November 2008 - Haskell

Re: ANNOUNCE: GHC version 6.10.1 - MacOS installer
by Manuel M T Chakravarty 05 Nov '08

05 Nov '08

Jason Dagit: > On Tue, Nov 4, 2008 at 10:11 AM, Ian Lynagh <igloo(a)earth.li> wrote: >> >> How to get it >> ~~~~~~~~~~~~~ >> >> The easy way is to go to the web page, which should be self- >> explanatory: >> >> http://www.haskell.org/ghc/ >> >> We supply binary builds in the native package format for many >> platforms, and the source distribution is available from the same >> place. >> >> Packages will appear as they are built - if the package for your >> system isn't available yet, please try again later. > > I'm on OSX and I currently have ghc-6.6.1 and ghc-6.8.3 (installed > from a pkg). I would like to add ghc-6.10.1 to my system. I tried to > do this with RC1 of 6.10, but I found that it uninstalled my > ghc-6.8.3. > > What will I need to do to get both 6.8.3 and 6.10.1? Are you sure it does deinstall the 6.8 compiler? Or does it just overwrite the symbolic links in /usr/bin? To check, have a look at /Library/Frameworks/GHC.framework/Versions After installing 6.10, there should be a 608/ and a 610/ directory. This certainly happens on my Mac and I am not aware of an option to change that behaviour. And while we are at it...a BIG FAT WARNING: If you installed the 6.10.200081007 pre-release installer package, uninstall that *before* installing the 6.10.1 package. For reasons, I don't understand, the installer otherwise half removes the old package, but doesn't seem to install the new one. Can a Mac expert shed any light on that behaviour? If you tried installing 6.10.1 before reading that, just remove the partial installation you are left with, and install again. Manuel

1 0

ANNOUNCE: GHC version 6.10.1
by Ian Lynagh 04 Nov '08

04 Nov '08

============================================================== The (Interactive) Glasgow Haskell Compiler -- version 6.10.1 ============================================================== The GHC Team is pleased to announce a new major release of GHC. There have been a number of significant changes since the last major release, including: * Some new language features have been implemented: * Record syntax: wild-card patterns, punning, and field disambiguation * Generalised quasi-quotes * Generalised list comprehensions * View patterns * Type families have been completely re-implemented * Now comes with Haddock 2, which supports all GHC extensions * Parallel garbage collection * Base provides extensible exceptions * The GHC API is easier to use * External core (output only) now works again * Data Parallel Haskell (DPH) comes as part of GHC The full release notes are here: http://haskell.org/ghc/docs/6.10.1/html/users_guide/release-6-10-1.html How to get it ~~~~~~~~~~~~~ The easy way is to go to the web page, which should be self-explanatory: http://www.haskell.org/ghc/ We supply binary builds in the native package format for many platforms, and the source distribution is available from the same place. Packages will appear as they are built - if the package for your system isn't available yet, please try again later. Background ~~~~~~~~~~ Haskell is a standard lazy functional programming language; the current language version is Haskell 98, agreed in December 1998 and revised December 2002. GHC is a state-of-the-art programming suite for Haskell. Included is an optimising compiler generating good code for a variety of platforms, together with an interactive system for convenient, quick development. The distribution includes space and time profiling facilities, a large collection of libraries, and support for various language extensions, including concurrency, exceptions, and foreign language interfaces (C, whatever). GHC is distributed under a BSD-style open source license. A wide variety of Haskell related resources (tutorials, libraries, specifications, documentation, compilers, interpreters, references, contact information, links to research groups) are available from the Haskell home page (see below). On-line GHC-related resources ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Relevant URLs on the World-Wide Web: GHC home page http://www.haskell.org/ghc/ GHC developers' home page http://hackage.haskell.org/trac/ghc/ Haskell home page http://www.haskell.org/ Supported Platforms ~~~~~~~~~~~~~~~~~~~ The list of platforms we support, and the people responsible for them, is here: http://hackage.haskell.org/trac/ghc/wiki/Contributors Ports to other platforms are possible with varying degrees of difficulty. The Building Guide describes how to go about porting to a new platform: http://hackage.haskell.org/trac/ghc/wiki/Building Developers ~~~~~~~~~~ We welcome new contributors. Instructions on accessing our source code repository, and getting started with hacking on GHC, are available from the GHC's developer's site run by Trac: http://hackage.haskell.org/trac/ghc/ Mailing lists ~~~~~~~~~~~~~ We run mailing lists for GHC users and bug reports; to subscribe, use the web interfaces at http://www.haskell.org/mailman/listinfo/glasgow-haskell-users http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs There are several other haskell and ghc-related mailing lists on www.haskell.org; for the full list, see http://www.haskell.org/mailman/listinfo/ Some GHC developers hang out on #haskell on IRC, too: http://www.haskell.org/haskellwiki/IRC_channel Please report bugs using our bug tracking system. Instructions on reporting bugs can be found here: http://www.haskell.org/ghc/reportabug

2 1

FMICS 2009: First Call for Papers
by FMICS 2009 workshop chair 04 Nov '08

04 Nov '08

FMICS 2009 - FIRST CALL FOR PAPERS Please visit: http://www.dsic.upv.es/workshops/fmics2009 ************************************************** * 14th International Workshop on * * Formal Methods for Industrial Critical Systems * * FMICS 2009 * * * * November 2-3, 2009 * * Eindhoven, The Netherlands * ************************************************** IMPORTANT DATES --------------- Deadline for abstracts: 1st April Deadline for papers: 7 April Accept/Reject notification: 15 June Camera-ready version: 15 July Workshop: 2-3 November SCOPE OF THE WORKSHOP --------------------- The aim of the ERCIM FMICS workshop series is to provide a forum for researchers who are interested in the development and application of formal methods in industry. In particular, these workshops bring together scientists and engineers that are active in the area of formal methods and interested in exchanging their experiences in the industrial usage of these methods. These workshops also strive to promote research and development for the improvement of formal methods and tools for industrial applications. Topics include, but are not restricted to: - Design, specification, code generation and testing based on formal methods. - Methods, techniques and tools to support automated analysis, certification, debugging, learning, optimization and transformation of complex, distributed, real-time systems and embedded systems. - Verification and validation methods that address shortcomings of existing methods with respect to their industrial applicability (e.g., scalability and usability issues). - Tools for the development of formal design descriptions. - Case studies and experience reports on industrial applications of formal methods, focusing on lessons learned or identification of new research directions. - Impact of the adoption of formal methods on the development process and associated costs. - Application of formal methods in standardization and industrial forums. INVITED SPEAKERS ---------------- To be announced CO-CHAIRS --------- Maria Alpuente (Technical University of Valencia, Spain) Byron Cook (Microsoft Research, UK) PROGRAM COMMITTEE ------------------- Hassan Ait-Kaci (Ilog, Canada) Maria Alpuente (Technical University of Valencia, Spain) Thomas Arts (IT-Universitetet i Goteborg, Sweden) Demis Ballis (Universita degli Studi di Udine, Italy) Josh Berdine (Microsoft Research, UK) Lubos Brim (Masarykova Univerzita, Czech Republic) Darren Cofer (Rockwell Collins, USA) Byron Cook (Microsoft Research, UK) Patrick Cousot (Ecole Normale Superieure, France) Santiago Escobar (Technical University of Valencia, Spain) Azadeh Farzan (University of Toronto, Canada) Hubert Garavel (INRIA Rhone-Alpes, France) Stefania Gnesi (ISTI-CNR, Italy) Alexey Gotsman (University of Cambridge, UK) Holger Hermanns (Universitat des Saarlandes, Germany) Christophe Joubert (Technical University of Valencia, Spain) Daniel Kroening (ETH Zurich, Switzerland) Michael Leuschel (Heinrich-Heine-Universitat Dusseldorf, Germany) Pedro Merino (Universidad de Malaga, Spain) Juan Jose Moreno-Navarro (Universidad Politecnica de Madrid, Spain) Corina Pasareanu (NASA Ames Research Center, USA) Jaco van de Pol (Universiteit Twente, The Netherlands) Murali Rangarajan (Honeywell, USA) Jakob Rehof (Technische Universitat Dortmund, Germany) Andrey Rybalchenko (Max-Planck-Gesellschaft, Germany) Marcel Verhoef (Chess, The Netherlands) Martin Wirsing (Ludwig-Maximilians-Universitat Munchen, Germany) Hongseok Yang (Queen Mary, University of London, UK) Greta Yorsh (IBM T.J. Watson Research Center, USA) ERCIM FMICS WG COORDINATOR -------------------------- Alessandro Fantechi (Universita degli Studi di Firenze and ISTI-CNR, Italy) WORKSHOP CHAIR -------------- Christophe Joubert (Technical University of Valencia, Spain) PAPER SUBMISSIONS ----------------- Submissions must be made electronically. Papers should be up to 16 pages in LNCS format, with the names and affiliations of the authors and a clear and informative abstract. Additional details may be included in a clearly marked appendix, which will be read at the discretion of the program committee. All submissions must report on original research. Submitted papers must not have previously appeared in a journal or conference with published proceedings and must not be concurrently submitted to any other peer-reviewed workshop, symposium, conference or archival journal. Any partial overlap with any such published or concurrently submitted paper must be clearly indicated. Case study papers should identify lessons learned, validate theoretical results (such as scalability of methods), or provide specific motivation for further research and development. Publication of the workshop proceedings in the Springer series Lecture No tes in Computer Science (LNCS) is envisaged. CO-LOCATION ----------- FMICS 2009 is part of the first Formal Methods Week (FMweek), which will bring together a choice of events in the area, including FM 2009 (16th symposium on Formal Methods), TESTCOM/FATES (conference on Testing of Communicating Systems and workshop on Formal Approaches to Testing of Software), FORMATS (Formal Modelling and Analysis of Timed Systems), PDMC (Parallel and Distributed Methods of verifiCation), and the REFINE Workshop. For the latest information on FMweek, please visit http://www.win.tue.nl/fmweek.

1 0

ANNOUNCE: htags-1.0
by David Sankel 04 Nov '08

04 Nov '08

http://hackage.haskell.org/cgi-bin/hackage-scripts/package/htags htags is a tag file generator to enable extra functionality in editors like vim. It expands upon hasktags by using a full Haskell 98 parser and options for recursion. -- David Sankel Sankel Software www.sankelsoftware.com 585 617 4748 (Office) 585 309 2016 (Mobile)

5 4

Re: [Haskell] ANNOUNCE: RefSerialize-0.2.1
by Alberto G. Corona 03 Nov '08

03 Nov '08

I uploadad RefSerialize<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/RefSerialize> to Hackage . Read, Show and Data.Binary do not check for repeated references to the same data address. As a result, the data is serialized multiple times when serialized. This is a waste of space in the filesystem and also a waste of serialization time. but the worst consequence is that, when the serialized data is read, it allocates multiple copies in memory for the same object referenced multiple times. Because multiple referenced data is very typical in a pure language such is Haskell, this means that the resulting data loose the beatiful economy of space and processing time that referential transparency permits. This package allows the serialization and deserialization of large data structures without duplication of data, with the result of optimized performance and memory usage. It is also useful for debugging purposes. There are automatic derived instances for instances of Read/Show, lists and strings. the deserializer contains a almos complete set of Parsec.Token parsers for deserialization. Every instance of Show/Read is also a instance of Data.RefSerialize The serialized string has the form "expr( var1, ...varn) where var1=value1,..valn=valueN " so that the string can ve EVALuated. See demo.hs and tutorial. I presumably will add a entry in haskell-web.blogspot.com To develop: -derived instances for Data.Binary -serialization to/from ByteStings I wrote this module because I needed to serialize lists of verisions of the same data with slight modifications between each version. This is a short tutorial (in tutorial.txt) runW applies showp, the serialization parser of the instance Int for the RefSerialize class Data.RefSerialize>let x= 5 :: Int Data.RefSerialize>runW $ showp x "5" every instance of Read and Show is an instance of RefSerialize. rshowp is derived from showp, it labels the serialized data with a variable name Data.RefSerialize>runW $ rshowp x " v8 where {v8= 5; }" Data.RefSerialize>runW $ rshowp [2::Int,3::Int] " v6 where {v6= [ v9, v10]; v9= 2; v10= 3; }" while showp does a normal show serialization Data.RefSerialize>runW $ showp [x,x] "[5, 5]" rshowp variables are serialized memory references: no piece of data that point to the same addrees is serialized but one time Data.RefSerialize>runW $ rshowp [x,x] " v9 where {v6= 5; v9= [ v6, v6]; }" This happens recursively Data.RefSerialize>let xs= [x,x] in str = runW $ rshowp [xs,xs] Data.RefSerialize>str " v8 where {v8= [ v10, v10]; v9= 5; v10= [ v9, v9]; }" the rshowp serialized data is read with rreadp. The showp serialized data is read by readp Data.RefSerialize>let xss= runR rreadp str :: [[Int]] Data.RefSerialize>print xss [[5,5],[5,5]] this is the deserialized data the deserialized data keep the references!! pointers are restored! That is the whole point! Data.RefSerialize>varName xss !! 0 == varName xss !! 1 True rShow= runW rshowp rRead= runR rreadp Data.RefSerialize>rShow x " v11 where {v11= 5; }" In the definition of a referencing parser non referencing parsers can be used and viceversa. Use a referencing parser when the piece of data is being referenced many times inside the serialized data. by default the referencing parser is constructed by: rshowp= insertVar showp rreadp= readVar readp but this can be redefined. See for example the instance of [] in RefSerialize.hs This is an example of a showp parser for a simple data structure. data S= S Int Int deriving ( Show, Eq) instance Serialize S where showp (S x y)= do xs <- rshowp x -- rshowp parsers can be inside showp parser ys <- rshowp y return $ "S "++xs++" "++ys readp = do symbol "S" -- I included a (almost) complete Parsec for deserialization x <- rreadp y <- rreadp return $ S x y there is a mix between referencing and no referencing parser here: Data.RefSerialize>putStrLn $ runW $ showp $ S x x S v23 v23 where {v23= 5; } (I corrected some errors in this file here)

1 1

Fwd: ACL2 2009 Call for Papers
by Simon Marlow 03 Nov '08

03 Nov '08

[ forwarding on behalf of Sandip Ray <sandip(a)cs.utexas.edu> ] [ Apologies if you get several copies of this call for papers. Please share it with students and colleagues who may be interested in the workshop. ] =============================================================================== CALL FOR PAPERS =============================================================================== ACL2 2009 International Workshop on the ACL2 Theorem Prover and Its Applications May 11-12, 2009 Northeastern University, Boston, MA, USA http://www.cs.utexas.edu/~sandip/acl2-09/ In cooperation with ACM SIGPLAN =============================================================================== IMPORTANT DATES Abstract Submission: January 12, 2009 Paper Submission: January 19, 2009 Acceptance Notification: February 23, 2009 Final Version: March 23, 2009 =============================================================================== SCOPE OF CONFERENCE ACL2 2009 is a major forum for the users of the ACL2 theorem proving system to present research related to the ACL2 theorem prover and its application, and is the eighth in the series of workshops, occurring at approximately 18-month intervals. ACL2 is a state-of-the-art automated reasoning system, the latest in the Boyer-Moore family of theorem provers, for which its authors received the 2005 ACM Software Systems Award. ACL2 2009 is planned as a two-day workshop to be held in Boston, MA, USA, on May 11-12, 2009. In addition to paper presentations, ACL2 2009 is anticipated to include two keynote lectures, a panel discussion, and several rump sessions discussing ongoing research. We invite submission of papers on any topic related to ACL2 and its applications. We strongly encourage the participation of users of other theorem provers and researchers and practitioners interested in theorem proving technology. Appropriate topics include, but are not limited to, the following: * Applications of ACL2 in hardware and software system verification * Formalization of mathematics in ACL2 * Use of ACL2 in emerging and novel application areas * New libraries, tools, and interfaces for ACL2 * Connection of ACL2 with other formal (and semi-formal) verification tools * Foundational issues related to ACL2 * Comparison of ACL2 with other formal verification tools * Reports and proposals on improvement of ACL2 * Challenge problems related to implementation and applications of ACL2 * Classroom and pedagogical experiences in the use of ACL2 =============================================================================== PAPER SUBMISSION Submissions must be made electronically in PDF format through the ACL2 2009 Web site. Submissions must use ACM SIG Proceedings format with letter-size paper (see URL http://www.acm.org/sigs/pubs/proceed/template.html) ACL2 2009 is organized in cooperation with ACM SIGPLAN and the proceedings are expected to be published in the ACM Digital Library. Two categories of papers will be accepted: long (at most 10 pages) and short (at most 4 pages). Authors may assume that the audience has a working knowledge of ACL2's syntax, basic commands, and modeling techniques. Papers should contain a short abstract of about 150 words, clearly stating the contribution of the submission. Papers should be self-contained, but we strongly encourage authors to follow the tradition (where applicable) of providing ACL2 "books", or script files, with instructions for their execution. For accepted papers, these books will be mirrored from the ACL2 Home Page and included in the future ACL2 distributions. At least one author of each accepted paper will be required to register for the workshop and present the paper. ============================================================================== ORGANIZATION Co-Chairmen: Sandip Ray, University of Texas at Austin, USA David Russinoff, Advanced Micro Devices, Inc., USA Local Arrangements: Panagiotis Manolios, Northeastern University, USA Publications: Ruben Gamboa, University of Wyoming Steering Committee: John Cowles, University of Wyoming, USA Ruben Gamboa, University of Wyoming, USA Matt Kaufmann, University of Texas at Austin, USA Panagiotis Manolios, Northeastern University, USA J Strother Moore, University of Texas at Austin, USA Jun Sawada, IBM Austin Research Laboratory, USA Matt Wilding, Rockwell Collins, Inc., USA ============================================================================== PROGRAM COMMITTEE * John Cowles, University of Wyoming, USA * Ruben Gamboa, University of Wyoming, USA * Mike Gordon, Cambridge University, UK * Matt Kaufmann, University of Texas at Austin, USA * Francisco Palomo Lozano, Universidad de Cadiz, Spain * Panagiotis Manolios, Northeastern University, USA * John Matthews, Galois, Inc., USA * J Strother Moore, University of Texas at Austin, USA * Rex Page, University of Oklahoma, USA * Jun Sawada, IBM Austin Research Laboratory, USA * Julien Schmaltz, Radboud University, Nijmegen, the Netherlands * Natarajan Shankar, SRI International, USA * Rob Sumners, Advanced Micro Devices, Inc., USA * Freek Wiedijk, Radboud University, Nijmegen, the Netherlands * Matt Wilding, Rockwell Collins, Inc., USA

1 0

ANNOUNCE: Graphalyze-0.5 and SourceGraph-0.3
by Ivan Lazar Miljenovic 03 Nov '08

03 Nov '08

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 I've just submitted my thesis this morning (w00t!!!) and as such I'm announcing the latest versions of Graphalyze [1,2] and SourceGraph [3,4], which fix a couple of bugs in the previous versions (these bugs were fixed whilst waiting for my supervisor to finish reading through my draft, and as such I had to re-write bits of my thesis that talked about the limitations of the software :s ). [1] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Graphalyze [2] http://code.haskell.org/Graphalyze [3] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/SourceGraph [4] http://code.haskell.org/SourceGraph Briefly, SourceGraph is a utility that uses the Graphalyze library to analyse Cabalized Haskell software. Its input/output is rather restrictive at the moment: it takes a single argument, which is the path to a .cabal file, and then produces an HTML report in: <project directory>/SourceGraph/<project name>.html This report contains visualisation of the code for each module, for the imports (similar to what graphmod [5] does) as well as the entire code base. Furthermore, the entire code base is also visualised with functions grouped by the modules they're defined in, as well some simple analyses (such as comparing the export list to what functions are actually roots, similar to the output for top-level functions returned by GHC when using -fwarn-unused-binds). Main changes in Graphalyze since version 0.4: * When writing my thesis, I found some obvious silly mistakes (such as copying the rootsOf function definition to leavesOf, but not changing the function definition). * Images in the document representation are now inline elements. * When using Pandoc [6] for document generation, the size of generated graphs is now customisable on a per-format basis; furthermore, for web pages graph visualisations link to larger versions. Also, graph visualisations can now be created in a sub-directory. Main changes in SourceGraph since version 0.2: * Now uses Cabal 1.6 * Improve visual layout of generated HTML report (still no CSS though). * "Smarter" analysis: don't show trivial analysis results, and when analysing the entire code base don't return cliques, etc. that contain functions all in the same module (as they would have been reported in the per-module section). Note, however, that the parsing limitations for version 0.2 still apply: cpp is still as-yet unsupported (as I'm not sure what I'll do about choosing cpp flags); Template Haskell, HaRP and HXML are still ignored and functions in class declarations/records are still ignored (the former because it's ambiguous which actual function you want, the latter because they're boring :p ). Also, SourceGraph is _still_ not a refactoring tool ;-) If anyone's interested, I'll soon be uploading the final version of my thesis to my blog. Also, if anyone is interested in hacking on any of this, feel free! I'll probably leave it for a while (I'm going to be doing Java coding over summer, blech :s ), but I intend to come back to it later on. - -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) iEYEARECAAYFAkkOcaAACgkQfEfFJ9JhvyjhIwCeM9VXsJeSVK2CdWURJDer6zoA A5YAoIfayHtjpw0qt/gyPZhhhypOwzSh =x+/X -----END PGP SIGNATURE-----

1 0

Need help with VXML again (fun deps and forall types)
by Marc Weber 02 Nov '08

02 Nov '08

Some time I've announced that I'm working on VXML, a validating xml library. The use case which makes trouble is elem+ (one or more) <!ELEMENT root (a|b|(c,d+))*> This example is encoded in this way: root -> St 1 id :1 endable : True a -> St 1 b -> St 1 c -> St 12 id :11 endable : True (a|b|c) -> St 1 d -> St 11 id :12 endable : False d -> St 11 to be read as: When creating a new root element start with state 1, then expect one of a,b,c subelemnts. If subelement c is added continue with state 12. The element may not be finalized (endable false because a "d" is expected). Following that we end in a loop at state 11 which is endable when only adding more d subelemnts. in VXML it looks like this print $ fStr $ runRoot $ vdo -- forceElements c e d e -- first, result has state 12 A d e -- second, result has state 11 X d e -- thrd, result has state 11 d e -- fourth, result has state 11 Y -- ... Now I'd like to do something convinient such as foldr1 (>>) print $ [1..10] I've called the corresponding function in VXML vxmlgtgt because it can be used like a monad and even do notation is supported using the vdo cpp macro rebinding (>>), (>>=) and return. Obviously I can only use foldr from X up to Y because A has a different return type. If you download the latest version of the library (git clone git://mawercer.de/vxml; git checkout fc160ab # is master branch ) you see that it actually works quite fine -- helper function: vxmlSeqPlus_ (f,fl) = f `vxmlgtgt` (foldr1 vxmlgtgt fl) -- usage example from testSimple.hs, note that both (d e) have different types vxmlSeqPlus_ ((d e), replicate 9 (d e)) d is actually a function creating the d element requiring a function as first argument which adds attrubutes and subelemnts (e is a nop here) This all makes d having a type which looks rather complicated: el*: the result type (String only in the current implementation) data VXML st el_ st2 el2_ st3 el3_ a = VXML { runVVXML :: (PT st el_ -> PT st2 el2_) -- [1] -> (a, PT st el_ -> PT st3 el3_) -- [2] } [1] : st -> st2 : The function which is passed [2] : st -> st3 : The type of function which is returned taking a function modyfiying the parent and adding "d" resulting in st3 (st3 is either State12 in A, or State11 in Y talking about the example given above) Its even getting more interesting now: Because I'd like to use different result types (String, ByteString, ...) I've used a type var to represent that type. I've called them el el2 el3 etc. When finally creating the document by using runRoot the result types propagates through the xml tree by functional dependencies. An example is the AddElT class which actually does add a subelement: class AddElT est el_ estc elc_ est2 el2_ | est estc -> est2 -- result state is determined by parent and child element state , est est2 estc el2_ -> el_ -- the result type of child and parent privious sibling are determined by the el2_ return type and the element states , est est2 estc el2_ -> elc_ where addElT :: PT est el_ -> PT estc elc_ -> PT est2 el2_ The instance has constraints like this determining el_ elc_ and st2 instance ( , DetermineElAddEl (NYV (Element elType AttrsOk st hchs)) el2 cest2 elc2 (NYV (Element elType AttrsOk st2 HTrue)) el3 , Consume st (Elem celType) st2 [..] ) => AddElT [..] Determining states form leafs to the root then propagating String or ByteString result type form the root to the leaf depending on states works fine until I start trying to use shortcut for the foldr1 example above. Instead of vxmlSeqPlus_ ((d e), replicate 9 (d e)) I'd like to write this. Of course the lamba here is polymorphic because it must return State 12 the first time and State 11 in the following cases. vxmlMapSeqPlus_ (\_ -> d e) [1..10] -- Ex I It's implementation is straight forward: vxmlMapSeqPlus_ f (x:xs) = vxmlSeqPlus_ (f x, map f xs) vxmlMapSeqPlus_ _ [] = error "vxmlSeqPlus has been called with empty list" My attempt to assign a type looks like this: vxmlMapSeqPlus_ :: ( VXMLMonad m st el st2 el2 st3 el3 st3 el3 , VXMLMonad m st el st3 el3 st3 el3 st3 el3 ) => (forall st' elA st'' elB . t -> m st el st' elA st'' elB ()) -> [t] -> m st el st2 el2 st3 el3 () vxmlMapSeqPlus_ f (x:xs) = vxmlSeqPlus_ (f x , map f xs) vxmlMapSeqPlus_ _ [] = error "vxmlSeqPlus has been called with empty list" where class VXMLMonad m st el_ st2 el2_ st3 el3_ st4 el4_ where vxmlgtgt :: m st el_ st2 el2_ st3 el3_ a -> m st el_ st3 el3_ st4 el4_ b -> m st el_ st2 el2_ st4 el4_ b vxmlgtgt a b = vxmlbind a $ const b vxmlbind :: m st el_ st2 el2_ st3 el3_ a -> (a -> m st el_ st3 el3_ st4 el4_ b) -> m st el_ st2 el2_ st4 el4_ b However when compiling the example (Ex I) there are a bunch of errors telling me that ghc can't find the matching instances caused by missing specialization of st.. That is ghc does no longer determine the resulting state based on parent and previous childs. Without state it can't propagate the el type ... You can see both examples in testSimple.hs vxmlSeqPlus_ ((d e), replicate 9 (d e)) vxmlMapSeqPlus_ (\n -> d e ) [1..10] So my question is: The second line does work fine, the first one dosen't. How to write vxmlMapSeqPlus_ so that I can compile the example? vxmlMapSeqPlus_ (\n -> d e ) [1..10] (d e) `vxmlgtgt` (foldr1 vxmlgtgt $ map (const $ d e) [2..10]) If you want to try this with ghc older than 6.10 you'll have to rewrite the vdo notation using vxmlbind and vxmlgtgt.. Do you have any idea how to make this work as expected? That's the last issue preventing me from trying to use it in real life projects. Sincerly Marc Weber

1 0

Publication of InputYourData.com + Project Announcement
by Enzo Haussecker 02 Nov '08

02 Nov '08

I would like to announce the publication of InputYourData.com (beta) − the online resource tool for financial, mathematical and scientific calculations. All web applications found at http://inputyourdata.com/ are written solely in Haskell and based on the Network.CGI framework. This website began as an experiment to familiarize myself with the monadic features of Haskell and their use in web programming. Namely, the mapping and manipulation of user inputs as typed objects. Through these experiments I found that Haskell allows for an efficient system where a variety of operations can be preformed while minimizing as many resources (such as time and memory space) as possible. I am now interested in developing a similar type of website, except wiki style − where all web applications are created by the user. Essentially, I am designing a web application where users can symbolically declare the arguments of a function and that function's call based on arbitrary variables. For example, say a user would like to create a web application to compute the roots of a second degree polynomial. He/she would simply declare the arguments to her function − three complex numbers a b and c, and the call of that function − (-b ± sqrt (b^2 - 4*a*c))/(2*a). The product of that users inputs will render a web application that looks similar to http://inputyourdata.com/cgi-bin/quadratic.cgi (all text is to be updated by the user as well). As one could imagine, other, more complex functions involving vectors, matrices, stock prices, and other arguments can also be defined in terms of arbitrary variables and declared as an inputs to my wiki-style web application. If you are intrigued by this project and you have substantial experience in designing Haskell-based web applications, please send me your resume and a brief summery of why you are interested. Regards, Enzo Haussecker ehaussecker(a)gmail.com

2 2

Haskell Weekly News: Issue 91 - November 1, 2008
by Brent Yorgey 01 Nov '08

01 Nov '08

--------------------------------------------------------------------------- Haskell Weekly News http://sequence.complete.org/hwn/20081101 Issue 91 - November 01, 2008 --------------------------------------------------------------------------- Welcome to issue 91 of HWN, a newsletter covering developments in the [1]Haskell community. Announcements blas version 0.6. Patrick Perry [2]announced a [3]new version of the Haskell BLAS bindings, now with support for the ST monad! darcs hacking sprint #1 (report). Eric Y. Kow [4]summarized the [5]progress made during the darcs hacking sprint last weekend. Looks like exciting stuff! Much more detail and links can be found in Eric's original email. LAST CALL: Haskell Communities and Activities Report. Janis Voigtlaender [6]is extending the submission deadline for the 15th edition of the Haskell Community and Activities Report by a few days. If you haven't already, please [7]write an entry for your new project or update your old entry. Data.TCache 0.5.1. Alberto G. Corona [8]announced the release of [9]Data.TCache, which implements a transactional cache with configurable persistence. It tries to simulate Hibernate for Java or Rails for Ruby; the main difference is that transactions are done in memory trough STM. multirec-0.1. Andres Loeh [10]announced the release of the [11]multirec package, which provides a mechanism to talk about fixed points of systems of datatypes that may be mutually recursive. On top of this representations, generic functions such as the fold or the Zipper can then be defined. Making 'Super Nario Bros.' in Haskell. Korcan Hussein [12]linked to a [13]super mario brothers clone which was [14]written in Haskell! Chart-0.9. Tim Docker [15]announced the 0.9 release of the [16]Chart library, a library for drawing 2D charts. Publication of InputYourData.com + Project Announcement. Enzo Haussecker [17]announced the publication of [18]InputYourData.com, an online tool, written in Haskell, for financial, mathematical and scientific calculations. Enzo also described an idea to create a similar website where web applications are created by the user. If you are intrigued by this project and have substantial experience in designing Haskell-based web applications, please send Enzo your resume and a brief summery of why you are interested. Blog noise [19]Haskell news from the [20]blogosphere. * Mark Jason Dominus: [21]Atypical Typing. Mark describes his OOPSLA talk about Haskell's type system. * Eric Kow (kowey): [22]official darcs blog!. * Ben Moseley: [23]2 Minute intro to Associated Types / Type Families. * Ivan Lazar Miljenovic: [24]Honours + LXDE. Ivan discusses the status of his Haskell-oriented Mathematics Honours thesis. * Jason Dagit: [25]Darcs Hacking Sprint - Summary from Portland Team. * Eric Kow (kowey): [26]darcs hacking sprint - Team Brighton Day 2. * Dan Piponi (sigfpe): [27]Operads and their Monads. Quotes of the Week * lispy: I just wanted to make sure that this was illegal first * quicksilver: it doesn't entirely help that SQL is a series of broken standards layered over very poor decisions by large corporations * Baughn: SingInTime> hello world <Baughn> SingInTime: Type mismatch: Expected type: IRC [a], inferred type: IO () About the Haskell Weekly News New editions are posted to [28]the Haskell mailing list as well as to [29]the Haskell Sequence and [30]Planet Haskell. [31]RSS is also available, and headlines appear on [32]haskell.org. To help create new editions of this newsletter, please see the information on [33]how to contribute. Send stories to byorgey at cis dot upenn dot edu. The darcs repository is available at darcs get [34]http://code.haskell.org/~byorgey/code/hwn/ . References 1. http://haskell.org/ 2. http://article.gmane.org/gmane.comp.lang.haskell.cafe/47117 3. http://quantile95.com/2008/10/31/ann-blas-bindings-for-haskell-version-06/ 4. http://article.gmane.org/gmane.comp.lang.haskell.cafe/47114 5. http://blog.darcs.net/2008/10/darcs-hacking-sprint-1-report.html 6. http://article.gmane.org/gmane.comp.lang.haskell.cafe/47078 7. http://www.haskell.org/pipermail/haskell/2008-October/020651.html 8. http://article.gmane.org/gmane.comp.lang.haskell.cafe/47016 9. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/TCache 10. http://article.gmane.org/gmane.comp.lang.haskell.general/16574 11. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/multirec 12. http://article.gmane.org/gmane.comp.lang.haskell.general/16572 13. http://uk.youtube.com/watch?v=gVLFGQGRsDw 14. http://svn.coderepos.org/share/lang/haskell/nario/ 15. http://article.gmane.org/gmane.comp.lang.haskell.general/16570 16. http://dockerz.net/software/chart.html 17. http://article.gmane.org/gmane.comp.lang.haskell.general/16550 18. http://inputyourdata.com/ 19. http://planet.haskell.org/ 20. http://haskell.org/haskellwiki/Blog_articles 21. http://blog.plover.com/talk/atypical-typing.html 22. http://koweycode.blogspot.com/2008/10/official-darcs-blog.html 23. http://nattermorphisms.blogspot.com/2008/10/2-minute-intro-to-associated-ty… 24. http://ivanmiljenovic.wordpress.com/2008/10/29/honours-lxde/ 25. http://blog.codersbase.com/2008/10/28/darcs-hacking-sprint-summary-from-por… 26. http://koweycode.blogspot.com/2008/10/darcs-hacking-sprint-team-brighton-da… 27. http://sigfpe.blogspot.com/2008/10/operads-and-their-monads.html 28. http://www.haskell.org/mailman/listinfo/haskell 29. http://sequence.complete.org/ 30. http://planet.haskell.org/ 31. http://sequence.complete.org/node/feed 32. http://haskell.org/ 33. http://haskell.org/haskellwiki/HWN 34. http://code.haskell.org/~byorgey/code/hwn/

1 0