November 2004 - Haskell

Re: [Haskell] Re: Global Variables and IO initializers
by MR K P SCHUPKE 05 Nov '04

05 Nov '04

>Eiffel can dispense with global variables not least because objects contain >mutable state. And the methods cann access this state inside their object >without taking it as an argument. All of which you can do in Haskell (including the objects) with no additional extensions, see: http://www.cwi.nl/~ralf/OOHaskell Which is a draft paper by Oleg, Ralf and myself. We can even do pure functional objects (don't think thats in the paper yet) of course if the object does IO it must be in the IO monad or if it has _mutable_ state it must be in the ST monad. Keean.

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Re: [Haskell] Re: Global Variables and IO initializers
by MR K P SCHUPKE 05 Nov '04

05 Nov '04

>The point is to avoid threading global state to IO actions manually. >Programming langages exist in order to conveniently write programs in, >not only to admire their beauty. So if you are not interested in beauty, why not use the IO monad! If something is IO then declare it. You should not lie to the type system, or try to cheat it. It is your friend, and will help prevent errors in code. The point is to write correct error free programs, If you find the requirements too constrictive you should use another language. We don't need yet another Visual Basic/Java/C whatever. I see no problem with threading global state to IO actions, that is after all making clear in the function type what is happening! If you hide this from the type system, it can only lead to problems in the long run. Keean.

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Re: [Haskell] Re: Global Variables and IO initializers
by George Russell 04 Nov '04

04 Nov '04

John Peterson wrote (snipped): > The implementer of these functions has to guarantee that the > actions do not destroy the commutativity of the CIO monad. Sorry, but several of my variable initialisation actions involve things like starting up child processes or rapid exits from the program if unsuccessful, which certainly cannot be guaranteed to be commutative. I still think the proposal I made to this list in June http://www.haskell.org//pipermail/haskell/2004-June/014104.html is sound. It requires nothing other than a new library, which is trivial to implement using the existing unsafePerformIO. It is safe. I don't think it's especially clunky. Essentially the only serious limitation is that you can only access a bit of initialised state from an IO action, but in my experience at least this is not a serious issue. However virtually everyone seems to have their own patent solution, and we are no closer to agreement. Might it be an idea to have a Wiki or something like that devoted to discussion of this problem, and we can all try to agree on the advantages and disadvantages of the competing methods?

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grammar for Haskell?
by Peter Schneider-Kamp 04 Nov '04

04 Nov '04

Hi! We are looking into parsing full Haskell98 (probably using SableCC) as an input language to our program verification environment (http://www-i2.informatik.rwth-aachen.de/AProVE) Does anyone know about and can point me to either a) a SableCC style Haskell98 grammar description, b) any LALR(1) gramamr for Haskell98, c) a Haskell98 grammar for either JavaCC, ANTLR or another Java-based compiler compiler, d) a Haskell98 grammar for a compiler compiler whose output can be compiled to Java classes/bytecode, or e) any other concise Haskell98 grammar which is less fragmented than the Haskell98 report. Any help in this matter is appreciated. The lower the letter, the better :-) Kind regards, Peter -- Peter Schneider-Kamp mailto:psk@informatik.rwth-aachen.de LuFG Informatik II http://www-i2.informatik.rwth-aachen.de/~nowonder RWTH Aachen phone: ++49 241 80-21211

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Litle problem with a haskell Function...
by Manuel Costa 03 Nov '04

03 Nov '04

Hello, I' a Haskell Newbie and i need some help about a function.. My problem is to update a list of values in Runtime. For example i have a initial list: list1=3D"a"=20 and a function: add::add::String->[String] add x =3D [list1] ++ [x]=20 I need to do=20 add "c"=20 and the "c" most be append to list1 to make list1=3D["a","c"] Then if i input list1 the output must be ["a","c"] But i can't do it... Could you help me ?!

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ICTCS'05 Call for affiliated workshops
by g. michele pinna 02 Nov '04

02 Nov '04

Please accept our apologies if you receive multiple copies of this call. _____________________________________________________________________ ICTCS 2005 http://ictcs05.dsmi.unisi.it/ Certosa di Pontignano, Siena, 12 - 14 October 2005 Call for Affiliated Workshops _____________________________________________________________________ This is an invitation to submit proposals for workshops affiliated with ICTCS 2005, to be held in Siena, at the Certosa di Pontignano, from October 12 (Wednesday) to October 14 (Friday). The workshops can be located either at the Certosa di Pontignano (http://www.unisi.it/servizi/certosa/) or at the Dipartimento di Scienze Matematiche ed Informatiche "R. Magari" (http://www.dsmi.unisi.it) in the days immediately preceding or following the Conference. Friday 14th afternoon is also available. Researchers and practitioners are invited to submit proposals for workshops on topics related to any field of theoretical computer science. Proposals should be submitted to the ICTCS organizing chair G. Michele Pinna (pinna(a)unisi.it) Proposals will be evaluated by the ICTCS Chairs Mario Coppo, Elena Lodi and G. Michele Pinna. Deadlines: In order to help ensure that space for the workshop will be available, please let us know as soon as possible if you are considering organizing a ICTCS-affiliated workshop, but in any case before December 31st. Workshop Proposals: Workshop proposals should consist of two parts: * A short scientific justification of the proposed topic, its scope and significance, and the particular benefits of the proposed workshop. One or two paragraphs are enough. * The following organizational details: - List of the organizers. - Address, email, phone, and fax of a single contact person. - Proposed format of the workshop. - Duration (number of days) of the workshop. - Expected number of participants and, for workshops that have been held in previous years, number of participants in the previous year(s). The ICTCS organization offers: - Link between ICTCS and Workshop web sites. - Support in the management of registration and hotel reservation. - Setup of meeting space, and related equipment. The workshop organization must take care of: - Workshop publicity and call for papers. - Providing a brief description of the workshop for inclusion on the ICTCS web page. - Scheduling workshop activities in collaboration with the ICTCS local organizer. - Printing (paper/CD) and distribution of the proceedings, if so desired. - Finding funding arrangements for their invited speakers.

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ANN: Flippi v0.03
by Philippa Cowderoy 01 Nov '04

01 Nov '04

I'm writing to announce the latest version of Flippi, a simple and lightweight Wiki clone written in plain Haskell 98 using the hierarchical libraries. The main new feature in this version is support for scripts built in to the binary (yes, you can build one to shell out to another lang if you want), and the all-important RecentChanges page implemented via the scripting interface. Aside from this, various bugs have been corrected and there's a little less room for users to do silly things such as creating pages they can't link to. Flippi can be found at http://www.flippac.org/projects/flippi/ , with a running copy at http://www.scannedinavian.org/cgi-bin/flippi/flippi where I hope things such as user modifications will be linked to once they're available (I'm hearing about some as I type this). The code's all available under the BSD license, and is known to compile under GHC6 (but not GHC 5). -- flippa(a)flippac.org

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Announcing: Postmaster ESMTP Server
by Peter Simons 01 Nov '04

01 Nov '04

Fellow Haskellers, at <http://postmaster.cryp.to/> you will find the first beta release of Postmaster, a mail transport agent written in Haskell. It can act as a full ESMTP server for leaf sites already, and if you have another MTA installed, then you can use it as a front-end for that to do mail relaying, too. I have been running the software in a pretty complex setup for a few days now and it works reliably. Mostly. :-) Have fun! Peter

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Announce: Cabal 0.1 (Library Infrastructure Project)
by Isaac Jones 01 Nov '04

01 Nov '04

Much thanks to all who've made this possible :) The Haskell Cabal The Common Architecture for Building Applications and Libraries. DOWNLOAD: The Haskell Cabal has reached pre-release stage, with a 0.1 version The community should use this release to evaluate the interfaces and explore the concepts of these tools. Download the Cabal here: http://www.haskell.org/cabal/download.html BUGS: Please report bugs and wish-list items here: http://sourceforge.net/tracker/?func=add&group_id=44807&atid=440922 Or email Isaac Jones: ijones(a)syntaxpolice.org ABOUT: The Haskell Cabal is meant to be a part of a larger infrastructure for distributing, organizing, and cataloging Haskell Libraries and Tools. It is an effort to provide a framework for developers to more effectively contribute their software to the Haskell community. Specifically, the Cabal describes what a Haskell package is, how these packages interact with the language, and what Haskell implementations must to do to support packages. The Cabal also specifies some infrastructure (code) that makes it easy for tool authors to build and distribute conforming packages. The Cabal is only one contribution to the larger goal. In particular, the Cabal says nothing about more global issues such as how authors decide where in the module name space their library should live; how users can find a package they want; how orphan packages find new owners; and so on. NOTES: This release is meant to provide the community with concrete information about how the interfaces are shaping up. This release does NOT fix the interfaces, we can't promise not to break anything that relies on these interfaces. We hope that Haskell authors will try to package their software using these tools, and let us know where they fall short. MORE INFORMATION: Please see the web site for the source code, interfaces, and especially the proposal, which will serve as documentation for this release: http://www.haskell.org/cabal/

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