March 2004 - Haskell - Haskell.org

New version of the HTTP module
by Bjorn Bringert 17 Mar '04

17 Mar '04

The Haskell HTTP client implementation available from [1] seems to be without a maintainer (if anyone knows how to reach Warrick Gray, who wrote it, let me know). I include a modified version of this module in the XML-RPC library [2]. Changes from the original module include: * made it Hugs compatible * disabled 100-continue transfers as they caused POST requests to HTTP/1.0 servers to stall * called it Network.HTTP instead of HTTP * added support for URIs with a port number * added a simple toggle for HTTP traffic logging The modified HTTP module is available from: http://www.dtek.chalmers.se/~d00bring/haskell-xml-rpc/http.html In line with Graham Klyne's suggestion [3] that a consistent version of this module be brought into some "community space", it will probably move to the haskell-libs project at SourceForge in the not too distant future. Yours truly, Bjorn Bringert [1] http://homepages.paradise.net.nz/warrickg/haskell/http/ [2] http://www.dtek.chalmers.se/~d00bring/haskell-xml-rpc/ [3] http://www.haskell.org/pipermail/libraries/2004-February/001693.html

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Announce: Takusen - an Oracle DBMS library
by Bayley, Alistair 17 Mar '04

17 Mar '04

In keeping with recent announcements regarding database libraries, Oleg Kiselyov and I present a library to interface to the Oracle DBMS. This library is a low-level interface for issuing SQL commands, similar to HSQL. It uses the Oracle Call Interface, a low-level C library provided with most Oracle installations. The library is currently hosted by the Haskell-libs project at SourceForge: http://sf.net/projects/haskell-libs Here's a link to the CVS folders: http://cvs.sf.net/viewcvs.py/haskell-libs/libs/takusen/ The library is designed around a left-fold enumerator, previously illustrated here: http://pobox.com/~oleg/ftp/Haskell/misc.html#fold-stream The enumerator is the preferred interface. We also support cursors, for those rare occasions where you may want to interleave results from more than one query. What distinguishes this library from HSQL/ODBC? - the groovy left-fold iterator - it works with Oracle :-) - it only works with Oracle :-( - it doesn't use any other libraries or pre-processors e.g. ODBC, hsc2hs Other features to note: - The library is designed to support any DBMS, although we've only provided one initial implementation, for Oracle. The Oracle-specific code is quite separate from the general code. There is also a stub so you can try it without Oracle. - The query function is "naturally polyvariadic". It can accept any number of arguments of the supported types. Type information is used to allocate data buffers and determine the correct conversion functions. Buffer allocation is transparent to the user. See examples in Database.Test.SimpleEnumeratorTest: http://cvs.sf.net/viewcvs.py/haskell-libs/libs/takusen/src/Database/Test/Sim pleEnumeratorTest.lhs?view=markup Deficiencies (we plan to rectify these soon, more-or-less in this order): - iteratee function should be monadic so you can do IO in it. - memory leaks exist (in the low-level OCI FFI code). - no performance tests (how well does it handle large result sets?). - no Haddock docs. - can't use OS-authenticated logon i.e. must provide username/password. - no bind variables. - support for multiple connections is limited. - limited set of Haskell/DBMS datatypes (String, Int, Double, CalendarTime) - doesn't support LOBs, user-defined DBMS types, and other exotic types. - CalendarTime support is incomplete, as Oracle doesn't store the Timezone with dates (this has been rectified in Oracle 9 with a new datatype: TIMESTAMP). We assume UTC. - doesn't support calling procedures, functions, or packages. - support for other DBMS's. * Why didn't we implement HSQL for Oracle? We started work on this long before we had any idea that HSQL was being overhauled. And it took a long time. * Do we have any plans to implement HSQL for Oracle? Maybe... not right now. I don't think there are any major technical impediments to writing it; I just lack time and motivation. Stability: Experimental. Still under active development. Portability: The library was developed on a Windows NT platform against Oracle 8. As far as I know, there are no Oracle 8 specific features, so it ought to work against an Oracle 7 DBMS without modification. It was compiled with GHC 6.01, and uses MPTC, fundeps, overlapping instances, and deriving Typeable. Alistair and Oleg. ----------------------------------------- ***************************************************************** Confidentiality Note: The information contained in this message, and any attachments, may contain confidential and/or privileged material. It is intended solely for the person(s) or entity to which it is addressed. Any review, retransmission, dissemination, or taking of any action in reliance upon this information by persons or entities other than the intended recipient(s) is prohibited. If you received this in error, please contact the sender and delete the material from any computer. *****************************************************************

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Hugs Nov2003 X Nov2002
by Stenio 17 Mar '04

17 Mar '04

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Win32 process spawning, POpen and Hugs, revisited
by Graham Klyne 16 Mar '04

16 Mar '04

Further to my previous messages: http://www.haskell.org//pipermail/haskell/2004-February/013522.html http://www.haskell.org//pipermail/haskell/2004-February/013679.html I've come back to my stripped-down test case, and recreated the C test program SpawnEchoShiftLetters.c [1] in Haskell SpawnEchoShiftLetters.hs [2]. I've also added some diagnostic code. To recap: the C code demonstrates that that the Win32 API used by spawnProc.c [4] is working as expected, so the problem appears to be in the Haskell interface to it. My problem seems to be occurring about here: [[ spawn cmd = withCString cmd $ \ p_cmd -> withObject 0 $ \ p_wIn -> withObject 0 $ \ p_rOut -> withObject 0 $ \ p_rErr -> do rc <- spawnProc p_cmd p_wIn p_rOut p_rErr when (rc /= 0) (ioError (userError ("runProc: unable to spawn " ++ show cmd))) wIn <- peek p_wIn (-1-} trace ("wIn "++show wIn) $ return () {- : -} (-2-} hIn <- openFd (fromIntegral wIn) False WriteMode False (-3-} trace ("hIn "++show hIn) $ return () ]] -- http://www.ninebynine.org/Software/HaskellUtils/Win32/POpen.hs Specifically: + the trace at {-1-} displays the expected value (i.e. the same as a similar trace in the C version of the code [1], namely the value 3), + the trace at {-3-} is not displayed, indicating... + failure of the openFd call at {-2-}, also indicated by a Hugs error message, thus: [[ SpawnEchoShiftLetters> runTest wIn 3 Program error: openFd: does not exist (file does not exist) SpawnEchoShiftLetters> ]] Thus, it would appear that I'm misunderstanding how to use the openFd function that is part of the Hugs-supplied library code, declared as a primitive: [[ -- Creating a handle from a file descriptor/socket. -- primitive openFd :: Int -- file descriptor -> Bool -- True => it's a socket. -> IOMode -- what mode to open the handle in. -> Bool -- binary? -> IO Handle ]] -- http://cvs.haskell.org/cgi-bin/cvsweb.cgi/hugs98/libraries/Hugs/IO.hs?rev=1… Can anyone help me out here? My current experimental code is all visible at [4]. Thanks. #g -- [1] http://www.ninebynine.org/Software/HaskellUtils/Win32/SpawnEchoShiftLetters… [2] http://www.ninebynine.org/Software/HaskellUtils/Win32/SpawnEchoShiftLetters… [3] http://www.ninebynine.org/Software/HaskellUtils/Win32/spawnProc.c [4] http://www.ninebynine.org/Software/HaskellUtils/Win32/ ------------ Graham Klyne For email: http://www.ninebynine.org/#Contact

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AW: [Haskell] Hugs Nov2003 X Nov2002
by Markus.Schnell＠infineon.com 16 Mar '04

16 Mar '04

try fromInt = fromInteger . toInteger Markus -- Markus Schnell -----Ursprüngliche Nachricht----- Von: haskell-bounces(a)haskell.org [mailto:haskell-bounces@haskell.org] Im Auftrag von Stenio Gesendet: Dienstag, 16. März 2004 10:29 An: Ketil Malde Cc: haskell(a)haskell.org Betreff: Re: [Haskell] Hugs Nov2003 X Nov2002 fromInteger works, but it converts from Integer to Float. In my script, I need fromInt because it converts from Int to Float. Example: average :: Int -> Float average n = fromInt ( sum n ) :: Float / fromInt n :: Float It works only in Hugs November 2002 Stenio. --------- Mensagem Original -------- De: "Ketil Malde" <ketil%2Bhaskell(a)ii.uib.no> Para: "Stenio" <stenio(a)uesb.br> Cópia: haskell(a)haskell.org Assunto: Re: [Haskell] Hugs Nov2003 X Nov2002 Data: 16/03/04 12:07 "Stenio" <stenio(a)uesb.br> writes: > I was using Hugs November 2002 and the function fromInt works fine, > but in the version November 2003 the same function doesn´t work. I'm too lazy to check the standard, so I'll just assume Hugs was wrong. I think the solution is to use "fromIntegral" instead. GHCi also has "fromInteger", although I'm not quite sure why we need this in addition to "fromIntegral"? (Possibly because it is a member of Num, and it would break too much code to remove it) -kzm -- If I haven't seen further, it is by standing in the footprints of giants

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Hugs Nov2003 X Nov2002
by Stenio 16 Mar '04

16 Mar '04

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Re: [Haskell] Hugs Nov2003 X Nov2002
by Stenio 16 Mar '04

16 Mar '04

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need help
by rui yang 16 Mar '04

16 Mar '04

Hi,all I'm a new comer in functional programming,I have defined some functions in Haskell and I want to know how much CPU time each function need and compare the efficiency of these functions. The question is how should I test the CPU time of my function? it seems that those functions to call the system clock should be of type IO, but my functions don't have IO actions, how should I deal with this type conflict? Thanks a lot. rui ---------------------------------------- This mail sent through www.mywaterloo.ca

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Sequential codes for LinSolv and Ray Tracer
by Heron 16 Mar '04

16 Mar '04

Hello, a simple question: how can I obtain the sequential code for LinSolv and Ray Tracer programs used in [Loidl, 2000] (see below) ? Is it available on-line ? I have downloaded their parallel GpH versions from http://cvs.haskell.org/cgi-bin/cvsweb.cgi/fptools/nofib/parallel/, but I need their sequential versions. Best Regards, Heron [Loidl, 2000] H.-W. Loidl, U. Klusik, K. Hammond, R. Loogen, and P. rinder. GpH and Eden: Comparing Two Parallel Functional Languages on a Beowulf Cluster. In SFP'00 - Scottish Funct. Progr. Workshop, rends in Functional Programming, Vol. 2, pages 39-52. Intellect, 2000. http://citeseer.ist.psu.edu/loidl00gph.html

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Announce: Haskell XML-RPC library
by Bjorn Bringert 15 Mar '04

15 Mar '04

Announcement: Haskell XML-RPC library ---------------------------------------------------------------------- I have written a Haskell XML-RPC client and server library which is available from: http://www.dtek.chalmers.se/~d00bring/haskell-xml-rpc/ XML-RPC (http://www.xmlrpc.com/) is "remote procedure calling using HTTP as the transport and XML as the encoding. XML-RPC is designed to be as simple as possible, while allowing complex data structures to be transmitted, processed and returned." Library features: - Easy to use interface, see code examples below. - Lower-level interface for explicit conversion between XML-RPC and Haskell types, e.g. to support heterogeneous arrays and structs. - Support for XML-RPC introspection in both client and server. Remote method declarations can be generated by using introspection, see test/make-stubs.hs. - Support for HTTP authentication. Code examples: This is a simple CGI-based server with only one method that takes two integers and returns their sum: > import Network.XmlRpc.Server > > add :: Int -> Int -> IO Int > add x y = return (x + y) > > main = cgiXmlRpcServer [("examples.add", fun add)] This is a client that calls the method implemented by the server above and prints the result: > import Network.XmlRpc.Client > > server = "http://localhost/~bjorn/cgi-bin/simple_server" > > add :: Int -> Int -> IO Int > add = remote server "examples.add" > > main = do > let x = 4 > y = 7 > z <- add x y > putStrLn (show x ++ " + " ++ show y ++ " = " ++ show z) Requirements: - GHC >= 6.01 or Hugs >= Nov2003 - HaXml >= 1.10 All comments, suggestions, bug reports and flames are welcome. Yours truly, Bjorn Bringert

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