- Haskell - Haskell.org

SUGGESTION: haskell-announce mailing list
by C.Reinke 10 May '02

10 May '02

Several contributors to the HC&A Report reported the same problem with the current setup of Haskell mailing lists: In spite of the split into haskell and haskell-cafe, they missed the general calls for contributions on haskell(a)haskell.org because some of them, being involved in other work as well, only browse the flood of traffic. When the list was originally split into haskell (for announcements and discussion starters) and haskell-cafe (for longer discussions), some of us suggested a separate haskell-announce instead (or indeed, support for client-based filtering instead of this server-based split). In my own setup, postings to haskell and haskell-cafe still go into a single folder, and I separate out announcements and similar things by hand (because I usually don't have the time to follow them up immediately, and because there's no reliable pattern to use for automatic filtering; e.g., this very email I'd filter out into the TODO area, even though it's not strictly speaking an announcement). Even though many discussions move quickly to haskell-cafe, which some of us are no longer subscribed to, the discussion starters and the more technical discussions still seem to generate enough traffic that some Haskellers miss announcements made on haskell. Based on this recent negative experience, I suggest to introduce a separate haskell-announce mailing list. To avoid upsetting the existing split, this ought to be split off the haskell list (i.e., everyone subscribed to haskell would initially be subscribed to haskell and to haskell-announce). Opinions? Suggestions? Cheers, Claus

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Re: ANNOUNCE: Haddock version 0.2, a Haskell documentation tool
by Ashley Yakeley 10 May '02

10 May '02

At 2002-05-09 09:44, Simon Marlow wrote: >I'm pleased to announce version 0.2 of Haddock, a documentation >generation tool for Haskell source code. It's available from > > http://www.haskell.org/haddock/ It's at <http://www.haskell.org/haddock/haddock-0.2-src.tar.gz>. -- Ashley Yakeley, Seattle WA

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Re: updating labelled fields
by Zdenek Dvorak 09 May '02

09 May '02

Hello. >I like this idea, but I think it will cause ambiguity in >parsing. Consider: > >blah = do {foo} ... > >should foo be parsed as a statement list (under the assumption that the >open brace is instead of using layout) or as an assignment, as in: > >blah = do {foo} > x <- bar > >(which probably wouldn't typecheck, but we don't know that at parsing.) i >could be wrong and it might be able to be made work, but i'm not >convinced... I don't think this is ambigous -- do is a keyword, so no record field update can be assumed after it. Zdenek _________________________________________________________________ Chat with friends online, try MSN Messenger: http://messenger.msn.com

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ANNOUNCE: Haddock version 0.2, a Haskell documentation tool
by Simon Marlow 09 May '02

09 May '02

I'm pleased to announce version 0.2 of Haddock, a documentation generation tool for Haskell source code. It's available from http://www.haskell.org/haddock/ The changes relative to version 0.1 are listed here: http://www.haskell.org/haddock/CHANGES.txt Cheers, Simon

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Summer School on Generic Programming: early reg deadline 17th May
by Jeremy Gibbons 09 May '02

09 May '02

A reminder: the early registration deadline for the Summer School on Generic Programming is Friday 17th May. Jeremy * Summer School and Workshop on Generic Programming St Anne's College, Oxford, UK 26th to 30th August 2002 In conjunction with Summer School and Workshop on Advanced Functional Programming This school is a successor to the Summer School and Workshop on Algebraic and Coalgebraic Methods in the Mathematics of Program Construction, held in Oxford in April 2000 and with lecture notes shortly to appear as LNCS 2297. For this school we have recruited an excellent group of lecturers on generic programming, that is, the construction of programs that work on different datatypes and yet may exploit the structure of that data. ************ Lecturers ************ * Roland Backhouse (University of Nottingham): A Generic Theory of Datatypes * Peter Buneman (University of Edinburgh): Semi-Structured Data * Roy Crole (University of Leicester): Categories and Types * Jose Luiz Fiadeiro (University of Lisbon and ATX Software): Theory and Practice of Software Architecture * Ralf Hinze (University of Bonn) and Johan Jeuring (University of Utrecht): Generic Haskell * Martin Odersky (Ecole Polytechnique Federale de Lausanne): Object-Oriented and Functional Approaches to Compositional Programming ************ Deadlines ************ For registration with an early-bird discount: 17th May 2002 For late registration: 12th July 2002 ************ Organizers ************ Roland Backhouse (University of Nottingham) Jeremy Gibbons (University of Oxford) ************ Further information ************ Web: http://www.comlab.ox.ac.uk/oucl/research/areas/ap/ssgp/info.html PDF poster: http://www.comlab.ox.ac.uk/oucl/research/areas/ap/ssgp/ssgp-poster.pdf Email: ssgp-info(a)comlab.ox.ac.uk Post: SSGP, c/o Jane Ellory, Oxford University Computing Laboratory, Wolfson Building, Parks Road, Oxford OX1 3QD, United Kingdom. Fax: +44 1865 273839; mark "fao SSGP (Jane Ellory)"

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by sales137＠163.com 09 May '02

09 May '02

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RE: duplicate instance declarations
by Simon Peyton-Jones 09 May '02

09 May '02

Two instances are duplicates if their 'head' (the part after the =>) is identical, modulo alpha renaming. Even with overlapping instances allowed, GHC never makes an arbitrary choice between two instance decls. It choses one over the other only if its head is more specific (i.e. a substitution instance). This will never happen in the case of duplicate instance decls, so GHC rejects duplicates up front. GHC's resolution of overlapping instances does not use backtracking, so it is quite weak. For example instance C a => X a where ... instance D a => X a where ... You might think that if a type T is an instance of C but not D, then it would be clear which of these two instances to use to resolve the constraint (X T), but GHC does not spot that. It uses only the instance head. I hope this clarifies a bit. Simon | -----Original Message----- | From: Hal Daume III [mailto:hdaume@ISI.EDU] | Sent: 03 May 2002 18:33 | To: C T McBride | Cc: Haskell Mailing List | Subject: Re: duplicate instance declarations | | | Cool, thanks, that made sense. | | > [lots of stuff snipped] | | What's the difference, then, between "duplicate instances" | and "overlapping" instances? It seems that even with | -fallow-overlapping-instances and even | -fallow-undecidable-instances ghc still rejects the code I had. | | _______________________________________________ | Haskell mailing list | Haskell(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell |

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Re: updating labelled fields
by Zdenek Dvorak 09 May '02

09 May '02

Hello. >DrIFT which i am now maintaining can derive such utility functions out >of the box. just add a {-!deriving: update -} to get update functions >for every labeled field in a datatype. quite useful, I have not updated >the web page yet, but the new DrIFT homepage will be at > >http://homer.netmar.com/~john/computer/haskell/DrIFT/ Nothing against DrIFT, but it requieres running preprocessing before real compilation; I don't like it for short programs, that I have defined just in one module and I'm debugging/modificating them. I've thought about syntax for set/update functions some time ago too. What I though about is: ({assignments}) desugars to \x->x{assignments} x{as, field =, bs} desugars to \y->x{as, field = y, bs} x{as, field, bs} desugars to \f->x{as, field = f (field x), bs} Then set function would be just ({field =}) and apply ({field}) (it does not need to create some artificial names for them that could colide with user names). Not really sure it does not conflict with rest of syntax, though. Zdenek Dvorak > > Anyway I'd prefer to have some way to 'derive' apply and set functions. > > Something like > > > data MyData = MyData { foo :: fooType, bar :: ..., .... } > > > deriving (Set, Apply) > > > > Using the keyword "deriving" would probably be a bad idea though :) > > The set and apply functions could be derived with a standard postfix or >maybe > > prefix... fooAp or apFoo. > > Maybe we could introduce sintax to specify it... > > > deriving (Set with "set", Apply with "ap") > > > > I don't know... I'm just brainstorming right now. > > Having actual functions is important. I don't think I have to explain >why to > > people in this mailing list :-) > > > > > Anyway, does such a thing exist, and, if not, is there any chance it >could > > > exist, or is it just syntactic salt to too many people? :) > > I whish you better luck than I've had so far whenever making posts about >this > > same issue ;) _________________________________________________________________ MSN Photos is the easiest way to share and print your photos: http://photos.msn.com/support/worldwide.aspx

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ANNOUNCE: Haskell Communities and Activities Report (2nd edition)
by C.Reinke 08 May '02

08 May '02

Dear fellow Haskellers, just about six months ago, the first edition of the HC&A Report was released, with the goal of helping to improve the communication between the various groups, projects, and individuals working on or with Haskell. The idea of these reports is simple: Every six months, a call goes out to all of you to contribute brief summaries of your own area of work. I then collect all these into a single report and feed it back to this very mailing list. Over the last few weeks, a lot of you have responded (eagerly, unprompted, and well in time for the deadline;-) to the call for contributions to the second edition of this report, and after the usual delays, I'm happy to announce that the Haskell Communities and Activities Report (2nd edition) is now available from the Haskell Communities home page http://www.haskell.org/communities/ The report is available for download in PDF (with working links and index, yet printable) or, for those who have problems with the PDF, in HTML (using John's secret weapon, thanks again) and Postscript. A big thanks here to everyone who contributed information to the report! I hope you will find it as interesting to read as we did. And when we try for the next update in six months, you might want to add your own work, project, research area or group as well. So, please, put that item for October 2002 into your diary now!-) Enjoy (and communicate;-)! Claus Reinke -- Computing Laboratory University of Kent at Canterbury http://www.cs.ukc.ac.uk/people/staff/cr3/

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(no subject)
by MRS. M SESE-SEKO 08 May '02

08 May '02

FROM:MRS. M SESE-SEKO DEAR FRIEND. I AM MRS. MARIAM SESE-SEKO WIDOW OF LATE PRESIDENT MOBUTU SESE-SEKO OF ZAIRE? NOW KNOWN AS DEMOCRATIC REPUBLIC OF CONGO (DRC). I AM MOVED TO WRITE YOU THIS LETTER, THIS WAS IN CONFIDENCE CONSIDERING MY PRESENT CIRCUMSTANCE AND SITUATION. I ESCAPED ALONG WITH MY HUSBAND AND TWO OF OUR SONS TIMOTHY AND BASHER OUT OF DEMOCRATIC REPUBLIC OF CONGO (DRC) TO ABIDJAN,COTE D'IVOIRE WHERE MY FAMILY AND I SETTLED, WHILE WE LATER MOVED TO SETTLED IN MORROCO WHERE MY HUSBAND LATER DIED OF CANCER DISEASE. HOWEVER DUE TO THIS SITUATION WE DECIDED TO CHANGED MOST OF MY HUSBAND'S BILLIONS OF DOLLARS DEPOSITED IN SWISS BANK AND OTHER COUNTRIES INTO OTHER FORMS OF MONEY CODED FOR SAFE PURPOSE BECAUSE THE NEW HEAD OF STATE OF (DR) MR LAURENT KABILA HAS MADE ARRANGEMENT WITH THE SWISS GOVERNMENT AND OTHER EUROPEAN COUNTRIES TO FREEZE ALL MY LATE HUSBAND'STREASURES DEPOSITED IN SOME EUROPEAN COUNTRIES. HENCE MY CHILDREN AND I DECIDED LAYING LOW IN AFRICA TO STUDY THE SITUATION TILL WHEN THINGS GETS BETTER, LIKE NOW THAT PRESIDENT KABILA IS DEAD AND THE SON TAKING OVER(JOSEPH KABILA). ONE OF MY LATE HUSBAND'S CHATEAUX IN SOUTHERN FRANCE WAS CONFISCATED BY THE FRENCH GOVERNMENT, AND AS SUCH I HAD TO CHANGE MY IDENTITY SO THAT MY INVESTMENT WILL NOT BE TRACED AND CONFISCATED. I HAVE DEPOSITED THE SUM OF $80 MLLION UNITED STATE DOLLARS (US$80,000,000,00.) WITH A SECURITY COMPANY , FOR SAFEKEEPING. THE FUNDS ARE SECURITY CODED TO PREVENT THEM FROM KNOWING THE CONTENT. WHAT I WANT YOU TO DO IS TO INDICATE YOUR INTEREST THAT YOU WILL ASSIST US BY RECEIVING THE MONEY ON OUR BEHALF IN EUROPE. I WANT YOU TO ASSIST IN INVESTING THIS MONEY, BUT I WILL NOT WANT MY IDENTITY REVEALED. I WILL ALSO WANT TO BUY PROPERTIES AND STOCK IN MULTI-NATIONAL COMPANIES AND TO ENGAGE IN OTHER SAFE AND NON-SPECULATIVE INVESTMENTS. MAY I AT THIS POINT EMPHASISE THE HIGH LEVEL OF CONFIDENTIALITY, WHICH THIS BUSINESS DEMANDS, AND HOPE YOU WILL NOT BETRAY THE TRUST AND CONFIDENCE, WHICH I REPOSE IN YOU IN CONCLUSION, IN THE EVENT YOU ARE INTRESTED TO ASSIST US I WILL LIKE YOU TO CONTACT MY LAWYER WHO I HAVE STATIONED IN HOLLAND TO WITHNESS THE TRANSACTION TO IS CONCLUTION.YOU CAN REACH HIM ON IS DIRECT LINE WHICH IS +31-612-480 860 OR VIA MAIL WESTEPHENS_4000(a)SPINFINDER.COM.HIS NAME IS STEPHENS AND I HAVE THE FALL TRUST IN HIME. I SINCERELY WILL APPRECAITE YOUR ACKNOWLEDGMENT AS SOON AS POSSIBLE. BEST REGARDS, MRS M. SESE SEKO

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