I/O multiplexing
Hi, I have a question concerning "manual" I/O multiplexing in Haskell, or specifically with GHC. I have written an interface to the C library ADNS, which performs asynchronous DNS queries. Everything is fine and dandy, but now comes the hard part: The function foreign import ccall adns_beforepoll :: State-- ADNS context -> Ptr Pollfd -- space for 'n' Pollfd -> Ptr CInt -- n -> Ptr CInt -- max timeout -> Ptr (Timeval)-- current time -> IO CInt generates an array of file descriptors, suitable for calling poll(2). The function foreign import ccall adns_afterpoll :: State -> Ptr Pollfd -> CInt -> Ptr (Timeval) -> IO CInt scans this array (after poll has been called), performs I/O on all readable/writable sockets, and processes any packets that have been received. Obviously, the library wants me to call poll myself, though. But since poll is not supported by Haskell's run-time system, the call would block _all_ running threads in my process, not just the thread doing the DNS resolving. I have considered the following options to solve this: 1. Run the DNS resolver in a forkOS thread. 2. Declare all imported functions to be thread-safe (what they are) and use forkIO. 3. Call poll(2) without blocking, then conjure some magic to decide when to call it again without busy polling. 4. Register the file descriptors with GHC's internal poll event loop. Option (1) seems to be straight-forward, but I don't want to rely on the non-standard forkOS function unless I really have to. The same goes for (4): This is probably a good solution, but it's not portable among compilers. (3) works fine, but is unsatisfactory because the resolver will have comparably large latency times. (I have been processing DNS queries every, say, second.) So option (2) seems quite attractive compared to the others ... But the question is: Would that even work? Any ideas, thoughts, recommendations? Peter ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Call for papers: Fourth International Workshop on Reduction Strategies in Rewriting and Programming (WRS'04)
=== We apologize for multiple copies of this call for participation === * * * WRS'04 CALL FOR PAPERS * * * http://www-i2.informatik.rwth-aachen.de/WRS04/ The Fourth International Workshop on Reduction Strategies in Rewriting and Programming (WRS'04) will be held on June, 2, 2003, in Aachen, Germany, as a part of the Federated Conference on Rewriting, Deduction, and Programming (RDP'04). IMPORTANT DATES: March 17, 2004 Deadline for electronic submission of papers April 14, 2004 Notification of acceptance of papers May2, 2004 Deadline for final versions of accepted papers June 2, 2004 Workshop TOPICS include, but are not restricted to: * theoretical foundations for the definition and semantic description of reduction strategies * strategies in different frameworks (term rewriting, graph rewriting, infinitary rewriting, lambda calculi, higher order rewriting, conditional rewriting, rewriting with built-ins, narrowing, constraint solving, etc.) and their application in (equational, functional, functional-logic) programming (languages) * properties of reduction strategies / computations under strategies (e.g., completeness, computability, decidability, complexity, optimality, (hyper-)normalization, cofinality, fairness, perpetuality, context-freeness, neededness, laziness, eagerness, strictness) * interrelations, combinations and applications of reduction under different strategies (e.g., evaluation mechanisms in programming languages, equivalence conditions for fundamental properties like termination and confluence, applications in modularity analysis, connections between strategies of different frameworks, etc.) * program analysis and other semantics-based optimization techniques dealing with reduction strategies * rewrite systems / tools / implementations with flexible / programmable strategies as essential concept / ingredient * specification of reduction strategies in (real) languages * tutorials and systems related to evaluation strategies INVITED TALKS will be given by: * Olivier Danvy (University of Aarhus, Denmark), Normalization by Evaluation * Jan Willem Klop (Vrije Universiteit Amsterdam, The Netherlands), Reduction Cycles PROGRAM COMMITTEE: Sergio Antoy Portland (USA) (co-chair) Roberto Di Cosmo Paris VII (France) Juergen Giesl Aachen (Germany) Bernhard Gramlich Wien (Austria) Salvador LucasValencia (Spain) Aart Middeldorp Innsbruck (Austria) Jaco van de Pol Amsterdam (The Netherlands) Pierre Rety Orleans (France) Amr Sabry Bloomington (USA) Yoshihito Toyama Sendai (Japan) (co-chair) SUBMISSIONS: We solicit papers on all aspects of reduction strategies in rewriting and programming. Submissions should describe unpublished work, except for survey papers which are explicitly welcome, too. Submissions should not exceed 10 pages (however, survey papers may be longer) and be sent in PostScript or PDF format to the PC co-chairs at [EMAIL PROTECTED] by March 17, 2004. The use of the style file available from the RDP workshop style page is encouraged. The call-for papers is also available in PDF format. Submissions should include the title, authors' names, affiliations, addresses, and e-mail. Selection of papers by the PC will be based on originality, significance, and correctness. Final versions will be due by May 2, 2004. PUBLICATION: Accepted papers will be included in the preliminary workshop proceedings that will be available at the workshop. The final workshop proceedings will be published in Elsevier's Electronic Notes in Theoretical Computer Science (ENTCS) series. For further questions please contact the program co-chairs: Sergio Antoy and Yoshihito Toyama at [EMAIL PROTECTED] ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: literate comments
You could make a utility that just strips code out of XML, using the XML nesting as indentation for the Haskell code. Run it as a preprocessor. It's hard to get stuff like that standardized though. I imagine any kind of development environment is free to pretty up or package the source however it wants, so long as the compiler gets what it needs. The easiest way to make a standard is to make a tool that uses it. Personally I would prefer the kind of all-in-one package of code editor and XML packager/unpackager. That way it all gets done transparently, behind the scenes, and I never have to look at the mess. Personally, not a big fan of LaTeX. I don't understand the bias towards it. Sean - Original Message - From: "Steffen Mazanek" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Monday, October 27, 2003 1:08 PM Subject: Re: literate comments > Hello, > > I have thought again about the relationship of Haskell > and XML. Finally I come up with the following idea. Why > not introduce a Haskell DTD? Not to gain better literate > programming facilities, but to represent _real_ Haskell > code in XML. Of course, no person would like to "program" > Haskell in XML, but a uniform representation has its > advantages nevertheless (cf. openmath [1]): > > * approved tools for further processing > * separation of the presentation layer, pretty printing > * interoperability > * cross-linking (e.g., generating library summaries or > in the manner of funnelweb [2], but xml-style) > * objects are often serializable as xml, too > > The following questions are still open for me: > > * would the literate programming facilities really be > improved? for now, Haskell plays nice with LaTeX, but > not at all with XML > * possible advantages of xml schema? > > What do you think about this? Do you see even more > advantages of this approach or would it be senseless > work? > > Regards, > Steffen Mazanek ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
