July 2001 - Haskell - Haskell.org

ICALP 2002 Call for Papers
by José Luis Triviño 25 Jul '01

25 Jul '01

We apologize for possible multiple postings. In http://www.lcc.uma.es/icalp2002/c4p-jul01.pdf you can find a pdf version of this call for paper. +++++++++++++++++++++++++++++++++++++ Call for Papers ICALP 2002 29th International Colloquium on Automata, Languages and Programming July 8-13, 2002, Málaga, Spain Camera Ready: April 16, 2002 The 29th annual meeting of the European Association of Theoretical Computer Science will be held in Málaga, Spain, July 8-13, 2002 (at the E.T.S. Ingeniería Informática). As with the Journal Theoretical Computer Science (TCS), the scientific program of the Colloquium will be split into two parts: Track A of the meeting will correspond to Algorithms, Automata, Complexity and Games, while Track B to Logic, Semantics and Theory of Programming. SUBMISIONS: Authors are invited to submit extended abstract of their papers, presenting original contributions to the theory of computer science. Detailed instructions for paper submissions will be found on the conference webpage (http://www.lcc.uma.es/icalp2002) and in future calls for papers. Submissions should consist of: a cover page, with the author's full name, address, fax number, e-mail address, a 100-word abstract, keywords and to which track (A or B) the paper is being submitted and an extended abstract describing original research. At least one author of an accepted paper should be available to present it at the conference. Simultaneous submission to other conferences with published proceedings is not allowed. Further information (dates and instructions for submissions, workshops, registration, location and travel) will be provided in future announcements. ORGANIZING COMMITEE: Buenaventura Clares (University of Granada), Ricardo Conejo (University of Málaga), Inmaculada Fortes (University of Málaga), Llanos Mora (University of Málaga), Rafael Morales (co-Chair, University of Málaga), Marlon Nuñez (University of Málaga), José Luis Pérez de la Cruz (University of Málaga), Gonzalo Ramos (University of Málaga), Francisco Triguero (co-Chair, University of Málaga), José Luis Triviño (University of Málaga). IMPORTANT DATES: Workshops proposal: November 8, 2001 Submissions: January 14, 2002 Notification: March 20, 2002 CONFERENCE CO-CHAIRS Prof. Francisco Triguero Prof. Rafael Morales Universidad de Málaga E.T.S. Ingeniería Informática Dept. Lenguajes y Ciencias de la Computación Bulevar Louis Pasteur, 35 29071 - Málaga (SPAIN) e-mail: icalp2002(a)informatica.uma.es PROGRAM COMMITEE Track A Ricardo Baeza-Yates (U. Chile) Volker Diekert (U. Stuttgart) Paolo Ferragina (U. Pisa) Catherine Greenhill (U. Melbourne) Torben Hagerup (U. Frankfurt) Johan Håstad (KTH, Stockholm) Gabriel Istrate (Los Alamos) Claire Kenyon (U. Paris XI) Der-Tsai Lee (Acad. Sinica, Taipei) Heikki Mannila (Nokia, Helsinki) Elvira Mayordomo (U. Zaragoza) Helmut Prodinger (U. Witwatersrand, South Africa) Jan van Leeuwen(U. Utrecht) Paul Vitányi (CWI, Amsterdam) Peter Widmayer (ETH Zürich) (Chair) Gerhard Woeginger (T.U. Graz) Christos Zaroliagis (U. Patras) Track B Martín Abadi (Bell Labs Research, Lucent) Roberto Amadio (U. Provence) Gilles Barthe (INRIA-SophiaAntipolis) Manfred Droste (University of Technology Dresden) Cédric Fournet (Microsoft Cambridge) Matthew Hennessy (U. Sussex) (Chair) Furio Honsell (U. Udine) Peter O'Hearn (Queen Mary & W. C. London) Fernando Orejas (U.P.Catalunya) Ernesto Pimentel (U. Málaga) David Sands (Chalmers University of Technology and Göteborg University) Dave Schmidt (U. Kansas) Gheorghe Stefanescu (U. Bucharest) Vasco Vasconcelos (U. Lisbon) Thomas Wilke (U. Kiel)

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Machine bit representations
by pachinko＠magicaldesk.com 25 Jul '01

25 Jul '01

Hello, Is it possible in Haskell to access the underlying machine bit representation of a Float or Double value? I need to be able to be able to send this bit representation as a list of bytes in network byte order to a process running on a different platform (with a different host byte order to my platform). For reference, I run Haskell under Linux on Intel. The processes I want to communicate with run under Sun Solaris, Hitachi HPUX and Java everywhere. Any suggestions, for any Haskell translator much appreciated. Thanks. _____________________________________________________________ Global Virtual Desktop http://www.magicaldesk.com

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http://www.video2flash.com. Convert your videos into flash format!
by video2flash＠boldyonline.com 25 Jul '01

25 Jul '01

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Re: Machine bit representations
by Ashley Yakeley 25 Jul '01

25 Jul '01

At 2001-07-24 16:51, pachinko(a)magicaldesk.com wrote: >Is it possible in Haskell to access the underlying machine bit >representation of a Float or Double value? If you mean the _actual_ bit representation, then I hope not! But maybe there should be (or are) functions for converting such values to _standard_ platform-independent bit representations... -- Ashley Yakeley, Seattle WA

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newbie syntax question
by Cagdas Ozgenc 24 Jul '01

24 Jul '01

Hi, I am extremely new to Haskell. This will be my first question, so go easy. I have just read Chapter 1 on Simon Thompson's book. for example a function declaration is given as follows scale : : Picture -> Int -> Picture If the first two types are input variables why does the syntax require me to use arrows twice? I mean isn't the following syntax more readable (hypothetically)? scale : : Picture , Int -> Picture Is there a specific reason not to be able to distinguish the input parameters from the output parameter? Thanks

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RE: newbie syntax question
by Memovich, Gary 24 Jul '01

24 Jul '01

Actually, all functions in Haskell take only one argument, although the people writing the program usually don't think of it this way. scale could alternatively have been defined with type scale :: (Picture, Int) -> Picture which looks more like what we would expect in a function of two arguments. But even here there is actually only a single argument, which happens to be a pair of values. The given declaration scale :: Picture -> Int -> Picture is written in 'curried' form. This means that scale is a function of one argument, 'Picture', and that its return value is a new function with type Int -> Picture. That new function can immediately be applied to an int value so that it appears as if you called scale with two values instead of just one. instead of writing scale pic 3 for example, you could have written (scale pic) 3 or even let x = scale pic in x 3 Which might make it a little easier to see what is actually happening. Hope this helps, -- Gary -----Original Message----- From: Cagdas Ozgenc [mailto:co19@cornell.edu] Sent: Tuesday, July 24, 2001 1:07 PM To: haskell(a)haskell.org Subject: newbie syntax question Hi, I am extremely new to Haskell. This will be my first question, so go easy. I have just read Chapter 1 on Simon Thompson's book. for example a function declaration is given as follows scale : : Picture -> Int -> Picture If the first two types are input variables why does the syntax require me to use arrows twice? I mean isn't the following syntax more readable (hypothetically)? scale : : Picture , Int -> Picture Is there a specific reason not to be able to distinguish the input parameters from the output parameter? Thanks

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Re: hGetContents and laziness in file io
by Hal Daume 24 Jul '01

24 Jul '01

Okay, I understand the problem. I would do something like the solution you propose, except that in the input file, trees span multiple lines. So the input file looks something like: (:cat S :subs ((() (:cat NP :subs ((() (:surf "John"))))) (() (:cat VP :subs ((() (:surf "bought")) (() (:cat NP :subs ((() (:surf "two")) (() (:surf "cars")))))))) (() (:surf ".")))) and then there will be another one directly following it (i detect the breaks because each one is completely surrounded in parens). So a line-by-line parse solution won't really do the job...

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Minor inconsistency in the report wrt to qualified names
by Wolfgang Lux 24 Jul '01

24 Jul '01

In section 5.5.1 the report states that a top-level declaration brings into scope qualified and unqualified names. Thus, the following declaration is legal: module Foo where ones = 1 : Foo.ones However, in section 2.4 the report says "External names may optionally be qualified in certain circumstances by prepending them with a module identifier." And also in section 3.2 the report says "Qualified names may only be used to reference and imported variable or constructor", from which the above program would not be legal (because Foo.ones is not an imported constructor or variable). In order to make the report consistent, I would suggest to change the section 3.2 to say: "Qualified names may be used to reference variables or constructors which are imported from other modules or defined at the top level." In section 2.4, the word "External" should be dropped from the sentence. Wolfgang -- Wolfgang Lux Phone: +49-251-83-38263 Institut fuer Wirtschaftinformatik FAX: +49-251-83-38259 Universitaet Muenster Email: wlux(a)uni-muenster.de

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Re: beginner's questions - fix f
by Marcin 'Qrczak' Kowalczyk 24 Jul '01

24 Jul '01

24 Jul 2001 12:04:33 -0000, Lars Henrik Mathiesen <thorinn(a)diku.dk> pisze: > Now, anything that's defined as "x = f x" is called a fixpoint of f. > It's possible to prove that there's only one (when f is a Haskell > function, at least) so we can talk of 'the' fixpoint. Not necessarily only one, e.g. any value is a fixpoint of identity function. But there is one *least* fixpoint wrt. definedness, and it can be effectively found. If the function is strict, the least fixpoint is not very interesting because it's bottom, a value representing nontermination or error. If the function is not strict, bottom is not its fixpoint, so the fixpoint obtained by "x = f x" or "fix f" is more interesting. BTW, a better definition than fix f = f (fix f) is fix f = let x = f x in x because it increases sharing, avoiding recomputation. > fix f = f (fix f) > > This looks like a recursive definition again, but if you want a system > without explicit recursion you have to disallow this as a function. In > such a system, fix is a builtin operator, You can define fix without recursion in a typeless lambda calculus: fix f = (\x -> f (x x)) (\x -> f (x x)) and this can even be stretched to fit Haskell's type system by smart use of algebraic types. > Note that operationally, this Haskell version of the fixpoint operator > is only sort-of equivalent to a Haskell recursive definition (which is > defined in terms of a 'real' fixpoint). That's even clearer with data > structures; compare > > zeroes = 0 :: zeroes > > and > > zer_step l = 0 :: l > zeroes2 = fix zer_step > > zeroes is a circular list with one element, while zeroes2 is an > infinite list with all zero elements. This is the difference between two definitions of fix above. -- __("< Marcin Kowalczyk * qrczak(a)knm.org.pl http://qrczak.ids.net.pl/ \__/ ^^ SYGNATURA ZASTÊPCZA QRCZAK

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RE: Haskell 98 Report possible errors, part one
by Simon Peyton-Jones 24 Jul '01

24 Jul '01

| 2.2. Identifiers can use small and large Unicode letters. | What about caseless scripts where letters are neither small | nor large? The description of module Char says: "For the | purposes of Haskell, any alphabetic character which is not | lower case is treated as upper case (Unicode actually has | three cases: upper, lower and title)". This suggests that the | only anomaly is that titlecase letters are considered | uppercase. But what is actually specified is that caseless | scripts can be used to write constructor names, but not to | variable names. I don't know how to solve this. I am woefully ignorant of Unicode, and I have no idea what to do about this one. I therefore propose to do nothing on the grounds that I might easily make matters worse. Simon

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