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Problem building HXQ on Mac OS 10.5.5
by Tobias Kräntzer 03 Dec '08

03 Dec '08

Hi, I'm new to haskell and wonted to start tinkering a bit with this language, specifically with HXQ. I have installed ghc with macports. Now while building HXQ I get the following error: Main.hs:20:9: Not in scope: type constructor or class `C.SomeException' Unfortunately I'm also new to Mac OS X. Before I developed on Linux. It would be great, if someone could give me a hint. Thanks, Tobias PS: Below the details -- ~$ cabal install hxq Resolving dependencies... 'HXQ-0.11.0' is cached. Configuring HXQ-0.11.0... Preprocessing library HXQ-0.11.0... Preprocessing executables for HXQ-0.11.0... Building HXQ-0.11.0... . . . Loading package haskell98 ... linking ... done. [20 of 21] Compiling Text.XML.HXQ.XQuery ( src/Text/XML/HXQ/XQuery.hs, dist/build/xquery/xquery-tmp/Text/XML/HXQ/XQuery.o ) [21 of 21] Compiling Main ( Main.hs, dist/build/xquery/ xquery-tmp/Main.o ) Main.hs:20:9: Not in scope: type constructor or class `C.SomeException' cabal: Error: some packages failed to install: HXQ-0.11.0 failed during the building phase. The exception was: exit: ExitFailure 1 -- ~$ ghc-pkg list /opt/local/lib/ghc-6.10.1/./package.conf: Cabal-1.6.0.1, HUnit-1.2.0.3, QuickCheck-1.2.0.0, array-0.2.0.0, base-3.0.3.0, base-4.0.0.0, bytestring-0.9.1.4, containers-0.2.0.0, directory-1.0.0.2, (dph-base-0.3), (dph-par-0.3), (dph-prim-interface-0.3), (dph-prim-par-0.3), (dph-prim-seq-0.3), (dph-seq-0.3), editline-0.2.1.0, filepath-1.1.0.1, (ghc-6.10.1), ghc-prim-0.1.0.0, haddock-2.3.0, haskell-src-1.0.1.3, haskell98-1.0.1.0, hpc-0.5.0.2, html-1.0.1.2, integer-0.1.0.0, mtl-1.1.0.2, network-2.2.0.1, old-locale-1.0.0.1, old-time-1.0.0.1, packedstring-0.1.0.1, parallel-1.1.0.0, parsec-2.1.0.1, pretty-1.0.1.0, process-1.0.1.0, random-1.0.0.1, regex-base-0.72.0.2, regex-compat-0.71.0.1, regex-posix-0.72.0.3, rts-1.0, stm-2.1.1.2, syb-0.1.0.0, template-haskell-2.3.0.0, time-1.1.2.2, unix-2.3.1.0, xhtml-3000.2.0.1 /Users/tobias/.ghc/i386-darwin-6.10.1/package.conf: readline-1.0.1.0 -- Tobias Kräntzer info(a)tobias-kraentzer.de

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handles and foreign C functions
by Andrea Rossato 03 Dec '08

03 Dec '08

Hello, suppose a simple C function like this: void printStuff(FILE *f) { fprintf (f, "Hello World\n"); } In order to use it I need to import fopen and pass to it a Ptr CFile: foreign import ccall unsafe "fopen" fopen :: CString -> CString -> IO (Ptr CFile) foreign import ccall unsafe "fclose" fclose :: Ptr CFile -> IO CInt foreign import ccall unsafe "printStuff" printStuff :: Ptr CFile -> IO () main = withCString "tmp.txt" $ \cpath -> withCString "w" $ \cmode -> do cfile <- throwErrnoIfNull "fopen: " (fopen cpath cmode) printStuff cfile fclose cfile How can I pass to printStuff a stdout FILE pointer? If, for instance, I do: foreign import ccall unsafe "stdout" c_stdout :: Ptr CFile main = withCString "tmp.txt" $ \cpath -> withCString "w" $ \cmode -> do printStuff c_stdout I get a segmentation fault. What am I missing? TIA Andrea

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Re: [Haskell-cafe] Problem building HXQ on Mac OS 10.5.5
by Tobias Kräntzer 03 Dec '08

03 Dec '08

Hi, Am 03.12.2008 um 02:00 schrieb Gwern Branwen: > I haven't looked at the source, so take this as off-the-cuff: try > importing not Control.Exception but Control.OldException. changing "Control.Exception"to "Control.OldException" didn't work. But changing "SomeException" to "Exception" seems to solve the problem (see below). At least I can now built it and use xquery. I think these days I get more in to it and understand what I was doing. ;-) Could it be a problem with the version of GHC? I'm using 6.10.1. Is "SomeException" still supported? At the moment I don't know how to look these things up. Regard, . . . Tobias -- Original: #if __GLASGOW_HASKELL__ >= 609 type E = C.SomeException #else type E = C.Exception #endif -- Modified: type E = C.Exception -- Tobias Kräntzer | Scharnweberstraße 52a | 10247 Berlin Telefon: +49-30-75636668 | +49-178-1353136 XMPP: anagrom_ataf(a)jabber.ccc.de

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Cabal and Hat?
by Magnus Therning 03 Dec '08

03 Dec '08

Is it possible to use cabal to build the files that hat would need to do tracing (i.e. .htx files)? /M -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus＠therning．org http://therning.org/magnus identi.ca|twitter: magthe

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ByteString web site papers
by Galchin, Vasili 03 Dec '08

03 Dec '08

Hello, http://www.cse.unsw.edu.au/~dons/fps.html Are the papers/slides still up-to-date for someone to get up-to-speed on ByteString motivation and implementation? Anything more recent? Regards, Vasili

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Data.ByteString vs Data.ByteString.Lazy vs Data.ByteString.Char8
by Galchin, Vasili 03 Dec '08

03 Dec '08

Hello, Some mention is made in corresponding web pages about implementation difference of these three different DataString impl. Any advice? Regards, Vasili

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Re: What causes <<loop>>?
by Martin Hofmann 03 Dec '08

03 Dec '08

I was not sure about it, so I just speculated. Anyway, thanks a lot. martin

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What causes <<loop>>?
by Martin Hofmann 03 Dec '08

03 Dec '08

I've already posted this mail on haskell-cafe, but apparently the subject suggested a too simple question, so I try it here again. I am picking up a discussion with the same topic from haskell-users on 8th November. Thunks with reference on themselves was mentioned as main reason for <<loop>>. > A safe recursive definition would be > let x = Foo (x+1) > However, if you leave out the constructor, > let x = x + 1 > you get a <<loop>> (or a deadlock). > Are there any other reasons? I am trying to debug monadic code which stores state information in a record maintaining several Data.Maps, but in vain so far. A state is modified/changed in several steps by a compound function i.e. changeA $ changeB $ changeC state Could this also lead to a deadlock? If so, can I prevent this using CPS? If the state transformation is the main purpose/computation of the monad at all, is it better to use CPS? Is code using mtl, records or Data.Map more prone to <<loop>> or does this not matter at all. How can I identify self-referencing thunks more easily? Is there any rule of thumb to prevent <<loop>>? Are there any less obvious newbie mistakes causing <<loop> then the one above? Sorry, a lot of questions at once, but I am kind of helpless because I can't find any reason of my <<loop>>, so any comments, experience, and tips are highly appreciated. Thanks, Martin

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Install Yi editor with GHC 6.10.1
by Andy Stewart 03 Dec '08

03 Dec '08

Hi all, I have install GHC 6.10.1 and Gtk2hs (darcs version) in Debian. So i want to ask, have anyone install Yi (darcs version) with GHC 6.10.1 successfully? And the best way to install darcs version Yi? Thank you very much! -- Andy

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Deriving
by Daryoush Mehrtash 03 Dec '08

03 Dec '08

What happens when a type adds driving such as: newtype SupplyT s m a = SupplyT (StateT [s] m a) deriving (Functor <http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#t:Funct…>, Monad <http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#t:Monad>, MonadTrans, MonadIO) Two questions: How does the deriving implement the instance? Is there a way for me to add my own classes in the deriving? for example newtype ..... deriving( xyz) Thanks

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