lib/python-support/python2.4/trac/web/main.py", line 387, in dispatch_request dispatcher.dispatch(req) File "/var/lib/python-support/python2.4/trac/web/main.py", line 237, in dispatch resp = chosen_handler.process_request(req) File "/var/lib/python-support/python2.4/trac/web/auth.py", line 100, in process_request self._do_login(req) File "/var/lib/python-support/python2.4/trac/web/auth.py", line 139, in _do_login "VALUES (%s, %s, %s, %s)", (cookie, remote_user, File "/var/lib/python-support/python2.4/trac/db/util.py", line 50, in execute return self.cursor.execute(sql_escape_percent(sql), args) File "/usr/lib/python2.4/site-packages/sqlite/main.py", line 237, in execute self.con._begin() File "/usr/lib/python2.4/site-packages/sqlite/main.py", line 503, in _begin self.db.execute("BEGIN") OperationalError: database is locked Please let me know if there is a more direct way to report failures such as this one, instead of posting to the list. Best Wishes, Greg

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Understanding the undefine flags passed to gcc when linking
by Bruce, Joseph R (Joe) 13 Mar '08

13 Mar '08

Hi, When I run 'ghc -v ...', the linking is done via gcc->ld with a large list of -u flags passed in. I'm hoping to find a way to link my object files without those flags, but first I need to understand what they are doing. Can someone explain it to me? Or point me to documentation that explains it? My ultimate goal is to build a static Haskell library and make it available to c programmers ignorant of Haskell. The undefines described above are a major obstacle. Does anyone know a way around them? Thanks, Joe Bruce Phone: 509.372.6198 Pacific Northwest National Laboratory 902 Battelle Blvd. Richland, WA

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swap (x, y)
by Serge D. Mechveliani 11 Mar '08

11 Mar '08

I define and use swap (x, y) = (y, x) because do not find such in the standard library. Please, can people point at it, in the standard library, or at least in GHC? Thank you in advance for your help. ----------------- Serge Mechveliani mechvel(a)botik.ru

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Release plans
by Ian Lynagh 10 Mar '08

10 Mar '08

Hi all, Here are our plans for the next couple of GHC releases. First, we intend to release the next version of GHC from the current stable branch, 6.8.3, around the end of May 2008. This will probably be the last release from this branch. We currently have 90 bugs in either the "6.8.3" or "6.8 branch" milestone, but we do not expect that we will have time to fix them all! So please take a few minutes to take a look through the list, and if there are any that are particularly important to you please: * add a comment to the bug report saying why it is important to you. It is not necessary to also send us a mail, as we get the comments e-mailed to us automatically. * add yourself to the CC list for the bug (we use this to get a count of the number of people interested in a bug). This will help us to make a release that fixes as many problems, for as many people, as possible. The list is here: http://hackage.haskell.org/trac/ghc/query?status=new&status=assigned&status… After that, around ICFP (late September 2008) we plan to make the first release, 6.10.1, from the next stable branch, 6.10. There will be more information on what exciting changes this will bring closer to the time. Thanks Ian, on behalf of the GHC team

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monomorphic or not?
by John Meacham 06 Mar '08

06 Mar '08

http://www.cse.unsw.edu.au/~dons/code/nobench/real/compress/compress.hs if you notice this program has the line > compress = map toEnum . codes_to_ascii . encode It seems to me this should run afoul of the monomorphism restriction due to the unknown ambiguous type in Enum, but ghc 6.8.2 happily accepts it. Jhc thinks it is illegal according to my reading of the specification. Any ideas about what is going on here? John -- John Meacham - ⑆repetae.net⑆john⑈

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