November 2001 - Haskell

tuple component functions
by trb＠eastpac.com.au 03 Jan '03

03 Jan '03

S.D.Mechveliani writes: > As Haskell has the standard functions fst, snd to decompose (a,b), > maybe, it worths to provide also > tuple31, tuple31, tuple31, > ... > tuple51, tuple52, tuple53, tuple54, tuple55 > > for the tuples of n = 3,4,5 ? I've found some of these useful, except I named them differently: > fst3 :: (a,b,c) -> a > fst3 (x,_,_) = x > snd3 :: (a,b,c) -> b > snd3 (_,x,_) = x > thd3 :: (a,b,c) -> c > thd3 (_,_,x) = x .... never got around to quadruples etc. I also defined (some of these may be untested): > tripl :: a -> (a,a,a) > tripl x = (x,x,x) > curry3 :: ((a, b, c) -> d) -> a -> b -> c -> d > curry3 f x y z = f (x, y, z) > uncurry3 :: (a -> b -> c -> d) -> ((a, b, c) -> d) > uncurry3 f t = f (fst3 t) (snd3 t) (thd3 t) > applyTriple :: (a -> b, a -> c, a -> d) -> a -> (b,c,d) > applyTriple (f,g,h) x = (f x, g x, h x) > cross3 :: (a -> b, c -> d, e -> f) -> (a,c,e) -> (b,d,f) > cross3 (f,g,h) (x,y,z) = (f x, g y, h z) > mapTriple :: (a -> b) -> (a, a, a) -> (b, b, b) > mapTriple = cross3 . tripl > applyFst3 :: (a -> b) -> (a, c, d) -> (b, c, d) > applyFst3 f = applyTriple (f . fst3, snd3, thd3) > applySnd3 :: (a -> b) -> (c, a, d) -> (c, b, d) > applySnd3 f = applyTriple (fst3, f . snd3, thd3) > applyThd3 :: (a -> b) -> (c, d, a) -> (c, d, b) > applyThd3 f = applyTriple (fst3, snd3, f . thd3) > applyArgs3 :: (a -> b) -> (c -> d) -> (e -> f) -> (b -> d -> f -> g) -> (a -> c -> e -> g) > applyArgs3 af1 af2 af3 f = \x y z -> f (af1 x) (af2 y) (af3 z) > rotl :: (a -> b -> c -> d) -> (b -> c -> a -> d) > rotl f y z x = f x y z > rotr :: (a -> b -> c -> d) -> (c -> a -> b -> d) > rotr f z x y = f x y z > rotl4 :: (a -> b -> c -> d -> e) -> (b -> c -> d -> a -> e) > rotl4 f y z t x = f x y z t > rotr4 :: (a -> b -> c -> d -> e) -> (d -> a -> b -> c -> e) > rotr4 f t x y z = f x y z t Some more combinators (only for pairs so far): > twin :: a -> (a,a) > twin x = (x,x) > swap :: (a,b) -> (b,a) > swap (x,y) = (y,x) -- apply a pair of functions to one argument > applyPair :: (a -> b, a -> c) -> a -> (b, c) > applyPair (f, g) x = (f x, g x) -- apply a pair of functions to a pair > cross :: (a -> b, c -> d) -> (a, c) -> (b, d) > cross (f, g) = applyPair (f . fst, g . snd) -- compose a pair of functions onto one function > dotPair :: (a -> b, a -> c) -> (d -> a) -> (d -> b, d -> c) > dotPair (f, g) h = (f . h, g . h) -- compose a pair of functions onto a pair of functions > dotCross :: (a -> b, c -> d) -> (e -> a, f -> c) -> (e -> b, f -> d) > dotCross (f, g) (h, i) = (f . h, g . i) > mapPair :: (a -> b) -> (a, a) -> (b, b) > mapPair = cross . twin > applyFst :: (a -> b) -> (a, c) -> (b, c) > applyFst f = applyPair (f . fst, snd) > applySnd :: (a -> b) -> (c, a) -> (c, b) > applySnd f = applyPair (fst, f . snd) > applyArgs :: (a -> b) -> (c -> d) -> (b -> d -> e) -> (a -> c -> e) > applyArgs af1 af2 f = \x y -> f (af1 x) (af2 y) > betweenFst :: (a -> b -> c) -> (a, d) -> (b, e) -> c > betweenFst = applyArgs fst fst > betweenSnd :: (a -> b -> c) -> (d, a) -> (e, b) -> c > betweenSnd = applyArgs snd snd I find these combinators useful, and probably other people have their own versions - it would be nice to get them standardised, so we all speak the same language. By standardised, I mean a prominent version that will be adopted by users, not necessarily a committee process. Tim

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ICFP programming contest
by trb＠eastpac.com.au 03 Jan '03

03 Jan '03

Michael Hobbs writes: > Just took a look at the results for the ICFP contest. Am I correct in > assuming that "LA" stands for Lennart Augustsson and that "Si^3" stands > for Simon Marlow, Simon Peyton-Jones, Sigbjorn Finne? Is there a URL for the results ? Tim

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Lazy Sound File IO
by Carl McTague 02 Dec '01

02 Dec '01

Please let me refine my question. Is there a general way to coerce an [Int] or [Double] etc. into a String, so that it may be written out to a binary file with hPutStr? There is toEnum, but this doesn't seem like a real solution, since it only works for Int values <256. Thanks, Carl

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ESSLLI 2002 Student Session
by Malvina Nissim 30 Nov '01

30 Nov '01

!!! Concerns all students in Logic, Linguistics and Computer Science !!! !!! Please circulate and post among students !!! We apologise if you receive this message more than once. ESSLLI-2002 STUDENT SESSION FIRST CALL FOR PAPERS August 5-16 2002, Trento, Italy Deadline: February 25th, 2002 www.iccs.informatics.ed.ac.uk/~malvi/esslli02 We are pleased to announce the Student Session of the 14th European Summer School in Logic, Language and Information (ESSLLI-2002) organised by the Centre for scientific and technological research (ITC-irst) in Trento and by the University of Trento, under the auspices of the European Association for Logic, Language and Information (FoLLI). ESSLLI-2002 will be held in Trento from August 5-16 2002. We invite submission of papers for presentation at the ESSLLI-2002 Student Session and for appearance in the proceedings. PURPOSE: This seventh ESSLLI Student Session will provide, like the other editions, an opportunity for ESSLLI participants who are students to present their own work in progress and get feedback from senior researchers and fellow-students. The ESSLLI Student Session encourages submissions from students at any level, from undergraduates (before completion of the Master Thesis) as well as postgraduates (before completion of the PhD degree). Papers co-authored by non-students will not be accepted. Papers may be accepted for full presentation (30 minutes including 10 minutes of discussion) or for a poster presentation. All the accepted papers will be published in the ESSLLI-2002 Student Session proceedings, which will be made available during the summer school. KLUWER BEST PAPER AWARD: As in previous years, the best paper will be selected by the programme committee and will be offered a prize by Kluwer Academic Publishers to be spent on books. REQUIREMENTS: The Student Session papers should describe original, unpublished work, completed or in progress that demonstrates insight, creativity, and promise. No previously published papers should be submitted. Note that the ESSLLI02 school will be focussed on the three main interdisciplinary areas (Logic & Language, Logic & Computation, and Language & Computation), while the single areas have been dropped. Given the high interest shown over the years, the Student Session will keep two of the single areas, namely Logic and Language, welcoming thus submissions within the following topics: Logic, Language, Logic & Language, Logic & Computation, Language & Computation. FORMAT OF SUBMISSION: Student authors should submit an anonymous full paper headed by the paper title, not to exceed 7 pages of length exclusive of references and send a separate identification page (see below). Note that the length of the final version of the accepted papers will not be allowed to exceed 10 pages. Since reviewing will be blind, the body of the abstract should omit author names and addresses. Furthermore, self-references that reveal the author's identity (e.g., "We previously showed (Smith, 1991)... ") should be avoided. It is possible to use instead references like "Smith (1991) previously showed...". For any submission, a plain ASCII text version of the identification page should be sent separately, using the following format: Title: title of the submission First author: firstname lastname Address: address of the first author ...... Last author: firstname lastname Address: address of the last author Short summary: abstract (5 lines) Subject area (one of): Logic | Language | Logic and Language | Logic and Computation | Language and Computation If necessary, the program committee may reassign papers to a more appropriate subject area. The submission of the extended abstract should be in one of the following formats: PostScript, PDF, RTF, or plain text. But note that, in case of acceptance, the final version of the paper has to be submitted in LaTeX format. Please, use A4 size pages, 11pt or 12pt fonts, and standard margins. Submissions outside the specified length and formatting requirements may be subject to rejection without review. The paper and separate identification page must be sent by e-mail to: malvi(a)cogsci.ed.ac.uk by FEBRUARY 25th 2002 ESSLLI-2002 INFORMATION: In order to present a paper at ESSLLI-2002 Student Session, at least one student author of each accepted paper has to register as a participant at ESSLLI-2002. The authors of accepted papers will be eligible for reduced registration fees. For all information concerning ESSLLI-2002, please consult the ESSLLI-2002 web site at www.esslli2002.it IMPORTANT DATES: Deadline for submission of abstracts: February 25, 2002. Authors Notifications: April 22, 2002. Final version due: May 20, 2002. ESSLLI-2002 Student Session: August 5-16, 2002. PROGRAMME COMMITTEE: David Ahn, University of Rochester (Language and Computation) Carlos Areces, University of Amsterdam (Logic) Reinhard Blutner, University of Berlin (Language) Kees van Deemter, University of Brighton (Language and Computation) Paul Dekker, University of Amsterdam (Logic and Language) Juergen Dix, University of Manchester (Logic and Computation) Marta Garcia-Matos, University of Helsinki (Logic) Juan Heguiabehere, University of Amsterdam (Logic and Computation) Elsi Kaiser, University of Pennsylvania (Language) Malvina Nissim, University of Edinburgh (Chair) Rick Nouwen, University of Utrecht (Logic and Language) For any specific question concerning ESSLLI-2002 Student Session, please, do not hesitate to contact me: Malvina Nissim ICCS, University of Edinburgh 2 Buccleuch Place, Edinburgh EH8 9LW, UK phone: +44 +(0)131 +650 4630 fax: +44 +(0)131 +650 6626 e-mail: malvi(a)cogsci.ed.ac.uk

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bug in report? empty datatypes
by Hal Daume III 30 Nov '01

30 Nov '01

we can now say: > data T for an empty datatype what about: > data T deriving (Show) -- or Eq, Ord, ... personally I think this should be legal. the actual semantics are irrelevant, as far as I can tell, since you won't ever have something of type T other than _|_ and so you could simply define the derived instance of equals to be something like: > instance Eq T where { (==) = undefined } though > instance Eq T where { _ (==) _ = True } seems also to be resonable. this isn't a big deal, but i'd like it fixed. ghc panics when you try to derive something. hugs gives you a syntax error and i can't get nhc to accept empty datatypes at all... - hal -- Hal Daume III "Computer science is no more about computers | hdaume(a)isi.edu than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume

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Haskell 98 prelude bug report
by Olaf Chitil 30 Nov '01

30 Nov '01

The prelude contains instance Bounded Char where minBound = '\0' maxBound = '\xffff' I didn't follow all the discussion about unicode, but the maxBound seems to be wrong. It probably should be '\x10ffff'. The exact specification could also be avoided by defining maxBound = primUnicodeMaxBound where primUnicodeMaxBound is imported from UnicodePrims. -- OLAF CHITIL, Dept. of Computer Science, University of York, York YO10 5DD, UK. URL: http://www.cs.york.ac.uk/~olaf/ Tel: +44 1904 434756; Fax: +44 1904 432767

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��Цʱ�� 12-3
by vcomic＠speed.sender.com 30 Nov '01

30 Nov '01

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RE: Confused about Random
by Simon Peyton-Jones 30 Nov '01

30 Nov '01

Yes, the implementation of instance Random Int in GHC's library pre-dates the existence of the genRange class operation for RandomGen. GHC's implementation of the instance behaves extremely badly when given a random generator with only two values (as in your example). I would love someone to send me a better implementation of the Random library. Preferably someone who understands the pitfalls. Simon | -----Original Message----- | From: Ian Lynagh [mailto:igloo@earth.li] | Sent: 29 November 2001 15:32 | To: haskell(a)haskell.org | Subject: Confused about Random | | | | With the following module: | | module Main where | | import Random | | data Foo = Foo StdGen | | main :: IO() | main = do let rs = randoms (Foo (mkStdGen 39)) :: [Int] | rRs = randomRs (0,9) (Foo (mkStdGen 39)) :: [Int] | putStrLn $ show $ take 100 rs | putStrLn $ show $ take 100 rRs | | instance RandomGen Foo where | genRange _ = (0, 1) | next (Foo g) = (val `mod` 2, Foo g') | where (val, g') = random g | split _ = error "Not implemented" | | ghc gives me | | [-2147476078,7482,-2147476078,-2147476078,-2147476079,-2147476 | 078,7483,7482,7482,-2147476079,-2147476078,-2147476079,-214747 | 6079,7482,-2147476078,-2147476078,-2147476078,-2147476079,7482 | ,7483,7482,7483,7482,-2147476078,-2147476078,-2147476078,7483, | -2147476079,7482,-2147476078,-2147476079,-2147476078,7483,-214 | 7476079,7483,7482,-2147476079,7483,7482,7483,-2147476078,-2147 | 476079,-2147476079,7482,-2147476078,7482,-2147476079,-21474760 | 79,7482,-2147476078,7483,7483,-2147476079,-2147476078,7483,748 | 3,-2147476078,-2147476079,-2147476078,-2147476079,-2147476078, | 7483,7483,7482,7482,7483,-2147476078,-2147476079,-2147476079,7 | 482,7483,-2147476078,-2147476079,-2147476079,-2147476078,7482, | 7483,-2147476079,7482,7482,7482,7483,-2147476079,-2147476079,- | 2147476078,7482,7482,7482,7482,-2147476079,7482,7482,-21474760 | 79,7483,-2147476078,7482,7483,-2147476079,-2147476079,7482] | [1,2,2,1,1,2,1,2,1,1,1,2,2,2,2,1,2,1,1,1,1,2,1,1,1,1,2,1,1,2,1 | ,2,1,2,1,1,2,1,2,2,2,1,2,2,2,1,1,2,1,2,1,2,2,2,1,1,2,1,1,2,1,1 | ,1,2,2,2,1,1,2,2,2,1,1,1,2,2,2,1,2,2,1,2,1,1,1,1,2,1,1,2,2,1,1 | ,1,1,1,2,1,1,2] | | The first list doesn't seem to cover the whole spectrum and I | was expecting the second list to be composed over 0s through | 9s. Is my understanding wrong? | | nhc complains | Context for Random.Random needed in left hand pattern at | 17:11. and hugs doesn't seem to know genRange exists. With it | commented out it returns the same as ghc. | | | Thanks | Ian | | | _______________________________________________ | Haskell mailing list | Haskell(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell |

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TCS 2002 - New submission date: December 20, 2001
by Michel Barbeau 29 Nov '01

29 Nov '01

----------------------------------------------------------------- CALL FOR PAPERS ----------------------------------------------------------------- 2nd IFIP International Conference on THEORETICAL COMPUTER SCIENCE (TCS 2002) Montreal, August 25-30, 2002 ----------------------------------------------------------------- co-sponsored by EATCS and ACM SIGACT ----------------------------------------------------------------- The program of of the conference will be composed of two tracks: Track 1 - Algorithms, Complexity and Models of Computation Track 2 - Logic, Semantics, Specification and Verification. ----------------------------------------------------------------- Important Dates: December 20, 2001: Submissions (EXTENDED) March 20, 2002: Notifications ----------------------------------------------------------------- Conference Chair ---------------- Nicola Santoro, Carleton University (santoro(a)scs.carleton.ca) Conference Co-Chairs ---------------------- Track (1) Ricardo Baeza-Yates, University of Chile (rbaeza(a)dcc.uchile.cl) Track (2) Ugo Montanari, University of Pisa, Italy (ugo(a)di.unipi.it) Program Committee ----------------- Track (1) Eric Allender (allender(a)aramis.rutgers.edu) JosÈ Balcazar (balqui(a)lsi.upc.es) Andrej Brodnik (Andrej.Brodnik(a)IMFM.Uni-Lj.SI) Volker Diekert (diekert(a)informatik.uni-stuttgart.de) David Fernandez-Baca (fernande(a)cs.iastate.edu) Kazuo Iwama (iwama(a)i.kyoto-u.ac.jp) John D. Kececioglu (kece(a)CS.Arizona.EDU) Jan van Leeuwen (jan(a)cs.uu.nl) Xuemin Lin (lxue(a)cse.unsw.EDU.AU) Alberto Marchetti Spaccamela (alberto(a)dis.uniroma1.it) David Peleg (peleg(a)wisdom.weizmann.ac.il) Prabhakar Raghavan (pragh(a)verity.com) Venkatesh Raman (vraman(a)imsc.ernet.in) Siang Song (song(a)ime.usp.br) Paul Spirakis (spirakis(a)cti.gr) Luca Trevisan (luca(a)eecs.berkeley.edu) Brigitte VallËe (Brigitte.Vallee(a)info.unicaen.fr) Alfredo Viola (viola(a)fing.edu.uy) Manfred Warmuth (manfred(a)cse.ucsc.edu) Sue Whitesides (sue(a)cs.mcgill.ca) Peter Widmayer (widmayer(a)inf.ethz.ch) Jiri Wiederman (wieder(a)uivt.cas.cz) Track (2) Gabriel Baum (gbaum(a)info.unlp.edu.ar) Luca Cardelli (luca(a)microsoft.com) Frank DeBoer (frankb(a)cs.ruu.nl) Ursula Goltz (u.goltz(a)tu-bs.de) Roberto Gorrieri (gorrieri(a)cs.unibo.it) Jieh Hsiang (hsiang(a)csie.ntu.edu.tw) Takayasu Ito (ito(a)ito.ecei.tohoku.ac.jp) Alexander Letichevsky (letichev(a)carrier.kiev.ua) Jean-Jacques Levy (Jean-Jacques.Levy(a)inria.fr) Huimin Lin (lhm(a)ox.ios.ac.cn) Kim Marriott (marriott(a)csse.monash.edu.au) Narciso Marti-Oliet (narciso(a)eucmos.sim.ucm.es) John Mitchell (mitchell(a)cs.stanford.edu) Luis Monteiro (lm(a)fct.unl.pt) Peter Mosses (pdmosses(a)daimi.aau.dk) Prakash Panangaden (prakash(a)cs.mcgill.ca) Benjamin Pierce (bcpierce(a)cis.upenn.edu) Amir Pnueli (amir(a)wisdom.weizmann.ac.il) Leila Ribeiro (leila(a)inf.ufrgs.br) Gheorghe Stefanescu (gheorghe(a)nus.comp.edu.sg) Andrzej Tarlecki (tarlecki(a)mimuw.edu.pl) P.S. Thiagarajan (pst(a)smi.ernet.in) Organizing Committee -------------------- Michel Barbeau (barbeau(a)scs.carleton.ca) -- Chair Amiya Nayak (nayak(a)nortelnetworks.com) Giuseppe Prencipe (prencipe(a)di.unipi.it) ----------------------------------------------------------------- SPECIAL FOCUS Foundations of IT in the Era of Network and Mobile Computing ------------------------------------------------------- ------------------------------------------------------------------- Original and significant contributions on the special focus and on foundational questions are sought from all areas of theoretical computer science. ------------------------------------------------------------------- Submissions ----------- http://www.scs.carleton.ca/~santoro/TCS2002/indexTCS2002.html Location --------- The conference will be held in Montreal, August 25-30, 2002, as part of the 17th IFIP World Computer Congress (http://www.wcc2002.org)

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Re: Global variables
by Ashley Yakeley 29 Nov '01

29 Nov '01

At 2001-11-29 11:13, Ashley Yakeley wrote: >Lifted monads look something like this: > > data MyAction a = MkMyAction ((consts,vars) -> (vars,a)); > instance Monad MyAction where etc. Whoops, should be data MyAction a = MkMyAction ((consts,vars) -> IO (vars,a)); -- Ashley Yakeley, Seattle WA

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