- Haskell-Cafe - Haskell.org

What does :*: mean again?
by Günther Schmidt 23 Oct '09

23 Oct '09

Günther

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ANN: haskell-src-exts-1.2.0
by Niklas Broberg 23 Oct '09

23 Oct '09

Fellow Haskelleers, I'm pleased to announce the release of haskell-src-exts-1.2.0! * On hackage: http://hackage.haskell.org/package/haskell-src-exts * Via cabal: cabal install haskell-src-exts * Darcs repo: http://code.haskell.org/haskell-src-exts Version 1.2.0 is a new major release, following the PVP, as it contains a few backwards-incompatible changes, as well as some major changes that are supposedly backwards-compatible in theory, but as much of it is new and untested in practice there may be some regressions (bugs). The main new thing in 1.2.0 is the integration of the Annotated machinery into the package proper, for instance all parsing is now handled by the fully location-aware parser. haskell-src-exts-1.2.0: ==================== * Language.Haskell.Exts.Annotated.Simplify provides translation from an annotated AST to the old simple AST. * Behind-the-scenes integration of the new exact parser and lexer to do all parsing (using the above mentioned simplifier if the old AST version is requested). * All syntactic nodes now derive Eq, Ord and Show. * Pretty instance for SrcSpan. * Top-level expressions are now treated as implicit TH splice declarations (as per GHC HEAD). Note that this incurs a non-backwards-compatible change to the AST. * Empty data declarations may now have explicit kind annotations. * AST (and Pretty/Exact) support for kind variables (not yet parser support). * Error messages now extensively use prettyPrint instead of show for AST elements and locations, leading to way neater messages. * Bug fix to not crash ungracefully when encountering type equality predicates in proper types. * Liberalise line comments (as per GHC) to allow a line comment on the last line of a source file. Please help me test and report! Grab a darcs version, put your source files in the Test/examples dir, and go cabal test (in the top dir). Any failing cases not due to CPP or literate source files (for the exact-printer), please report to the trac: http://trac.haskell.org/haskell-src-exts Cheers, /Niklas

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Announcing: PastePipe -- a CLI for hpaste instances
by Rogan Creswick 23 Oct '09

23 Oct '09

I'm happy to announce PastePipe (v1.3)! PastePipe reads from stdin and publishes whatever it reads to the hpaste instance of your choice (defaulting to hpaste.org) This makes it trivial to..... * post a file to hpaste.org: `cat <file> | pastepipe' * turn a terminal into a pastebin window: 'pastepipe' (ctrl-d to close & send) * upload error output as a paste: 'faultyProgram | pastepipe -t "faultyProgram error output" -l bash' * paste to a local hpaste instance: 'pastepipe --uri http://my.local.hpaste/fastcgi/hpaste.fgci/' * add a title, select different languages, specify a user name, etc... see pastepipe --help for details. PastePipe will output the resulting url for your new paste to stdout, so you can script it, or just copy / paste that as you need. Availability: ------------------------------------------------------------------------------------------------------- It is available on Hackage (so you can 'cabal install PastePipe'): http://hackage.haskell.org/package/PastePipe The project for pastepipe is hosted at Google Code, with the source in mercurial: Homepage (issue tracker, etc): http://code.google.com/p/pastepipe/ Mercurial repo: hg clone https://pastepipe.googlecode.com/hg/ pastepipe --------------------------------------------------------------------------------------------------------------- Please let me know of any bugs / feature requests / etc. (or just post them to the issue tracker.) Thanks! Rogan

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Re: \Statically checked binomail heaps?
by Okasaki, C. DR EECS 23 Oct '09

23 Oct '09

Maciej Kotowicz asked about implementing binomial heaps using types to enforce the shape invariants. I dug up an old email from 1998 talking about how to do this with nested types, and posted it to my blog: http://okasaki.blogspot.com/2009/10/binomial-queues-as-nested-type.html -- Chris

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Help me improve design of my project.
by Andy Stewart 23 Oct '09

23 Oct '09

Hi all, I develop some Haskell IDE, below is screenshots: http://farm4.static.flickr.com/3483/3947340553_933df88a22_o.png http://farm3.static.flickr.com/2628/3952175905_9295a7421a_o.png http://farm3.static.flickr.com/2544/3957610799_70fab5eb57_o.png http://farm3.static.flickr.com/2703/4016163374_493e3738c7_o.png Below is source code. You only can compile it with darcs version of gtk2hs. The simple usage is press `F4` open terminal, then press `F7` to type file-path for open. Now is really simple, now i haven't stable time maintain project, so i will opensource my project when i have stable time. Okay, question is, IORefObject module and most module reference each other, so i will got `recursive reference problem` (looks how many .hs-boot in my project). So anyone can help me improve design to split IORefObject and other modules, make them less depend? Thanks, -- Andy

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FW: Free Pizza, C++, and Haskell
by Simon Peyton-Jones 23 Oct '09

23 Oct '09

You may enjoy this interesting blog post by Bartosz Milewski about understanding C++ template metaprogramming by starting with Haskell. http://bartoszmilewski.wordpress.com/2009/10/21/what-does-haskell-have-to-d… Bartosz gave the talk at the Northwest C++ users group; the video for the talk will be linked eventually on the NWCPP website: http://nwcpp.org/ Simon

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Time Typeable Instances
by John Goerzen 23 Oct '09

23 Oct '09

Hugo Gomes wrote: > The Glorious Glasgow Haskell Compilation System, version 6.10.4 > with old-time-1.0.0.2 and time-1.1.2.4 > > This is a standard haskell platform on a windows xp. Cabal install > didn't work complaining about missing instances of typeable for posix > time and other datatypes, yet, after removing the macros (thus, adding > those instances), hdbc and convertible compiled and installed fine. > > Removing the macros might be a bit overkill, probably finetuning them so > that they add only the necessary instances for typeable in ghc > 610 > might be a better solution. I'm going to CC haskell-cafe on this because I am confused. Hugo, can you confirm what version of convertible you have? Back on May 21, I started a thread [1] on haskell-cafe complaining that GHC 6.10.3 included a newer time that included instances of Typeable for NominalDiffTime and UTCTime. This broke my code, which had manually defined instances for these types, as they were needed. Things got complicated, as only time's minor version number got incremented (x.x.x.Y) [2]. Cabal can't test against that version number. I wanted my code to work with old and new versions of GHC. Since testing against the version of time was impossible, I did the next best thing: tested against the version of GHC. #if __GLASGOW_HASKELL__ >= 610 -- instances added in GHC 6.10.3 #else instance Typeable NominalDiffTime where typeOf _ = mkTypeName "NominalDiffTime" instance Typeable UTCTime where typeOf _ = mkTypeName "UTCTime" #endif Also, in the .cabal, there is a build-depends on time>=1.1.2.4. Now, that would break for GHC 6.10.1 and 6.10.2 users, but will work for 6.10.3 and above, or 6.8 and below. Or so I thought. Now I'm getting complaints from people using 6.10.4 saying that there are now missing instances of Typeable with time 1.1.2.4. 1) Did the Typeable instances get dropped again from time? 2) What exactly should I do so this library compiles on GHC 6.8 and 6.10.x? I'm looking at the darcs repo for time and don't see the instances ever getting dropped. [1] http://osdir.com/ml/haskell-cafe@haskell.org/2009-05/msg00982.html [2] http://osdir.com/ml/haskell-cafe@haskell.org/2009-05/msg00985.html .... later addendum .... so it appears that what's happening here is that GHC 6.10.3 extralibs included time 1.1.3, but then haskell-platform standardized on 1.1.2.4. This is pretty annoying -- that haskell-platform would standardize on a version older than what shipped with a GHC release -- but I guess I can work around it by restricting my build-dep to be time < 1.1.3 and re-adding the instances. Does this sound right? > > > On Tue, Oct 13, 2009 at 2:51 AM, John Goerzen <jgoerzen(a)complete.org > <mailto:jgoerzen@complete.org>> wrote: > > Hugo Gomes wrote: > > Hi, > > > > convertible and hdbc packages fail to compile in my standard > instalation > > of the haskell platform. I think this has to do with those "if ghc >= > > 610" macros on the typeable instances for some datatypes. I > removed them > > and now they work fine... > > > > > > > > > What version of GHC and time do you have? > > -- John > >

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Newbie has trouble using QuickCheck
by steenreem 23 Oct '09

23 Oct '09

Hello. I have made a simple test.hs file that imports the module QuickCheck. However, when I load this module in ghci, it says that the module QuickCheck is not found. I have looked in my haskell platform folder and find the folder "QuickCheck 1.2.0.0". I also tried to :set -package QuickCheck. This added QuickCheck to the list of loaded packages. However when loading my test module it still says "Could not find module QuickCheck". Locations searched were "QuickCheck.hs" and "QuickCheck.lhs" What's wrong? Thanks, Remy. -- View this message in context: http://www.nabble.com/Newbie-has-trouble-using-QuickCheck-tp26024248p260242… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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ANN: Data.Stream 0.4
by Wouter Swierstra 23 Oct '09

23 Oct '09

I'm happy to announce a new release of the Data.Stream library. http://hackage.haskell.org/package/Stream The only change with the previous version has been to add irrefutable patterns to several function definitions. This is rather delicate design decision: too many irrefutable patterns could result in thunks not being evaluated; too few irrefutable patterns could cause your functions diverge. As a rule of thumb I've chosen only to use irrefutable patterns in functions that produce streams from streams. The operations that observe finite information (a prefix, the element at index i, etc.) do not have have irrefutable patterns and force evaluation to weak head normal form. I've uploaded a new version to Hackage. I'd be interested to hear if any existing code takes a performance hit as a result of these changes. Wouter

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What's this pattern called?
by Martijn van Steenbergen 23 Oct '09

23 Oct '09

Bonjour café, > data ExprF r > = Add r r > | Sub r r > | Mul r r > | Div r r > | Num Int This is a well-known pattern that for example allows nice notation of morphisms. But what is it called? I've heard fixed-point view, open datatypes and some others, but I'm curious where this pattern comes up in literature and what it is called there. Thanks, Martijn.

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