- Haskell - Haskell.org

Subtyping
by Steffen Mazanek 27 Apr '03

27 Apr '03

Hello. Yet another question: Consider a type structure like in "Typing Haskell in Haskell" where types are curried, e.g. data Type = TAp Type Type | TCon Id Kind | TVar Id Kind This means, "(->) Int" is a valid type. In a subtype calculus you can say, that "a->b" is a subtype of "c->d" if "b" is a subtype of "d" and "c" is a subtype of "a", because "->" is contravariant in its first and covariant in its second argument. So far so good, how can be dealt with subtyping and "partial" types? E.g. is it acceptable to say that "(->) a" is a subtype of "(->) b" if "b" is a subtype of "a"? Any ideas? Or can someone point me to an online-resource which addresses this topic? Thanks in advance, Steffen -- Haskell: that's where I just curry until fail, unwords any error, drop all undefined, maybe break, otherwise in sequence span isControl and take max $, id: (d:[])

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[ANNOUNCE] Haskell on FreeBSD web site <URL:http://haskell.org/fr eebsd/>
by Oliver Braun 26 Apr '03

26 Apr '03

Hi, I have just uploaded a first approach for an "Haskell on FreeBSD" web site: http://haskell.org/freebsd/ Please feel free to give me feedback! Regards, Olli -- Oliver Braun :: <obraun(a)unsane.org> :: <obraun(a)FreeBSD.org>

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RE: problems invoking haddock
by Simon Marlow 26 Apr '03

26 Apr '03

> I was not able to make Haddock run... Invoking it for a > simple hello world example > > > module Main where > > > > main :: IO() > > main = putStrLn "Hello World" > > gives me the following errors: > > Warning: module not found: Prelude > Warning: Main: the following names could not be resolved: > IO Prelude.() > > Fail: does not exist > Action: openFile > Reason: No such file or directory > File: /usr/local/lib/haddock-0.4/haddock.css Sounds like Haddock isn't installed properly. What procedure did you use to build/install it? Cheers, Simon

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binary input of 2d and 3d arrays
by Andrew French 25 Apr '03

25 Apr '03

Can someone point me to information sources on how to input/output multidimensional binary arrays? I am quite new to Haskell, have read some of Hudak and Thompson, but cant seem to find out how to do this basic task. There must surely be examples posted, but I havent been able to find any. -Andrew French

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Re: Super Haddock (was Re: Literate Programming)
by Andy Moran 25 Apr '03

25 Apr '03

[ Simon moved the thread to cafe, but I note there is still some activity in the main list, hence the crosspost. ] On Friday 25 April 2003 02:34 am, Simon Marlow wrote: > Ketil Z. Malde writes: > > "Simon Marlow" <simonmar(a)microsoft.com> writes: > > > Somebody else¹ wrote: > > >> This seems like a good way of transitioning from .lhs to > > >> haddock'd .hs. In the long run, I think we (meaning Simon :-) > > >> should to extend haddock to take the place of the .lhs style of > > >> documenting code. > > > > > > That's an interesting idea. It's not at all what Haddock > > > > was intended > > > > > for, but that's not to say it couldn't be done! > > > > I'm not sure I would like this. I guess I'm one of (the apparently > > very few?) who are using LaTeX lhs style (using \begin/\end{code}). > > Would a Haddock replacement give me the same kind of functionality in > > producing a nice printable copy? I definitely have grown attached to > > having math, footnotes, page headings, sections, and so on. > > Haddock isn't (intended to be) a literate programming system, so I don't > imagine it will replace full LaTeX literate source any time soon. The > suggestion is just that it could produce nicely-formatted source code > complete with lightly marked-up comments - which I think is a fine idea, > and not too difficult to implement using the existing framework. I just want to back Simon up here. My original post was intended to motivate a lightweight alternative to LaTeX lhs style, _not_ a replacement. I'm delighted that there are people that use literate Haskell. I don't: it's too unwieldy for my purposes. When documenting code for a small team of developers, when that code is fluid, and must be maintained, having professional, very attractive, browsable source code documentation is a wonderful thing. When you can produce that documentation with such minimal mark-up, it's going to get used. Cheers, Andy -- Andy Moran Ph. (503) 526 3472 Galois Connections Inc. Fax. (503) 350 0833 3875 SW Hall Blvd. http://www.galois.com Beaverton, OR 97005 moran(a)galois.com

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[ OT ]: unsubscribe without password?
by oliver＠first.in-berlin.de 25 Apr '03

25 Apr '03

Hello, the listserv-help does not help me to unsubscribe. How can I unsubscribe, when I've forgotten my password (it's on an old hard-disk, which is not available now...)? Ciao, Oliver

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problems invoking haddock
by Andre W B Furtado 25 Apr '03

25 Apr '03

I was not able to make Haddock run... Invoking it for a simple hello world example > module Main where > > main :: IO() > main = putStrLn "Hello World" gives me the following errors: Warning: module not found: Prelude Warning: Main: the following names could not be resolved: IO Prelude.() Fail: does not exist Action: openFile Reason: No such file or directory File: /usr/local/lib/haddock-0.4/haddock.css Using the option --no-implicit-prelude solves the first problem, but I wonder if this is the correct way to get around it. Using a specified stylesheet instead of the default one that comes with Haddock (--css=filename) solves the last problem, but introduces a new one: Fail: does not exist Action: openFile Reason: No such file or directory File: /usr/local/lib/haddock-0.4/haskell_icon.gif Putting /usr/local/lib/haddock-0.4 in the PATH does not solve the problem... Another attempt to invoke Haddock for other example such as module Test where test :: Int test = 3 gave me the problem: "Warning: Test: the following names could not be resolved: Int" Any ideas of what's going wrong? (My config: WindowsXP + GHC-5.04.2 + Cygwin) Thanks, -- Andre

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Extracting values from several data constructors
by Steffen Mazanek 24 Apr '03

24 Apr '03

Hello. I am sure this question is not new. Even so, please give me the solution or point me to an old thread. How can I implement something like: data Test = T1 Int | T2 Int test::Test->Int test (_ x) = x Or is this impossible? In case of yes, why? This would save a lot of case differentiations in my application. Or is there an appropriate compiler option? Good night, Steffen

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WAIT 2003: Deadline approaching
by WAIT 2003 24 Apr '03

24 Apr '03

---------------------------------------------------------------------- CALL FOR PAPERS 32 JAIIO - WAIT 2003 Argentinian Workshop on Theoretical Computer Science Buenos Aires - Argentina September 1-5, 2003 Deadline for reception of papers: May 4 ---------------------------------------------------------------------- The Argentinian Workshop on Theoretical Computer Science (WAIT) has become an important Latin American forum for the exchange of ideas and the presentation of research in theoretical computer science and its applications. The workshop aims are to build a bridge between academic and applied research and to stimulate the exchange of ideas and experience between theory and practise in computer science. The meeting includes contributed and invited talks, and tutorials. Further, we are very pleased to announce that there will be a special issue of ENTCS (http://www.elsevier.nl/locate/entcs) dedicated to WAIT 2003 publishing a selection of outstanding contributions. WAIT 2003 (http://wait2003.famaf.unc.edu.ar) the 7-th workshop in the series, will be held in Buenos Aires during September 1-5 (2003) as part of the 32-nd Argentinian Conference on Informatics and Operations Research (32 JAIIO, http://www.jaiio2003.uade.edu.ar) Buenos Aires (http://www.buenosaires.gov.ar/areas/turismo/en/) is a cosmopolitan and modern urban centre easily accessible by plane from most mayor cities in the world. The city is characterised by the multiplicity of its artistic expressions, ranging from the great assortment of sculptures and monuments to streets and corners that surprise with their allegorical reliefs and murals. The climate of Buenos Aires ---oceanic and warm--- is mild all year round, allowing visitors to discover the city on foot in any season. The city offers all categories of accommodation, and food ---which is something of a cult--- is of high quality. TOPICS Submissions are welcome in all fields of Theoretical Computer Science. Specific topics of WAIT 2003 include (but are not limited to): * Logical and algebraic foundations of computer science (logics for computation, category theory, relation algebras, type theory); * Formal methods (formal specification of sequential and concurrent programs, analysis, verification and transformation of programs, model checking); * Algorithms and data structures (sequential, parallel, distributed and on-line computing, probabilistic algorithms); * Automata theory and computational complexity; * Symbolic and algebraic computation; * Quantum Computing; * Bioinformatics. Submissions are expected to contain original research and will be refereed by international experts. Research papers must contain previously unpublished results. They will be judged on the base of originality and importance of their contributions and clarity of presentation. Papers should not exceed 12 pages, including figures and references. PROGRAM COMMITTEE: Martin Abadi (University of California at Santa Cruz) Gilles Barthe (INRIA Sophia-Antipolis) Gabriel Baum (Universidad de La Plata) Veronica Becher (Universidad de Buenos Aires) Vincent Danos (CNRS, Paris VII) Peter Dybjer (University of Gothenburg) Roberto Di Cosmo (PPS, Paris VII) Esteban Feuerstein (Universidad de Buenos Aires) Marcelo Fiore (Cambridge University) (co-chair) Daniel Fridlender (Universidad de Cordoba) (co-chair) Joos Heintz (Universidad de Buenos Aires) Gonzalo Navarro (Universidad de Chile) Peter O'Hearn (QMW, University of London) Alfredo Viola (Universidad de la Republica) IMPORTANT DATES: Deadline for reception of papers.................................May 4 Notification of acceptance.....................................June 27 Deadline for reception of the final version....................July 18 INSTRUCTIONS FOR AUTHORS: To facilitate the dissemination of papers and results, authors are invited to submit their papers in English. However, papers in Spanish or Portuguese are also welcome. Accepted contributions will be published in the Proceedings of the 32 JAIIO. Further, a selection of outstanding contributions will be invited to be published (in English) in a special issue of ENTCS dedicated to WAIT 2003. Papers should respond to ENTCS format (obtainable from http://math.tulane.edu/~entcs/) or similar, and must be submitted electronically in PostScript format (ghostview-readable) or PDF to the following e-mail address: wait2003(a)famaf.unc.edu.ar. Authors should communicate in a separate e-mail (in ASCII format) the title of the paper together with a short abstract, name and affiliation of all co-authors and their e-mail addresses, phone and FAX numbers. The message should also contain a list of keywords describing the area of the paper. ----------------------------------------------------------------------

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Literate Programming
by Steffen Mazanek 24 Apr '03

24 Apr '03

Hello. Simon Marlow wrote: >I don't think that's entirely fair. Most of the libraries that come >with GHC (and Hugs, and soon Nhc) are documented. See for example > > http://www.haskell.org/ghc/docs/latest/html/base/index.html As far as I know (please correct me, if I err) one shortcoming of Haddock is its restriction to .hs-files. I think there are a lot of real literate programmers out there which would prefer a Haskell documentation tool for their literate Haskell scripts. Therefore I present the tool lhs2hs, which may seem very puristic and errorprone at this time (in fact it is). It transforms a .lhs-file into a .hs file. Furthermore tex-comments are used to pass information to e.g. Haddock: Example: %%Haddock:this function... %%Haddock:... >testfun... %%Haddock:another function... \begin{code} ... \end{code} This .lhs file becomes transformed to {-| this function... ... -} testfun... {-| another function... -} ... Ok, its simple, but it can be useful and it is extensible! I have attached the very first version. Type: ghc --make Main.lhs -package util -o lhs2hs ./lhs2hs -h Main.lhs haddock -h Main.hs latex Main.lhs Another idea to simplify literate programming with Haskell: allow XML (introduce a new file extension .xhs), e.g.: <hscomment describes="quicksort"> sorts a list </hscomment> <hsdecl defines "quicksort"> quicksort... </hsdecl> This would allow more transformations! Bye, Steffen

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