- Haskell - Haskell.org

ANNOUNCE: HAppS 0.8
by Einar Karttunen 14 Apr '06

14 Apr '06

Hello, HAppS - Haskell Application Server version 0.8 has been released and contains a complete rewrite of the ACID and HTTP functionalities. Features include: * MACID - Monadic framework for ACID transactions: Write apps as a set of simple state transformers. MACID write-ahead logging and checkpointing make it easy for you to guarantee application integrity in the face of unplanned outages. MACID even guarantees that your side effects will be executed at-least-once if they can complete within a timelimit you define. * HTTP Server: Performs better than Apache/PHP in our informal benchmarks (thanks to Data.FastPackedString), handles serving both large (video) files and lazy (javascript) streaming, supports HTTP-Auth, and more. * SMTP Server Handle incoming email in your application without worrying about .procmail or other user level inbound mail configuration hackery. Just have the HAppS.SMTP listen on port 25 or have the system mail server SMTP forward mail for your app to some internal port. * Mail delivery agent Stop worrying about making sure a separate local mail server or DNS is up and running to deliver your mail. HAppS takes care of making sure your mail is delivered as long as your application itself is running and makes sure no outbound mail is lost even with unplanned restarts. * DNS resolver in pure Haskell For resolving MX records and concurrent queries. Can use an upstream DNS server or root servers directly. * XML and XSLT Separate application logic from presentation using XML/XSLT. With HAppS, you can have your application output XML (via HTTP or SMTP) and handle style/presentation via separate XSLT files at runtime. HAppS takes care of doing server side XSLT for outbound mail and HTTP user-agents that don't support it client side. * Sessions and much more! Where to get? http://happs.org/ darcs get http://happs.org/HAppS -- Einar Karttunen

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QuickCheck revival and Cabal
by Koen Claessen 13 Apr '06

13 Apr '06

Dear all, For the past couple of years, I have been quietly hacking on a brand new version of QuickCheck with lots of cool features. I have been distributing copies to some friends, but have not released any official package. Now, after lots of peer pressure, the time has come that I want to release the current version as a Cabal package. I have been agonizing however over where in the module hierarchy the new QuickCheck package should be. There is currently an old QuickCheck version in the standard hierarchy in Test.QuickCheck. As the new QuickCheck is incompatible with the old one, I do not want to override that place. Rather, I would like to create my own little space in the hierarchy where the new version can sit and develop. It feels to me that there should be a convention that people use to add their own contributions to the module hierarchy without the danger of clashing with other packages. Proposals: Contrib.Chalmers.QuickCheck External.Chalmers.QuickCheck Chalmers.QuickCheck Contrib.Test.QuickCheck Contrib.QuickCheck The first three I like -- but not the last one; I don't want to rule out anyone else (except for my own colleagues :-) making their own version of QuickCheck and releasing it somewhere in the tree. What does one think? Regards, /Koen PS1. Previously discussions about this were referred to the libraries mailing list but I feel that this is of interest to the larger crowd too. PS2. I welcome myself back to the Haskell mailing list after years of inactivity :-)

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ANN: MissingH 0.14.2
by John Goerzen 13 Apr '06

13 Apr '06

Hello, I'm pleased to announce the release of version 0.14.2 of MissingH. New features since 0.14.0 include: * New module MissingH.Path.Glob. This module expands wildcards by examining the filesystem. For instance, given the pattern /*bin/*sh, you might get back ["/bin/bash", "/bin/sh", "/sbin/sash"] * New module MissingH.Path.WildMatch. This module evaluates whether a given string matches a POSIX-style wildcard. It can also convert such a wildcard into a regular expression for use with Text.Regex. * New function MissingH.List.hasAny :: Eq a => [a] -> [a] -> Bool It returns true if the given list contains any of the elements in the search list * New function MissingH.IO.HVFS.vDoesExist, which returns true if the named object exists on the filesystem, regardless of what type of object it is * New function MissingH.Str.escapeRe, which takes a string and makes a regular expression that matches the string literally. It takes care to properly escape all characters that could have special meaning in a regular expression. * ConfigParser now gives more helpful error messages when possible, including section and option in most error messages * Total number of unit tests for MissingH now stands at 716. As always, MissingH can be downloaded from http://quux.org/devel/missingh or, after a few days, from http://http.us.debian.org/debian/pool/main/m/missingh MissingH.Path.Glob and WildMatch are high-level ports of similar modules in Python. Thanks, -- John Goerzen Author, Foundations of Python Network Programming http://www.amazon.com/exec/obidos/tg/detail/-/1590593715

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standard prelude and specifications
by Laszlo Nemeth 13 Apr '06

13 Apr '06

Hi, Chp 8 of the Haskell Report says: > In this chapter the entire Haskell Prelude is given. It constitutes a > *specification* for the Prelude. > Many of the definitions are written with clarity rather than > efficiency in mind, and it is not required > that the specification be implemented as shown here. My question is how strictly this word "specification" is to be interpreted? I can think of a strict and a loose interpretation: (1 - strict) Whatever invariant I can read out from the code which is given I am allowed to interpret it as part of the specification. e.g here is the code for filter: filter :: (a -> Bool) -> [a] -> [a] filter p [] = [] filter p (x:xs) | p x = x : filter p xs | otherwise = filter p xs Primarily this states that the resulting list have no elements for which the predicate 'p' does not hold. But I can also read out from the code that filter does not rearrange the elements in the list: for example if the list was sorted, it remains so afterwards. Under the strict interpretation this is also taken as part of specification for filter. (2 - loose) Filter is meant to drop elements for which the predicate 'p' doesn' t hold, and an implementation is free to rearrange the elements. There must have been some discussion of this earlier but google didn't find anything useful. Thanks, Laszlo

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Announcing Halfs, a Haskell Filesystem
by Isaac Jones 12 Apr '06

12 Apr '06

Halfs is a filesystem implemented in the functional programming language Haskell. Halfs can be mounted and used like any other Linux filesystem, or used as a library. Halfs is a fork (and a port) of the filesystem developed by Galois Connections. We've created a virtual machine to make using Halfs extremely easy. You don't need an extra partition or a thumb drive, or even Linux (Windows and Mac OS can emulate the virtual machine). For the impatient, go to the quick start: http://hackage.haskell.org/trac/halfs/wiki/QuickStart The Halfs web page is here: http://www.haskell.org/halfs/ Background: In the course of developing a web server for an embedded operating system, Galois Connections had need of a filesystem which was small enough to alter to our needs and written in a high-level language so that we could show certain high assurance properties about its behavior. Since we had already ported the Haskell runtime to this operating system, Haskell was the obvious language of choice. Halfs is a port of our filesystem to Linux, with some modifications. High assurance development is a methodology for creating software systems that meet rigorously-defined specifications with a high degree of confidence. That methodology comprises tools and practices. Its goal is to produce such systems reliably and effectively, with an ordinary degree of developer effort. Haskell is particularly well-suited to high assurance development. It is a high-level, fully-expressive, pure, functional language, with a powerful type system. One of the obligations of high assurance development is the demonstration of strong correspondence between high-level executable models and the eventual implementation. Haskell supports this directly: it can describe systems all the way from high-level executable models through to system implementations. The fact that Haskell is pure comes from its mathematical basis, and means that, by default, a function does not interfere with other functions. The type system is an automatic and scalable proof engine that can encode and enforce desirable properties. Together, these features allow the correctness of complex systems to be established, making Haskell ideal for high assurance development. The question was whether Haskell is well suited as the implementation language for a filesystem, which involves fixed sized buffers, lots of IO, and binary data structures. Though correctness is much more important to us than performance, we hoped that a Haskell filesystem would have acceptable performance, and that writing such low-level code would not be awkward or error-prone. We have developed a filesystem, Halfs, which aims to answer the above questions. One may mount a Halfs filesystem in Linux using the FUSE (Filesystem in Userspace) kernel module. We have created two new monads, FSRead and FSWrite which restrict the IO monad to reading and writing operations respectively. For performance, Halfs uses efficient mutable arrays for block IO, as well as caching for blocks and inodes.

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Haskell concepts in the next Visual Basic
by Paul Johnson 11 Apr '06

11 Apr '06

In the recent discussion on "Haskell as a disruptive technology" I predicted that MS would incorporate functional programming into its languages. See here for details. http://lambda-the-ultimate.org/node/1406 Paul.

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Deadline Extension: Mathematically Structured Functional Programming
by Conor McBride 11 Apr '06

11 Apr '06

+*->+*->+*->+*->+*->+*->+*->+*->+*->+*->+*->+*->+*->+*->+*->+*->+*->+*->+*-> DEADLINE-EXTENSION-DEADLINE-EXTENSION-DEADLINE-EXTENSION-DEADLINE-EXTENSION Workshop on Mathematically Structured Functional Programming http://cs.ioc.ee/mpc-amast06/msfp/ New deadlines: 17 April (abstracts); 21 April (papers) DEADLINE-EXTENSION-DEADLINE-EXTENSION-DEADLINE-EXTENSION-DEADLINE-EXTENSION +*->+*->+*->+*->+*->+*->+*->+*->+*->+*->+*->+*->+*->+*->+*->+*->+*->+*->+*-> We're delighted to be able to extend the deadline for MSFP 2006. The Workshop on Mathematically Structured Functional Programming will be held in Kuressaare, Estonia, on 2 July 2006, with invited speakers Andrzej Filinski and John Power. MSFP 2006 is a satellite workshop of MPC 2006 and a "small workshop" of the TYPES project. MSFP is about organizing functional programs more effectively with the aid of mathematical structures from semantics and elsewhere. The proceedings of MSFP 2006 will be published in the Electronic Workshops in Computing (eWiC) series of the British Computer Society. After the workshop, the authors of the best papers will be invited to submit revised and expanded versions to a special issue of the Journal of Functional Programming from Cambridge University Press. We look forward to hearing from you Conor McBride Tarmo Uustalu

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ANNOUNCE: DrIFT-2.2.0
by John Meacham 10 Apr '06

10 Apr '06

DrIFT 2.2.0 has been released. you can learn about and download it here http://repetae.net/john/computer/haskell/DrIFT/ a summary of changes since the last resease follows DrIFT-2.2.0: Mon Apr 10 00:39:24 PDT 2006 John Meacham <john(a)repetae.net> * add note about reconf script * make the parser handle newtype deriving without bailing out * fix bug in Ord deriving rule Wed Jan 18 03:59:21 PST 2006 David Roundy <droundy(a)darcs.net> * fix typo in src/Makefile.am Sun Nov 27 02:59:14 PST 2005 Malcolm.Wallace(a)cs.york.ac.uk * Change rule for Haskell2XmlNew into XmlContent, add Parse rule. The Haskell2XmlNew class was a temporary staging post on the way to developing a new XmlContent class, available in HaXml-1.14 onwards. This patch updates the name, and the rule, to match the latest developments. It also adds support for the textual (non-XML) Parse class, which is an experimental replacement for the Read class, using monadic parser combinators. This is also currently defined in HaXml-1.14. * docs should refer to StandardRules.hs, not .lhs * fix docs for Hugs usage * keep docs of --list option up-to-date Tue Nov 15 18:09:40 PST 2005 Einar Karttunen <ekarttun(a)cs.helsinki.fi> * Hook Arbitrary into DrIFT proper * Add UserRuleArbitrary Thu Nov 3 02:52:38 PST 2005 John Meacham <john(a)repetae.net> * fix data derving for new versions of ghc -- John Meacham - ⑆repetae.net⑆john⑈

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Haskell Weekly News: April 10, 2006
by dons＠cse.unsw.edu.au 10 Apr '06

10 Apr '06

Haskell Weekly News: April 10, 2006 Greetings, and thanks for reading issue 32 of HWN, a weekly newsletter covering developments in the Haskell community. Each Monday, new editions are posted to [1]the Haskell mailing list and to [2]The Haskell Sequence. [3]RSS is also available. Headlines also go to [4]haskell.org. 1. http://www.haskell.org/mailman/listinfo/haskell 2. http://sequence.complete.org/ 3. http://sequence.complete.org/node/feed 4. http://haskell.org/ Announcements hImerge: a graphical user interface for emerge. Luis Araujo released [5]hImerge, a graphical user interface for emerge, (Gentoo's Portage system) written in Haskell using gtk2hs. [6]Here's a jpg. The main idea is to simplify browsing the entire portage tree as well as of running the most basic and common options from the emerge command. hImerge also offers several handy tools, like global and local use flags browsers, and a minimal web browser. 5. http://haskell.org/~luisfaraujo/himerge/ 6. http://haskell.org/~luisfaraujo/rhimerge.jpeg MissingH 0.14.0. John Goerzen [7]announced MissingH 0.14.0, a library of "missing" functions. MissingH is available [8]here. 7. http://article.gmane.org/gmane.comp.lang.haskell.general/13531 8. http://quux.org/devel/missingh/ Haskell mailing list archives. Don Stewart [9]converted the Haskell mailing list archives from 1990-2000, into html format. The archive is available to view [10]here. 9. http://article.gmane.org/gmane.comp.lang.haskell.general/13521 10. http://www.cse.unsw.edu.au/~dons/haskell-1990-2000/threads.html Chapter 4 of Hitchhikers Guide to the Haskell. Dmitry Astapov [11]announced that the 4th chapter of the Hitchhikers Guide to Haskell is now [12]available. 11. http://article.gmane.org/gmane.comp.lang.haskell.cafe/12338 12. http://www.haskell.org/haskellwiki/Hitchhikers_Guide_to_the_Haskell Edison 1.2 rc3. Robert Dockins [13]announced that the 3rd release candidate for Edison 1.2 is now avaliable. 13. http://article.gmane.org/gmane.comp.lang.haskell.libraries/4508 Haskell' This section covers activity on [14]Haskell' standardisation process. * [15]State threads * [16]Terminating instances * [17]deriving Tree * [18]deriving Typeable * [19]deriving for newtypes * [20]deepSeq * [21]Asynchronous exceptions * [22]Exceptions 14. http://hackage.haskell.org/trac/haskell-prime 15. http://article.gmane.org/gmane.comp.lang.haskell.prime/1197 16. http://article.gmane.org/gmane.comp.lang.haskell.prime/1203 17. http://thread.gmane.org/gmane.comp.lang.haskell.prime/1218/focus=1218 18. http://article.gmane.org/gmane.comp.lang.haskell.prime/1243 19. http://thread.gmane.org/gmane.comp.lang.haskell.prime/1219/focus=1219 20. http://article.gmane.org/gmane.comp.lang.haskell.prime/1266 21. http://thread.gmane.org/gmane.comp.lang.haskell.prime/1222/focus=1222 22. http://thread.gmane.org/gmane.comp.lang.haskell.prime/1282/focus=1282 Code watch Wed Apr 5 06:33:44 PDT 2006 Simon Marlow * add support for x86_64; foreign import is now supported in GHCi on x86_64 Thu Apr 6 10:57:53 PDT 2006 Lemmih * GHC.Base.breakpoint isn't vaporware anymore. -fignore-breakpoints can be used to ignore breakpoints. Thu Apr 6 19:05:11 PDT 2006 Simon Marlow * Reorganisation of the source tree Most of the other users of the fptools build system have migrated to Cabal, and with the move to darcs we can now flatten the source tree without losing history, so here goes. The main change is that the ghc/ subdir is gone, and most of what it contained is now at the top level. The build system now makes no pretense at being multi-project, it is just the GHC build system. Quotes of the Week JaffaCake :: gcc is getting smarter, so we need to hit it with a bigger stick ihope :: Oops, I forgot that Djinn doesn't do GADT's. malig :: quantum mechanics actually strikes me as less weird than lazy evaluation sometimes. at least it disallows time travel Contributing to HWN Thanks to Luis Araujo for help preparing this issue. You can help us create new editions of this newsletter. Please see the [23]contributing information, send stories to dons -at- cse.unsw.edu.au. The darcs repository is available at darcs get http://www.cse.unsw.edu.au/~dons/code/hwn 23. http://haskell.org/haskellwiki/HWN

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Ignoring input
by UnfitElf 09 Apr '06

09 Apr '06

Hi everyone, Im new to haskell and finding it quite hard to pickup as im a C/C++ programmer however, im sticking with it as i think its a good thing to know. I have a problem were i have the user input a string, i then want to disregard the punctuation marks and spaces and change the case of the string to lower case. I was thinking that with the case i could work out the difference of the capital 'A' and the small 'a' and then change them somehow? As for ignoring punctuation marks and spaces im clueless. Thanks for any help Daniel -- View this message in context: http://www.nabble.com/Ignoring-input-t1422239.html#a3833983 Sent from the Haskell - Haskell forum at Nabble.com.

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