July 2008 - Haskell-Cafe

parsec linking problem
by naruto canada 07 Jul '08

07 Jul '08

hi I've just managed to get ghc-6.8.3 installed and tried to run an example from "http://en.wikibooks.org/wiki/Write_Yourself_a_Scheme_in_48_Hours/Parsing" I run into linking error with parsec: Here is the code: module Main where import System.Environment import Text.ParserCombinators.Parsec hiding (spaces) symbol :: Parser Char symbol = oneOf "!#$%&|*+-/:<=>?@^_~" main :: IO () main = do -- args <- getArgs -- putStrLn ("Hello, " ++ (args!!0) ++ " " ++ (args!!1) ) -- putStrLn ( show( read(args!!0) + read(args!!1) ) ) putStrLn ( "give me a name:" ) name <- getLine putStrLn ( name ) ghc -o /tmp/a.out accu.hs accu.o: In function `so8_info': : undefined reference to `parseczm2zi1zi0zi1_TextziParserCombinatorsziParsecziChar_oneOf_closure' accu.o: In function `spP_info': : undefined reference to `__stginit_parseczm2zi1zi0zi1_TextziParserCombinatorsziParsec_' accu.o: In function `so8_closure': : undefined reference to `parseczm2zi1zi0zi1_TextziParserCombinatorsziParsecziChar_oneOf_closure' collect2: ld returned 1 exit status Thanks my installation steps (just in case you need to know): WGET_UNPACK http://ftp.gnu.org/gnu/readline/readline-4.3.tar.gz ./configure --prefix=/usr make clean ; make || INTERVENTION find . -name libhistory.so* find . -name libreadline.so* cp shlib/libhistory.so.4.3 /lib cp shlib/libreadline.so.4.3 /lib ln -sfvn libhistory.so.4.3 /lib/libhistory.so.4 ln -sfvn libreadline.so.4.3 /lib/libreadline.so.4 WGET_UNPACK http://haskell.org/ghc/dist/6.8.2/ghc-6.8.2-i386-unknown-linux.tar.bz2 cd ghc-6.8.2 autoreconf ./configure --prefix=/usr make install echo 'main = putStrLn "hello"' > t.hs ghc t.hs ./a.out | grep hello || INTERVENTION rm -rf /build/ghc-6.8.2 WGET_UNPACK http://haskell.org/ghc/dist/6.8.3/ghc-6.8.3-src-extralibs.tar.bz2 WGET_UNPACK http://haskell.org/ghc/dist/6.8.3/ghc-6.8.3-src.tar.bz2 cd ghc-6.8.3 autoreconf ./configure --prefix=/usr make clean ; make || INTERVENTION make || INTERVENTION make install echo 'main = putStrLn "hello"' > t.hs ghc t.hs ./a.out | grep hello || INTERVENTION ghc --version | grep 6.8.3 || INTERVENTION

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Re: [Gtk2hs-users] ANN: Gtk2Hs 0.9.13 released
by Peter Gavin 07 Jul '08

07 Jul '08

Peter Hercek wrote: > Thanks for the package. > I experienced some bugs with it on windows. When showing a dynamically > built context menu, I'm getting errors like these: > > _cairo_win32_surface_show_glyphs(ExtTextOutW failed): The operation completed successfully. > _flush_glyphs: The operation completed successfully. > > ... and the text of some menu items is not shown (otherwise the menu > items do work - actions are called when they are clicked). > > When I try to run the app under ghci I get error like this: > > Loading package glib-0.9.13 ... <interactive>: Unknown PEi386 section name `.reloc' (while processing: > C:/tools/Gtk2Hs/HSglib.o) > ghc.exe: panic! (the 'impossible' happened) > (GHC version 6.8.3 for i386-unknown-mingw32): > loadObj: failed > Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug > > Using older Gtk (2.10.13) helps for the first one. > Using my own compile of Gtk2Hs (I compiled older version 0.9.12.1 > myself) helps for the second one. > > Peter. Hi Peter, The first problem looks like a problem in cairo. I'm pretty sure the functions named are cairo internal API, you may want to report a bug to their list. I suppose it's possible those functions always print the error message (even on success), but behave correctly otherwise. It looks like the second problem is a GHC bug, since there isn't anything special about our library (that I can think of) that might cause that to happen. Pete > > Peter Gavin wrote: >> Hello everyone, >> >> Gtk2Hs version 0.9.13 is now available. [1] >> >> New features: >> >> * bindings for Gnome VFS and GStreamer >> * a new Gtk+ tutorial has been adapted by Hans van Thiel >> * cairo image stride support >> * many new demos >> * compiles with GHC 6.8.3 >> * lots of bug fixes >> >> This release has been tested on a variety of platforms with different >> versions of Gtk+ and GHC, so you should have no trouble compiling it if >> you're using an older version of Gtk+. >> >> Note that the binaries for Win32 for this release are only provided for >> GHC 6.8.3 and Gtk+ 2.12. As with older releases, all the C libraries >> needed are included in the installer, so you don't need to download >> anything else to get up an running. I've also created zip files >> containing only the C libraries that can be used for redistribution. >> The sources for these binaries are available at [2] >> >> Links: >> [1] >> http://sourceforge.net/project/showfiles.php?group_id=49207&package_id=42440 >> [2] http://ftp.gnome.org/pub/GNOME/sources/ >> >> >> -- >> Pete >> >> ------------------------------------------------------------------------- >> Check out the new SourceForge.net Marketplace. >> It's the best place to buy or sell services for >> just about anything Open Source. >> http://sourceforge.net/services/buy/index.php > > > > ------------------------------------------------------------------------- > Sponsored by: SourceForge.net Community Choice Awards: VOTE NOW! > Studies have shown that voting for your favorite open source project, > along with a healthy diet, reduces your potential for chronic lameness > and boredom. Vote Now at http://www.sourceforge.net/community/cca08 > _______________________________________________ > Gtk2hs-users mailing list > Gtk2hs-users(a)lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/gtk2hs-users

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ANN: Gtk2Hs 0.9.13 released
by Peter Gavin 07 Jul '08

07 Jul '08

Hello everyone, Gtk2Hs version 0.9.13 is now available. [1] New features: * bindings for Gnome VFS and GStreamer * a new Gtk+ tutorial has been adapted by Hans van Thiel * cairo image stride support * many new demos * compiles with GHC 6.8.3 * lots of bug fixes This release has been tested on a variety of platforms with different versions of Gtk+ and GHC, so you should have no trouble compiling it if you're using an older version of Gtk+. Note that the binaries for Win32 for this release are only provided for GHC 6.8.3 and Gtk+ 2.12. As with older releases, all the C libraries needed are included in the installer, so you don't need to download anything else to get up an running. I've also created zip files containing only the C libraries that can be used for redistribution. The sources for these binaries are available at [2] Links: [1] http://sourceforge.net/project/showfiles.php?group_id=49207&package_id=42440 [2] http://ftp.gnome.org/pub/GNOME/sources/ -- Pete

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Re: [Haskell-cafe] Is there a nicer way to do this?
by Don Stewart 07 Jul '08

07 Jul '08

mfeathers: > Don Stewart wrote: > >mfeathers: > >> > >>segment :: Int -> [a] -> [[a]] > >>segment 0 _ = [] > >>segment _ [] = [] > >>segment n x = (take n x) : segment n (drop n x) > > > >The first set of parens can go, > > > > segment n x = take n x : segment n (drop n x) > > > >>I did a version of this which used splitAt but I wasn't sure whether it > >>was going to buy me anything re performance that would justify its > >>ugliness. > > > >Besides, > > > > splitAt n xs = (take n xs, drop n xs) > > Thanks. That is odd, though. It makes me wonder what to expect re > optimization. Would the compiler/runtime know that splitAt could be > done in a single pass? Not with that definition. It would require some moderately unusual fusion combining the take and drop into a single fold with the (,) on the inside, rather than on the outside. However, GHC actually implements splitAt as: splitAt (I n) ls | n < 0 = ([], ls) | otherwise = splitAt' n ls where splitAt' :: Int -> [a] -> ([a], [a]) splitAt' 0 xs = ([], xs) splitAt' _ xs@[] = (xs, xs) splitAt' m (x:xs) = (x:xs', xs'') where (xs', xs'') = splitAt' (m - 1) xs So there may be some benefit. -- Don

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Compiling GHC 6.8.3 on OS X with readline support
by Chris Eidhof 07 Jul '08

07 Jul '08

Hey all, When compiling GHC 6.8.3 on OS X, I ended up with a GHCi without readline support. That makes interacting quite hard, especially because the Backspace-key didn't even work. With some help on irc from Baughn and by reading a blog post from Paul Brown, I managed to get readline working after all. After installing readline from fink, I had to pass the following options to configure: ./configure --with-readline-includes=/sw/include/readline --with- readline-libraries=/sw/lib After that make and sudo make install worked just fine, and I had readline again! I wrote this down in case anybody else has had the same problems. -chris

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Re: [Haskell-cafe] OpenSSL.Digest linking error: EVP_mdc2
by Donn Cave 07 Jul '08

07 Jul '08

Quoth "Ken Takusagawa" <ken.takusagawa.2(a)gmail.com>: | $ ghc --make test-hopenssl.hs -lcrypto | [1 of 1] Compiling Main ( test-hopenssl.hs, test-hopenssl.o ) | Linking test-hopenssl ... | /tmp/ken/lib/hopenssl-1.0/ghc-6.8.2/libHShopenssl-1.0.a(Digest.o): In | function `s2O8_info': | (.text+0xf3a): undefined reference to `EVP_mdc2' | /tmp/ken/lib/hopenssl-1.0/ghc-6.8.2/libHShopenssl-1.0.a(Digest.o): In | function `s2TQ_info': | (.text+0x1435): undefined reference to `EVP_mdc2' | collect2: ld returned 1 exit status I see the following in the Configure file for openssl-0.9.8h: my $default_depflags = "-DOPENSSL_NO_CAMELLIA -DOPENSSL_NO_CMS -DOPENSSL_NO_GMP -DOPENSSL_NO_MDC2 -DOPENSSL_NO_RC5 -DOPENSSL_NO_RFC3779 -DOPENSSL_NO_SEED -DOPENSSL_NO_TLSEXT ";my $default_depflags = "-DOPENSSL_NO_CAMELLIA -DOPENSSL_NO_CMS -DOPENSSL_NO_GMP I don't know why this would be, but I infer that the function hopenssl was looking for is commonly missing in SSL builds. Donn Cave, donn(a)avvanta.com

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Definition of hidden instance members (bug in GHC or Hugs+Yhc)
by Neil Mitchell 07 Jul '08

07 Jul '08

Hi, This is either a GHC bug, or a Yhc+Hugs bug - I'm not sure which, but the compilers disagree: import Prelude hiding ((==)) data Foo = Foo instance Eq Foo where (==) a b = True GHC says: Temp.hs:14:4: `==' is not a (visible) method of class `Eq' Yhc and Hugs both successfully compile the module. Does anyone know which compiler(s) are in the wrong, and need bugs filing? Thanks Neil

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Santana on my evil ways
by John D. Ramsdell 07 Jul '08

07 Jul '08

My son's nickname is Rama, so let me adopt it. I am a functional programmer, even when I use languages such as C. Scheme facilitated my development into a functional programmer, however, I appreciate the benefits of pure function programming at times. Yet when I use Haskell, I hear reminders of my Scheme past cast in the music of Santana. The words I hear are set to "Eval Ways": You've got to change your evil ways... Rama Before I stop respecting you. You've got to change... Rama And every word that I say, it's true. You use strange syntax and typing And offset rules You don't mutate locations You use strange do's This can't go on... Lord knows you got to change. John

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Type families versus functional dependencies question
by Alexey Rodriguez 07 Jul '08

07 Jul '08

Hi guys, We are having trouble with the following program that uses type families: > class Blah f a where > blah :: a -> T f f a > class A f where > type T f :: (* -> *) -> * -> * the following function does not type: > wrapper :: forall a f . Blah f a => a -> T f f a > wrapper x = blah x GHC gives the error: Couldn't match expected type `T f1 f1 a' against inferred type `T f f a' In the expression: blah x In the definition of `wrapper': wrapper x = blah x Maybe it is a problem with ambiguous types, namely "f" appears only in applications of "T". But that is not the case, there is a "naked" f appearing as the argument of "T f". But perhaps the type checker does not want to unify those two f's precisely because they are the arguments of "T f". I have tried to encode the above program using FunDeps, because this procedure helps me understand type errors. But in this case I get no type error! > class A' (f :: * -> *) (g :: (* -> *) -> * -> *) | f -> g where > class Blah' f a where > blah' :: A' f g => a -> g f a > wrapper' :: forall a f g . (Blah' f a,A' f g) => a -> g f a > wrapper' x = blah' x So my question is whether my encoding is correct. And if it is, why isn't the type families version working? Thanks! Alexey

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not for me, guv!
by Evan Laforge 07 Jul '08

07 Jul '08

So I wrote a big email about this mysterious message I was getting, but then after some research and poking and debugging tracked it down to a dangling pointer in C that was causing a callback to point to an invalid address, which somehow worked anyway 99% of the time. That all said, I'm not totally convinced that "freeHaskellFunctionPtr: not for me, guv! 0x23143f0" is the clearest error message ever. Now, if it were in a more contemporary American idiom such as "wtf this ptr ain't from MY house lol!!!" I probably would have found the bug in half the time. Anyway, I fixed my bug and I'm happy about that, but I didn't want to waste a chance to send an email with this title...

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