- Haskell-Cafe - Haskell.org

[Colin Paul Adams] Re: [Haskell-cafe] Ready for testing: Unicode support for Handle I/O
by Colin Paul Adams 04 Feb '09

04 Feb '09

>>>>> "John" == John Goerzen <jgoerzen(a)complete.org> writes: >> latin1, utf8, utf16, utf16le, utf16be, utf32, utf32le, utf32be, >> localeEncoding, John> Will there also be something to handle the UTF-16 BOM John> marker? I'm not sure what the best API for that is, since John> it may or may not be present, but it should be considered -- John> and could perhaps help autodetect encoding. Not really. The UTF-16 BOM is only allowed for utf16. Utf16le and utf16be do not have a BOM. What it does is alloww you to auto-detect the endianness if utf16 has been requested as the encoding (if it is not present the big-endian is assumed). Ditto for utf32/utf32be/utf32le. A BOM is thesedays allowed (but deprecated - it should never have been allowed and originally wasn't) for utf8 also. But it has no value other than to introduce ambiguity. :-( -- Colin Adams Preston Lancashire

2 2

Verifying Haskell Programs
by Paulo J. Matos 03 Feb '09

03 Feb '09

Hi all, Much is talked that Haskell, since it is purely functional is easier to be verified. However, most of the research I have seen in software verification (either through model checking or theorem proving) targets C/C++ or subsets of these. What's the state of the art of automatically verifying properties of programs written in Haskell? Cheers, -- Paulo Jorge Matos - pocmatos at gmail.com Webpage: http://www.personal.soton.ac.uk/pocm

7 10

type and data constructors in CT
by Gregg Reynolds 03 Feb '09

03 Feb '09

Hi, I think I've finally figured out what a monad is, but there's one thing I haven't seen addressed in category theory stuff I've found online. That is the relation between type constructors and data constructors. As I understand it, a type constructor Tcon a is basically the object component of a functor T that maps one Haskell type to another. Haskell types are construed as the objects of category "HaskellType". I think that's a pretty straightforward interpretation of the CT definition of functor. But a data constructor Dcon a is an /element/ mapping taking elements (values) of one type to elements of another type. So it too can be construed as a functor, if each type itself is construed as a category. So this gives us two functors, but they operate on different things, and I don't see how to get from one to the other in CT terms. Or rather, they're obviously related, but I don't see how to express that relation formally. If somebody could point me in the right direction I'd be grateful. Might even write a tutorial. Can't have too many of those. Thanks, Gregg

5 13

FP simulators for real-time systems?
by Lee Pike 03 Feb '09

03 Feb '09

Hello, I'm interested to hear if anyone out there has used Haskell (or other functional languages for that matter) to build simulators for real- time systems. I'm somewhat familiar with Timber <http://www.timber-lang.org/> and similar languages for actually constructing real-time systems. However, I'm more interested in documented uses of FP "out-of-the- box" to build simulators and associated test harnesses. Pointers to published papers are particularly appreciated. Thanks! Lee

3 2

Cabal and more than one version
by Jason Dusek 03 Feb '09

03 Feb '09

I'd like to be able to do something like: if (template-haskell < 2.3) cpp-options: -D TH_THE_YOUNGER else cpp-options: -D TH_THE_ELDER I guess this kind of thing is not possible at present? -- _jsn

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Re: 1,000 packages, so let's build a few!
by John Lato 03 Feb '09

03 Feb '09

Duncan Coutts wrote: > > Some are trivial and should be done away with. For example the ones that > just check if a C header / lib is present are unnecessary (and typically > do not work correctly). The next point release of Cabal can do these > checks automatically, eg: > > Configuring foo-1.0... > cabal: Missing dependencies on foreign libraries: > * Missing header file: foo.h > * Missing C libraries: foo, bar, baz > This problem can usually be solved by installing the system > packages that provide these libraries (you may need the "-dev" > versions). If the libraries are already installed but in a > non-standard location then you can use the flags > --extra-include-dirs= and --extra-lib-dirs= to specify where > they are. Thank you! Thank you! Thank you! For those of us who want to write cross-platform (i.e. Windows) bindings to C libraries, this is great news. John Lato

4 4

Re: type metaphysics
by oleg＠okmij.org 03 Feb '09

03 Feb '09

I believe the original notion of type by Russell is most insightful, bridging the semantic notion of type (type as a set of values) and the syntactic notion (type system as a syntactic discipline, a statically decidable restriction on terms). That point is discussed at some length in Sec 3 (pp. 7-8) of http://okmij.org/ftp/Computation/FLOLAC/lecture.pdf The one of the main points of these FLOLAC lecture notes was to justify and illustrate the claim that A type is a (quickly decidable) approximation of a dynamic behavior that can be derived from the form of an expression. (The other claim was the relationship between sharing and polymorphism). Incidentally, Russell has published his paper that introduced types as we in Computer Science know them in 1908. Last year there was 100th anniversary of types. I have been trying to prompt people to have a party and celebrate the occasion -- alas, to no avail.

2 1

Parallel term reduction
by John D. Ramsdell 03 Feb '09

03 Feb '09

I have a reduction system in which a rule takes a term and returns a set of terms. The reduction system creates a tree that originates at a starting value called the root. For most problems, the reduction system terminates, but a step count limit protects from non-termination. Rule application is expensive, so it is essential that a rule is never applied to the same problem twice. This check makes my program sequential, in that parallel annotations don't improve performance on SMPs. There isn't even an obvious place to add them in my program, at least not to me. How do people write parallel reduction systems that avoid redundant rule application? John > module Main (main) where > import System.Time (ClockTime(..), getClockTime > data Eq a => Item a > = Item { item :: a, > parent :: Maybe (Item a) } > instance Eq a => Eq (Item a) where > x == y = item x == item y The reduction system takes a rule, a step count, and an initial value, and computes a tree of reductions. The order of the items in the returned list is irrelevant, because the tree is assembled as a post processing step. > reduce :: (Eq a, Monad m) => (a -> [a]) -> Int -> a -> m [Item a] > reduce rule limit root = > step rule limit [top] [top] > where > top = Item { item = root, parent = Nothing } step rule limit seen todo, where seen in the items already seen, and todo is the items on the queue. > step :: (Eq a, Monad m) => (a -> [a]) -> Int -> > [Item a] -> [Item a] -> m [Item a] > step _ limit _ _ > | limit <= 0 = fail "Step limit exceeded" > step _ _ seen [] = return seen > step rule limit seen (next : rest) = > loop seen rest children > where > children = map child (rule (item next)) > child i = Item { item = i, parent = Just next } > loop seen rest [] = > step rule (limit - 1) seen rest > loop seen rest (kid : kids) = > if elem kid seen then > loop seen rest kids > else > loop (kid : seen) (rest ++ [kid]) kids A silly rule > rule :: Int -> [Int] > rule n = filter (>= 0) [n - 1, n - 2, n - 3] > secDiff :: ClockTime -> ClockTime -> Float > secDiff (TOD secs1 psecs1) (TOD secs2 psecs2) > = fromInteger (psecs2 - psecs1) / 1e12 + fromInteger (secs2 - secs1) > main :: IO () > main = > do > t0 <- getClockTime > ns <- reduce rule 20000 5000 > t1 <- getClockTime > putStrLn $ "length: " ++ show (length ns) > putStrLn $ "time: " ++ show (secDiff t0 t1) ++ " seconds" The makefile ------------ PROG = reduce GHCFLAGS = -Wall -fno-warn-name-shadowing -O %: %.lhs ghc $(GHCFLAGS) -o $@ $< all: $(PROG) clean: -rm *.o *.hi $(PROG)

2 4

why typeRepArgs (typeOf "hello") is [Char] ?
by minh thu 03 Feb '09

03 Feb '09

Hello, With Data.Typeable : *Graph> typeRepArgs (typeOf 1) [] *Graph> typeRepArgs (typeOf 'a') [] *Graph> typeRepArgs (typeOf True) [] *Graph> typeRepArgs (typeOf "hello") [Char] I don't understand why the latter is not []. Could someone explain it ? Thank you, Thu

4 6

ANN: HDBC v2.0 now available
by John Goerzen 03 Feb '09

03 Feb '09

Hi everyone, I'm pleased to announce that HDBC v2.0 is now available. Simultaneously, HDBC-sqlite3, HDBC-postgresql, and HDBC-odbc v2.0 have also been uploaded. All may be found from Hackage, or at software.complete.org. A guide to new features and migration can be found at: http://software.complete.org/software/wiki/hdbc/NewIn20 A partial summary of it follows: New Features: * Pervasive Unicode support now part of the HDBC API and implemented by all backend drivers. Based on utf8-string and conversions between UTF-8 ByteStrings and Haskell Strings. * Full support for GHC 6.10 is new. Full support for GHC 6.8 is maintained. * Native support for the new exception handling in GHC 6.10, with CPP conditional compilation to continue supporting the old-style exceptions for users of GHC 6.8 or Hugs. * HDBC now has direct support for marshalling virtually all of the Data.Time.* types to and from SQL database date/time types. toSql and fromSql/safeFromSql now support conversions between Data.Time.* types and SqlValue. Conversions between System.Time.* types were present from the beginning and will remain. Automatic conversions are, of course, contingent on support in database engines and HDBC database backend drivers and may not be possible with all databases. * Major expansion of SqlValue to be able to carry date/time data to/from databases in terms of Data.Time.* types. + The old SqlTimeDiff and SqlEpochTime types continue to be present, but are deprecated and will be removed in a future. toSql no longer converts anything to them. The System.Time.* types are converted to the new Data.Time-based SqlValues. It should be exceptionally rare that any user code would use these types directly, but they are being retained in this version out of an abundance of caution. * Replace fromSql with safeFromSql, which returns Left on impossible conversions instead of raising an exception. + Wrote a new fromSql that behaves just like the old one, but is implemented in terms of safeFromSql. It converts the safeFromSql errors to exceptions. + The new structure made it possible to greatly enhance many error messages throughout the conversion process instances. + Removed SqlType typeclass. Re-implemented SqlValue conversions in terms of the generic infrastructure in the convertible package. Simplified code significantly due to this. * Lots of additional docs. * New skeleton test suite for HDBC itself (to be expanded upon later). Richer Date and Time Support HDBC 1.x had only two ways of getting dates and times between Haskell and a database: an epoch (an Integer representing the number of seconds since midnight Jan 1 1970 UTC) and an Integer representing a TimeDiff (a count of elapsed time). While this approach could represent a precise instant in time, it was not always the most helpful. Most notably, you might sometimes want to load date information without time, time without date, or record what timezone the time was measured within. HDBC can now convert all of these things with much greater precision. Thanks to Phil Wise for adding the first Unicode support (to HDBC-postgresql originally) and to Alson Kemp for adding the first advanced date/time marshalling support (also to HDBC-postgresql originally). The experience of adding these features to a single backend driver first made clear a good way to add them to HDBC API as a whole. -- John

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ANN: regex-posix-unittest-1.0 AND regex-posix-0.94.1 AND regex-tdfa-0.97.1
by ChrisK 03 Feb '09

03 Feb '09

I have three announcements to make about regex-* related packages. The regex-posix-0.94.1 package update provides better semantics for multiple matches. Below version 0.94, if any match was empty the matching would stop. Now the empty match is returned and the position is incremented and the searching continues. The regex-tdfa-0.71.1 package update provides the same new multiple match semantics. It also fixes a bug I found. I know of no outstanding bugs in regex-tdfa, and version 0.71.1 now passes all the tests used in regex-posix-unittest-1.0 announced below. We should care about the correctness of our operating system libraries. To help with this, I have a NEW package to announce: regex-posix-unittest-1.0 The accompanying wiki page is http://www.haskell.org/haskellwiki/Regex_Posix This new package provides an executable called regex-posix-unittest which you can install as --user or --global. The regex-posix-unittest executable with no arguments runs a suite of unit tests, all of which are described by text files in the package, the format is documented in the wiki page. By editing the text files in the package you can add to or delete from the unit tests being run. With two arguments the program expects the text first and the pattern second and will run just that match and print all the results. How does regex-posix-unittest help us care about the OS libraries? The regex-posix distributed in the GHC bundle uses the OS C library's "regex.h" API. The regex-posix-unittest package will quite likely show you that your OS C library "regex.h" API is full of bugs. If you are on Linux, it will show you a plethora of GLIBC bugs in Posix conformance. If you are on OS X, FreeBSD, or NetBSD, it will show you many bugs including a critical bug where it fail to find a match where one actually exists. These bugs in the OS library are inherited by your "sed" program as well as regex-posix and Haskell. If you are on Windows, or OpenBSD, or Solaris, or anything else, then please update the wiki page at http://www.haskell.org/haskellwiki/Regex_Posix or email me with your results so I can update the wiki. You may have evil and ingenious tests of Posix extended regular expressions to add to the test suite. Adding them is easy and if you send them to me I will put them in an updated version of regex-posix-unittest. Cheers, Chris

1 0

System.Posix.Files.isDirectory and System.Posix.Files.isSymbolicLink
by Erik de Castro Lopo 03 Feb '09

03 Feb '09

Hi all, The following code creates a symbolic link in the current directory and then uses System.Posix.Files.getFileStatus to get the status of the link. However, isDirectory returns True and isSymbolicLink returns False which is very different from what the stat() system call on a POSIX system would return. I consider this a bug. I'm using ghc-6.8.2. Has this been fixed in a later version? Cheers, Erik module Main where import qualified System.Directory import qualified System.Posix.Files main :: IO () main = do let linkName = "tmp-link" cwd <- System.Directory.getCurrentDirectory System.Posix.Files.createSymbolicLink "/tmp" linkName stat <- System.Posix.Files.getFileStatus linkName if System.Posix.Files.isDirectory stat then putStrLn "Is a directory?????" else putStrLn "Not a directory." if System.Posix.Files.isSymbolicLink stat then putStrLn "Is a symlink" else putStrLn "Not a symlink?????" -- ----------------------------------------------------------------- Erik de Castro Lopo ----------------------------------------------------------------- "Anyone who considers arithmetical methods of producing random digits is, of course, in a state of sin." - John Von Neumann (1951)

3 4

ICFP09 Final CFP
by Matthew Fluet (ICFP Publicity Chair) 02 Feb '09

02 Feb '09

Final Call for Papers ICFP 2009: International Conference on Functional Programming Edinburgh, Scotland, 31 August - 2 September 2009 http://www.cs.nott.ac.uk/~gmh/icfp09.html ** Submission deadline: 2 March 2009 ** Submission URL: https://www.softconf.com/a/icfp09/ ICFP 2009 seeks original papers on the art and science of functional programming. Submissions are invited on all topics from principles to practice, from foundations to features, from abstraction to application. The scope includes all languages that encourage functional programming, including both purely applicative and imperative languages, as well as languages with objects or concurrency. Particular topics of interest include * Language Design * Implementation * Software-Development Techniques * Foundations * Applications and Domain-Specific Languages * Functional Pearls The conference also solicits Experience Reports, which are short papers that provide evidence that functional programming really works or describe obstacles that have kept it from working in a particular application. Important Dates (at 20:00 UTC) ~~~~~~~~~~~~~~~ Submission: 2 March 2009 https://www.softconf.com/a/icfp09/ Author response: 21-23 April 2009 Notification: 5 May 2009 Final papers due: 8 June 2009 Call for Papers (full text) ~~~~~~~~~~~~~~~ http://web.cecs.pdx.edu/~apt/icfp09_cfp.html Call for Experience Reports (full text) ~~~~~~~~~~~~~~~~~~~~~~~~~~~ http://web.cecs.pdx.edu/~apt/icfp09_cfer.html Program Chair ~~~~~~~~~~~~~ Andrew Tolmach Department of Computer Science Portland State University P.O. Box 751, Portland, OR 97207 USA Email: apt(a)cs.pdx.edu Phone: +1 503 725 5492 Fax: +1 503 725 3211 Mail sent to the address above is filtered for spam. If you send mail and do not receive a prompt response, particularly if the deadline is looming, feel free to telephone.

1 0

UDP
by Andrew Coppin 02 Feb '09

02 Feb '09

I'm trying to write a simple program that involves UDP. I was hoping something like this would work: module Main where import Network.Socket main = withSocketsDo main2 main2 = do s <- socket AF_INET Datagram defaultProtocol putStrLn "Waiting..." x <- recv s 100 putStrLn x Unfortunately, that doesn't work at all. It immediately throws an exception ("unknown error"). But then, the whole module seems to be completely undocumented. I managed to find a tiny amount of info online about the underlying C API, but I still don't get how the Haskell interface is supposed to be used. Any hints?

6 8

cURL under Windows again
by Iliya Kuznetsov 02 Feb '09

02 Feb '09

Hello cafe-subscribers, I saw some issues about installing haskell bindings for cURL under Windows, and now I'm trapped too. So, here is actions' log for everything (very detail; you can PgDn to the end with questions): 1. Windows Vista without UAC 2. ghc-6.10.1-i386-windows.exe is installed to C:\Program Files\Haskell "C:\Program Files\Haskell\package.conf" wasn't touched after installation (Cabal nor manually) 3. MinGW-5.1.4 installed to C:\temp\MinGW 4. MSys-1.0 installed to C:\temp\msys\1.0\ 5. curl-7.19.3.tar.bz2 had taken from http://curl.haxx.se/download/curl-7.19.3.tar.bz2 6. Under msys, curl-7.19.3.tar.bz2 is untared into /home/Kuznetsov/curl-7.19.3 7. cURL is made as: cd curl-7.19.3 $ ./configure configure: Configured to build curl/libcurl: ... curl version: 7.19.3 Host setup: i686-pc-mingw32 Install prefix: /usr/local Compiler: gcc SSL support: no (--with-ssl / --with-gnutls) SSH support: no (--with-libssh2) zlib support: no (--with-zlib) krb4 support: no (--with-krb4*) GSSAPI support: no (--with-gssapi) SPNEGO support: no (--with-spnego) c-ares support: no (--enable-ares) ipv6 support: no (--enable-ipv6) IDN support: no (--with-libidn) Build libcurl: Shared=yes, Static=yes Built-in manual: no (--enable-manual) Verbose errors: enabled (--disable-verbose) SSPI support: no (--enable-sspi) ca cert bundle: no ca cert path: no LDAP support: enabled (winldap) LDAPS support: no (--enable-ldaps) $ make ... make[2]: Leaving directory `/home/Kuznetsov/curl-7.19.3/src' make[1]: Leaving directory `/home/Kuznetsov/curl-7.19.3/src' make[1]: Entering directory `/home/Kuznetsov/curl-7.19.3' make[1]: Nothing to be done for `all-am'. make[1]: Leaving directory `/home/Kuznetsov/curl-7.19.3' $ make install ... libtool: install: /bin/install -c .libs/libcurl.dll.a /usr/local/lib/libcurl.dll.a libtool: install: base_file=`basename libcurl.la` libtool: install: dlpath=`/bin/sh 2>&1 -c '. .libs/'libcurl.la'i; echo libcurl-4.dll'` libtool: install: dldir=/usr/local/lib/`dirname ../bin/libcurl-4.dll` libtool: install: test -d /usr/local/lib/../bin || mkdir -p /usr/local/lib/../bin libtool: install: /bin/install -c .libs/libcurl-4.dll /usr/local/lib/../bin/libcurl-4.dll libtool: install: chmod a+x /usr/local/lib/../bin/libcurl-4.dll libtool: install: if test -n '' && test -n 'strip --strip-unneeded'; then eval 'strip --strip-unneeded /usr/local/lib/../bin/libcurl-4.dll' || exit 0; fi libtool: install: /bin/install -c .libs/libcurl.lai /usr/local/lib/ libcurl.la libtool: install: /bin/install -c .libs/libcurl.a /usr/local/lib/libcurl.a libtool: install: chmod 644 /usr/local/lib/libcurl.a libtool: install: ranlib /usr/local/lib/libcurl.a ---------------------------------------------------------------------- Libraries have been installed in: /usr/local/lib If you ever happen to want to link against installed libraries in a given directory, LIBDIR, you must either use libtool, and specify the full pathname of the library, or use the `-LLIBDIR' flag during linking and do at least one of the following: - add LIBDIR to the `PATH' environment variable during execution - add LIBDIR to the `LD_RUN_PATH' environment variable during linking - use the `-LLIBDIR' linker flag ... /bin/install -c -m 644 'curl.h' '/usr/local/include/curl/curl.h' /bin/install -c -m 644 'curlver.h' '/usr/local/include/curl/curlver.h' /bin/install -c -m 644 'easy.h' '/usr/local/include/curl/easy.h' /bin/install -c -m 644 'mprintf.h' '/usr/local/include/curl/mprintf.h' /bin/install -c -m 644 'stdcheaders.h' '/usr/local/include/curl/stdcheaders.h' /bin/install -c -m 644 'types.h' '/usr/local/include/curl/types.h' /bin/install -c -m 644 'multi.h' '/usr/local/include/curl/multi.h' /bin/install -c -m 644 'typecheck-gcc.h' '/usr/local/include/curl/typecheck-gcc.h' /bin/install -c -m 644 'curlbuild.h' '/usr/local/include/curl/curlbuild.h' /bin/install -c -m 644 'curlrules.h' '/usr/local/include/curl/curlrules.h' ... 8. $ which curl && curl /usr/local/bin/curl curl: try 'curl --help' for more information I have following files in C:\temp\msys\1.0\local\bin\ (/usr/local/bin in Unix-scheme): 02.02.2009 15:10 4 029 curl-config 02.02.2009 15:10 98 591 curl.exe 02.02.2009 15:09 262 934 libcurl-4.dll In /usr/local/include/curl ten includes: 02.02.2009 15:10 67 183 curl.h 02.02.2009 15:10 5 865 curlbuild.h 02.02.2009 15:10 7 478 curlrules.h 02.02.2009 15:10 2 799 curlver.h 02.02.2009 15:10 3 526 easy.h 02.02.2009 15:10 2 850 mprintf.h 02.02.2009 15:10 13 039 multi.h 02.02.2009 15:10 1 383 stdcheaders.h 02.02.2009 15:10 33 337 typecheck-gcc.h 02.02.2009 15:10 15 types.h ---- Sorry for many details, but now I can show the wrong behaviour of the haskell bindings for cURL under windows: 9. curl-1.3.4 is taken from hackage and unzipped to /home/Kuznetsov $ cd ~/curl-1.3.4 $ runhaskell Setup.hs configure --extra-include-dirs=/usr/local/include --extra-lib-dirs=/usr/local/lib Configuring curl-1.3.4... $ runhaskell Setup.hs build Preprocessing library curl-1.3.4... Building curl-1.3.4... [1 of 8] Compiling Network.Curl.Debug ( Network\Curl\Debug.hs, dist\build\Network\Curl\Debug.o ) [2 of 8] Compiling Network.Curl.Types ( Network\Curl\Types.hs, dist\build\Network\Curl\Types.o ) [3 of 8] Compiling Network.Curl.Post ( Network\Curl\Post.hs, dist\build\Network\Curl\Post.o ) [4 of 8] Compiling Network.Curl.Opts ( Network\Curl\Opts.hs, dist\build\Network\Curl\Opts.o ) [5 of 8] Compiling Network.Curl.Code ( Network\Curl\Code.hs, dist\build\Network\Curl\Code.o ) [6 of 8] Compiling Network.Curl.Info ( Network\Curl\Info.hs, dist\build\Network\Curl\Info.o ) Network\Curl\Info.hs:80:0: Warning: Defined but not used: `stringTag' Network\Curl\Info.hs:83:0: Warning: Defined but not used: `longTag' Network\Curl\Info.hs:86:0: Warning: Defined but not used: `doubleTag' Network\Curl\Info.hs:89:0: Warning: Defined but not used: `slistTag' [7 of 8] Compiling Network.Curl.Easy ( Network\Curl\Easy.hs, dist\build\Network\Curl\Easy.o ) [8 of 8] Compiling Network.Curl ( Network\Curl.hs, dist\build\Network\Curl.o ) C:\Program Files\Haskell\bin\ar.exe: creating dist\build\libHScurl-1.3.4.a $ runhaskell Setup.hs install Installing library in C:\Program Files\Haskell\curl-1.3.4\ghc-6.10.1 Registering curl-1.3.4... Reading package info from "dist\\installed-pkg-config" ... done. Writing new package config file... done. 10. In package.conf I have seen: InstalledPackageInfo {package = PackageIdentifier {pkgName = PackageName "curl", pkgVersion = Version {versionBranch = [1,3,4], versionTags = []}}, license = BSD3, copyright = "", maintainer = "Sigbjorn Finne < sigbjorn.finne(a)gmail.com>", author = "Sigbjorn Finne", stability = "", homepage = "", pkgUrl = "", description = "libcurl is a client-side URL transfer library, supporting FTP, FTPS, HTTP,\nHTTPS, SCP, SFTP, TFTP, TELNET, DICT, LDAP, LDAPS and FILE.\nlibcurl supports SSL certificates, HTTP POST, HTTP PUT, FTP uploading,\nHTTP form based upload, proxies, cookies, user+password authentication\n(Basic, Digest, NTLM, Negotiate, Kerberos4), file transfer resume,\nhttp proxy tunneling and more!\n\nThis package provides a Haskell binding to libcurl.", category = "Network", exposed = True, exposedModules = ["Network.Curl","Network.Curl.Code"," Network.Curl.Info","Network.Curl.Opts","Network.Curl.Post","Network.Curl.Types","Network.Curl.Easy","Network.Curl.Debug"], hiddenModules = [], importDirs = ["C:\\Program Files\\Haskell\\curl-1.3.4\\ghc-6.10.1"], libraryDirs = ["C:\\Program Files\\Haskell\\curl-1.3.4\\ghc-6.10.1","C:/temp/msys/1.0/local/lib"], hsLibraries = ["HScurl-1.3.4"], extraLibraries = ["curl"], extraGHCiLibraries = [], includeDirs = ["C:/temp/msys/1.0/local/include"], includes = [], depends = [PackageIdentifier {pkgName = PackageName "base", pkgVersion = Version {versionBranch = [3,0,3,0], versionTags = []}},PackageIdentifier {pkgName = PackageName "bytestring", pkgVersion = Version {versionBranch = [0,9,1,4], versionTags = []}},PackageIdentifier {pkgName = PackageName "containers", pkgVersion = Version {versionBranch = [0,2,0,0], versionTags = []}}], hugsOptions = [], ccOptions = [], ldOptions = [], frameworkDirs = [], frameworks = [], haddockInterfaces = ["C:\\Program Files\\Haskell\\doc\\curl-1.3.4\\html\\curl.haddock"], haddockHTMLs = ["C:\\Program Files\\Haskell\\doc\\curl-1.3.4\\html"]} In "C:\Program Files\Haskell\curl-1.3.4\ghc-6.10.1\" I have seen HScurl-1.3.4.o , libHScurl-1.3.4.a and other Curl files. 11. Final tests: under msys: $ ghci Prelude> :m Network.Curl module `Network.Curl' is not loaded Bad, but not a disaster. under windows: C:\> ghci GHCi, version 6.10.1: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. Prelude> :m Network.Curl Prelude Network.Curl> let a = curlGet Loading package syb ... linking ... done. Loading package base-3.0.3.0 ... linking ... done. Loading package array-0.2.0.0 ... linking ... done. Loading package containers-0.2.0.0 ... linking ... done. Loading package bytestring-0.9.1.4 ... linking ... done. Loading package curl-1.3.4 ... <interactive>: curl: Не найден указанный модуль. (text in russian here because of localized Vista. The message is near "Can't load specified module") can't load .so/.DLL for: curl (addDLL: could not load DLL) Prelude Network.Curl> So, the question is why curl doesn't work? I tried to use Cabal but it failed with building too. How can I test the fact that C:\temp\msys\1.0\local\bin\libcurl-4.dll is used in curl-1.3.4 ? -- Iliya Kuznetsov +7-916-878-75-70

1 0

Haskeline, pcre-light, iconv and Cabal on OSX
by Antoine Latter 02 Feb '09

02 Feb '09

Funny story, If I do the following three things, I get errors on my Intel Mac OS 10.5: * Build an executable with Cabal * Have the executable have a build-dep of pcre-light in the .cabal * use haskeline in the executable itself I get crazy linker errors relating to haskeline and libiconv: Shell output: >>>>> $ cabal clean && cabal configure && cabal build cleaning... Configuring test-0.0.0... Preprocessing executables for test-0.0.0... Building test-0.0.0... [1 of 1] Compiling Main ( test.hs, dist/build/test/test-tmp/Main.o ) Linking dist/build/test/test ... Undefined symbols: "_iconv_open", referenced from: _s9Qa_info in libHShaskeline-0.6.0.1.a(IConv.o) "_iconv_close", referenced from: _iconv_close$non_lazy_ptr in libHShaskeline-0.6.0.1.a(IConv.o) "_iconv", referenced from: _sa0K_info in libHShaskeline-0.6.0.1.a(IConv.o) ld: symbol(s) not found collect2: ld returned 1 exit status <<<<< But all three above conditions need to be true - if I build using 'ghc --make' everything works great, even if the executable imports pcre-light and haskeline. If I have build-deps on haskeline and pcre-light, but don't actually import haskeline, everything also works great. Here are the files I've used: test.hs: >>>>> import System.Console.Haskeline main :: IO () main = print "Hello!" <<<<< test.cabal >>>>> Name: test version: 0.0.0 cabal-version: >= 1.2 build-type: Simple Executable test main-is: test.hs build-depends: base, haskeline, pcre-light>=0.3 <<<<< Is there some way I need to be building haskeline on OS X to make this work? Thanks, Antoine more details: >>>>> $ cabal --version cabal-install version 0.6.0 using version 1.6.0.1 of the Cabal library <<<<< >>>>> $ ghc --version The Glorious Glasgow Haskell Compilation System, version 6.10.0.20081007 <<<<< links: pcre-light: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/pcre-light haskeline: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/haskeline

5 10

cabal list can't find Glob.cabal file?
by Dougal Stanton 02 Feb '09

02 Feb '09

I get a curious message when trying to run 'cabal list': $ cabal list ....omit some lines... ...................... Latest version available: 0.3 Category: Network Synopsis: Pure bindings for the MaxMind IP database. License: OtherLicense cabal: Couldn't read cabal file "./Glob/0.1/Glob.cabal" Any ideas? As far as Hackage and the local index are concerned, 0.1 isn't even a recent version of Glob. Why should it be looking for the file? cabal-install version 0.5.1 using version 1.4.0.1 of the Cabal library -- Dougal Stanton dougal(a)dougalstanton.net // http://www.dougalstanton.net

2 2

Re: [Haskell-cafe] pure crisis :)
by Sergey Zaharchenko 02 Feb '09

02 Feb '09

Hello Bulat! Sun, Feb 01, 2009 at 10:19:18PM +0300 you wrote: > Hello haskell-cafe, > pure functional denotation for crisis: > (_|_) Thus, when people try to evaluate the amount of savings they have left, their behavior frequently becomes _undefined_ :) -- DoubleF

1 0

Network.UrlDisp
by Pieter Laeremans 02 Feb '09

02 Feb '09

Hello, Has anyone some exampe usages of : Network.UrlDisp ? thanks in advance, Pieter -- Pieter Laeremans <pieter(a)laeremans.org>

4 4

Newtype deriving with functional dependencies
by Louis Wasserman 02 Feb '09

02 Feb '09

Is there any sensible way to make newtype FooT m e = FooT (StateT Bar m e) deriving (MonadState) work to give instance MonadState Bar (FooT m e)? That is, I'm asking if there would be a semantically sensible way of modifying GeneralizedNewtypeDeriving to handle multi-parameter type classes when there is a functional dependency involved, assuming by default that the newtype is the more general of the types, perhaps? Louis Wasserman wasserman.louis(a)gmail.com

2 1

Question re: denotational semantics in SPJ's "Implementation of FPLs" book
by Devin Mullins 02 Feb '09

02 Feb '09

I'm reading SPJ's "The Implementation of Functional Programming Languages," and on page 32, it defines the multiplication operator in its extended lambda calculus as: Eval[[ * ]] a b = a x b Eval[[ * ]] _|_ b = _|_ Eval[[ * ]] a _|_ = _|_ Is that complete? What are the denotational semantics of * applied to things not in the domain of the multiplication operator x, such as TRUE (in the extended lambda defined by this book) and functions (in normal lambda calc)? Do these things just eval to bottom? Or is this just to be ignored, since the extended calculus will only be applied to properly "typed" expressions in the context of this book?

2 1

Takusen 0.8.3 install problems
by Praki Prakash 02 Feb '09

02 Feb '09

I am trying to install Takusen 0.8.3 with ghc 6.10.1 on Ubuntu 8.04 (same issue on Win XP as well). I get the following complaint from cabal. Module `Distribution.PackageDescription' does not export `writeHookedBuildInfo' cabal: Error: some packages failed to install: Takusen-0.8.3 failed during the configure step. The exception was: exit: ExitFailure 1 Any suggestions on how to fix this issue? Thanks, Praki

4 6

Howto debug erros occuring just by linking to non-Haskell libraries
by Mads Lindstrøm 02 Feb '09

02 Feb '09

Hi Haskeleers I am trying to track down the cause of an error occurring in the Linux version of wxHaskell. The error occurs before the main function is executed. That is, it occurs if one imports the wxHaskell libraries, and it occurs even if one do not execute any wxHaskell function. Specifically, GLib complains that a initialization-function has not been called. My guess is, that it has something to do with the wxWidgets (and gtk or glib) libraries wxHaskell links to. Some people have suggested it may be an error in the way GHC links with C libraries. But that is all guesswork, I would need something more solid if I were to file GHC bugreport. Here is a simple Haskell program to illustrate the problem: module Main where import Graphics.UI.WX main = print "sdfjkl" and when we compile and execute this program we get: (process:13986): GLib-GObject-CRITICAL **: gtype.c:2240: initialization assertion failed, use IA__g_type_init() prior to this function (process:13986): Gdk-CRITICAL **: gdk_cursor_new_for_display: assertion `GDK_IS_DISPLAY (display)' failed (process:13986): GLib-GObject-CRITICAL **: gtype.c:2240: initialization assertion failed, use IA__g_type_init() prior to this function (process:13986): Gdk-CRITICAL **: gdk_cursor_new_for_display: assertion `GDK_IS_DISPLAY (display)' failed "sdfjkl" So even if I do not call any wxHaskell functions, just by linking to wxHaskell, I get these errors. As Jeroen Janssen reports here http://www.mail-archive.com/wxhaskell-users@lists.sourceforge.net/msg00540.… , he is experiencing the same error, but his wxPython programs works. Thus, wxHaskell (or GHC or ...) must do something different. Could this error be related to the order which external libraries are loaded in? If so, do anybody know how to specify the load order? Can anybody help med with a good approach for debugging this error? Greetings, Mads Lindstrøm

1 0

Panic with GTK2HS 0.10.0 RC under Vista with GHCi 6.10.1; GHCi or GTK bug?
by Peter Verswyvelen 01 Feb '09

01 Feb '09

Often when trying to run my GTK2HS application the first time with GHCi I get : panic! (the 'impossible' happened) (GHC version 6.10.1 for i386-unknown-mingw32): loadObj: failed Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug This only occurs when I forgot to set my current directory correctly; then GHCi gives an error since it can't find modules GHCi, version 6.10.1: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. Boxes.hs:23:17: Could not find module `NM8.GUI.Layout': Use -v to see a list of the files searched for. Failed, modules loaded: none. If I then correctly set my current directory using the :cd command, and try again, I get the panic crash. When I start GHCi again and immediately set the correct current directory, it works fine. I haven't tried to isolate the problem, but maybe others have experienced this problem? It's not really a show-stopper, just but a bit annoying

1 0

ANN: regex-xmlschema
by Uwe Schmidt 01 Feb '09

01 Feb '09

I'm pleased to announce (yet another) package for processing text with regular expressions: regex-xmlschema The W3C XML Schema specification (http://www.w3.org/TR/xmlschema11-2/#regexs) defines a language for regular expressions. This language is used in the XML Schema spec when defining the data type library part. This regex-xmlschema package contains a complete implementation of this spec. It is implemented with the technique of derivations of regular expression. Main features are: * full support of Unicode including all Unicode code blocks and character properties * a purely functional interface * 100% Haskell, no other packages except parsec needed * cabal build file * extensions for intersection, set difference, exclusive or and interleave of regular sets (regular expressions), * extensions for subexpression matches * functions for matching, for grep like searching, for stream like editing (sed like) and for tokenizing. With this package, it becomes rather easy to build lightweight tokenizers e.g. for colourizing arbitrary programming languages, like hscolor does it for Haskell. The package is available from Hackage: "http://hackage.haskell.org/cgi-bin/hackage-scripts/package/regex-xmlschema", there's a darcs repo for the latest source: "http://darcs2.fh-wedel.de/hxt/regex/" and a wiki page, describing the extension and giving some examples for using the library: "http://www.haskell.org/haskellwiki/Regular_expressions_for_XML_Schema" Cheers, Uwe -- Uwe Schmidt FH Wedel http://www.fh-wedel.de/~si/

1 0

can't build testpack
by Ezekiel Smithburg 01 Feb '09

01 Feb '09

this is the error message i get: ezekiel-smithburgs-macbook-pro-15% runhaskell Setup.* build Preprocessing library testpack-1.0.0... Building testpack-1.0.0... [1 of 3] Compiling Test.QuickCheck.Instances ( src/Test/QuickCheck/Instances.hs, dist/build/Test/QuickCheck/Instances.o ) [2 of 3] Compiling Test.QuickCheck.Tools ( src/Test/QuickCheck/Tools.hs, dist/build/Test/QuickCheck/Tools.o ) [3 of 3] Compiling Test.HUnit.Tools ( src/Test/HUnit/Tools.hs, dist/build/Test/HUnit/Tools.o ) src/Test/HUnit/Tools.hs:28:36: Class `Control.Exception.Exception' used as a type In the type `Control.Exception.Exception' In the type `Control.Exception.Exception -> IO a -> IO ()' In the type `String -> Control.Exception.Exception -> IO a -> IO ()' what should i do? need this in order to build hdbc 2.0, which i'm hoping solves a problem i was having earlier (memory leak).

3 8

Re: [Haskell-cafe] can't build testpack
by Ezekiel Smithburg 01 Feb '09

01 Feb '09

tried that version, it gets rid of that error message but now i have this one: ezekiel-smithburgs-macbook-pro-15% cabal --flag=split-base configure -p Configuring testpack-1.0.0... ezekiel-smithburgs-macbook-pro-15% cabal build Preprocessing library testpack-1.0.0... Building testpack-1.0.0... [1 of 3] Compiling Test.QuickCheck.Instances ( src/Test/QuickCheck/Instances.hs, dist/build/Test/QuickCheck/Instances.o ) [2 of 3] Compiling Test.QuickCheck.Tools ( src/Test/QuickCheck/Tools.hs, dist/build/Test/QuickCheck/Tools.o ) [3 of 3] Compiling Test.HUnit.Tools ( src/Test/HUnit/Tools.hs, dist/build/Test/HUnit/Tools.o ) src/Test/HUnit/Tools.hs:23:7: Could not find module `System.Random': Perhaps you haven't installed the profiling libraries for package random-1.0.0.1? Use -v to see a list of the files searched for. i'll start reading the cabal user guide and see if i can figure it out on my own, but i figure progress on this should be up on the list so if someone else has this problem, they can find this and solve it on their own. also, if someone else can figure it out before i do, that's cool too. thanks for your help so far! On Sat, Jan 31, 2009 at 8:14 PM, Krzysztof Skrzętnicki <gtener(a)gmail.com>wrote: > Ok, sorry for the confusion, I should have checked it before: testpack > doesn't really need base-4, it needs base-3.The right dependency line is > (for both 6.10.1 and 6.8.3): > > Build-Depends: base >= 3 && < 4 , containers, random > > I really need to get some sleep... > > All best > > Christopher Skrzętnicki > > > On Sun, Feb 1, 2009 at 03:07, Krzysztof Skrzętnicki <gtener(a)gmail.com>wrote: > >> Trying to follow Ezekiel's steps I bumped into this: >> >> >>> >> D:\biblioteki\testpack-1.0.0>cabal configure >> Configuring testpack-1.0.0... >> >> D:\biblioteki\testpack-1.0.0>cabal build >> Preprocessing library testpack-1.0.0... >> Building testpack-1.0.0... >> [1 of 3] Compiling Test.QuickCheck.Instances ( >> src\Test\QuickCheck\Instances.hs, dist\build\Test\QuickCheck\Instances.o ) >> [2 of 3] Compiling Test.QuickCheck.Tools ( src\Test\QuickCheck\Tools.hs, >> dist\build\Test\QuickCheck\Tools.o ) >> [3 of 3] Compiling Test.HUnit.Tools ( src\Test\HUnit\Tools.hs, >> dist\build\Test\HUnit\Tools.o ) >> >> src\Test\HUnit\Tools.hs:28:36: >> Class `Control.Exception.Exception' used as a type >> In the type `Control.Exception.Exception' >> In the type `Control.Exception.Exception -> IO a -> IO ()' >> In the type `String >> -> Control.Exception.Exception -> IO a -> IO ()' >> >> D:\biblioteki\testpack-1.0.0>cabal install >> Resolving dependencies... >> Configuring testpack-1.0.0... >> Preprocessing library testpack-1.0.0... >> Building testpack-1.0.0... >> [3 of 3] Compiling Test.HUnit.Tools ( src\Test\HUnit\Tools.hs, >> dist\build\Test\HUnit\Tools.o ) >> C:\ghc\ghc-6.10.1\bin\ar.exe: creating dist\build\libHStestpack-1.0.0.a >> Installing library in C:\Program Files\Haskell\testpack-1.0.0\ghc-6.10.1 >> Registering testpack-1.0.0... >> Reading package info from "dist\\installed-pkg-config" ... done. >> Writing new package config file... done. >> <<< >> >> In short: "cabal configure && cabal build" fails, whereas "cabal install" >> builds fine. Looks like a bug in cabal-install. Am I right? >> >> All best >> >> Christopher Skrzętnicki >> >> >> >> On Sun, Feb 1, 2009 at 03:01, Krzysztof Skrzętnicki <gtener(a)gmail.com>wrote: >> >>> testpack builds fine for me. In the original .cabal file there are >>> following lines: >>> >>> >>> >>> If flag(splitBase) >>> Build-Depends: base >= 3, containers, random >>> Else >>> Build-Depends: base < 3 >>> <<< >>> >>> Now that I think about it you didn't actually said what is your GHC >>> version. >>> Knowing that you can replace lines above with one line that matches your >>> specific configuration. >>> >>> GHC 6.8.3 : >>> Build-Depends: base >= 4, containers, random >>> GHC 6.10.1 : >>> Build-Depends: base >= 3, containers, random >>> >>> Please take care to restore and modify the original file. >>> >>> I think you should read Cabal user guide. This will save your time in the >>> future: >>> http://www.haskell.org/ghc/docs/latest/html/Cabal/index.html >>> >>> I *hope* those changes will fix your installation. I can't really test >>> it, because testpack build fine with my version of cabal: >>> >>> C:\Documents and Settings\Metharius>cabal install testpack --reinstall >>> Resolving dependencies... >>> 'testpack-1.0.0' is cached. >>> Configuring testpack-1.0.0... >>> Preprocessing library testpack-1.0.0... >>> Building testpack-1.0.0... >>> [1 of 3] Compiling Test.QuickCheck.Instances ( >>> src\Test\QuickCheck\Instances.hs, dist\build\Test\QuickCheck\Instances.o ) >>> [2 of 3] Compiling Test.QuickCheck.Tools ( src\Test\QuickCheck\Tools.hs, >>> dist\build\Test\QuickCheck\Tools.o ) >>> [3 of 3] Compiling Test.HUnit.Tools ( src\Test\HUnit\Tools.hs, >>> dist\build\Test\HUnit\Tools.o ) >>> C:\ghc\ghc-6.10.1\bin\ar.exe: creating dist\build\libHStestpack-1.0.0.a >>> Installing library in C:\Program Files\Haskell\testpack-1.0.0\ghc-6.10.1 >>> Registering testpack-1.0.0... >>> Reading package info from "dist\\installed-pkg-config" ... done. >>> Writing new package config file... done. >>> >>> C:\Documents and Settings\Metharius>cabal install -w >>> c:\ghc\ghc-6.8.3\bin\ghc testpack --reinstall >>> Resolving dependencies... >>> 'testpack-1.0.0' is cached. >>> Configuring testpack-1.0.0... >>> Preprocessing library testpack-1.0.0... >>> Building testpack-1.0.0... >>> [1 of 3] Compiling Test.QuickCheck.Instances ( >>> src/Test/QuickCheck/Instances.hs, dist\build/Test/QuickCheck/Instances.o ) >>> [2 of 3] Compiling Test.QuickCheck.Tools ( src/Test/QuickCheck/Tools.hs, >>> dist\build/Test/QuickCheck/Tools.o ) >>> [3 of 3] Compiling Test.HUnit.Tools ( src/Test/HUnit/Tools.hs, >>> dist\build/Test/HUnit/Tools.o ) >>> C:\ghc\ghc-6.10.1\bin\ar.exe: creating dist\build\libHStestpack-1.0.0.a >>> Installing library in C:\Program Files\Haskell\testpack-1.0.0\ghc-6.8.3 >>> Registering testpack-1.0.0... >>> Reading package info from "dist\\installed-pkg-config" ... done. >>> Saving old package config file... done. >>> Writing new package config file... done. >>> >>> Perhaps it may also be the difference of installing with "cabal install" >>> and "runhaskell Setup build". >>> >>> All best >>> >>> Christopher Skrzętnicki >>> >>> >>> 2009/2/1 Ezekiel Smithburg <tehgeekmeister(a)gmail.com> >>> >>>> oddly, when i do that, i'm back to the original error message. and >>>> sorry, i didn't understand what you meant, apparently. >>>> >>>> >>>> On Sat, Jan 31, 2009 at 7:41 PM, Krzysztof Skrzętnicki < >>>> gtener(a)gmail.com> wrote: >>>> >>>>> >>>>> 2009/2/1 Ezekiel Smithburg <tehgeekmeister(a)gmail.com> >>>>> >>>>>> solution to that problem: >>>>>> >>>>>> deleted the lines from "If flag(splitBase)" on and changed base in >>>>>> Build-Depends to base >= 4. >>>>>> >>>>> >>>>> Well, this is exactly what I suggested in the first place: >>>>> >>>>> > This error is due to usage of old base package in version 3.> In >>>>> .cabal file add dependency on base-4, in form "base >= 4". >>>>> >>>>> Regarding second qustion: >>>>> >>>>> > random 1.0.0.1 is installed, i've verified that. what does this >>>>> error mean? >>>>> >>>>> It means that .cabal file fails to specify dependancy on random >>>>> package. Add dependancy on "random" package next to "base>=4". This should >>>>> help. >>>>> >>>>> All best >>>>> >>>>> Christopher Skrzętnicki >>>>> >>>> >>>> >>> >> >

2 2

Buttons and Clicks - State Monad
by guenni68 01 Feb '09

01 Feb '09

Hi, in this piece here http://moonpatio.com/fastcgi/hpaste.fcgi/view?id=1083#a1083 I'm trying to create a button that, every time when clicked, increases a counter by one and does a putStrLn of the counters current value. I'm trying to write this without any use of IORef but merely using the state monad. Can anybody show me how to do this? Günther The UI Code is wxHaskell

4 3

Haskell Weekly News: Issue 103 - January 31, 2009
by Brent Yorgey 31 Jan '09

31 Jan '09

--------------------------------------------------------------------------- Haskell Weekly News http://sequence.complete.org/hwn/20090131 Issue 103 - January 31, 2009 --------------------------------------------------------------------------- Welcome to issue 103 of HWN, a newsletter covering developments in the [1]Haskell community. Announcements HDBC v2.0 now available. John Goerzen [2]announced that [3]HDBC v2.0 is now available. Simultaneously, [4]HDBC-sqlite3, [5]HDBC-postgresql, and [6]HDBC-odbc v2.0 have also been uploaded to Hackage. A guide to new features and migration can be [7]found here. Extensible and Modular Generics for the Masses: emgm-0.2. Sean Leather [8]announced the second major release of [9]Extensible and Modular Generics for the Masses (EMGM), a library for generic programming in Haskell using type classes and a sum-of-products view. Improvements over emgm-0.1 include type representation derivation using Template Haskell, documentation improvements, a bimap function, and more. incremental-sat-solver. Sebastian Fischer [10]announced the [11]incremental-sat-solver library, which provides an implementation of the [12]Davis-Putnam-Logemann-Loveland algorithm for the Boolean satisfiability problem. It not only allows solving Boolean formulas in one go, but also adding constraints and query bindings of variables incrementally. data-spacepart - space partitioning data structure[s] (initial release). Corey O'Connor [13]announced the [14]data-spacepart package, the goal of which is to be a collection of space partitioning data structures. Currently, there is only a simple quadtree implementation. Wired 0.2. Emil Axelsson [15]announced a new release of [16]Wired. The most important news in this release is that it now contains a 45nm cell library, which means that you can use Wired to create and analyze modern VLSI designs today! CFP Haskell Symposium 2009. Stephanie Weirich [17]announced a call for papers for the [18]2009 Haskell Symposium in Edinburgh, Scotland. The deadline for submissions is May 8. testpack (first release). John Goerzen [19]announced the release of [20]testpack, a collection of a few utilities for tests: some tools to convert QuickCheck properties into HUnit test cases, and various shortcuts and tools to increase verbosity while running tests in both QuickCheck and HUnit. convertible (first release). John Goerzen [21]announced a new package, [22]convertible. At its heart, it's a very simple typeclass that's designed to enable a reasonable default conversion between two different types without having to remember a bunch of functions. The return type from this conversion is "Either ConvertError a", and conversions are expected to do sanity checking (such as bounds checking when converting to types like Int), so as to produce neither garbage nor exceptions as part of the conversion process. The package also includes instances of the Convertible typeclass for common type conversions. working with numeric types as well as dates and times. Notably, it has code to convert between System.Time types and their Data.Time siblings, and vice versa, a capability I found annoyingly lacking in the standard library. Progress with IDE. Juergen Nicklisch-Franken [23]announced that the [24]Leksah 0.4.0 pre-release is now available. Current features include a Haskell customized editor with candy, project management support based on Cabal, a visual editor for Cabal files, navigation aids, a module browser, session support, and more. Hayoo! beta 0.3. Timo B. [25]announced the next beta version 0.3 of [26]Hayoo!, the Haskell API search engine with find-as-you-type and suggestions. Hayoo! now works even if your browser does not support JavaScript. DecisionTree 0.0. Adrian Neumann [27]announced the [28]DecisionTree package, which provides an implementation of the ID3 algorithm and can be used to classify data with discrete valued attributes. orchid-0.0.7. Sebastiaan Visser [29]announced a new release of [30]Orchid, just another Haskell Wiki. This release features a number of improvements, including a [31]filestore backend, searching, deleting and renaming support, and more. Check out the [32]demo. gitit 0.5. John MacFarlane [33]announced the latest release of [34]Gitit, the multitalented distributed wiki written in Haskell. This release uses the [35]filestore library and hence also supports a darcs backend, and also features optimizations, better search, better diffs, and more. You can check out a [36]running example. filestore 0.1. Gwern Branwen [37]announced [38]filestore 0.1, which provides a uniform, abstract, generic interface for storing versioned files on disk. It allows calling programs to use generic commands to store strings or binary data and perform various queries, such as 'what files are in this repository?' or 'what were the contents of this file at revision XXXXXXX?' or 'give me a diff of this file between revision XXXXXXX and revision YYYYYYY.' Because the interface is abstract, the calling program is insulated from the messy details of the backend (which might be a VCS or a database). Darcs and Git are fully supported. There are plans for a SQLite backend. Scurry :: A cross platform (if you put your mind to it) P2P VPN. John Van Enk [39]announced the release of [40]Scurry, a P2P VPN application written in Haskell (and a little C). Discussion Why binding to existing widget toolkits doesn't make any sense. Achim Schneider began an interesting [41]discussion on the proper approach to GUI toolkits in Haskell. Laws and partial values. Henning Thielemann began [42]a long thread on the semantics of laws (such as the monoid laws). Blog noise [43]Haskell news from the [44]blogosphere. * Sebastian Fischer: [45]Using SmallCheck to Shatter an Audacious Claim. * Xmonad: [46]Quad head xmonad. * Darcs: [47]darcs weekly news #15. * Osfameron: [48]More longest paths, and sick folds.. * Eric Kow (kowey): [49]haskell-ji. * Jeff Heard: [50]Control.Monad.IfElse. * Conal Elliott: [51]What is automatic differentiation, and why does it work?. * Luke Palmer: [52]Fun with PiSigma. * Neil Mitchell: [53]Small scripts with Haskell. * LHC Team: [54]Release notes.. * LHC Team: [55]Thoughts on a new code generator. * Xmonad: [56]contribs review: ThreeColumnsMiddle, CenteredMaster, Mosaic. * Osfameron: [57]There's the nub (snippet in Perl and Haskell). * Malcolm Wallace: [58]codec implementations. * Sebastian Fischer: [59]Fun with Infinite Global Constants. Just-in-time, memoized binomial coefficients. * Chris Done: [60]Some libgd changes. * Luke Palmer: [61]A world without orphans. Luke muses on the benefits to be gained by outlawing orphan instances. * Creighton Hogg: [62]Fear of releasing code. * LHC Team: [63]Thoughts on a new code generator. * Don Stewart (dons): [64]What is Haskell good for?. Lots of things, if this tag cloud has anything to say about it. * Arch Haskell News: [65]Haskell wiki stack in Arch. * Conal Elliott: [66]Comparing formulations of higher-dimensional, higher-order derivatives. * Conal Elliott: [67]Fostering creativity by relinquishing the obvious. * Arch Haskell News: [68]Arch Haskell News: Jan 11 2009. * Dan Piponi (sigfpe): [69]Fast incremental regular expression matching with monoids. A very cool article showing how to use fingertrees storing memoized automaton transition functions to do fast incremental regular expression matching (or, in general, fast incremental lexing). Quotes of the Week * lilac: is happy with his infinite type. it's ducks all the way across and down. * Gracenotes: You are likely to be eaten by a poset * RossMellgren: Apparently 64-bit GHC is sufficiently advanced to be indistinguishable from magic. * cjb: It's all fun and games until somebody loses an IOVar. * sigfpe: If I took some Ritalin, maybe I could write an entire book on Haskell and algebra. * ddarius: Nothing is evaluated until it is. About the Haskell Weekly News New editions are posted to [70]the Haskell mailing list as well as to [71]the Haskell Sequence and [72]Planet Haskell. [73]RSS is also available, and headlines appear on [74]haskell.org. To help create new editions of this newsletter, please see the information on [75]how to contribute. Send stories to byorgey at cis dot upenn dot edu. The darcs repository is available at darcs get [76]http://code.haskell.org/~byorgey/code/hwn/ . References 1. http://haskell.org/ 2. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51664 3. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/HDBC 4. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/HDBC%2Dsqlite3 5. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/HDBC%2Dpostgresql 6. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/HDBC%2Dodbc 7. http://software.complete.org/software/wiki/hdbc/NewIn20 8. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51646 9. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/emgm 10. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51564 11. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/incremental-sat-… 12. http://en.wikipedia.org/wiki/DPLL_algorithm 13. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51505 14. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/data-spacepart 15. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51484 16. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Wired 17. http://article.gmane.org/gmane.comp.lang.haskell.general/16818 18. http://haskell.org/haskell-symposium/2009/ 19. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51482 20. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/testpack 21. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51481 22. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/convertible 23. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51475 24. http://www.leksah.org/ 25. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51450 26. http://holumbus.fh-wedel.de/hayoo 27. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51407 28. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/DecisionTree 29. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51395 30. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/orchid 31. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/filestore 32. http://funct.org/wiki/ 33. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51392 34. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/gitit 35. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/filestore 36. http://gitit.johnmacfarlane.net/ 37. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51388 38. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/filestore 39. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51364 40. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Scurry 41. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/51478 42. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/51299 43. http://planet.haskell.org/ 44. http://haskell.org/haskellwiki/Blog_articles 45. http://www-ps.informatik.uni-kiel.de/~sebf/haskell/smallcheck-experience.ht… 46. http://xmonad.wordpress.com/2009/01/31/quad-head-xmonad/ 47. http://blog.darcs.net/2009/01/darcs-weekly-news-15.html 48. http://greenokapi.net/blog/2009/01/31/more-longest-paths-and-sick-folds/ 49. http://koweycode.blogspot.com/2009/01/haskell-ji.html 50. http://vis.renci.org/jeff/?p=96 51. http://conal.net/blog/posts/what-is-automatic-differentiation-and-why-does-… 52. http://lukepalmer.wordpress.com/2009/01/28/fun-wth/ 53. http://neilmitchell.blogspot.com/2009/01/small-scripts-with-haskell.html 54. http://lhc-compiler.blogspot.com/2009/01/release-notes.html 55. http://lhc-compiler.blogspot.com/2009/01/thoughts-on-new-code-generator.html 56. http://xmonad.wordpress.com/2009/01/27/contribs-review-threecolumnsmiddle-c… 57. http://greenokapi.net/blog/2009/01/27/theres-the-nub-snippet-in-perl-and-ha… 58. http://feeds.feedburner.com/~r/malcolm/~3/523603226/codec-implementations.h… 59. http://www-ps.informatik.uni-kiel.de/~sebf/haskell/infinite-constants.html 60. http://chrisdone.com/blog/2009/01/26/Some-libgd-changes 61. http://lukepalmer.wordpress.com/2009/01/25/a-world-without-orphans/ 62. http://abstractabsurd.blogspot.com/2009/01/fear-of-releasing-code.html 63. http://lhc-compiler.blogspot.com/2009/01/thoughts-on-new-code-generator.html 64. http://donsbot.wordpress.com/2009/01/24/what-is-haskell-good-for/ 65. http://archhaskell.wordpress.com/2009/01/25/haskell-wiki-stack-in-arch/ 66. http://conal.net/blog/posts/comparing-formulations-of-higher-dimensional-hi… 67. http://conal.net/blog/posts/fostering-creativity-by-relinquishing-the-obvio… 68. http://archhaskell.wordpress.com/2009/01/11/arch-haskell-news-jan-11-2009/ 69. http://sigfpe.blogspot.com/2009/01/fast-incremental-regular-expression.html 70. http://www.haskell.org/mailman/listinfo/haskell 71. http://sequence.complete.org/ 72. http://planet.haskell.org/ 73. http://sequence.complete.org/node/feed 74. http://haskell.org/ 75. http://haskell.org/haskellwiki/HWN 76. http://code.haskell.org/~byorgey/code/hwn/

1 0

Re[Haskell-cafe] cursive referencing
by Belka 31 Jan '09

31 Jan '09

Hello! I'm puzzled, if in Haskell it's possible to create a (pure) data structure, consisting of 2 substructures referencing each other: ------------------------- data AA = AA { someData1 :: SomeData1 bb :: BB } data BB = BB { someData2 :: SomeData2 aa :: AA } f :: SomeData1 -> SomeData2 -> AA f somedata1 somedata2 = ?????????? -- Always True: ghci> f == aa $ bb f True ------------------------- Any ideas? Belka -- View this message in context: http://www.nabble.com/Recursive-referencing-tp21722002p21722002.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

3 8

GHCi Memory Leak in Windows Vista
by spam.andir＠gmail.com 31 Jan '09

31 Jan '09

Hi all! Environment: Windows Vista + SP1, GHC 6.10.1. Description: If use ghci.exe and run separate ghc.exe compiler process, memory leak in ghci occurred. After exhausting available memory Vista has no responding. Steps for reproduce: 1) After run GHCi, process list has 2 processes: ghci.exe (a), ghc.exe (b), 2) Then I run separated compilation process 20 times: Command Line: for /L %i in (1,1,20) do ghc -fforce-recomp -O --make "problem.hs" -o "problem.exe" Sample Haskell Program listing (problem.hs): main :: IO () main = do print $ [x | x <- [1..]] putStrLn "Hello, world!" 3) In process list (taskmgr.exe) I can see some processor activity and increasing value of "Memory (Private Working Set)" for process (b). 4) After run "Memory (Private Working Set)" increased about 100Mb. Best regards.

5 4

darcs-client on ghc 6.10.1
by Phil 31 Jan '09

31 Jan '09

Hi, Was wondering if anyone knew if darcs-server is still maintained? The author¹s e-mail address bounces. The Haskell client is broken in ghc 6.10. I have a straightforward fix for it: phil$ darcs whatsnew hunk ./client/build 2 -ghc -Wall -O2 -o darcs-client -package network Http.hs DarcsClient.hs +ghc -Wall -O2 -o darcs-client.exe -package base-3.0.3.0 -package network Http.hs DarcsClient.hs Phil.

1 0

UI-state, using State Monad or IORef?
by guenni68 31 Jan '09

31 Jan '09

Hi, at one point I generate n elements of dropdowns dynamically. Whenever I make a selection in any of those choices the others should also be updated, ie. the list of available choices needs to be altered. But I also need to update in place the "model" that is associated with each individual dropdown. Should I simply use IORefs for this purpose, or should I rather use a more functional code with the State Monad? Is there a tutorial or an example on how to use the State monad? Günther

1 0

"Standard C" available in cabal package
by Maurício 31 Jan '09

31 Jan '09

Hi, I see that cabal allows me to say: c-sources: (...) and then have a few C files built with my program. I see that I can have lines like #include <some usual C header> in those files, and that makes me think that, even if I add no C files to my .cabal, I still can count on what would be standard C functions available, and that I could use them with Foreign, like, say: foreign import ccall "memcpy" :: Ptr a -> Ptr a -> CSize -> IO Ptr a Am I right to guess that? If so, what would be the available set of functions? I imagined standard C (C99?), but searching around I see that there are a few different stabdard C libraries, like, for instance, glibc, which seems to be used in Linux, and a few others. Supposed I wanted to write a module with all C functions always available, what could I let be there? Thanks, Maurício

3 4

Fwd: [Haskell-cafe] HPC and literate haskell
by Pavel Perikov 31 Jan '09

31 Jan '09

> No I do not process it using lhs2tex. I just compile literate haskell code. The necessity of preprocessing kills the entire idea of having literate source. I just feed lhs files to ghc and everything works fine except code coverage. > > > On 30.01.2009, at 5:35, Robin Green wrote: > >> Have you tried processing the file with lhs2tex first, to unlit it? >> (Or >> is that what you are doing? It's unclear from your email.) >> -- >> Robin

1 0

Re: Haskell on ARM (was Re: ANN: Topkata)
by Jeremy Apthorp 31 Jan '09

31 Jan '09

2008/6/25 Braden Shepherdson <Braden.Shepherdson(a)gmail.com>: > Jeremy Shaw wrote: >> >> If any does attempt to build for the ARM, please, please, please, >> document what you do in the wiki. And, if you do, edit the wiki as you >> go, you definitely won't be able to remember what you did after the >> fact. (Or, at the very least, use some program to capture everything >> you do so that you can refer to it later). >> >> And, finally, I heard vague rumors a while ago that made me think that >> GHC 6.10 might have a pure ANSI-C backend? Is there any truth to this? >> That would make porting much easier if it meant you did not have to do >> steps 1-4. >> >> j. >> ps. I would be happy to try to answer any questions if someone tries a >> port. I would still like to run GHC on my 770, and I hope to own an >> iPhone if they fix a few ommisions (bluetooth keyboard support, and >> similar stuff). >> > > > I recently acquired the ARM-based Nokia N810 (and <3 it), powered by Maemo. > Running a uname -a on it: > > Linux Nokia-N810-42-19 2.6.21-omap1 #2 Fri Nov 16 16:24:58 EET 2007 armv6l > unknown > > I would love a working GHC implementation on it, if for nothing else than > how awesome it would be. Whether that means using a C back-end or native > compilation doesn't matter to me so much. > > I might be one to attempt this, as I know C and ARM-ish asm decently well > and have a powerful desktop to compile on. I have no familiarity > with GHC internals, though. Lastly, I won't have anything like the time to > attempt this seriously until mid-September or so. Oops, forgot to Cc the list. Next year I'll be working on a project for my undergraduate computing course at UNSW that will involve getting GHC to target the Nintendo DS. It'll require cross-compilation, because the DS isn't powerful enough to actually run GHC (4M main ram and a 66MHz processor). It'll also require that I significantly strip down the runtime system, as the current RTS won't fit in 4M and leave any left over for the main application. I'll be documenting the whole process, but I won't be starting until next year... Jeremy

11 15

experience with SmallCheck
by Sebastian Fischer 30 Jan '09

30 Jan '09

Today I played with SmallCheck. Interested in what happened when I tried to find a small unsatisfiable boolean formula that is not easily detected as such? Watch my attempts: <http://www-ps.informatik.uni-kiel.de/~sebf/haskell/unsatisfiable-formula-th… > (strip `.html` suffix for executable Haskell file) Cheers, Sebastian

1 0

The case of the missing Arrow function
by Henk-Jan van Tuyl 30 Jan '09

30 Jan '09

L.S., The function 'liftA2' is mentioned in many documents about Arrows; yet I cannot find it in the Control.Arrow module, as it comes with GHC 6.10.1 and Hugs Sep 2006. Is there a special reason for this? -- Regards, Henk-Jan van Tuyl -- http://functor.bamikanarie.com http://Van.Tuyl.eu/ --

3 2

ANNOUNCE: Extensible and Modular Generics for the Masses: emgm-0.2
by Sean Leather 30 Jan '09

30 Jan '09

============================================== Extensible and Modular Generics for the Masses ============================================== Extensible and Modular Generics for the Masses (EMGM) is a library for generic programming in Haskell using type classes and a sum-of-products view. ------------ Introduction ------------ emgm-0.2 is the second major release of the EMGM library. A lot of work has been done since the initial release to build a solid set of functions that will allow you to derive the necessary declarations for using EMGM with your datatype. Thus, you don't have to write much code to get started. A great deal of documentation has also been added. There's a comprehensive new entry page for Generics.EMGM that should help one figure out what to do with this library. We plan to publish articles providing more examples as well. With these two improvements, you have no more excuses for not trying it out. Download EMGM and see what you can do, generically! ------------ New Features ------------ Improvements over emgm-0.1 include: * Derive type representation using Template Haskell [1] * Major improvement in documentation with Haddock * bimap function [2] [1] Here is a snippet from the documentation that shows what you save when using TH over manual implementation. > {-# LANGUAGE TemplateHaskell #-} > {-# LANGUAGE MultiParamTypeClasses #-} > {-# LANGUAGE FlexibleContexts #-} > {-# LANGUAGE FlexibleInstances #-} > {-# LANGUAGE OverlappingInstances #-} > {-# LANGUAGE UndecidableInstances #-} > module Example where > import Generics.EMGM > data T a = C a Int > $(derive ''T) The $(derive ''T) declaration in the above example generates the following code: 1. Constructor description declarations (1 per constructor) > conC :: ConDescr > conC = ConDescr "C" 2 [] Nonfix 2. Embedding-projection pair declarations (1 per type) > epT :: EP (T a) (a :*: Int) > epT = EP fromT toT > where fromT (C v1 v2) = v1 :*: v2 > toT (v1 :*: v2) = C v1 v2 3. Rep instance (1 per type) > instance (Generic g, Rep g a, Rep g Int) => Rep g (T a) where > rep = rtype epT (rcon conC (rprod rep rep)) 4. Higher arity instances if applicable (either FRep, FRep2, and FRep3 together, or BiFRep2) > instance (Generic g) => FRep g T where > frep ra = rtype epT (rcon conC (rprod ra rint)) In this case, similar instances would be generated for FRep2 and FRep3. 5. Function-specific instances (1 per type) > instance Rep (Collect Char) Char where > rep = Collect (:[]) [2] EMGM has a new function bimap and its related representation type class BiFRep2: > bimap :: (BiFRep2 Map f) => (a -> c) -> (b -> d) -> f a b -> f c d With bimap, you can do the following in GHCi: *Generics.EMGM Data.Char Prelude> bimap ord chr ('a',65) (97,'A') *Generics.EMGM Data.Char Prelude> bimap (++" So Long!") (const 42) (Right "Earth") Right 42 ------------------- General Information ------------------- Visit the home page: http://www.cs.uu.nl/wiki/GenericProgramming/EMGM ---------------- General Features ---------------- The primary features of EMGM include: * Datatype-generic programming using sum-of-product views * Large collection of ready-to-use generic functions * Included support for standard datatypes: lists, Maybe, tuples * Easy to add support for new datatypes * Type classes make writing new functions straightforward in a structurally inductive style * Generic functions are extensible with ad-hoc cases for arbitrary datatypes * Good performance of generic functions The features of this distribution include: * The API is thoroughly documented with Haddock * Fully tested with QuickCheck and HUnit * Program coverage ensures that all useful code has been touched by tests * Tested on both Mac and Windows systems ------------ Requirements ------------ EMGM has the following requirements: * GHC 6.8.1 - It has been tested with versions 6.8.3 and 6.10.1 * Cabal library 1.2.1 - It has been tested with versions 1.2.4.0 and 1.6.0.1. ----------------- Download & Source ----------------- Use caball-install: cabal install emgm Get the package: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/emgm Check out the current source with Subversion: svn checkout https://svn.cs.uu.nl:12443/repos/dgp-haskell/EMGM/trunk Or view it online: https://svn.cs.uu.nl:12443/viewvc/dgp-haskell/EMGM/trunk/ -------- Examples -------- Check out the examples: https://svn.cs.uu.nl:12443/viewvc/dgp-haskell/EMGM/trunk/examples/ -------------- Bugs & Support -------------- Report issues or request features: http://code.google.com/p/emgm/issues/list Discuss EMGM with the authors, maintainers, and other interested persons: http://www.haskell.org/mailman/listinfo/generics ------- Credits ------- The research for EMGM originated with Ralf Hinze. It was extended with work by Bruno Oliveira and Andres Löh. More details of the library functionality were explored by Alexey Rodriguez. We are very grateful to all of these people for the foundation on which this library was built. The current authors and maintainers of EMGM are: * Sean Leather * José Pedro Magalhães * Alexey Rodriguez * Andres Löh

1 0

Re: [Haskell-cafe] C-like Haskell
by Duncan Coutts 30 Jan '09

30 Jan '09

On Wed, 2009-01-28 at 20:42 -0500, Ross Mellgren wrote: > Very possibly -- I'm on a mac so no prebuilt 64-bit binary. I'm not > good enough at reading core to tell, but I can tell from the core that > it's calling out to external C functions to do the 64-bit math. Right, that'll make it really slow but does not explain the allocations. > It could be that it's crossing over from machine register size to > managed heap object and so without additional help on 32-bit it wants > to allocate thunks. If it's using Int64 then there's no transition, that only happens with Integer (which is always heap allocated anyway). The sum parameter in the inner loop is an accumulating parameter that is not inspected until the final value is returned. In the case of the simple direct Int64 implementation the strictness analyser does notice that it really is strict so can be evaluated as we go along. I bet that's the source of the problem, that for the indirect Int64 impl used on 32bit machines the strictness analyser does not discover the same property. So that would explain the allocations. It's worth investigating the indirect Int64 implementation to see if this could be improved. > Does your core indicate that it's making a bunch of external __ccalls? No, it's all unboxed Int# types and primitive # operations. Lovely. In particular the inner loop is all unboxed types with no allocations. Duncan

3 2

WYSIWYG literate programming
by Massimiliano Gubinelli 30 Jan '09

30 Jan '09

Hi, I would like to "advertise" TeXmacs (http://www.texmacs.org/) to the Haskell comunity as a possible front-end for literate programming in Haskell (and GHCI interaction). TeXmacs is a system which allows the production of documents featuring high quality typesetting (comparable to TeX) and high level of customizability (a la Emacs). It does not rely on TeX for the typesetting (but can export to Latex, HTML, etc..). It is written in C++ (unfortunately not Haskell) and use Scheme as extension language (specifically Guile). It has been in use for at least 10 years and has plugins for many external applications like Pari, Axiom, Maxima, Octave, R, Yacas, etc... >From the webpage: "GNU TeXmacs is a free wysiwyw (what you see is what you want) editing platform with special features for scientists. The software aims to provide a unified and user friendly framework for editing structured documents with different types of content (text, graphics, mathematics, interactive content, etc.). The rendering engine uses high-quality typesetting algorithms so as to produce professionally looking documents, which can either be printed out or presented from a laptop." It would be nice to develop a pluging for GHC/GHCI to allow "direct" literate programming style with high-quality rendering. (If someone want to try before I find the time to do it myself.... ) Massimiliano -- View this message in context: http://www.nabble.com/WYSIWYG-literate-programming-tp21682184p21682184.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

7 12

haddock-2.3.0 error: file name does not match module name
by Alistair Bayley 30 Jan '09

30 Jan '09

I'm getting an error when I run setup haddock-2.3.0 on the Takusen src: haddock.exe: File name does not match module name: Saw: `Main' Expected: `Database.Enumerator' I assume that it's procesing file Database.Enumerator.lhs when it emits this, but I'm puzzled because the module name in Database.Enumerator.lhs is certainly Database.Enumerator, and not Main. Or am I looking in the wrong place? Alistair

3 4

databases in Haskell & type-safety
by Gour 30 Jan '09

30 Jan '09

Hi! I'd like to use sqlite3 as application storage in my haskell project... Browsing the available database options in Haskell it seems that: a) HSQL is dead (hackage reports build-failure with 6.8 & 6.10) b) haskelldb is also not in a good shape - build fails with 6.8 & 6.10 For Haskell-newbie as myself, it looks that haskelldb is the one which provide(ed)s the most secure API (I was reading draft paper about MetaHDBC but, apparently, the type inference support in open-source databases is poor and that's why, according to the author "This is unfortunately as it makes MetaHDBC a lot less valuable." What remains is: c) Takusen which is also not up-to-date (it fails with 6.10) and d) HDBC and sqlite bindings which are the only packages which build with 6.10. However options in d) do not offer, afaik, type-safety which is emblem of Haskell language, so I wonder how much this could be the problem for real-world usage? So, considering that HDBC nicely abstracts API enabling one to easily switch from e.g. Sqlite3 to Postgres, and it is used as in example for database programming, it seems as logical (and the only) choice for Haskell database programming in a real-world? I'm not familiar with Takusen which says: "Takusen's unique selling point is safety and efficiency..." and I would appreciate if someone could shed some more light to its 'safety' and the present status? Sincerely, Gour -- Gour | Zagreb, Croatia | GPG key: C6E7162D ----------------------------------------------------------------

11 29

HPC and literate haskell
by Pavel Perikov 30 Jan '09

30 Jan '09

Hi, list! I have a file: \begin{code} module Main where import MyModule main=do print "hello" \end{code} MyModule is in MyModule.lhs when building with ghc -o main -fhpc --make Main.lhs I get perfectly working code, but MyModule.mix lacks any usable coverage information: Mix "./MyModule.lhs" 1233320065 1385570408 1 [] After renaming MyModule.lhs to MyModule.hs and unlitting it everything works fine: Mix "./MyModule.hs" 1233320249 3220649115 1 [(3:8-3:8,ExpBox False), (3:9-3:9,Exp Box False),(3:7-3:10,ExpBox False),(3:1-3:10,TopLevelBox ["func2"])] I'm using ghc 6.10.1 on Mac OSX. Does anyone have this problem? are any workarounds available? Pavel

2 1

A ghc-6.10.1 bug or a feature?
by Juraj Hercek 30 Jan '09

30 Jan '09

Hello people, I've recently tried this: $ uname -smpr Linux 2.6.28-ARCH x86_64 Intel(R) Core(TM)2 CPU 6600 @ 2.40GHz $ ghci GHCi, version 6.10.1: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. Prelude> a <- readFile "/sys/devices/system/cpu/online" Prelude> length a `seq` a "^CInterrupted. Prelude> writeFile "/tmp/test.txt" "12345\n" Prelude> b <- readFile "/tmp/test.txt" Prelude> length b `seq` b "12345\n" Prelude> The main problem is the "C^Interrupted." above. The input doesn't get read out till the end of the file for some reason when dealing with files in /sys directory (tried also others: /sys/devices/plaform/coretemp.0/temp1_input or /sys/devices/system/cpu/cpu0/cpufreq/cpufreq_cur_freq). Sometimes, the string from file in /sys gets read (with a slow delay), but most of the times it didn't. Everything works fine for a file in /tmp. Cat-ing files from shell works perfectly in /sys and /tmp. I tried also other machine: % uname -smpr Linux 2.6.28-ARCH i686 Intel(R) Pentium(R) 4 CPU 2.00GHz with the same effect. I didn't have this problem with ghc-6.8.2. Any idea? -- Juraj

3 4

The future of purely functional user interfaces?
by Andrzej Jaworski 30 Jan '09

30 Jan '09

Yes, it is something unhealthy to seat on a bunch of far reaching ideas and still use artifact that even Microsoft tries to shake off (outsourcing their Office XML Ribbons). But as recent roar about monoids have shown - those who are Haskell most productive programmers are also most unlikely to tap on anything theoretical. Researchers on the other hand wouldn't be who they are if they thought mainly in terms of code. Perhaps some new model of cooperation between a researcher and a group of volunteers should be worked out. > Other work [4] seems to indicate that arrows are too general for the > dataflow programming and co-monads are more suitable and hence might be > usable for interactive interfaces. I would be careful with moderating ambition here. It should be extremely open framework that could allow to accommodate all present experimental (mostly reactive) stuff but also allow close integration with functional database in the future. The GUI should also lower overheads for Geometric Algebra. I think that in the future GA, fractals and wavelets will be inbuilt on graphic cards and GUI might take a role of a sort of a synthesizer. But of course anything functional would open lots of new possibilities and give us a lot of fun. Cheers, Andrzej

1 0

Current research on overlapping/closed type families?
by Ryan Ingram 30 Jan '09

30 Jan '09

What's the status of overlapping/closed type families? I'm interested in something like the following, which can currently be implemented in GHC with Oleg-magic using functional dependencies, but cannot, to my knowledge, be implemented with type families: data HTrue = HTrue data HFalse = HFalse type family IsFunction f {- not legal in GHC6.10 -} type instances IsFunction (a -> b) = HTrue IsFunction a = HFalse -- ryan

3 4

Re: C-like Haskell
by John Lato 29 Jan '09

29 Jan '09

> On Wed, 2009-01-28 at 20:11 -0500, sam lee wrote: >> Did you print it? I'm using same code with ghc --make -O2 and it >> takes forever to finish. > > Yes, you can see in the output that it prints the same answer in each > case. I was using r = 10^9 as you suggested. I wouldn't call these answers the same. Can this be ascribed to an overflow error? > >> > C version: >> > $ time ./circ >> > 3141592649589764829 ^^ > >> > Haskell version: >> > time ./circ2 >> > 3141592653589764829 ^^ John Lato

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ANN: logfloat 0.10, 0.11
by wren ng thornton 29 Jan '09

29 Jan '09

-------------------------------------------- -- logfloat 0.10, 0.11 -------------------------------------------- This package provides a type for storing numbers in the log-domain, primarily useful for preventing underflow when multiplying many probabilities as in HMMs and other probabilistic models. The package also provides modules for dealing with floating numbers correctly. -------------------------------------------- -- Compatibility / Portability -------------------------------------------- The package is compatible with Hugs (September 2006) and GHC (6.8, 6.10). For anyone still using GHC 6.6, the code should still work if you replace LANGUAGE pragma by equivalent OPTIONS_GHC pragma. The package is not compatible with nhc98 and Yhc because Data.Number.RealToFrac uses MPTCs. The other modules should be compatible. -------------------------------------------- -- Changes for 0.11 (since 0.10) -------------------------------------------- * Moved the RealToFrac class from Data.Number.Transfinite to Data.Number.RealToFrac. This breaks backwards compatibility if you depended directly on that module for the class. If you imported the class from Data.Number.LogFloat then you're still fine. -------------------------------------------- -- Changes for 0.10 (since 0.9.1) -------------------------------------------- * Hugs' Prelude definitions of isInfinite and isNaN for Float and Double are buggy. The new Hugs.RealFloat module provides correct implementations (defaulting to the Prelude definition for non-Hugs compilers). * The PartialOrd and Transfinite instances for Double and Float have been updated to use these corrected functions. * Added maxPO and minPO to PartialOrd and added comparingPO to Data.Number.PartialOrd. * Minor changes to circumvent bugs in Hackage's new version of Haddock. You should be able to see all the documentation now. * (0.9.1.1) Minor changes to compile cleanly on GHC 6.10 -------------------------------------------- -- Links -------------------------------------------- Homepage: http://code.haskell.org/~wren/ Hackage: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/logfloat Darcs: http://code.haskell.org/~wren/logfloat/ Haddock (Darcs version): http://code.haskell.org/~wren/logfloat/dist/doc/html/logfloat/ code.haskell.org is down at present so the Darcs repo is lagging Hackage. This will be corrected soon. -- Live well, ~wren

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clean's gui toolkit
by Martin DeMello 29 Jan '09

29 Jan '09

I've been wondering - Clean ships with a fairly capable looking GUI toolkit [http://clean.cs.ru.nl/About_Clean/Standard_I_O_Lib/standard_i_o_lib.html] - has anyone used it? How does it compare to the available Haskell options? martin

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