- Haskell-Cafe - Haskell.org

HDBC or HSQL
by George Moschovitis 19 Oct '08

19 Oct '08

Dear devs, I am a Haskell newbie and I would like to hear your suggestions regarding a Database conectivity library: HSQL or HDBC ? which one is better / more actively supported? thanks in advance, -g. -- http://phidz.com http://blog.gmosx.com http://cull.gr http://www.joy.gr http://nitroproject.org

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Re: [Haskell-cafe] File handles and pipes
by Donn Cave 19 Oct '08

19 Oct '08

Quoth "Stephen Hicks" <sdh33(a)cornell.edu>: > In general, given a handful of system calls (and/or > read/write handles), is there a way to combine them all together? Well, sure - if I understand what you mean. Not "Handles", in the sense of a Haskell library construct, but UNIX pipes and processes are reasonably simple to work with in a general purpose programming language. I'm sorry to say the following isn't real code, since GHC doesn't run on the platform I'm using to write this mail, but I hope it will serve to demonstrate the principles using bare UNIX system calls, and that it doesn't contain any serious errors. forkProcess $ do -- pipe tail (pa0, pa1) <- createPipe -- Command exec'd in this fork reads from this pipe, -- so dup 0 (input) from pipe input fd. Both ends of -- pipe will be inherited by child forks. dupTo pa0 0 forkProcess $ do -- first pipe head -- Command exec'd in this fork writes to parent's pipe. dupTo pa1 1 -- Close parent's pipe so fds won't be inherited by -- next fork. closeFd pa0 closeFd pa1 forkProcess $ execFile "/bin/df" ... -- second pipe head execFile "/bin/df" ... -- Close own pipe write end, so child process exit(s) will cause EOF closeFd pa1 execFile "/usr/bin/sort" ... Key points: Input, output and error are file descriptors 0, 1 and 2, by definition (pronounced "unit 0", etc.) dupTo (UNIX system call dup2()) duplexes an I/O stream, so "dupTo p0 0" sets up a pipe for a standard UNIX command that reads from unit 0. Reads from the pipe's read fd will either return data or block, until exit of the *last* process with the pipe's write end open. Hence the importance of closing the write end of your own pipe, and not letting pipe fds "leak" into child processes. Donn Cave, donn(a)avvanta.com

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Template Haskell and unsafePerformIO
by Achim Schneider 18 Oct '08

18 Oct '08

Shouldn't be there some kind of way to run IO code once at the beginning of template processing? Something like a pair of templateInit :: IO a and templateData :: a where the a of both functions is the same and the latter is automagically generated by TH. Right now, I have to either use unsafePerformIO or runIO and IORef's to load a file only once. Both solutions aren't necessarily pretty. -- (c) this sig last receiving data processing entity. Inspect headers for copyright history. All rights reserved. Copying, hiring, renting, performance and/or quoting of this signature prohibited.

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Arch Haskell News: Oct 18 2008
by Don Stewart 18 Oct '08

18 Oct '08

= News about Haskell on Arch Linux = Arch Linux now has 639 Haskell packages in AUR. That’s an increase of 15 new Haskell packages in the last 7 days. Growth appears to be holding steady at just over 2 new packages a day on Hackage this month. Noteworthy * haskell-gnuplot-0.2: “2D and 3D plots using gnuplot” * alex-2.3: “Alex is a tool for generating lexical analysers in Haskell” * happy-1.18.1: “Happy is a parser generator for Haskell” * haskell-tfp-0.1: “Type-level programming library using type families” Full details on the site. http://archhaskell.wordpress.com/2008/10/18/arch-haskell-news-oct-18-2008/

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Linux binary dist problems
by Leif Warner 18 Oct '08

18 Oct '08

I had the same problem with the 6.8.3 install on Dreamhost, "unable to determine current path" or something. Ended up using 6.8.2 install, and had to crack open the rpm of the old readline version they linked, put it in $HOME/lib, and set $LD_RUN_PATH to point to that. http://www.haskell.org/ghc/dist/6.8.2/ghc-6.8.2-i386-unknown-linux.tar.bz2 And there is actually an Eclipse plugin for Haskell: http://eclipsefp.sourceforge.net/ Not that I break it out for work. -Leif Warner

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2008-10-13 Hackage status with GHC 6.10 release candidate
by Don Stewart 18 Oct '08

18 Oct '08

Hey all. The GHC 6.10 RCs are out, and we're preparing the release of GHC proper. To help manage the transistion to GHC 6.10 it is now possible to actually build all the 3rd party Haskell packages, and publish their results wrt. the release candidate. For the first time ever, we're able to have all the 3rd party code tested and ready to go *prior* to the release of the new compiler and base libraries. Using GHC 6.10 RC from today, Cabal 1.6 and cabal-install 1.16, of 682 libraries and apps tried in total, 1 UnpackFailed 2 DownloadFailed 2 InstallFailed 16 ConfigureFailed 68 DependencyFailed 122 BuildFailed 469 InstallOk Since yesterday, * dependency failures have reduced by 5 * build failures have reduced by 10 * total successfully installed packages are **up by 14** These new packages now all build ok with the GHC 6.10 release candidate, Graphalyze-0.4 alsa-midi calc glome-hs harpy heap hmp3 ircbouncer mohws panda pandoc roguestar-engine type-level typeof unicode-prelude urlcheck Good work everyone! Some packages are still not ready though, if you maintain one of the following packages, and are able to fix it before GHC 6.10 is released, your users will be happy. The most common issues for these differences are, * Changes to Arrow class definition * Changes to types of Map and Set functions * Cabal changes * Changes to ghc-api * Changes to when 'forall' is parsed (add Rank2Types) * GHC.Prim was moved, * Changes to -fvia-C and headers * GADT changes, * pragma warnings tightened * Integer constructors have moved * New warnings and used -Werror The following packages are still producing different results than with ghc 6.8.2. Package maintainers are invited to look at them. I've marked the easy ones. ArrayRef-0.1.2 Easy: duplicate type signatures CLASE-2008.9.23.2 Hard: GADT changes EdisonCore-1.2.1.2 Easy: Monadic Map HPDF-1.4 Easy: Monadic Map HaLeX-1.1 Easy: Name clash with permutations Hashell-0.15 ? : GHC API Hipmunk-0.2 Easy: Monadic Map MemoTrie-0.0 Easy: 'forall' parsing NewBinary-0.1.1 Easy: Integer constructors moved PArrows-0.1 Easy: GHC.Prim moved (use GHC.Exts) TypeCompose-0.5 Easy: Arrow class changes YamlReference-0.9.2 Hard. Unknown Yampa-0.9.2.2 Arrow class changes arrows-0.4 Arrow class changes bytestring-show-0.2 Easy: Integer constructors moved cabal-setup-1.2.1 Hard: Cabal changes chp-1.1.0 Easy: Arrow class changes cmath-0.3 Hard: -fvia-C changes fixpoint-0.1 Easy: Uses -Werror unnecessarily hasim-0.1 Hard: GADT changes hask-home-2007.12.6 Easy: Cabal changes hetris-0.2 Easy: header macros/-fvia-C hexpat-0.2 Easy: 'forall' parsing in RULES hinstaller-2008.2.16 Easy: Cabal changes hint-0.2.4.1 Hard? GHC API hslackbuilder-0.0.1 Easy: Cabal changes hxt-8.1.0 Easy: Arrow class change iException-0.0.1 ? Exception changes libGenI-0.16.1 Easy: Monadic Map changes mage-1.1.0 Hard: -fvia-C changes numeric-prelude-0.0.4 Easy: Lanuage pragma plugins-1.3 Easy: Cabal changes quantum-arrow-0.0.4 Easy: Arrow class changes regex-tdfa-0.94 Easy: Map changes streamproc-1.1 Easy: Arrow class changes stringtable-atom-0.0.4 Easy: Monadic Map typalyze-0.1.1 ? GHC API xmonad-utils-0.1 ? GHC API yhccore-0.9 ? Pragma parsing Build reports for everything, produced today, are here, http://galois.com/~dons/tmp/build-logs-2008-10-13/ How to address these, as library maintainers, is addressed here, http://haskell.org/haskellwiki/Upgrading_packages If you'd like to try your own build of all of hackage, grab a package list (such as this one), http://www.galois.com/~dons/tmp/pkgs-6.10 Install a GHC 6.10 release candidate, upgrade to Cabal 1.6 (on hackage), and cabal-install 0.6 (on hackage), and then simply, cabal install -v -O0 $(cat pkgs-6.10) --build-reports This will construct a clever plan to install all the packages in the right order, and write logs to ~/.cabal/logs and a full structured build report into ~/.cabal/packages/hackage.*/build-report.log I'll start mailing maintainers personally tomorrow. -- Don

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Re: [Haskell-cafe] ANNOUNCE: Glob 0.1, globbing library
by Krzysztof Skrzętnicki 18 Oct '08

18 Oct '08

On Sat, Oct 18, 2008 at 19:28, Matti Niemenmaa <matti.niemenmaa%2Bnews(a)iki.fi> wrote: > Gah, I fail at posting to mailing lists. For posterity, the message I sent to > Krzysztof: > > Krzysztof Skrzętnicki wrote: >> On Fri, Oct 17, 2008 at 22:02, Matti Niemenmaa <matti.niemenmaa%2Bnews(a)iki.fi> >> wrote: >>> Web page at: http://iki.fi/matti.niemenmaa/glob/index.html Hackage: >>> http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Glob >> >> I tried out your package, but it doesn't seem to work correctly on Windows. I >> checked the code and it has directory separator hard coded, which seem to be >> the source of problems. > > Interesting, given that I've only tested it on Windows. ;-) Can you give an > example which doesn't work? > Ouch... I feel like I deserve an entry on http://failblog.org/ Somehow I assumed that globDir has type [Pattern] -> FilePath -> IO [FilePath] where in reality it has type [Pattern] -> FilePath -> IO ([[FilePath]], [FilePath]) When I saw lots of files that didn't match my query I thought there is a bug... I'll certainly doublecheck any bug reports before submitting. Sorry for the noise. All best Christopher Skrzętnicki

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ANNOUNCE: Glob 0.1, globbing library
by Matti Niemenmaa 18 Oct '08

18 Oct '08

Greetings to all, I hereby announce the release of Glob 0.1, a small library for glob-matching purposes based on a subset of zsh's syntax. Web page at: http://iki.fi/matti.niemenmaa/glob/index.html Hackage: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Glob Simple example: match (compile "foo*baz") "foobarbaz" == True. It can also group the contents of a directory given a list of patterns to match: globDir [compile "foo*baz"] "<a directory containing foobarbaz and joe>" gives (["dir/foobarbaz"],["dir/joe"]). Comments, complaints, feature requests, bug reports are all welcome. It should work on both GHC 6.8 and 6.10, but I've only tested the latter.

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Haskell Weekly News: Issue 89 - October 18, 2008
by Brent Yorgey 18 Oct '08

18 Oct '08

--------------------------------------------------------------------------- Haskell Weekly News http://sequence.complete.org/hwn/20081018 Issue 89 - October 18, 2008 --------------------------------------------------------------------------- Welcome to issue 89 of HWN, a newsletter covering developments in the [1]Haskell community. Announcements New Haskell tutorial. Miran Lipovaca (BONUS) has written a new and most excellent Haskell tutorial, [2]"Learn You a Haskell For Great Good!". Glob 0.1, globbing library. Matti Niemenmaa [3]announced the release of [4]Glob 0.1, a [5]small library for glob-matching purposes based on a subset of zsh's syntax. hledger 0.1, command-line accounting tool. Simon Michael [6]announced the [7]first release of [8]hledger, a command-line accounting tool similar to John Wiegley's c++ ledger. hledger generates simple ledger-compatible transaction and account balance reports from a plain text ledger file. [ANN] Haskell Cheatsheet v1.0. Justin Bailey [9]announced a [10]"cheat sheet" for Haskell, a PDF that tries to summarize Haskell 98's syntax, keywords and other language elements. Salsa: A .NET Bridge for Haskell. Andrew Appleyard [11]announced the [12]first release of [13]Salsa, an experimental Haskell library that allows Haskell programs to access .NET libraries. Salsa operates by loading the .NET runtime into your Haskell process and using the FFI (and run-time code generation) to marshall calls between the .NET and Haskell runtimes. It includes a code generator and a type-level library (which uses type families) to provide type-safe access to .NET libraries in Haskell with C#-style method overload resolution and implicit conversions. maccatcher-1.0.0. Jason Dusek [14]announced the [15]maccatcher package, which obtains a MAC address on *NIX and Windows. Call for Contributions - Haskell Communities and Activities Report, November 2008 edition. Janis Voigtlaender sent out [16]call for contributions to the 15th edition of the [17]Haskell Communities & Activities Report. The submission deadline is 31 October 2008. If you are working on any project that is in some way related to Haskell, please write a short entry and submit it. Even if the project is very small or unfinished or you think it is not important enough -- please reconsider and submit an entry anyway! Data.IVar 0.1. Luke Palmer [18]announced the release of the [19]Data.IVar module, which provides write-once variables that can be blocked on in parallel. Unlike other implementations, Data.IVar does not use thread racing, since empirical tests have shown that the GHC scheduler is not quite good enough to handle thread-racing efficiently. A wiki page for managing the 6.10 handover. Don Stewart [20]announced a [21]wiki page to help with the transition to GHC 6.10. It collects the 7 or so known issues that break code with GHC 6.10. Please feel free to clean up, and especially add techniques for handling each change. GHC 6.10.1 RC 1. Ian Lynagh [22]announced [23]GHC 6.10.0.20081007, the first release candidate for GHC 6.10.1. There is also a [24]status page for GHC 6.10.1. Graphalyze-0.4 and SourceGraph-0.2. Ivan Lazar Miljenovic [25]announced the release of version 0.4 of the [26]Graphalyze library and version 0.2 of the [27]SourceGraph programme. SourceGraph is a programme designed to help you analyse the static complexity of your Haskell code when represented as a graph. These releases fix the bugs reported by Gwern Branwen, Magnus Therning, and Christopher Hinson. ListZipper-1.1.0.0. Ryan Ingram [28]announced the release of a simple list zipper library to Hackage, [29]ListZipper-1.1.0.0. darcs 2.1.0. Eric Kow [30]announced the release of [31]darcs 2.1.0. This version provides over 20 bug fixes and 7 new features since darcs 2.0.2. Most notably, the darcs-2 repository format is now the default, there is better HTTP support, and a longstanding 'pending patch' regression has been fixed. Yi 0.5.0.1. Jean-Phillipe Bernardy [32]announced the [33]0.5 release of Yi, a text editor written and extensible in Haskell. The long-term goal of the Yi project is to provide the editor of choice for Haskell programmers. Discussion OT: Haskell desktop wallpaper?. Magnus Therning [34]asked for Haskell-themed desktop wallpapers, and the community responded with quite a few nice images. Abusing quickcheck to check existential properties. Norman Ramsey [35]asked about using QuickCheck to check existential properties; suggestions involved SmallCheck and skolemization. Repair to floating point enumerations?. Malcolm Wallace began a [36]discussion on the merits of changing the (admittedly wonky) H98 [37]semantics for the Enum instances of Float and Double in Haskell Prime. A general question about the use of classes in defining interfaces. S. Doaitse Swierstra [38]asked about the feasibility of including top-level functions implemented using Applicative combinators as class methods with default implementations, to allow for the possibility of giving them more efficient implementations in specific instances. Proposal #2659: Add sortOn and friends to Data.List. Twan van Laarhoven [39]proposed adding sortOn (:: Ord b => (a -> b) -> [40]-> [a) and related functions to Data.List. Blog noise [41]Haskell news from the [42]blogosphere. * Andy Gill: [43]Pretty Printing Code with Markup. writes about a [44]new version of the HughesPJ pretty printing library which allows for pretty-printing with markup. * "FP Lunch": [45]Is purity inefficient?. Are idiomatic pure functional programs less efficient than idiomatic impure ones? * Eric Kow (kowey): [46]darcs weekly news #8. * Conal Elliott: [47]Composing memo tries. * Conal Elliott: [48]Elegant memoization with functional memo tries. * >>> Paolo Capriotti: [49]Monads for Markov chains. * Real-World Haskell: [50]Production status update: we're in QC1. * Joachim Breitner: [51]Infinite loops in Haskell. * Luke Palmer: [52]FRP Rant. * Luke Palmer: [53]data-memocombinators. * Bryan O'Sullivan: [54]Using Bloom filters for large scale gene sequence analysis in Haskell. Bryan and Ketil Malde's paper was accepted to PADL 09! * Arnar Birgisson: [55]Generating legal subsets of a dependency graph. * Creighton Hogg: [56]A silly example and a brief history. * >>> Robert Ottaway: [57]Sorting using Haskell. * Dan Piponi (sigfpe): [58]Untangling with Continued Fractions: part 5. * Holumbus: [59]Source Links Are Back!. * London Haskell Users Group: [60]Getting things going again. * >>> Justin Bailey: [61]The Haskell Cheatsheet. * >>> Nathan Sanders: [62]Type-directed programming. * >>> Micah Cowan: [63]Adventures in Haskell, Part 2: Kewlness. * Manuel M T Chakravarty: [64]GpuGen: Bringing the Power of GPUs to Haskell.. * >>> Binu Raghavan: [65]Haskell.... Binu is trying to learn Haskell. * Bjoern Edstroem: [66]Let's build an MP3-decoder!. Quotes of the Week * mckinna: you don't need to produce elements of an *arbitrary* whatever-it-is when you can produce elements of the *initial* whatever-it-is * tristes_tigres: thinks that programming languages can be divided into two broad classes: functional and dysfunctional * luqui: Down with the IO bourgeoisie! Long live the purely functional proletariat * ystael: it seems like every time i switch channels over to #haskell someone is talking about launching missiles. one might be inclined to draw freudian conclusions. About the Haskell Weekly News New editions are posted to [67]the Haskell mailing list as well as to [68]the Haskell Sequence and [69]Planet Haskell. [70]RSS is also available, and headlines appear on [71]haskell.org. To help create new editions of this newsletter, please see the information on [72]how to contribute. Send stories to byorgey at cis dot upenn dot edu. The darcs repository is available at darcs get [73]http://code.haskell.org/~byorgey/code/hwn/ . References 1. http://haskell.org/ 2. http://learnyouahaskell.com/ 3. http://article.gmane.org/gmane.comp.lang.haskell.cafe/46583 4. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Glob 5. http://iki.fi/matti.niemenmaa/glob/index.html 6. http://article.gmane.org/gmane.comp.lang.haskell.cafe/46461 7. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hledger 8. http://joyful.com/Ledger#hledger 9. http://article.gmane.org/gmane.comp.lang.haskell.cafe/46122 10. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/CheatSheet 11. http://article.gmane.org/gmane.comp.lang.haskell.cafe/46076 12. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Salsa 13. http://haskell.org/haskellwiki/Salsa 14. http://article.gmane.org/gmane.comp.lang.haskell.cafe/46072 15. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/maccatcher 16. http://article.gmane.org/gmane.comp.lang.haskell.cafe/45967 17. http://www.haskell.org/communities/ 18. http://article.gmane.org/gmane.comp.lang.haskell.cafe/45953 19. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/data-ivar 20. http://article.gmane.org/gmane.comp.lang.haskell.glasgow.user/15442 21. http://haskell.org/haskellwiki/Upgrading_packages#Typical_breakages_with_GH… 22. http://article.gmane.org/gmane.comp.lang.haskell.glasgow.user/15376 23. http://www.haskell.org/ghc/dist/stable/dist/6.10.1-rc-1/rc.html 24. http://hackage.haskell.org/trac/ghc/wiki/GHC-6.10.1 25. http://article.gmane.org/gmane.comp.lang.haskell.general/16473 26. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Graphalyze 27. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/SourceGraph 28. http://article.gmane.org/gmane.comp.lang.haskell.general/16468 29. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/ListZipper 30. http://article.gmane.org/gmane.comp.lang.haskell.general/16465 31. http://darcs.net/darcs-2.1.0.tar.gz 32. http://www.haskell.org//pipermail/haskell/2008-October/020648.html 33. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/yi 34. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/45961 35. http://thread.gmane.org/gmane.comp.lang.haskell.general/16477 36. http://thread.gmane.org/gmane.comp.lang.haskell.prime/2678 37. http://haskell.org/onlinereport/basic.html#sect6.3.4 38. http://thread.gmane.org/gmane.comp.lang.haskell.libraries/10206 39. http://thread.gmane.org/gmane.comp.lang.haskell.libraries/10184 40. file://localhost/home/brent/haskell/hwn/a] 41. http://planet.haskell.org/ 42. http://haskell.org/haskellwiki/Blog_articles 43. http://blog.unsafeperformio.com/?p=31 44. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/marked%2Dpretty 45. http://sneezy.cs.nott.ac.uk/fplunch/weblog/?p=113 46. http://koweycode.blogspot.com/2008/10/darcs-weekly-news-8.html 47. http://feeds.feedburner.com/~r/conal/~3/422189172/ 48. http://feeds.feedburner.com/~r/conal/~3/422171822/ 49. http://pcapriotti.wordpress.com/2008/10/16/monads-for-markov-chains/ 50. http://www.realworldhaskell.org/blog/2008/10/15/production-status-update-we… 51. https://www.joachim-breitner.de/blog/archives/308-Infinite-loops-in-Haskell… 52. http://luqui.org/blog/archives/2008/10/15/frp-rant/ 53. http://luqui.org/blog/archives/2008/10/14/data-memocombinators/ 54. http://www.serpentine.com/blog/2008/09/28/using-bloom-filters-for-large-sca… 55. http://www.hvergi.net/2008/10/generating-legal-subsets-of-a-dependency-grap… 56. http://abstractabsurd.blogspot.com/2008/10/silly-example-and-brief-history.… 57. http://tech-nickel.blogspot.com/2008/10/sorting-using-haskell.html 58. http://sigfpe.blogspot.com/2008/10/untangling-with-continued-fractions.html 59. http://holumbus.fh-wedel.de/blog/?p=15 60. http://www.londonhug.net/2008/10/11/getting-things-going-again/ 61. http://blog.codeslower.com/2008/10/The-Haskell-Cheatsheet 62. http://sandersn.com/blog/index.php?title=type_directed_programming 63. http://micah.cowan.name/2008/10/10/computers/software-development/adventure… 64. http://justtesting.org/post/53418059 65. http://variably-volatile.blogspot.com/2008/10/haskell.html 66. http://blog.bjrn.se/2008/10/lets-build-mp3-decoder.html 67. http://www.haskell.org/mailman/listinfo/haskell 68. http://sequence.complete.org/ 69. http://planet.haskell.org/ 70. http://sequence.complete.org/node/feed 71. http://haskell.org/ 72. http://haskell.org/haskellwiki/HWN 73. http://code.haskell.org/~byorgey/code/hwn/

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Implementing pi-calculus using STM
by Edsko de Vries 18 Oct '08

18 Oct '08

Hi, (Note: assumes knowledge of pi-calculus.) I am playing with writing a simple interpreter for the pi-calculus using STM. The implementation of most of the operators of the pi- calculus is straightforward, but I am unsure on how to implement the replication operator. The interpretation of !P should be the interpretation of the infinite number of parallel processes P | P | P ... . I am implementing parallel processes using the fork operation, but spawning an infinite amount of processes -- even if the (infinite) majority of them all immediately lock -- seems like a bad idea. So I would prefer to spawn one P, and as soon as the thread that interprets P makes any progress at all, spawn another, and so on. I'm not too sure however how to achieve this. Any ideas? Edsko

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