- Haskell-Cafe - Haskell.org

RE: [Haskell-cafe] Thread priority?
by John Van Enk 25 Apr '09

25 Apr '09

+1 Incredibly interested if this goes anywhere. Willing to help! -----Original Message----- From: Christopher Lane Hinson <lane(a)downstairspeople.org> Sent: Friday, April 24, 2009 10:48 PM To: haskell-cafe(a)haskell.org Subject: [Haskell-cafe] Thread priority? Is there any interest or movement in developing thread priority or any other realtime support in Haskell? Right now, if I have tasks that need to be responsive in real time, even if the realtime needs are very soft, it seems that the only option is to try to ensure that at least one hardware thread is kept clear of any other activity. To be very useful to me, thread priority would not need to come with very strict guarantees, but there would need to be a way to make sure that `par` sparks and DPH inherit the priority of the sparking thread. In part I ask because I'm working on a small library to support a degree of cooperative task prioritization. Friendly, --Lane _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

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Haskell consultant wanted to develop small, Mac-based utility in Haskell or AppleScript
by R J 24 Apr '09

24 Apr '09

I need someone to code a short program for use on a Mac OS X (Leopard) that, in essence, takes as input a file containing a list of English words, and produces as output a file containing the words plus definitions, as extracted from any good dictionary. Though Haskell might not be the ideal language for this project, the utility is almost trivial, I'm a fan of Haskell, and would like to support the community. Those interested should email me at rj248842(a)hotmail.com. The specs are: 1. Takes as input a .txt file containing lines delimited by newline characters, with each line containing either no characters, an English word or phrase, or a comment (denoted by, for example, "--"). Thus, the input file might look like: -- Comment 1frustum bon mot -- Comment 2octagon rectangle 2. Produces as output a file (.txt, .rtf, or .docx format) containing the comments, the words or phrases (in bold), and their definitions, using either the dictionary (New Oxford American Dictionary, "NOAD") bundled with OS X or some credible online dictionary (such as merriam-webster.com) for words whose definitions aren't found in the NOAD. For example, given the above input file, the output file would be: -- Comment 1frustum |ˈfrəstəm| noun ( pl. -ta |-tə| or -tums ) Geometry the portion of a cone or pyramid that remains after its upper part has been cut off by a plane parallel to its base, or that is intercepted between two such planes. ORIGIN mid 17th cent.: from Latin, ‘piece cut off.’ bon mot |ˈbän ˈmō; ˌbô n ˈmō| noun ( pl. bons mots pronunc. same or |ˈmōz|) a witty remark. ORIGIN mid 18th cent.: French, literally ‘good word.’ -- Comment 2 octagon |ˈäktəˌgän; -gən| noun a plane figure with eight straight sides and eight angles. • an object or building with a plan or cross section of this shape. DERIVATIVES octagonal |äkˈtagənl| |ɑkˈtøgənl| |-ˈtag(ə)n(ə)l| adjective octagonally |äkˈtagənəlē| |ɑkˈtøgənəli| |ɑkˈtøgənli| |-ˈtag(ə)n(ə)li| adverbORIGIN late 16th cent.: via Latin from Greek octagōnos ‘eight-angled.’ rectangle |ˈrekˌta ng gəl|noun a plane figure with four straight sides and four right angles, esp. one with unequal adjacent sides, in contrast to a square. ORIGIN late 16th cent.: from medieval Latin rectangulum, from late Latin rectiangulum, based on Latin rectus ‘straight’ + angulus ‘an angle.’ I've attached a (zipped) AppleScript--it's just a few lines--and Automator workflow that work ok using Automator's "Get Definition of a Word" action. It took about fifteen minutes to write, but for some reason, that action doesn't extract the entire definition from the dictionary. If it would save time, you could work off of that code and deliver an AppleScript solution, or you could write Haskell code. _________________________________________________________________ Rediscover Hotmail®: Now available on your iPhone or BlackBerry http://windowslive.com/RediscoverHotmail?ocid=TXT_TAGLM_WL_HM_Rediscover_Mo…

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GHC 6.10.2 compatible problem.
by Andy Stewart 24 Apr '09

24 Apr '09

Hi, all! I saw GHC release new version now, and fix some bug. I want to know below pacakges whether works fine with GHC-6.10.2 before i upgrade it: cabal, gtk2hs, xmonad, yi, leksah Thanks! -- Andy

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Being impure within a 'pure' function
by Daniel K. 24 Apr '09

24 Apr '09

Hello, imagine the following situation: You want to implement e.g. Dijkstra's algorithm to find a shortest path between nodes u and v in a graph. This algorithm relies heavily on mutating arrays, so the type signature would look something like getDistance :: Graph -> Node -> Node -> IO Int Not mutating the underlying arrays would probably result in poor performance. BUT: For a constant graph, the distance between two nodes stays the same all the time, so in fact getDistance should be a pure function! So here is my question: Is there a way to write functions in Haskell that do some IO internally, but that are guaranteed to be side-effect free? Of course one would have to make sure that the array that is mutated inside getDistance must not be accessible from outside the function. Is that possible? If not, wouldn't that be desirable? If not, why not? Thanks Daniel

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ANNOUNCE: vacuum-cairo: a cairo frontend to vacuum for live Haskell data visualization
by Don Stewart 24 Apr '09

24 Apr '09

I am pleased to announce the release of vacuum-cairo, a Haskell library for interactive rendering and display of values on the GHC heap using Matt Morrow's vacuum library. This library takes vacuum's output, generates dot graph format from it, renders it to SVG with graphviz, and displays the resulting structure using the gtk2hs Cairo vector graphics bindings ... all at the GHCi command line. This tool is useful for examining Haskell data structures as they are represented directly in the heap. In particular, it makes sharing visible for the first time, as well as unboxed values. It should be useful for teaching Haskell, or for library authors debugging the design of their data structures. You can see pictures of the rendered display here: http://code.haskell.org/~dons/images/vacuum/intmap.png And youtube screencasts of vacuum-cairo in action: http://www.youtube.com/watch?v=oujaqo9GAmA Get it: cabal install vacuum-cairo And on Hackage: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/vacuum-cairo -- Don

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darcs hacking sprint 2 and hac5 report
by Eric Kow 24 Apr '09

24 Apr '09

Dear darcs users and Haskellers, Here's our report from the 2nd darcs hacking sprint, held as part of the Haskell Hackathon. http://blog.darcs.net/2009/04/darcs-hacking-sprint-2-report.html Thanks very much to the Hac5 team, to Hac5 sponsors, darcs donors, and to all participants at the Hackathon. We really enjoyed meeting everybody and hope to see you soon at the next event! -- Eric Kow <http://www.nltg.brighton.ac.uk/home/Eric.Kow> PGP Key ID: 08AC04F9

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Confusing change causing space leak
by Denis Bueno 24 Apr '09

24 Apr '09

Hi all, I discussed this with a few people in #haskell-in-depth, and we thought I should send this to the list. The following paste shows the only changes required to remove a space leak: http://hpaste.org/fastcgi/hpaste.fcgi/view?id=4185#a4185. Summary: if I reduce a tuple-from-IO to whnf in the "allocate" function passed to "bracket", no leak. For example, this also doesn't leak: http://hpaste.org/fastcgi/hpaste.fcgi/view?id=4185#a4189 That paste page also contains the code for "externalSort". The "externalSort" function used in the example corresponds to the "sort" function provided by the Algorithms.ExternalSort module. Can anyone explain why the leak happens at all, or why it goes away? Denis

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Template Haskell + Profiling
by Krzysztof Skrzętnicki 24 Apr '09

24 Apr '09

Hi I'm trying to build some modules that use TH with profiling enabled. The normal build works: $ ghc -fforce-recomp --make -cpp -O -DXQUERY2_TEST Main [1 of 8] Compiling Text.XML.Expat.FormatCustom ( Text/XML/Expat/FormatCustom.hs, Text/XML/Expat/FormatCustom.o ) [2 of 8] Compiling DataStructures ( DataStructures.hs, DataStructures.o ) Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. Loading package syb ... linking ... done. Loading package array-0.2.0.0 ... linking ... done. Loading package packedstring-0.1.0.1 ... linking ... done. Loading package containers-0.2.0.1 ... linking ... done. Loading package pretty-1.0.1.0 ... linking ... done. Loading package template-haskell ... linking ... done. Loading package mtl-1.1.0.2 ... linking ... done. Loading package filepath-1.1.0.2 ... linking ... done. Loading package old-locale-1.0.0.1 ... linking ... done. Loading package old-time-1.0.0.2 ... linking ... done. Loading package unix-2.3.2.0 ... linking ... done. Loading package directory-1.0.0.3 ... linking ... done. Loading package process-1.0.1.1 ... linking ... done. Loading package random-1.0.0.1 ... linking ... done. Loading package derive-0.1.4 ... linking ... done. [3 of 8] Compiling Utils ( Utils.hs, Utils.o ) [4 of 8] Compiling Semantics.Pure ( Semantics/Pure.hs, Semantics/Pure.o ) [5 of 8] Compiling Database ( Database.hs, Database.o ) [6 of 8] Compiling XPathDSL ( XPathDSL.hs, XPathDSL.o ) [7 of 8] Compiling QueryParse ( QueryParse.hs, QueryParse.o ) [8 of 8] Compiling Main ( Main.hs, Main.o ) Linking Main ... But profiling one fails: $ ghc -prof -auto -auto-all -fforce-recomp --make -cpp -O -DXQUERY2_TEST Main [1 of 8] Compiling Text.XML.Expat.FormatCustom ( Text/XML/Expat/FormatCustom.hs, Text/XML/Expat/FormatCustom.o ) [2 of 8] Compiling DataStructures ( DataStructures.hs, DataStructures.o ) Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. DataStructures.hs:1:0: Dynamic linking required, but this is a non-standard build (eg. prof). You need to build the program twice: once the normal way, and then in the desired way using -osuf to set the object file suffix. The error message is somewhat cryptic to me. Does anyone know how to perform profiling build when using TH? Regards Christopher Skrzętnicki

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(integer) linear programming
by Johannes Waldmann 24 Apr '09

24 Apr '09

Hi. I'm looking for linear programming solvers in Haskell (or a Haskell binding for glpk, or similar). - Thanks, J.W.

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ANNOUNCE: Utrecht Haskell Compiler (UHC) -- first release
by atze＠cs.uu.nl 24 Apr '09

24 Apr '09

Utrecht Haskell Compiler -- first release, version 1.0.0 ======================================================== The UHC team is happy to announce the first public release of the Utrecht Haskell Compiler (UHC). UHC supports almost all Haskell98 features plus many experimental extensions. The compiler runs on MacOSX, Windows (cygwin), and various Unix flavors. Features: * Multiple backends, including a bytecode interpreter backend and a GRIN based, full program analysing backend, both via C. * Experimental language extensions, some of which have not been implemented before. * Implementation via attribute grammars and other high-level tools. * Ease of experimentation with language variants, thanks to an aspect-oriented internal organisation. Getting started & Download -------------------------- UHC is available for download as source distribution via the UHC home page: http://www.cs.uu.nl/wiki/UHC Here you will also find instructions to get started. Status of the implementation ---------------------------- Like any university project UHC is very much work in progress. We feel that it is mature and stable enough to offer to the public, but much work still needs to be done; hence we welcome contributions by others. UHC grew out of our Haskell compiler project (called Essential Haskell Compiler, or EHC) over the past 5 years. UHC internally is organised as a combination of separate aspects, which makes UHC very suitable to experiment with; it is relatively easy to build compilers for sublanguages, or to generate related tools such as documentation generators, all from the same code base. Extensions to the language can be described separately, and be switched on or of as need arises. Warning ------- Although we think that the compiler is stable enough to compile subtantial Haskell programs, we do not recommend yet to use it for any serious development work in Haskell. We ourselves use the GHC as a development platform! We think however that it provides a great platform for experimenting with language implementations, language extensions, etc. Mailing lists ------------- For UHC users and developers respectively: http://mail.cs.uu.nl/mailman/listinfo/uhc-users http://mail.cs.uu.nl/mailman/listinfo/uhc-developers Bug reporting ------------- Please report bugs at: http://code.google.com/p/uhc/issues/list The UHC Team -- Atze Dijkstra, Department of Information and Computing Sciences. /|\ Utrecht University, PO Box 80089, 3508 TB Utrecht, Netherlands. / | \ Tel.: +31-30-2534118/1454 | WWW : http://www.cs.uu.nl/~atze . /--| \ Fax : +31-30-2513971 .... | Email: atze(a)cs.uu.nl ............ / |___\

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