November 2003 - Haskell

Re: time since the epoch
by Stefan Karrmann 13 Nov '03

13 Nov '03

Hi, a while ago time calculation was subject on this list. Now, I have a time library based on the TAI (international atomic time) time scale. >Peter Thiemann (Thu, Feb 06, 2003 at 12:40:14PM -0800): >> John's code illustrates TimeDiff's deficiencies perfectly: >> >> There is also a more fundamental problem with the TimeDiff data >> type. While seconds, minutes, hours, and days are clearly specified >> amounts of time, the duration of a month or a year may vary depending >> on the reference point where the time difference is applied. > newtype TimeDiff = TimeDiff Rational > deriving (Eq, Ord) >> Hmm, this is underspecified! >> As another poster said, (pointing out http://cr.yp.to/libtai, but it >> is better to look at http://cr.yp.to/time.html, which has a discussion >> on UTC vs TAI vs UNIX time) the official source of time is TAI, so it >> is best to base a time library >> *on the number of TAI seconds since a reference date* >> (which is btw what the libtai is all about). >> For compatibility with UNIX time, "Arthur David Olson's popular time >> library uses an epoch of 1970-01-01 00:00:10 TAI" >> [http://cr.yp.to/proto/utctai.html] >> So this mostly means that you need to set your system clock correctly:-) Sincerly, -- Stefan Karrmann

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ANNOUNCE: Release of Vital, an interactive visual programming environment for Haskell
by Keith Hanna 13 Nov '03

13 Nov '03

Dear Haskellers, I am pleased to announce the release of Vital, an interactive visual programming environment based on Haskell. Vital provides the user with a workspace within which Haskell expressions and declarations can be located and their values displayed textually or graphically. The display is 'live' in the sense that the effects of graphical Copy and Paste operations carried out displayed values are automatically reflected in the Haskell source code. The long-term aim of the Vital project is to make Haskell available in a form that supports the open-ended, incremental style of program development that end users (engineers, scientists, analysts, etc.) often prefer. It may also be useful in teaching Haskell. This release of the Vital system is available from: http://www.cs.kent.ac.uk/projects/vital/ The site includes screenshots and a downloadable implementation with demo programs. If you happen to have Java installed on your machine, you can (in principle!) run the Vital interpreter and these demo programs simply by clicking on this link http://www.cs.kent.ac.uk/projects/vital/download/start.jnlp Enjoy! Keith Hanna

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haskell httpd
by S. Alexander Jacobson 13 Nov '03

13 Nov '03

I've been working on a new project and evaluating the Twisted python framework which relies on asynchIO rather than threading to achieve speed. The resulting idioms feel like they would be much more elegant in Haskell. So my question at this point is: Is there a reasonably efficient Haskell httpd implementation around that uses poll/select? -Alex- ___________________________________________________________________ S. Alexander Jacobson Check out my new blog!!! 1-212-787-1914 voice http://alexjacobson.com

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set representation question
by Hal Daume III 13 Nov '03

13 Nov '03

this is somewhat off topic, but i'll add "does anyone have a haskell implementation of..." to the beginning to make it more on topic :). anyway there are a lot of smart people here... i'm looking for a representation for a set of natural numbers. right now, my representation is sorted array, which works well. *all* i care about is being able to quickly calculate the size of the intersection of two sets. these sets are, in general, very sparse, which means that the intersections tend to be small. for example, i might have two sets reprsented by the arrays: {0,1,10,346,398,1039,3289,3853,9811,89231,50913} {0,3,98,183,398,1038,5319,7642,9811,13893,93123} and all i need to be able to do is respond with "3" very very quickly. using sorted arrays, this takes O(n+m) time (where n and m are the sizes of the arrays). i'm willing to pay some up front cost for creating a data structure that could do this more quickly (i.e., in logarithmic time). is such a thing possible? "does anyone have a haskell implementation of" such a thing? :P thanks! - hal -- Hal Daume III | hdaume(a)isi.edu "Arrest this man, he talks in maths." | www.isi.edu/~hdaume

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Postdoc and PhD positions at CWI, Amsterdam
by Farhad.Arbab＠cwi.nl 12 Nov '03

12 Nov '03

Position Description ==================== The Coordination and Component Based Software group in SEN3 at CWI has two open positions for: (1) a postdoc for a period of four years, and (2) a PhD student (OIO) for four years. Both positions are within the project number 600.065.120.03N02 Compositional Construction of Component Connectors (C-Quattro), recently funded by the NWO (the Dutch government's funding agency for academic scientific research), with F. Arbab (CWI) and J. Rutten (CWI and VUA) as Principal Investigators. The project C-Quattro is in fact a collaboration of SEN3 at CWI with the Section Theoretical Computer Science at the Free University of Amsterdam (VUA). The postdoc will be employed by CWI; the PhD student will be employed by the VUA but will spend part of his or her time at CWI. The main goal of the C-Quattro project is to develop an operational semantics based on a calculus of component connectors, as the foundation for further development of practical tools and programming environments for the actual deployment of Reo. Reo is a recently introduced channel-based coordination model wherein complex coordinators, called connectors, are compositionally built out of simpler ones. Reo is intended as a ``glue language'' for construction of connectors that orchestrate component instances in a component-based system. The emphasis in Reo is on connectors and their composition only, not on the components that are being connected. The activities under C-Quattro involve both system oriented and theoretical work. On the systems side, we develop tools supporting visual connector programming, as well as the automation of equivalence proofs, e.g., for optimization. On the theoretical side, the semantic modeling is based on the coalgebraic methodology, and coinduction, with its potential for automation, will be the main reasoning principle. The candidate for the postdoc position is expected to have a strong background in Software Engineering, maturity in formal methods and their practical applications, familiarity with component-based software, concurrency, and coordination. Teamwork and leadership, as well as the ability to work effectively with academic colleagues and PhD students, are all important qualifications for this position. The candidate for the PhD position should have a master degree in computer science or mathematics, with a clear interest in questions from theoretical computer science. Ideally, the candidate has a background both in mathematical disciplines such as algebra, analysis and discrete mathematics, and in such elements of theoretical computer science as automata theory and semantics. The Theme SEN3 (http://www.cwi.nl/sen3) at CWI is a dynamic group of internationally recognized researchers who work on Coordination Models and Languages and Component-Based Software Composition. The activity in SEN3 is a productive, healthy mix of theoretical, foundational, and experimental work in Computer Science, ranging in a spectrum covering mathematical foundations of models of computation, formal methods and semantics, implementation of advanced research software systems, as well as their real-life applications. General information =================== CWI is an internationally renowned research institute in mathematics and computer science, located in Amsterdam, The Netherlands. The focus is on fundamental research problems, derived from societal needs. Research is carried out in 15 research themes. More information about these themes can be found on the website www.cwi.nl where you can also take a look at our Annual Report. A substantial part of this research is carried out in the framework of national or international programs. CWI maintains excellent relations with industry and the academic world, at home as well as abroad. After their research careers at CWI, an increasing number of young staff members find employment in these sectors, for example in spin-off companies that are based on research results from CWI. Of course, library and computing facilities are first-rate. CWI's non-scientific services to its personnel include career planning, training & courses, assistance in finding housing, and tailor-made solutions to problems that may occasionally arise. Terms of employment =================== The salary is in accordance with the "CAO-onderzoekinstellingen" and is commensurate with experience. For instance, the postdoc base salary for a fresh PhD with no additional experience in scale 10 is around 2800 Euros/month, and for an experienced PhD in scale 12 it is around 4500 Euros/month. The current starting salary for a first year PhD student is around 1500 Euros/month with an incremental raise for each subsequent year. (Note: a considerable increase in the salaries of all PhD students is currently under negotiation). Besides the salary, CWI offers very attractive and flexible terms of employment, like a collective health insurance, pension-fund, etc. Application =========== For more information on these vacancies you can contact either of the PIs: F. Arbab, telephone +31-20-5924056, e-mail Farhad.Arbab(a)cwi.nl J. Rutten, telephone +31-20-592-4116, email Jan.Rutten(a)cwi.nl Official applications, together with curriculum vitae, letters of references, and lists of publications must be sent to Mrs. J. Koster, head of Personnel Department, P.O. box 94079, 1090 GB Amsterdam, The Netherlands.

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Network.CGI, (embedded) graphics
by Johannes Waldmann 12 Nov '03

12 Nov '03

I'd like to embed pictures (.png) in a CGI-generated output. This doesn't seem to fit directly into ghc's Network.CGI setting. (Not entirely ghc's fault, of course :-) By the html definition, including a picture seems to require an indirection. But I don't want to expose a static address, so I am thinking of something like <IMG SRC="Get.cgi?identifier"> But this can't be done with ghc's CGI library (it assumes that text/html is output). So the library should export some more of its functions. (Yes, I can easily patch this in a copy of the source code http://cvs.haskell.org/cgi-bin/cvsweb.cgi/~checkout~/fptools/libraries/netw… Ideally, I am thinking of class Picture a where picture :: a -> IO [ Byte ] and I want to call Get.cgi with argument `urlencoded (show a)'. The underlying program should then emit the byte stream (from scratch, or from a cache). But then it would need to do `read (urldecode input)' and this would require to transmit a representation of the type as well. Any ideas? BTW, my application would be drawings of finite automata (which can be nicely done by dot/neato), in order to make this a bit more friendly to the eye: http://elearning.htwk-leipzig.de/~autotool/cgi-bin/Face.cgi (test account: matrikel 318, passwort guest, then check problem Determine-D-Quiz) -- -- Johannes Waldmann, Tel/Fax: (0341) 3076 6479 / 6480 -- ------ http://www.imn.htwk-leipzig.de/~waldmann/ ---------

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RE: Question about how GUM works
by Simon Peyton-Jones 12 Nov '03

12 Nov '03

I think you'll maximise your chances by sending mail about GUM and Glasgow Parallel Haskell to the GpH mailing list http://www.macs.hw.ac.uk/~dsg/gph/ Simon | -----Original Message----- | From: haskell-bounces(a)haskell.org [mailto:haskell-bounces@haskell.org] On Behalf Of Yang, Qing | Sent: 12 November 2003 08:37 | To: haskell(a)haskell.org | Subject: Question about how GUM works | | Hi All, | | I have a question about GUM - the runtime system for Parallel Haskell. | There are below words in the paper addressing GUM architecture: | "The first action of GUM program is to create a PVM manager task, whose | job is to control startup and termination. The manager spawns the | required number of logical PEs as PVM tasks, which PVM maps to the | available processors." | | So my question is how many PEs the PVM mamager task will spawn? The | number is accordant with the processor number or determined by some | other things? And will the number of PEs be changed during the execution | of the program or not? | | Thanks, | | Qing Yang | qing.yang(a)intel.com | | _______________________________________________ | Haskell mailing list | Haskell(a)haskell.org | http://www.haskell.org/mailman/listinfo/haskell

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Question about how GUM works
by Yang, Qing 12 Nov '03

12 Nov '03

Hi All, I have a question about GUM - the runtime system for Parallel Haskell. There are below words in the paper addressing GUM architecture: "The first action of GUM program is to create a PVM manager task, whose job is to control startup and termination. The manager spawns the required number of logical PEs as PVM tasks, which PVM maps to the available processors." So my question is how many PEs the PVM mamager task will spawn? The number is accordant with the processor number or determined by some other things? And will the number of PEs be changed during the execution of the program or not? Thanks, Qing Yang qing.yang(a)intel.com

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RE: ANNOUNCE: HC&A Report (5th edition, November 2003)
by Simon Peyton-Jones 12 Nov '03

12 Nov '03

I think we all owe Claus a big "Thank You" for initiating and running the Haskell Communities Report. It's done a great job of telling us what's going on. Thank you Claus! I hope someone else will step in for May 2004... Simon | -----Original Message----- | From: haskell-bounces(a)haskell.org [mailto:haskell-bounces@haskell.org] On Behalf Of C.Reinke | Sent: 11 November 2003 21:16 | To: haskell(a)haskell.org | Subject: ANNOUNCE: HC&A Report (5th edition, November 2003) | | | On behalf of the many contributors, I am happy to announce that the | | ----------------------------------------- | Haskell Communities and Activities Report | (5th edition, November 2003) | | http://www.haskell.org/communities/ | ----------------------------------------- | | is now available from the Haskell Communities home

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ANNOUNCE: HC&A Report (5th edition, November 2003)
by C.Reinke 11 Nov '03

11 Nov '03

On behalf of the many contributors, I am happy to announce that the ----------------------------------------- Haskell Communities and Activities Report (5th edition, November 2003) http://www.haskell.org/communities/ ----------------------------------------- is now available from the Haskell Communities home page in several formats: in PDF (for those who haven't noticed: that format is not just for printing, but also for online viewing, with working links and table of contents) or, for those who have problems with the PDF, in HTML (using John's secret weapon yet again) and Postscript. A big thanks here to everyone who contributed, be it by making sure that there are so many interesting activities to report on, or by sending in descriptions to make sure that we can read about these activities! I hope you will find it as interesting to read as we did. For those of you who haven't heard of these reports before (and have filtered all previous calls into the spam-folder..), the first edition of the HC&A Report was released in November 2001, with the goal of helping to improve the communication between the increasingly diverse groups, projects, and individuals working on, with or inspired by Haskell. The idea of these reports is simple: Every six months, a call goes out to all of you on the Haskell mailing list to contribute brief summaries of your own area of work. Many of you respond (eagerly, unprompted, and well in time for the deadline;-) to the call. The editor then collects all these into a single report and feeds it back to this very mailing list. 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 into your diary now! --------------------------------------- End of April 2004: target deadline for contributions to the May 2004 edition of the HC&A Report --------------------------------------- It has become clear that many Haskellers who work on interesting projects no longer have the time to follow the Haskell mailing list closely and may thus miss the calls for contribution. If you are a member, user or friend of such projects, please point them to the current edition, and invite them to "register" with me for a simple email-reminder in the middle of April (and no, you can't register anyone else:). Of course, they'll still have to act on that reminder, but perhaps we can extend our reach this way.. Enjoy (and communicate;-)! Claus Reinke -- Computing Laboratory University of Kent http://www.cs.kent.ac.uk/~cr3/ PS. Please note the preface: as announced at this year's Haskell workshop, there'll be a change of editor after this edition. Andres Loeh has kindly offered to take over starting with the November 2004 edition, but we are still looking for someone to take on the May 2004 edition. If you're interested, please get in touch with me! _______________________________________________ Haskell mailing list Haskell(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell

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