June 2002 - Haskell - Haskell.org

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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Research Job: Compositional Analysis & Reasoning for Software Systems @ Heriot-Watt U., Scotland, UK
by Joe Wells 30 Jun '02

30 Jun '02

Research Position Useful Logics, Types, Rewriting, and their Automation (ULTRA) Group Computer Science Department School of Mathematical and Computer Sciences Heriot-Watt University Edinburgh, Scotland, UK The HTML version of this job posting can be found at: http://www.cee.hw.ac.uk/~jbw/position-ad.html Description of the Position A research position is available working on modular reasoning and compositional analysis for software at Heriot-Watt University working with Joe Wells. The position is in the ULTRA (Useful Logics, Types, Rewriting, and their Automation) group in the Computer Science Department in the School of Mathematical and Computer Sciences (formerly the Department of Computing and Electrical Engineering) at Heriot-Watt University in Edinburgh, the capital of Scotland. The position involves close collaboration with both the EC-funded DART (Dynamic Assembly, Reconfiguration, and Type-checking) project (members: Genova Univ., Heriot-Watt Univ., Imperial Coll., and Torino Univ.) and the EC, EPSRC, NATO, and NSF-funded Church Project (members: Boston Coll., Boston Univ., Harvard Univ., Heriot-Watt Univ., Wellesley Coll., etc.). It will be helpful if the researcher is competent in 1 or more of the following knowledge areas which are likely to be used in the project. * Formal calculi for reasoning about the meaning of computer systems (including computer programs), especially those with aspects of (a) modules, linking, and loading, (b) concurrency, (c) mobility, (d) staged compilation, (e) objects, (f) resource usage, etc. * Analysis of systems represented in formal calculi. * Constraint solving and unification. * Type systems, especially those with intersection and union types. * Programming languages used for any of the above. The duration of the position is from 6 months to 2.5 years, depending on the circumstances of the researcher, with extensions possible depending on salary, experience, performance, and funding. Applications to spend a shorter period (e.g., the sabbatical leave of an established academic) will be considered. The initial salary will be commensurate with qualifications and experience in the range from 19681 GBP to 26491 GBP per year. The position is available immediately, with the ideal start date being 2002-09-01. It is preferred that before starting the researcher will have completed a Ph.D. in a relevant discipline within Computer Science. Very good Ph.D. students who want to spend a year of their studies this way will be considered. Applicants from outside the European Economic Area (EEA) will be considered. The researcher will probably collaborate on 1 or more of the following activities. The specific activities will be matched to the strengths of the researcher. * Designing new type systems for compositional (modular) analysis of systems that may involve one or more aspects of concurrency, mobility, modularity, objects, run-time code generation, etc. * Designing analysis algorithms for the new type systems. * Designing theories (e.g., "calculi") for reasoning about the meaning of dynamic software assembly, i.e., doing in a non-traditional order one or more of type checking, code generation, linking, loading, etc. * Making software systems incorporating the new type systems, algorithms, and calculi. * Writing scientific reports on the work done. Contact Information Informal inquiries should be directed to Joe Wells at: web: http://www.cee.hw.ac.uk/~jbw/ e-mail: jbw(a)cee.hw.ac.uk fax: +44 131 449 3834 Formal applications should be directed to the Heriot-Watt Personnel Office at: web: http://www.hw.ac.uk/personnel/ e-mail: personnel(a)hw.ac.uk voice mail: +44 131 451 3475 fax: +44 131 451 3475 minicom: +44 131 451 8212 post: The Personnel Office Lord Balerno Building Heriot-Watt University EDINBURGH EH14 4AS GREAT BRITAIN Applying for the Position Please use the reference code 106/02/L to help prevent your application from getting mixed up. Please convert Microsoft Word documents to a public, standard, and non-proprietary format. The best format is PDF, because some of our staff will encounter difficulties with HTML or PostScript. To formally apply for this position, please do as many as possible of the items in the following list by 2002-07-24. The first 2 are absolutely necessary and the 4th is quite important. * Cause 3 reference letters to be sent. (If someone in the Heriot-Watt Personnel Office tells you the letters are not needed yet, please ignore them, because we want to see the letters before choosing who to interview.) * Send the following yourself: + your complete curriculum vitae, and + contact details for the people writing your reference letters. * Optionally, also send either of the following: + a brief statement about why your research accomplishments and interests are a good match for the position, and + up to 3 relevant publications of yours. * Get the Heriot-Watt Personnel Office to send you an "application pack". (This contains an application form, an equal opportunities monitoring form, information for applicants with disabilities, and some additional information about Heriot-Watt and the position.) Fill out and return the application form and optionally the equal opportunities monitoring form. If your curriculum vitae is well constructed, then some information requested will be redundant, so just write "see c.v." in those blanks, but return the form anyway. * It is helpful to inform Joe Wells that you are applying so that he knows to ask our personnel office for your application materials. * Anyone who might need a work permit if hired (usually someone who is not a citizen of an EEA country) should also do the following. In addition to possibly being e-mailed or faxed, each letter of reference should also be sent by post on official-looking headed stationery paper and should include details on your whereabouts over the last two years. A work permit application also needs copies of any degree certificates, so it is a good idea to send those also at the same time as you send the rest of your application. For your information, the standard solicitation for a reference letter by Heriot-Watt Personnel Office asks the letter writer for details of: * the capacity in which they know the candidate, * the candidate's skills, abilities and performance in relation to the post applied for, * the candidate's employment record including details of the candidate's role and service dates, * their view of the candidate's suitability for the post as a whole, in light of the attached details and their knowledge of the candidate's experience and abilities, * any further relevant information which would assist us in making an appointment.

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Re: arrows
by Ashley Yakeley 29 Jun '02

29 Jun '02

At 2002-06-07 06:18, Wolfgang Jeltsch wrote: >Of course! My Parser type. What's its implementation? -- Ashley Yakeley, Seattle WA

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Re: Haskell digest, Vol 1 #656 - 3 msgs
by Zdenek Dvorak 29 Jun '02

29 Jun '02

Hello. >Can I write dependencies like this: > > > class C x y z | x -> (y, z) > > class D x y z | (x, y) -> z > >in hugs? in ghc? The ghc doc refers to >Mark Jones: "Type Classes with Functional Dependencies", >http://www.cse.ogi.edu/~mpj/pubs/fundeps.html >where this seems to be allowed (section 4, page 9) > >Especially, I would need class D above. class C can be rewritten to >class C x y z | x -> y, x -> z concerning class D, I used (in GHC) >class D x y z | x y -> z and it seemed to do what I wanted. I guess >class C x y z | x -> y z would work too. Zdenek Dvorak _________________________________________________________________ MSN Photos is the easiest way to share and print your photos: http://photos.msn.com/support/worldwide.aspx

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functional dependencies
by Johannes Waldmann 29 Jun '02

29 Jun '02

Can I write dependencies like this: > class C x y z | x -> (y, z) > class D x y z | (x, y) -> z in hugs? in ghc? The ghc doc refers to Mark Jones: "Type Classes with Functional Dependencies", http://www.cse.ogi.edu/~mpj/pubs/fundeps.html where this seems to be allowed (section 4, page 9) Especially, I would need class D above. -- -- Johannes Waldmann ---- http://www.informatik.uni-leipzig.de/~joe/ -- -- joe(a)informatik.uni-leipzig.de -- phone/fax (+49) 341 9732 204/252 --

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Spam
by John Peterson 29 Jun '02

29 Jun '02

I've decided to see how painful it is to restrict the list to member only posting. This should definitely stop the spam flood - we'll see if it works out OK. Complain to me if there are any problems. I've also cut the max message size down to 20K before moderator approval is required. This should keep the viruses away. John

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Greencard-Canada-Aupair
by Greencard 28 Jun '02

28 Jun '02

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[ADMINISTRIVIA]: Change list submission policy please?
by Joe English 28 Jun '02

28 Jun '02

The haskell mailing list is getting an increasing amount of spam, viruses, and virus warnings. Would it be possible to change the list policy to only allow submissions from subscribed members? Please? --Joe English jenglish(a)flightlab.com

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ESSLLI Student Session - Call for Participation
by Malvina Nissim 28 Jun '02

28 Jun '02

[apologies for cross-posting] ESSLLI-2002 STUDENT SESSION CALL FOR PARTICIPATION August 5-16 2002, Trento, Italy www.iccs.informatics.ed.ac.uk/~malvi/esslli02 The 7th ESSLLI Student Session will be held in Trento, Italy, as part of the 14th European Summer School in Logic, Language, and Information, from August 5-16. The programme is available at http://www.iccs.informatics.ed.ac.uk/~malvi/esslli02/programme/ All those interested are invited to register for the Summer School at the ESSLLI main site: http://www.esslli2002.it For further information: Malvina Nissim (chair) malvi(a)cogsci.ed.ac.uk 0044 131 650 4630 (tel) 0044 131 650 6626 (fax)

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