- Libraries - Haskell.org

Add Applicative instances for MTL types
by Bas van Dijk 16 Jan '09

16 Jan '09

Hello, In a project of mine I needed an Applicative instance for Identity and noticed it didn't exist. So I decided to add Applicative (and Alternative instances where possible) for all MTL types. When I was about to submit a library proposal I saw there already existed one. So I added my patch to that ticket. My patch I different in that my Applicative instances don't require a Monad constraint. This also means that most Functor instances now also depend on Applicative rather than on Monad. See the ticket for the details: http://hackage.haskell.org/trac/ghc/ticket/2316 Discussion period: 5 weeks (taking the holidays into account) This is the old thread about this proposal: http://thread.gmane.org/gmane.comp.lang.haskell.libraries/9140/focus=9154 regards, Bas

5 9

Control.Monad.Writer.Strict .... enough?
by Ben Moseley 15 Jan '09

15 Jan '09

Hi, In most of the 'mtl' variants on Hackage (with the notable exception of 'monadLib'), the Control.Monad.Writer.Strict main instance is: newtype Writer w a = Writer { runWriter :: (a, w) } instance (Monoid w) => Monad (Writer w) where return a = Writer (a, mempty) m >>= k = Writer $ case runWriter m of (a, w) -> case runWriter (k a) of (b, w') -> (b, w `mappend` w') ...ie the `mappend` is hidden inside a lazy "(,)" constructor. ...shouldn't the bind really be strict in the written monoid? (eg by replacing "(a,w)" with "(a,!w)" and using Bang Patterns). ...if so, is it worth submitting patch? --Ben

1 0

Haskell platform related proposal: update regex to latest versions
by Chris Kuklewicz 14 Jan '09

14 Jan '09

I have added this to the trac wiki at http://trac.haskell.org/haskell-platform/wiki/Library/regex-base Chris Kuklewicz proposes: As the writer and maintainer of the regex-(base|posix|compat) packages I would like suggest the following. The Haskell platform should upgrade from the 0.72 version of regex-base to the 0.93.1 version. Similar updates to the latest releases of regex-posix and regex-compat would also be made. The old version has been kicking around too long, partly because I have not bothered to push updating the GHC bundle. The regex-base update adds makeRegexM and makeRegexOptsM which allow for saner error handling when compiling regular expressions, they use "fail" instead of "error". It would be possible to switch to !MonadError or perhaps the new exceptions, discussion of this is welcome. The older version of regex-base has lazy overlapping instances of !RegexContex which GHC allows and Hugs forbids, so the new version of regex-base has newtypes that force the user to be more explicit: {{{ newtype AllSubmatches f b = AllSubmatches {getAllSubmatches :: (f b)} newtype AllTextSubmatches f b = AllTextSubmatches {getAllTextSubmatches :: (f b)} newtype AllMatches f b = AllMatches {getAllMatches :: (f b)} newtype AllTextMatches f b = AllTextMatches {getAllTextMatches :: (f b) } }}} It would be possible to include most (or perhaps all) of the old instances, either as a sub-module or conditionally compiled, again discussion of this is welcome.

1 0

Policy question re: Haskell Platform installer on OSX
by Gregory Collins 14 Jan '09

14 Jan '09

Hi all, I'm currently writing a program to take Cabal libraries and turn them into OSX .pkg files, for the Haskell platform's Mac installer. Where should the libraries be installed? The current GHC installer plops them down into /Library/Frameworks/GHC.framework/Versions/xxx/usr, and my thinking is that I'll keep it that way so that we can piggyback on GHC's uninstall script. Otherwise the platform project will need an uninstaller of its own. Thanks, G. -- Gregory Collins <greg(a)gregorycollins.net>

4 6

ghc-6.10 and Exception vs OldException
by Alistair Bayley 13 Jan '09

13 Jan '09

I'm upgrading Takusen to compile with ghc-6.10, and I'm wondering what the recommended approach is for dealing with the new Exception module. What does one do if one wants to maintain a library that will build with ghc-6.10 and also older versions, as far back as 6.4, say? CPP hackery, or is there something more elegant? Alistair

2 1

Arch Haskell News: Jan 11 2009
by Don Stewart 13 Jan '09

13 Jan '09

Arch Haskell News: Jan 11 2009 Hey all, welcome to the first Arch Haskell News of 2009. (News about Haskell on the Arch Linux platform). Arch now has 827 Haskell packages in AUR. That’s an increase of 93 new packages in the last 48 days, or 1.9 new Haskell apps and libraries a day over the holiday season. Well done everyone!. Noteworthy * lhc-0.6.20081127: “LHC Haskell Compiler” * cabal2arch-0.4.2: “Create Arch Linux packages from Cabal packages” * timberc-1.0.2: “The Timber Compiler.” * haskell-x11-1.4.5: “A binding to the X11 graphics library” * haskell-curl-1.3.2.2: “Haskell binding to libcurl” * alex-2.3.1: “Alex is a tool for generating lexical analysers in Haskel * haskell-bytestring-trie-0.1: “Efficient map from strings to values.” * haskell-llvm-0.5.0.1: “Bindings to the LLVM compiler toolkit” * tetris-0.27178: “A 2-D clone of Tetris” * haskell-network-bytestring-0.1.1.4: “Fast and memory efficient low-level networking” * haskell-hdbc-1.1.6: “Haskell Database Connectivity” http://archhaskell.wordpress.com/2009/01/11/arch-haskell-news-jan-11-2009/ Other news: * llvm support, http://archhaskell.wordpress.com/2009/01/11/llvm-haskell-bindings/ * new hdbc release, http://archhaskell.wordpress.com/2009/01/11/hdbc-haskell-database-suite-upd… * salvia, new web framework, supported http://archhaskell.wordpress.com/2009/01/11/new-haskell-web-framework-salvi… Bring on 2009 and the era of ubiquitous Haskell! -- Don

2 2

Policy change for regex libraries
by Chris Kuklewicz 12 Jan '09

12 Jan '09

Before I go and add or change anything in the Haskell regex-posix library, I wanted to get some feedback. regex-posix provides Text.Regex.Posix, and is built on the regex-base package. regex-posix is also used as the backend for Text.Regex (the regex-compat package does this). I do not intend to change the behavior of the old Text.Regex API. The main issue is the behavior when returning a list of all matches of a Regex against a target text. I no longer think the current behavior is the right choice when it comes to zero-length matches. The current behavior is to return non-overlapping matches with the caveat that after the first zero-length match the search is ended. Note that the zero-length match may be occur at the end position of a previous non-zero-length match. Notably, no one has complained about this policy. But I no longer like it. So here are a few of my ideas of what to change it to: 0) No change, not worth the effort. 1) return the zero-length match, skip forward 1 character, and continue searching. If the consumer wishes the old policy they can truncate the list. This could also be filtered to resemble option 2 below. 2) Mimic "sed". It seems "sed" has a policy where a zero-length match is forbidden to occur at the end position of a non-zero-length match. "sed" does not stop with the first zero-length match. 3) implement additional execution options, so the user can choose a policy. The default policy choice left with the current behavior. 4) implement additional execution options, so the user can choose a policy. The default policy choice set to he behavior in (1). 5) Return valid matches starting from all positions, including overlapping matches. This I really do not like and one can run the search starting one character after the start of the last match to get this information. Matching "0123" and replacing all matches with themselves wrapped in angle brackets. The policies of 0, 1, and 2 above lead to (computed partly by hand): regex of "[0123]?" 0): "<0><1><2><3><>" 1): "<0><1><2><3><>" 2): "<0><1><2><3>" regex of "[012]?" 0): "<0><1><2>3<>" 1): "<0><1><2>3<>" 2): "<0><1><2>3<>" regex of "[013]?" 0): "<0><1><>23" 1): "<0><1><>2<3><>" 2): "<0><1>2<3>" regex of "[023]?" 0): "<0><>123" 1): "<0><>1<2><3><>" 2): "<0>1<2><3>" regex of "[123]?" 0): "<>0123" 1): "<>0<1><2><3><>" 2): "<>0<1><2><3>" regex of "[03]?" 0): "<0><>123" 1): "<0><>1<>2<3><>" 2): "<0>1<>2<3>" regex of "[03]?" 0): "<0><>123" 1): "<0><>1<>2<3><>" 2): "<0>1<>2<3>" regex of "[12]?" 0): "<>0123" 1): "<>0<1><2><>3<>" 2): "<>0<1><2>3<>" I am leaning to simply changing it from policy 0 to policy 1. Are there any objections? Perhaps I should set a deadline? Now where is that library policy... -- Chris

3 6

Missing -lrt for shm* functions in the unix package
by Don Stewart 12 Jan '09

12 Jan '09

The module System.Posix.SharedMem was silently disabling the shm_* functions due to failing configuration tests on linux (needs the -lrt lib). This patch adds -lrt to the configure test/ buildinfo. -- Don Mon Jan 12 15:07:58 PST 2009 Don Stewart <dons(a)galois.com> * Add check for -lrt to get the shm* functions. Subst. in buildinfo New patches: [Add check for -lrt to get the shm* functions. Subst. in buildinfo Don Stewart <dons(a)galois.com>**20090112230758] hunk ./configure.ac 30 AC_CHECK_FUNCS([nanosleep]) AC_CHECK_FUNCS([ptsname]) AC_CHECK_FUNCS([setitimer]) + +# Avoid adding rt if absent or unneeded +AC_CHECK_LIB(rt, shm_open, [EXTRA_LIBS="$EXTRA_LIBS rt" CFLAGS="$CFLAGS -lrt"]) + +# needs -lrt on linux AC_CHECK_FUNCS([shm_open shm_unlink]) FP_CHECK_CONSTS([SIGABRT SIGALRM SIGBUS SIGCHLD SIGCONT SIGFPE SIGHUP SIGILL SIGINT SIGKILL SIGPIPE SIGQUIT SIGSEGV SIGSTOP SIGTERM SIGTSTP SIGTTIN SIGTTOU SIGUSR1 SIGUSR2 SIGPOLL SIGPROF SIGSYS SIGTRAP SIGURG SIGVTALRM SIGXCPU SIGXFSZ SIG_BLOCK SIG_SETMASK SIG_UNBLOCK], [ Context: [Avoid using IOError internals Ian Lynagh <igloo(a)earth.li>**20090104173221] [fix pthread linkage problem for openbsd Matthias Kilian <kili(a)outback.escape.de>**20081129000638 This should make my openbsd build slave happy when SplitObjs=NO. May be useful for other BSDs and even Linux, regardless wether you need -pthread or -lpthread. Time will tell... ] [catch up with exception changes Simon Marlow <marlowsd(a)gmail.com>**20080927135428] [Bump version number to 2.3.1.0 Ian Lynagh <igloo(a)earth.li>**20080920160248] [TAG 6.10 branch has been forked Ian Lynagh <igloo(a)earth.li>**20080919123439] [follow library changes Ian Lynagh <igloo(a)earth.li>**20080903223616] [add category field Ross Paterson <ross(a)soi.city.ac.uk>**20080824003014] [We now depend on concurrent (split off from base) Ian Lynagh <igloo(a)earth.li>**20080824135158] [Fix the build when CONST_SIGPOLL == -1 Ian Lynagh <igloo(a)earth.li>**20080823160346 We were defining, but not using, sigPOLL ] [Fix warnings in the unix package Ian Lynagh <igloo(a)earth.li>**20080821120138] [move some stuff here from System.Directory, now the dependencies are reversed Simon Marlow <marlowsd(a)gmail.com>**20080821144754] [Follow extensible exceptions changes Ian Lynagh <igloo(a)earth.li>**20080623193152] [Allow C's unsetenv to return either void or int Ian Lynagh <igloo(a)earth.li>**20080703190603 Fixes, and patch from donn in, trac #2352. ] [Avoid using deprecated flags Ian Lynagh <igloo(a)earth.li>**20080616145425] [move __hscore_{mkstemp,getrlimit,setrlimit} here from base Ross Paterson <ross(a)soi.city.ac.uk>**20080615224248] [TAG 2008-05-28 Ian Lynagh <igloo(a)earth.li>**20080528004441] Patch bundle hash: dd0767ff90044fe756b71c7e1bf58467ba9d7203

1 0

haskell-platform mailing list
by Duncan Coutts 12 Jan '09

12 Jan '09

Hi all, If you are interested in helping out with the haskell platform project then we invite you to subscribe to the haskell-platform mailing list. http://projects.haskell.org/cgi-bin/mailman/listinfo/haskell-platform This mailing list is for discussing practical stuff. We expect to discuss policy questions on the libraries mailing list. Issues like which packages to pick, what package QA standards to use etc would be discussed on the libraries mailing list. Those issues are for the community as a whole. Building and coordinating the actual releases will be done via the haskell-platform mailing list. Duncan

1 0

different flavours of Monad Template Library
by Henning Thielemann 12 Jan '09

12 Jan '09

I see now at least three MTL libraries at hackage, namely mtl mmtl mtl-tf They all define both the example data types and according type classes in modules with the same name. This way you can only use one of these packages in all packages you import. However the data types are defined the same way in the packages, only the classes differ. I wished, there would be one package defining only the datatypes, say "mtl-data", and three ones with the names "mtl", "mmtl", "mtl-tf" that define their classes with corresponding instances. These classes should be in different modules, so you can use different class frameworks in the same project. The data type package would be useful on its own and could be run on the simplest Haskell compilers, since no functional dependencies are required. However there is the compatibility problem: Currently Control.Monad.State exports also the MonadState class, which would no longer work. Maybe we can reserve Control.Monad.State for mtl, which exports Control.Monad.State.Data.Lazy from mtl-data and Control.Monad.State.Class from mtl. I assume that mmtl and mtl-tf are not as much used as mtl, such that it would not too bad to break compatibility for them. They could no longer export Control.Monad.State, but instead the user of mmtl has to import Control.Monad.State.Data from mtl-data. The class file of mmtl could be named Control.Monad.Modular.State.Class. (Replace "State" by "Writer", "Reader" and so on, and "mmtl" by "mtl-tf" in order to get all names that need to be adapted.)

4 23