April 2008 - Haskell-Cafe

Re: [Haskell] Some old and quite old news.
by gwern0＠gmail.com 06 Apr '08

06 Apr '08

On 2008.04.05 17:42:00 +0400, Serguey Zefirov <s_zefirov(a)ipmce.ru> scribbled 0.6K characters: > gwern0(a)gmail.com пишет: >> Hmm. I'm having trouble getting it through SVN: >> >> gwern@localhost:1003~>svn co http://thesz.mskhug.ru/browser/hiersort [ >> 1:44PM] >> svn: PROPFIND request failed on '/browser/hiersort' >> svn: PROPFIND of '/browser/hiersort': 200 OK (http://thesz.mskhug.ru) >> >> Is there some trick that as a Darcser I don't know about? >> > Actually, I do not know too. Maybe, just a version mismatch? > > Did you tried to access files using just a web browser? > > I CC'd that to myself at home and will try to resolve matters ASAP. At > least I will make a tarball and post it somewhere at MskHUG website. > > Thank you for your interest. ;) Well, I looked at some of the files with a browser, and that worked fine. It's just when I tried to do a checkout that fails. I've asked the guys in #svn, and they said the 'real' repo is elsewhere, so I went and asked #trac where the real repo's URL is. One of them said 12:37 < thatch> gwern: the faq can't cover it. Trac only knows the local filesystem path to the repo, not its web-accessible path. So I dunno. After some guessing, thatch came up with <http://thesz.mskhug.ru/svn/hiersort/> as the repo URL. It's downloading now, although slowly. -- gwern Z7 Service NSG Sayeret FIPS140-1 encryption data-haven continuous black-bag illuminati

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DEFUN08: Call for Talks & Tutorials (co-located w/ ICFP08)
by Matthew Fluet (ICFP Publicity Chair) 06 Apr '08

06 Apr '08

Call for Talks and Tutorials ACM SIGPLAN 2008 Developer Tracks on Functional Programming http://www.deinprogramm.de/defun-2008/ Victoria, BC, Canada, 25, 27 September, 2008 The workshop will be held in conjunction with ICFP 2008. http://www.icfpconference.org/icfp2008/ Important dates Proposal Deadline: June 27, 2008, 0:00 UTC Notification: July 14, 2008 DEFUN 2008 invites functional programmers who know how to solve problems with functional prorgamming to give talks and lead tutorials at the The ICFP Developer Tracks. We want to know about your favorite programming techniques, powerful libraries, and engineering approaches you've used that the world should know about and apply to other projects. We want to know how to be productive using functional programming, write better code, and avoid common pitfals. We invite proposals for presentations in the following categories: How-to talks: 45-minute "how-to" talks that provide specific information on how to solve specific problems using functional programming. These talks focus on concrete examples, but provide useful information for developers working on different projects or in different contexts. Examples: - "How I made Haskell an extension language for SAP R/3." - "How I replaced /sbin/init by a Scheme program." - "How I hooked up my home appliances to an Erlang control system." - "How I got an SML program to drive my BMW." General language tutorials Half-day general language tutorials for specific functional languages, given by recognized experts for the respective languages. Technology tutorials Half-day tutorials on techniques, technologies, or solving specific problems in functional programming such as: - how to make the best use of specific FP programming techniques - how to inject FP into a development team used to more conventional technologies - how to connect FP to existing libraries / frameworks / platforms - how to deliver high-performance systems with FP - how to deliver high-reliability systems with FP Remember that your audience will include computing professionals who are not academics and who may not already be experts on functional programming. Presenters of tutorials will receive free registration to ICFP 2008. Submission guidelines Submit a proposal of 150 words or less for either a 45-minute talk with a short Q&A session at the end, or a 300-word-or-less proposal for a 3-hour tutorial, where you present your material, but also give participants a chance to practice it on their own laptops. Some advice: - Give it a simple and straightforward title or name; avoid fancy titles or puns that would make it harder for attendees to figure out what you'll be talking about. - Clearly identify the level of the talk: What knowledge should people have when they come to the presentation or tutorial? - Explain why people will want to attend: is the language or library useful for a wide range of attendees? Is the pitfall you're identifying common enough that a wide range of attendees is likely to encounter it? - Explain what benefits attendees are expected to take home to their own projects. - For a tutorial, explain how you want to structure the time, and what you expect to have attendees to do on their laptops. List what software you'll expect attendees to have installed prior to coming. Submit your proposal in plain text electronically to defun-2008-submission-AT-deinprogramm.de by the beginning of Friday, June 27, Universal Coordinated Time. Organizers Kathleen Fisher AT&T Labs Simon Peyton Jones Microsoft Research Mike Sperber (co-chair) DeinProgramm Don Stewart (co-chair) Galois

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Doing without IORef
by Jinwoo Lee 05 Apr '08

05 Apr '08

Hi, Recently I wrote a code that uses readline library (System.Console.Readline). I had to maintain a state (file path) and do IO throughout the code, so I decided to use StateT monad. The problem was that in order to retrieve the current state (file path) inside the handler that had been registered by using bindKey function of readline, I had to resort back to using IORef rather than using the state stored in the StateT monad. It's because the handler for bindKey should have the type of Int -> Char -> IO Int. Here is my code snippet. type MyState a = StateT FilePath IO a rootDir :: FilePath rootDir = "/root/" main :: IO () main = do hSetBuffering stdout NoBuffering execStateT (do pwd <- get pwdRef <- lift $ newIORef pwd lift $ bindKey '\t' (tabHandler pwdRef) lift $ bindKey '\^L' ctlLHandler commandLoop pwdRef) rootDir return () tabHandler :: IORef FilePath -> Int -> Char -> IO Int tabHandler pwdRef _ _ = do *pwd <- readIORef pwdRef* insertText pwd return 0 ... commandLoop :: IORef FilePath -> MyState () commandLoop pwdRef = commandLoop' where commandLoop' = do pwd <- get *lift $ writeIORef pwdRef pwd* maybeLine <- lift $ readline $ makePrompt $ dropTrailingPathSeparator pwd case maybeLine of Nothing -> return () Just "exit" -> return () Just line -> do let tokens = words line case tokens of [] -> commandLoop' ("exit":_) -> return () _ -> do lift $ addHistory line processLine tokens commandLoop' ... Is there any way in which I can do without IORef in tabHandler and commandLoop (written in red and bold, if you can see)? Thanks, Jinwoo -- Jinwoo Lee Always remember that you are unique. Just like everyone else.

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Strange behavior of float literals
by Vladimir Reshetnikov 05 Apr '08

05 Apr '08

The float literal 1e-100000000000000000000000000000000000000000000 in GHC evaluates to 1.0, and 1e-999999999999999999999999999999999999999999999 evaluates to 10.0. Is it a bug, or a documented overflow behavior? What it the correct place to submit bug reports concerning GHC? -- Thank you, Vladimir Reshetnikov (aka nikov), Microsoft MVP

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HDBC, character encoding
by Adrian Neumann 05 Apr '08

05 Apr '08

Hi, I wrote a CGI program to access a Postgres database using HDBC. The database stores books and I want to display those from a certain author. Everything works fine, unless I search for someone with an umlaut in his name. Böll, for example. I have a function like this > bookByAuthor :: Connection -> AutorName -> IO [[String]] > bookByAuthor c aName = do > writeFile "./err.log" ((show aName)++" "++(show $ toSql aName)) > rows <- quickQuery c "SELECT * FROM buecher WHERE lower (autor_name) LIKE ? ORDER BY autor_name, buch_name" [toSql $ map toLower $ '%':aName++"%"] > return $ map (map fromSql) rows It returns me a SqlError. However, doing the same in ghci works perfectly. I can't understand why. err.log contains > "b\195\182ll" SqlString "b\195\182ll" which is ok I think. Since > quickQuery c "SELECT * FROM buecher WHERE lower(autor_name) LIKE ? ORDER BY autor_name, buch_name" [toSql "%b\195\182%"] works in ghci. I have tried "b\246ll", but that doesn't even work in ghci, although the database-encoding is utf-8. This all is really annoying... Adrian

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Bug in Hugs, Haskell behavior question
by Fritz Ruehr 05 Apr '08

05 Apr '08

In lab the other day I was showing pattern bindings to a student and broached a limiting case, one with no variables to be bound in the pattern. I was surprised to find that Hugs crashed when I tried a pattern binding at top level like this: (2,[1,4],5) = (2,[1,4],5) It also crashed on the simpler: [2] = [2] On the other hand, this turns out to be acceptable: 2 = 2 In fact, even this goes through without a hitch! 2 = 3 I'm not sure from the language definition yet whether this last should give an "Unmatched pattern" error, but if it's intended behavior, it does look a little odd. Would anyone care to argue for or against allowing this? In any case, the more structured patterns cause the latest (Sep 06) Hugs release to crash, with "INTERNAL ERROR: compileGlobalFunction". (GHC allows the strange "2 = 3" and handles the structured ones fine, including even "(1,[2,3],4) = (4,[3,37],42)". I haven't checked any other compilers.) -- Fritz

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mostly for Neil: tagsoup problems
by Magnus Therning 05 Apr '08

05 Apr '08

Neil, and others, Does the cabal file for Tagsoup require a version of Cabal newer than 1.1.6? In case it does it doesn't say so. I suspect this is the cause of the rather cryptic error message: "setup: tagsoup.cabal:20: 'Executable' stanza starting with field 'ghc-options'". I also noticed that the Haddock-umentation on Neil's side is for version 0.1, while Hackage has version 0.4. I was rather confused by that at first, since the module names had changed :) /M

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Re: [Haskell-cafe] Windows CE, Xscale Compiler?
by PR Stanley 04 Apr '08

04 Apr '08

At 14:37 04/04/2008, you wrote: >And how would I cross compile something for that platform with ghc? >(There seems to be no port, which is fine) > > Don't look at me mate. :-) >PR Stanley schrieb: >>I'm surprised you can't use the Glasgow implementation on CE. >>At 13:55 04/04/2008, you wrote: >>>Is there any Haskell compiler for Windows CE on a XScale platform? >>>I googled around a bit and found references to a Hugs >>>implementation but couldn't find any place to download it. >>> >>>I have the opportunity to program a teledrive[1] and would very >>>much like to avoid something disfunctional like C. >>> >>>[1] http://www.iavproducts.com/de/produkte/teledrive/teledrive.php >>> >>> >>> >>> >>>_______________________________________________ >>>Haskell-Cafe mailing list >>>Haskell-Cafe(a)haskell.org >>>http://www.haskell.org/mailman/listinfo/haskell-cafe >>_______________________________________________ >>Haskell-Cafe mailing list >>Haskell-Cafe(a)haskell.org >>http://www.haskell.org/mailman/listinfo/haskell-cafe > > > >

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Windows CE, Xscale Compiler?
by Adrian Neumann 04 Apr '08

04 Apr '08

Is there any Haskell compiler for Windows CE on a XScale platform? I googled around a bit and found references to a Hugs implementation but couldn't find any place to download it. I have the opportunity to program a teledrive[1] and would very much like to avoid something disfunctional like C. [1] http://www.iavproducts.com/de/produkte/teledrive/teledrive.php

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trying to install ghc-6.8.2 both binaries and sources
by michael＠schmong.org 04 Apr '08

04 Apr '08

I am operating under the assumption that Idid have a broken gcc. I installed a new one This is what happened when I tried compiling ghc-6.8.2 make all /usr/bin/ghc -H16m -O -w -I. -Iinclude -Rghc-timing -ignore-package Cabal -ignore-package filepath -I../libraries -fglasgow-exts -no-recomp -c System/FilePath/Posix.hs -o System/FilePath/Posix.o -ohi System/FilePath/Posix.hi cc1: error: unrecognized option `-fno-unit-at-a-time' <<ghc: 129595404 bytes, 17 GCs, 2640525/5069484 avg/max bytes residency (3 samples), 20M in use, 0.00 INIT (0.00 elapsed), 0.59 MUT (0.80 elapsed), 0.09 GC (0.14 elapsed) :ghc>> make[2]: *** [System/FilePath/Posix.o] Error 1 make[1]: *** [boot] Error 2 make: *** [stage1] Error 1 this is exactly what happened prior to installing a new gcc. Here's what config.log says $ ./configure --prefix=/home/michael ## --------- ## ## Platform. ## ## --------- ## hostname = schmong.org uname -m = i686 uname -r = 2.6.16.33-vpsX uname -s = Linux uname -v = #2 SMP Tue Jan 23 22:53:20 EST 2007 /usr/bin/uname -p = unknown /bin/uname -X = unknown /bin/arch = i686 /usr/bin/arch -k = unknown /usr/convex/getsysinfo = unknown hostinfo = unknown /bin/machine = unknown /usr/bin/oslevel = unknown /bin/universe = unknown PATH: /usr/local/bin PATH: /usr/bin PATH: /bin PATH: /usr/bin/X11 PATH: /usr/games PATH: /usr/lib ## ----------- ## ## Core tests. ## ## ----------- ## running configure, to aid debugging if configure makes a mistake. It was created by The Glorious Glasgow Haskell Compilation System configure 6.8. 2, which was generated by GNU Autoconf 2.59. Invocation command line was $ ./configure --prefix=/home/michael ## --------- ## ## Platform. ## ## --------- ## hostname = schmong.org uname -m = i686 uname -r = 2.6.16.33-vpsX uname -s = Linux uname -v = #2 SMP Tue Jan 23 22:53:20 EST 2007 /usr/bin/uname -p = unknown /bin/uname -X = unknown /bin/arch = i686 /usr/bin/arch -k = unknown /usr/convex/getsysinfo = unknown hostinfo = unknown /bin/machine = unknown /usr/bin/oslevel = unknown /bin/universe = unknown PATH: /usr/local/bin PATH: /usr/bin PATH: /bin PATH: /usr/bin/X11 PATH: /usr/games PATH: /usr/lib ## ----------- ## ## Core tests. ## ## ----------- ## configure:1502: checking build system type configure:1520: result: i686-pc-linux-gnu configure:1528: checking host system type configure:1542: result: i686-pc-linux-gnu configure:1550: checking target system type configure:1564: result: i686-pc-linux-gnu configure:2121: checking for ghc configure:2139: found /usr/bin/ghc configure:2151: result: /usr/bin/ghc configure:2175: checking version of ghc The Glorious Glasgow Haskell Compilation System, version 6.6 configure:2204: result: 6.6 configure:2217: checking for ghc-pkg matching /usr/bin/ghc configure:2229: result: /usr/bin/ghc-pkg configure:2275: checking whether ghc has readline package configure:2286: result: yes configure:2296: checking for nhc configure:2329: result: no configure:2296: checking for nhc98 configure:2329: result: no configure:2338: checking for hbc configure:2371: result: no configure:2508: checking for ld configure:2526: found /usr/bin/ld configure:2538: result: /usr/bin/ld configure:2642: checking for path to top of build tree configure:2667: result: /home/michael/src/ghcsrc/ghc-6.8.2 configure:2728: checking whether #! works in shell scripts configure:2745: result: yes configure:2796: checking for perl configure:2814: found /usr/bin/perl configure:2826: result: /usr/bin/perl configure:2852: checking if your perl works in shell scripts configure:2870: result: yes configure:2875: checking for python configure:2893: found /usr/bin/python configure:2905: result: /usr/bin/python configure:2959: checking for gcc configure:2985: result: /home/michael/bin/gcc configure:3229: checking for C compiler version configure:3232: /home/michael/bin/gcc --version </dev/null >&5 gcc (GCC) 3.4.6 Copyright (C) 2006 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. configure:3235: $? = 0 configure:3237: /home/michael/bin/gcc -v </dev/null >&5 Reading specs from /home/michael/lib/gcc/i686-pc-linux-gnu/3.4.6/specs I have also tried to install the binaries, this may be more promising. ./configure --prefix=$HOME checking build system type... i686-pc-linux-gnu checking host system type... i686-pc-linux-gnu checking target system type... i686-pc-linux-gnu Which we'll further canonicalise into: i386-unknown-linux checking for path to top of build tree... pwd: timer_create: Operation not supported configure: error: cannot determine current directory this is exactly what happened when I tried to install the binaries with the old gcc. Here's the config.log $ ./configure --prefix=/home/michael ## --------- ## ## Platform. ## ## --------- ## hostname = schmong.org uname -m = i686 uname -r = 2.6.16.33-vpsX uname -s = Linux uname -v = #2 SMP Tue Jan 23 22:53:20 EST 2007 /usr/bin/uname -p = unknown /bin/uname -X = unknown /bin/arch = i686 /usr/bin/arch -k = unknown /usr/convex/getsysinfo = unknown /usr/bin/hostinfo = unknown /bin/machine = unknown /usr/bin/oslevel = unknown /bin/universe = unknown PATH: /usr/local/bin PATH: /usr/bin PATH: /bin PATH: /usr/bin/X11 PATH: /usr/games PATH: /usr/lib ## ----------- ## ## Core tests. ## ## ----------- ## configure:1692: checking build system type configure:1710: result: i686-pc-linux-gnu configure:1732: checking host system type configure:1747: result: i686-pc-linux-gnu configure:1769: checking target system type configure:1784: result: i686-pc-linux-gnu configure:1907: checking for path to top of build tree configure:1923: error: cannot determine current directory ## ---------------- ## ## Cache variables. ## ## ---------------- ## ac_cv_build=i686-pc-linux-gnu ac_cv_env_CC_set=set ac_cv_env_CC_value=/home/michael/bin/gcc ac_cv_env_CFLAGS_set= ac_cv_env_CFLAGS_value= ac_cv_env_CPPFLAGS_set= ac_cv_env_CPPFLAGS_value= ac_cv_env_CPP_set= ac_cv_env_CPP_value= ac_cv_env_LDFLAGS_set= ac_cv_env_LDFLAGS_value= ac_cv_env_build_alias_set= ac_cv_env_build_alias_value= ac_cv_env_host_alias_set= ac_cv_env_host_alias_value= ac_cv_env_target_alias_set= ac_cv_env_target_alias_value= ac_cv_host=i686-pc-linux-gnu ac_cv_target=i686-pc-linux-gnu ## ----------------- ## ## Output variables. ## ## ----------------- ## ArCmd='' CC='/home/michael/bin/gcc' CFLAGS='' CPP='' CPPFLAGS='' DEFS='' ECHO_C='' ECHO_N='-n' ECHO_T='' EXEEXT='' GccExtraViaCOpts='' GccVersion='' HaveGcc='' INSTALL_DATA='' INSTALL_PROGRAM='' INSTALL_SCRIPT='' LDFLAGS='' LIBOBJS='' LIBS='' LN_S='' LTLIBOBJS='' OBJEXT='' PACKAGE_BUGREPORT='' PACKAGE_NAME='' PACKAGE_STRING='' PACKAGE_TARNAME='' PACKAGE_VERSION='' PATH_SEPARATOR=':' PerlCmd='' RANLIB='' SHELL='/bin/sh' SedCmd='' TargetPlatform='i386-unknown-linux' ac_ct_CC='' bindir='${exec_prefix}/bin' build='i686-pc-linux-gnu' build_alias='' build_cpu='i686' build_os='linux-gnu' build_vendor='pc' datadir='${datarootdir}' datarootdir='${prefix}/share' docdir='${datarootdir}/doc/${PACKAGE}' dvidir='${docdir}' exec_prefix='NONE' exeext='' fp_prog_ar_raw='' hardtop='' host='i686-pc-linux-gnu' host_alias='' host_cpu='i686' host_os='linux-gnu' host_vendor='pc' htmldir='${docdir}' includedir='${prefix}/include' infodir='${datarootdir}/info' libdir='${exec_prefix}/lib' libexecdir='${exec_prefix}/libexec' localedir='${datarootdir}/locale' localstatedir='${prefix}/var' mandir='${datarootdir}/man' oldincludedir='/usr/include' pdfdir='${docdir}' prefix='/home/michael' program_transform_name='s,x,x,' psdir='${docdir}' sbindir='${exec_prefix}/sbin' sharedstatedir='${prefix}/com' sysconfdir='${prefix}/etc' target='i686-pc-linux-gnu' target_alias='' target_cpu='i686' target_os='linux-gnu' target_vendor='pc' ## ----------- ## ## confdefs.h. ## ## ----------- ## #define PACKAGE_NAME "" #define PACKAGE_TARNAME "" #define PACKAGE_VERSION "" #define PACKAGE_STRING "" #define PACKAGE_BUGREPORT "" configure: exit 1 whew. Okay can anyone give me ideas on how to proceed? I have also verified I have the correct libreadline.so.5, libncurses.so.5. michael litchard

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