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ANN: binary arithmetic type library over natural kinds
by oleg＠pobox.com 08 Mar '07

08 Mar '07

Chung-chieh Shan and I would like to announce the type-level Haskell library for arbitrary precision binary arithmetic over natural kinds. The library supports addition/subtraction, predecessor/successor, multiplication/division, exp2, full comparisons, GCD, and the maximum. At the core of the library are multi-mode ternary relations Add and Mul where _any_ two arguments determine the third. Such relations are especially suitable for specifying static arithmetic constraints on computations. The type-level numerals have no run-time representation; correspondingly, all arithmetic operations are done at compile time and have no effect on run-time. http://pobox.com/~oleg/ftp/Computation/resource-aware-prog/BinaryNumber.hs We used the arithmetic type library to statically enforce validity, range, size, and alignment constraints of raw memory pointers, and to statically enforce protocol and time-related constraints when accessing device registers. The following near final full paper http://pobox.com/~oleg/ftp/Computation/resource-aware-prog/tfp.pdf describes the arithmetic type library, type-level records, type-level programming with regular Haskell terms, and two sample applications. We will greatly appreciate all the comments (especially those received before noon on Friday).

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Re: ANN: binary arithmetic type library over natural kinds
by oleg＠pobox.com 08 Mar '07

08 Mar '07

David Roundy wrote: > data Arr a n = ... -- n is a type-level variable describing the dimension > -- a is the data type stored > withArrayFromList :: [a] -> (Nat n => Arr a n -> b) -> b > ... > But what I'm dreaming of is that the type system would enforce those > run-time checks when necesary. e.g. > > catArray :: Add n1 n2 n3 => Arr a n1 -> Arr a n2 -> Arr a n3 > > I imagine this is harder, but it's needed if these type-level binaries > will be useful for the sorts of programs I tend to write--which have > run-time sizes. I believe the lightweight static capabilities approach will be more appropriate here. It already provides the function withArrayFromList, which is called `brand'. For example, KMP-deptype.hs includes > -- brand the packed string > brandPS:: PackedString > -> (forall r. (BPackedString r, BIndexP1 r) -> w) -> w -> w which is quite like `withArrayFromList' only using `r' rather that 'n' and with an extra argument which is returned when the source packed string turns out empty. The approach almost fulfills your dream: only, instead of the `system' inserting run-time checks, it is the programmer who inserts the checks, to please the typechecker. In the catArray example, one would write something like that > -- kernel > data Arr a = ... > newtype BArr n a = BArr{unBArr:: Arr a} -- BArr data ctor not exported > brand :: Arr a -> (forall n. (BArr n a, BIx n) -> w) -> w > -- User code > catArray :: BArr n1 a -> BArr n2 a -> Arr a > catArray a1 a2 = concatArr (unBArr a1) (unBArr a2) > test a1 a2 = brand (catArray a1 a2) (\newarray itsbound -> ...) The user can easily write catArray to create an unbranded array. One needs branding however to be able to index into the array: thus one has to invoke brand (the `smart' constructor of the BArr type), which will do the run-time check. The kernel may provide other constructors of BArr from arguments of some particular types, which let us avoid the run-time check. Alas, the style of writing is a bit like CPS -- OTH, we write monadic code, which is CPS in thin disguise, with no complaints... One can use existentials to make the code look more direct-style, however. The programming becomes a bit like theorem proving: the indexing operation needs BArr, so we have to consider all the ways we can get a value of that type. The kernel provides a few constructors; one of which, brand, always applies, but it involves a run-time check. There may be other constructors; but they require arguments of particular types. We should see if we can produce the values of those types from already available values, etc. This is back-chaining theorem proving.

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method annotations
by John Meacham 07 Mar '07

07 Mar '07

On Sat, Mar 03, 2007 at 08:23:08AM -0500, Isaac Dupree wrote: > Unfortunately it would be difficult for the compiler to know that no-one > is going to make an instance that does depend on its argument (as long > as it does not do full-program analysis to determine the layout of data > structures). Maybe there should be some sort of annotation on class > method arguments that are supposed to be ignored, even if only a pragma, > if it would help compilers figure this out. indeed, I have given this some thought too, but not just for whether a type will be unused. my current thinking is something like > class Bits a where > shift :: a -> !Int -> a > > class Eq a where > (==) :: a -> a -> !Bool > > class Typeable a where > getType :: ~a -> TypeRep where '!Int' means that the class is strict in the Int argument. and ~ means it is unused. note, these are not just hints, but actually affect the class translation. shift as above would translate to something ilke > shift :: BitsDict a -> Int -> a > shift bd x i = i `seq` shiftInstance bd x i where shiftInstance selects the appropriate value from the dictionary of course, the real benefit is now that we can do unboxing on class methods! we can treat the above class declaration as if it were class Bits a where shift :: a -> Int# -> a safely and rewrite instance declarations appropriately likewise, the ! on the return value in Eq means that we should unbox it. (this is actually always safe, so perhaps a pragma will do for this, "UNPACK" seems appropriate) for the other case > class Typeable a where > getType :: ~a -> TypeRep would create a method like so > getType :: TypeableDict a -> a -> TypeRep > getType td a = getTypeInstance td (undefined `asTypeOf` a) which causes getType to always throw away its argument, allowing the compiler to make assumptions based on it. another implicit optimization that is going on in my translations above is eta-expansion of the class methods (which is independent of the optimizations given above). this is potentially unsafe, but I have been performing the optimization in jhc without ill effect and with noticable benefit. however, you can specify the "NOETA" pragma in order to suppress this auto-eta-expansion as it does decrease sharing. another option for controlling eta expansion would be something like class Eq a where (==) :: a -> !(a -> Bool) which makes explicit that the partial result of (==) applied to one argument could usefully be shared. currently, these optimization are availabe in jhc, but only via pragmas and some built in heuristics/special knowledge in the compiler. Implementing the above syntax has been on my todo list. Anecdotal examination of core leads me to believe they could be signifigantly beneficial. John -- John Meacham - ⑆repetae.net⑆john⑈

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Google summer of code
by Malcolm Wallace 07 Mar '07

07 Mar '07

Google Summer of Code As many of you will already know, Google is running its "Summer of Code" project again this year, and haskell.org is once again going to apply to be a mentoring organisation. Are you a student who would like to earn money for hacking in Haskell? Or are you a non-student who has a cool idea for a coding project but no time to do it yourself? Well, our wiki to gather ideas is now up-and-running again: http://hackage.haskell.org/trac/summer-of-code Add yourself to the list of interested people! There are some ideas still there from last year. Add new ones! Google will start accepting student applications in just over a week's time, but now is the time to start using our own wiki to match up interesting ideas with interested people. The official timeline is as follows: March 12: Mentoring organization application deadline March 14: List of accepted mentoring organizations published March 14: Student application period opens March 24: Student application deadline Interim Period: we review and rank student proposals April 9: List of accepted student applications published Interim Period: Students learn more about their project communities May 28: Students begin coding; Google begins issuing initial payments July 9: Students upload code to code.google.com/hosting; July 16: Google begins issuing mid-term payments August 20: Students upload code to code.google.com/hosting; August 31: Final evaluation deadline; Google begins issuing final payments Regards, Malcolm

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Fwd: HFL07, student stipend(s) available
by Koen Claessen 07 Mar '07

07 Mar '07

Workshop on Hardware design and Functional Languages HFL'07, Braga, Portugal, March 24 and 25 (with the ETAPS conferences) Student stipend(s) available, deadline March 13 HFL07 is pleased to announce the availability of one or two stipends for students to attend the workshop. We will give preference to undergraduate or masters students, but will also consider PhD students. The stipend should cover all or part of registration at the workshop, the workshop dinner on sunday night, travel and student accommodation. The student should write a letter to the workshop chairs (hfl07(a)hflworkshop.org) outlining their costs, other financial support that they have obtained (e.g. from their own university) and why they would like to attend the workshop. They should also include a statement from a teacher or supervisor supporting their case (and including an email address). Deadline for receipt of this application is midnight on tuesday March 13th, UK time. For information on the workshop programme, see http://www.hflworkshop.org/ Information about the ETAPS group of conferences, registration, student rooms etc. is at http://www.di.uminho.pt/etaps07/ Please encourage a good undergrad. or masters student to apply for a stipend and come to the workshop! with best wishes Andy Martin, Carl-Johan Seger and Mary Sheeran

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Re: [Haskell] Haskell Dependency/Installation of packages (FilePath/MissingPy)
by Gottfried F. Zojer 06 Mar '07

06 Mar '07

> -----Ursprüngliche Nachricht----- > Von: "Neil Mitchell" <ndmitchell(a)gmail.com> > Gesendet: 06.03.07 10:33:11 > An: "Gottfried F. Zojer" <goenzoy(a)web.de> > CC: haskell(a)haskell.org > Betreff: Re: [Haskell] Haskell Dependency/Installation FilePath > Hi > > > Loading package base ... linking ... done. > > [1 of 1] Compiling Main ( C:/ghc/ghc-6.6/filepath-0.11/filepath/Setu > > p.hs, interpreted ) > > Ok, modules loaded: Main. > > *Main> > > You have probably downloaded FilePath, but not installed it. Try: > > cd C:/ghc/ghc-6.6/filepath-0.11/filepath > runhaskell Setup configure > runhaskell Setup build > runhaskell Setup install > > Then attempt the installation of MissingH again. > > Thanks > > Neil > Hallo Neil , Thanks for the advice.Well Filepath was installed and at the end everything looked fine. MissingH installation with (winbuild) was going through.I m further now with MissingPy and its the same symptom.(see compile log) Like on the first attempt with MissingH !? [44 of 46] Compiling System.Path.Glob ( src/System/Path/Glob.hs, dist\build/Syst em/Path/Glob.o ) [45 of 46] Compiling System.Debian.ControlParser ( src/System/Debian/ControlPars er.hs, dist\build/System/Debian/ControlParser.o ) [46 of 46] Compiling System.Debian ( src/System/Debian.hs, dist\build/System/ Debian.o ) C:\ghc\ghc-6.6\bin\ar.exe: creating dist\build\libHSMissingH-0.18.0.a C:\server\missingh_0.18.1\missingh> C:\Python24\missingpy_0.1.0\missingpy>runhaskell Setup configure Setup: Warning: Unknown field 'options-ghc' Setup: Warning: Unknown field 'hidden-modules' Setup: Warning: Unknown field 'extra-libs' Setup: Warning: No license-file field. Configuring MissingPy-0.1.0... configure: Dependency haskell-src-any: using haskell-src-1.0 Setup: cannot satisfy dependency MissingH>=0.9.0 <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< C:\Python24\missingpy_0.1.0\missingpy>runhaskell Setup build Setup: Warning: Unknown field 'options-ghc' Setup: Warning: Unknown field 'hidden-modules' Setup: Warning: Unknown field 'extra-libs' Setup: error reading ./.setup-config; run "setup configure" command? C:\Python24\missingpy_0.1.0\missingpy> C:\Python24\missingpy_0.1.0\missingpy>python gencabal.py *** Generating MissingPy.cabal based on these settings *** Please edit MissingPy.cabal if the detected settings are *** incorrect. Include path for Python headers: C:\Python24\include Library paths for Python library: None, C:\Python24\Lib\site-packages Python library name: python2.4 Thanks for any feedback Best regards Gottfried www.wirtschaftswunder.co.uk www.5152.eu

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Haddock not being able to read interface file
by Wolfgang Jeltsch 06 Mar '07

06 Mar '07

Hello, I want to generate Haddock documentation for some Haskell files and want to create hyperlinks to the base package’s documentation. I’ve downloaded <http://www.haskell.org/ghc/docs/latest/html/libraries/base/base.haddock> and use the option --read-interface=http://www.haskell.org/ghc/docs/latest/html/libraries/base,base.haddock in my Haddock command line. However, Haddock outputs the following: haddock: Warning: The interface file "base.haddock" could not be read. Maybe it's from a later version of Haddock? This happens with Haddock 0.8 as well as the current development version of Haddock. What’s wrong here? Best wishes, Wolfgang

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Haskell Dependency/Installation FilePath
by Gottfried F. Zojer 06 Mar '07

06 Mar '07

Hallo to all, Tried to install MissingH ,something what failed because Filepath is missing. Any idea why the setup file isnt in the position to find it,even if it is there(see GHCi log down ) Any feedback welcome Best regards Gottfried www.wirtschaftswunder.co.uk www.5152.eu ___________________________________________________________________________________ missingh>setup configure setup: Warning: No license-file field. Configuring MissingH-0.18.0... configure: C:\ghc\ghc-6.6\bin\ghc-pkg.exe configure: Dependency network-any: using network-2.0 configure: Dependency parsec-any: using parsec-2.0 configure: Dependency base-any: using base-2.0 configure: Dependency haskell98-any: using haskell98-1.0 configure: Dependency mtl-any: using mtl-1.0 configure: Dependency HUnit-any: using HUnit-1.1 configure: Dependency regex-compat-any: using regex-compat-0.71 configure: Dependency QuickCheck-any: using QuickCheck-1.0 setup: cannot satisfy dependency FilePath-any C:\server\missingh_0.18.1\missingh>setup build setup: error reading ./.setup-config; run "setup configure" command? ___ ___ _ / _ \ /\ /\/ __(_) / /_\// /_/ / / | | GHC Interactive, version 6.6, for Haskell 98. / /_\\/ __ / /___| | http://www.haskell.org/ghc/ \____/\/ /_/\____/|_| Type :? for help. Loading package base ... linking ... done. [1 of 1] Compiling Main ( C:/ghc/ghc-6.6/filepath-0.11/filepath/Setu p.hs, interpreted ) Ok, modules loaded: Main. *Main>

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Haskell Weekly News: March 05, 2007
by dons＠cse.unsw.edu.au 04 Mar '07

04 Mar '07

--------------------------------------------------------------------------- Haskell Weekly News http://sequence.complete.org/hwn/20070305 Issue 58 - March 05, 2007 --------------------------------------------------------------------------- Welcome to issue 58 of HWN, a weekly newsletter covering developments in the [1]Haskell community. 1. http://haskell.org/ Announcements New Book - Programming in Haskell. Graham Hutton [2]announced a new Haskell textbook: [3]Programming in Haskell. This introduction is ideal for beginner programmers: it requires no previous programming experience and all concepts are explained from first principles via carefully chosen examples. Each chapter includes exercises that range from the straightforward to extended projects, plus suggestions for further reading on more advanced topics. The presentation is clear and simple, and benefits from having been refined and class-tested over several years. 2. http://article.gmane.org/gmane.comp.lang.haskell.general/14849 3. http://www.cs.nott.ac.uk/~gmh/book.html Gtk2Hs version 0.9.11. Duncan Coutts [4]announced Gtk2Hs - a GUI Library for Haskell based on Gtk+, version 0.9.11, is [5]now available. Gtk2Hs features: automatic memory management; Unicode support; nearly full coverage of Gtk+ 2.8 API; support for several additional Gtk+/Gnome modules (Glade visual GUI builder, cairo vector graphics, SVG rendering, OpenGL extension and more). 4. http://article.gmane.org/gmane.comp.lang.haskell.general/14934 5. http://haskell.org/gtk2hs/download/ cabal-make version 0.1. Conal Elliott [6]announced Cabal-make, a GNU make include file to be used with Cabal in creating and sharing Haskell packages. A few highlights: web-based, cross-package links in Haddock docs; syntax coloring via hscolour, with per-project CSS; links from the Haddock docs to hscolour'd code and to wiki-based user comment pages. [7]It is available here. 6. http://article.gmane.org/gmane.comp.lang.haskell.general/14891 7. http://haskell.org/haskellwiki/Cabal-make Vty 3.0.0. Stefan O'Rear [8]announced a new major of [9]vty, featuring improved performance. vty is notably used in yi to provide a terminal interface supporting syntax highlighting. 8. http://article.gmane.org/gmane.comp.lang.haskell.general/14876 9. http://members.cox.net/stefanor/vty/dist/doc/html/index.html Haskell Xcode Plugin. Lyndon Tremblay [10]announced the first release of [11]a plugin for Xcode enabling Haskell syntax highlighting, Xcode projects compiling and linking, and a couple missing features, for Haskell (GHC). 10. http://article.gmane.org/gmane.comp.lang.haskell.general/14875 11. http://www.hoovy.org/HaskellXcodePlugin/ urlcheck 0.1: parallel link checker. Don Stewart [12]announced the first release of [13]urlcheck, an parallel link checker, written in Haskell. Frustrated with the resources and time consumed by 'linkchecker', urlcheck is a lightweight, smp-capable replacement in Haskell. urlcheck pings urls found in the input file, checking they aren't 404s. It uses Haskell threads to run queries concurrently, and can transparently utilise multiple cores if you have them. 12. http://article.gmane.org/gmane.comp.lang.haskell.general/14863 13. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/urlcheck-0.1 The Monad.Reader: call for copy. Wouter Swierstra [14]welcomed articles for the next issue of The Monad.Reader. Submit articles for the next issue by e-mail before April 13th, 2007. Articles should be written according to the guidelines available from [15]The Monad Reader home. 14. http://article.gmane.org/gmane.comp.lang.haskell.general/14870 15. http://www.haskell.org/haskellwiki/TheMonadReader TV-0.2 and GuiTV-0.2. Conal Elliott [16]announced TV, a library for composing tangible values ('TVs'), values that carry along external interfaces. In particular, TVs can be composed to create new TVs, and they can be directly executed with various kinds of interfaces. Values and interfaces are combined for direct use, and separable for composition. GuiTV adds graphical user interfaces to the TV (tangible value) framework, using Phooey. The functionality was part of TV up to version 0.1.1, and is now moved out to a new package to eliminate the dependency of core TV on Phooey and hence on wxHaskell, as the latter can be difficult to install. 16. http://article.gmane.org/gmane.comp.lang.haskell.general/14862 Haskell-mode 2.2. Stefan Monnier [17]released version 2.2 of [18]the Haskell-mode package for Emacs. It has very few visible changes, mostly some commands to query an underlying interactive hugs/ghci in order to get type/info about specific identifiers. 17. http://article.gmane.org/gmane.comp.lang.haskell.general/14857 18. http://www.iro.umontreal.ca/~monnier/elisp/ Data.CompactString 0.1. Twan van Laarhoven [19]announced a beta [20]Unicode version of Data.ByteString. The library uses a variable length encoding (1 to 3 bytes) of Chars into Word8s, which are then stored in a ByteString. 19. http://thread.gmane.org/gmane.comp.lang.haskell.general/14834 20. http://twan.home.fmf.nl/compact-string/ HSXML version 1.13. Oleg Kiselyov [21]announced version 1.13 of [22]HSXML. HSXML is a library for writing and transforming typed semi-structured data in Haskell -- in S-expression syntax, with the extensible set of `tags', and statically enforced content model restrictions. A particular application is writing web pages in Haskell. We obtain HTML, XHTML or other output formats by running the Haskell web page in an appropriate rendering monad. The benefit of representing XML-like documents as a typed data structure/Haskell code is static rejection of bad documents -- not only those with undeclared tags but also those where elements appear in wrong contexts. 21. http://thread.gmane.org/gmane.comp.lang.haskell.general/14835 22. http://pobox.com/~oleg/ftp/Scheme/xml.html#typed-SXML Haskell XML Toolbox 7.1. Uwe Schmidt [23]announced a new version of [24]the Haskell XML Toolbox. The main change is the step from cvs to darcs. The documentation has source links into [25]the darcs repository. [26]A tutorial is available in the Haskell wiki. 23. http://article.gmane.org/gmane.comp.lang.haskell.general/14831 24. http://www.fh-wedel.de/~si/HXmlToolbox/index.html 25. http://darcs.fh-wedel.de/hxt 26. http://www.haskell.org/haskellwiki/HXT OmegaGB, Haskell Game Boy Emulator. Bit Connor [27]announced OmegaGB, an emulator for the Nintendo Game Boy, written in pure Haskell. It uses gtk2hs for the user interface, but there is also a version that doesn't require gtk2hs and uses ascii art. You can find more information about the program at [28]the website. 27. http://article.gmane.org/gmane.comp.lang.haskell.general/14938 28. http://www.mutantlemon.com/omegagb/ Takusen 0.6. Oleg and Alistair [29]announced a new release of [30]Takusen, the database library for Haskell. There are a large number of changes and bug-fixes in this release, including improved Oracle and PostgreSQL support. 29. http://article.gmane.org/gmane.comp.lang.haskell.libraries/6209/ 30. http://darcs.haskell.org/takusen hoogle.el. David House [31]announced Hoogle.el, a simple Emacs Lisp library that nicely integrates [32]Hoogle into Emacs. 31. http://article.gmane.org/gmane.comp.lang.haskell.general/14944 32. http://haskell.org/haskellwiki/Hoogle.el Buggy nofib. Josep Silva Galiana [33]announced a 'buggy' version of the nofib collection of Haskell programs. [34]All programs contain one of these bugs: a bug that produces an incorrect result; a bug that produces non-termination; a bug that produces an exception (e.g., div by zero). [35]The buggy nofib suite can be used to test debugging tools. 33. http://article.gmane.org/gmane.comp.lang.haskell.general/14825 34. http://einstein.dsic.upv.es/darcs/nofib 35. http://einstein.dsic.upv.es/nofib nobench: Haskell implementation shootout. Don Stewart [36]announced nobench, a cross-implementation performance benchmark suite, based on nofib, [37]comparing the performance of various Haskell compilers and bytecode interpreters on a range of programs. 36. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/19684 37. http://www.cse.unsw.edu.au/~dons/nobench.html Derangement version 0.1.0. Dennis Griffith [38]announced the initial version of derangement, a library for finding a derangement of a set. A derangement of a set is a permutation with no fixed points, like many constrained matching problems it is susceptible to solution via a Max-flow algorithm. 38. http://article.gmane.org/gmane.comp.lang.haskell.cafe/19714 HSH 1.0.0. John Goerzen [39]announced the first release of HSH. HSH is designed to let you mix and match shell expressions with Haskell programs. With HSH, it is possible to easily run shell commands, capture their output or provide their input, and pipe them to/from other shell commands and arbitrary Haskell functions at will. HSH makes it easy to run shell commands. But its real power is in piping. You can pipe -- arbitrarily -- between external programs, pure Haskell functions, and Haskell IO functions 39. http://article.gmane.org/gmane.comp.lang.haskell.cafe/20053 A new Haskell cookbook. Martin Bishop [40]began a preliminary page, and fleshed out some of the headers/sub-headers on the wiki page for a good Haskell Cookbook (not a PLEAC clone). [41]Please contribute. 40. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/19790 41. http://haskell.org/haskellwiki/Cookbook Haskell' This section covers the [42]Haskell' standardisation process. * [43]Global variables * [44]Polymorphic components, so far * [45]do-and-if-then-else modification * [46]Fixity resolution, possible specification * [47]Disjunctive tuples 42. http://hackage.haskell.org/trac/haskell-prime 43. http://thread.gmane.org/gmane.comp.lang.haskell.prime/2054 44. http://thread.gmane.org/gmane.comp.lang.haskell.prime/2076 45. http://thread.gmane.org/gmane.comp.lang.haskell.prime/2120 46. http://thread.gmane.org/gmane.comp.lang.haskell.prime/2121 47. http://thread.gmane.org/gmane.comp.lang.haskell.prime/2133 Libraries This week's proposals and extensions to the [48]standard libraries. * [49]Data.Proxy * [50]Add extra readline completion functionality * [51]Control.Monad.Cont documentation * [52]Add First and Last wrappers around Maybe to Data.Monoid * [53]Add ioeGetLocation, ioeSetLocation to System/IO/Error.hs 48. http://haskell.org/haskellwiki/Library_submissions 49. http://thread.gmane.org/gmane.comp.lang.haskell.libraries/6238 50. http://thread.gmane.org/gmane.comp.lang.haskell.libraries/6256 51. http://thread.gmane.org/gmane.comp.lang.haskell.libraries/6287 52. http://thread.gmane.org/gmane.comp.lang.haskell.libraries/6319 53. http://thread.gmane.org/gmane.comp.lang.haskell.libraries/6320 Discussion Haskell with only one typeclass. Oleg Kiselyov [54]described how, if the ability to define typeclasses is removed from Haskell, no expressivity is lost. If Haskell had only one, pre-defined typeclass with only one method, we could still do normal Haskell programming with standard and user-defined overloaded numerical functions, monads, monad transformers, etc. Haskell with only one typeclass can express all of Haskell98 typeclass programming idioms including constructor classes, plus multi-parameter type classes and some functional dependencies. 54. http://article.gmane.org/gmane.comp.lang.haskell.general/14936 Data type declarations are implicitly moduled. Chris Moline [55]proposed an idea to allow multiple data declarations to share constructors by having them be implicitly declared inside a module. 55. http://article.gmane.org/gmane.comp.lang.haskell.general/14847 Importance of MonadRandom. Yitzchak Gale [56]pointed out the importance of Cale Gibbard's [57]MonadRandom. This monad makes it possible to write functions that use randomness without having to specify in advance whether the source of randomness will be a pure pseudorandom number generator, as in System.Random, or physical randomness via the IO monad, such as your operating system's source of physical randomness, or random.org, or a hardware random generator. 56. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/19058 57. http://www.haskell.org/haskellwiki/New_monads/MonadRandom Become a GHC build slave!. Simon Marlow [58]pointed out that, thanks largely to Ian Lynagh, GHC now has a BuildBot infrastructure to automate nightly builds on multiple platforms. This replaces the old set of shell scripts that we used to run nightly builds; now adding new clients to the setup is [59]relatively easy. So far we have various Windows builds running, and I'll be moving over the existing Linux nightly builds in due course. 58. http://article.gmane.org/gmane.comp.lang.haskell.cafe/19103 59. http://hackage.haskell.org/trac/ghc/wiki/BuildBot Editor support for low level hacking. Don Stewart [60]mentioned some tools used for making low level optimisation of GHC Haskell code easier 60. http://article.gmane.org/gmane.comp.lang.haskell.cafe/19348 Optimisation fun. Creighton Hogg [61]sparked a long thread on optimising prime sieves in Haskell 61. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/19380 OO Design in Haskell Example. Steve Downey [62]began a thread on OO design in Haskell 62. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/19897 Safe lists with GADTs. Neil Mitchell [63]explored a safe version of head and tail, on a safe version of lists, using GADTs 63. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/19901 Jobs Research position at Nokia Research Center. Jamey Hicks [64]announced the availability of a senior research engineer position at Nokia Research Center Cambridge, US. They are seeking an exceptional, highly motivated individual who is interested in a unique opportunity to collaborate with a world-class academic research community. This position is for the Armo project at NRC Cambridge, using Bluespec hardware description language to radically improve Nokia's ability to develop advanced SOCs and corresponding software for future mobile phones and mobile computers. We are investigating co-development of hardware and software components for such devices. Success in the project will lead to both academic publication as well as a significant positive impact on Nokia products and engineering. 64. http://article.gmane.org/gmane.comp.lang.haskell.general/14901 New PhD Positions Computing Science, Chalmers University. Koen Claessen [65]announced new [66]PhD positions for 2007, at Chalmers University of Technology. The focus is on algorithms, bioinformatics, distributed systems and computing, functional programming, formal methods, interaction design, language technology, language based security, parallel and high performance computing, programming logic and type theory, but research is not restricted to these topics. 65. http://article.gmane.org/gmane.comp.lang.haskell.general/14900 66. http://chalmersnyheter.chalmers.se/chalmers03/english/eng_vacanciesarticle.… Positions at Oxford: refactoring tools. Oege.de.Moor [67]announced the availability of positions in the Programming Tools Group at Oxford, researching aspect refactoring tools 67. http://article.gmane.org/gmane.comp.lang.haskell.general/14860 Blog noise [68]Haskell news from the blogosphere. * [69]Writing a Simple Search Engine in Haskell: Part 0 - Introduction * [70]Writing a Simple Search Engine in Haskell: Part 1 Maybe and List * [71]Haskell IO for Imperative Programmers * [72]Quotient Types for Information Hiding * [73]How Many Functions are There of Type Bool -> Bool? * [74]Macros for Haskell? Done. * [75]More on Haskell, Side Effects and Code Reuse * [76]The theory of monads * [77]Writing code by types * [78]Haskell: open secret in Ruby land * [79]Ruby vs Haskell: choose what works * [80]Real time Haskell * [81]Folds and functional programming * [82]Countable Ordinals in Haskell * [83]Haskell * [84]Programming and the Metaphorical Mind * [85]Languages and the semiskilled developer * [86]Building a Firewall Against Complexity * [87]The Killer App for a new language * [88]Time travel in Haskell * [89]Comonads and reading from the future * [90]Flirting with Functional Programming * [91]A fold-like procedure in C * [92]Monads in Qi * [93]Monads work because they have a tight interface * [94]What's wrong with for loops * [95]More on what's wrong with for loops * [96]Haskell, CAL and Scala * [97]Haskell: Queues without pointers * [98]Type Classes: Not Quite Overloading * [99]Generalised Algebraic Data Types, Phantom Types, and Dependent Types * [100]An IRC client/server in Haskell * [101]Language design: grand architecture versus feature collections * [102]Thoughts on one week in Haskell * [103]Why its hard for imperative programmers to learn Haskell * [104]Refunctoring with polymorphism * [105]Introductory console IO in Haskell * [106]Learn the lambda calculus * [107]Haskell for Alphas and Betas * [108]My evolution as a Haskell programmer * [109]On learning Haskell * [110]Greenspun's Tenth Rule applied to Haskell * [111]Cabal with rpm goodness * [112]F# * [113]Arithemtic coding in Haskell * [114]A filesystem tree printer * [115]Using Bayesian filtering instead of 'if' in Haskell * [116]Combinator parsing * [117]Monads for vector spaces, probability and quantum mechanics pt. I * [118]Monads, Vector Spaces and Quantum Mechanics pt. II * [119]Learning the Haskell programming language * [120]A twisted history of monad transformers * [121]Monadic parsing * [122]Forth as a Haskell DSL * [123]A better environment for shell scripting * [124]Smart classification using Bayesian monads in Haskell * [125]Haskell like data structures in Common Lisp 68. http://planet.haskell.org/ 69. http://blogs.nubgames.com/code/?p=18 70. http://blogs.nubgames.com/code/?p=19 71. http://blogs.nubgames.com/code/?p=22 72. http://japple.blogspot.com/2007/01/quotient-types-for-information-hiding.ht… 73. http://japple.blogspot.com/2007/01/how-many-functions-are-there-of-type.html 74. http://clemens.endorphin.org/weblog/archives/2007-01.shtml#e2007-01-31T12_2… 75. http://neilbartlett.name/blog/?p=13 76. http://scienceblogs.com/goodmath/2007/01/the_theory_of_monads_and_the_m_1.p… 77. http://neilmitchell.blogspot.com/2007/01/writing-code-by-types.html 78. http://notes-on-haskell.blogspot.com/2007/01/haskell-open-secret.html 79. http://notes-on-haskell.blogspot.com/2007/01/ruby-vs-haskell-choose-what-wo… 80. http://mikeburrell.wordpress.com/2007/02/01/real-time-haskell/ 81. http://mikeburrell.wordpress.com/2007/02/01/functional-idempotence-optimiza… 82. http://japple.blogspot.com/2007/02/countable-ordinals-in-haskell.html 83. http://vanirsystems.com/danielsblog/?p=103 84. http://toomuchcode.blogspot.com/2007/02/part-1-programming-and-metaphorical… 85. http://toomuchcode.blogspot.com/2007/02/part-2-languages-and-lesser-skilled… 86. http://toomuchcode.blogspot.com/2007/02/building-firewall-against-complexit… 87. http://toomuchcode.blogspot.com/2007/02/part-4-killer-app.html 88. http://community.livejournal.com/evan_tech/216270.html 89. http://sigfpe.blogspot.com/2007/02/comonads-and-reading-from-future.html 90. http://johnleesmiller.blogspot.com/2007/02/first-post.html 91. http://www.yomi.at/archive/2007/02/115 92. http://programmingkungfuqi.blogspot.com/2007/02/monads-in-qi.html 93. http://www.sdowney.org/2007/01/monads-rest-and-c-template.html 94. http://notes-on-haskell.blogspot.com/2007/02/whats-wrong-with-for-loop.html 95. http://notes-on-haskell.blogspot.com/2007/02/whats-wrong-with-for-loop-revi… 96. http://blog.tmorris.net/ignorance-is-mostly-bliss-but-not-always/ 97. http://www.randomhacks.net/articles/2007/02/08/haskell-queues-without-point… 98. http://www.cs.nott.ac.uk/~pni/Papers/Notes/typeClassOvld.html 99. http://www.cs.nott.ac.uk/~pni/Papers/Notes/GADTs.html 100. http://blog.nurd.se/hype/?p=30 101. http://www.dysfunctor.org/2007/02/13/architecture-vs-features/ 102. http://kevin.scaldeferri.com/blog/2007/02/12/OneWeek.html 103. http://qftblog.wordpress.com/2007/02/14/why-its-so-hard-for-imperative-prog… 104. http://blog.tmorris.net/refunctoring/ 105. http://cod3po37ry.blogspot.com/2007/02/more-on-haskell-io-and-interact.html 106. http://foreigndispatches.typepad.com/dispatches/2007/02/an_introduction.html 107. http://paulspontifications.blogspot.com/2007/02/haskell-for-alphas-and-beta… 108. http://onthebalcony.wordpress.com/2007/02/19/my-evolution-as-a-haskell-prog… 109. http://osfameron.vox.com/library/post/on-learning-haskell.html 110. http://japple.blogspot.com/2007/02/conors-rule.html 111. http://www.serpentine.com/blog/2007/02/20/haskell-cabal-now-with-extra-crun… 112. http://reddevnews.com/news/devnews/article.aspx?editorialsid=164 113. http://vandreev.wordpress.com/2007/01/07/arithmetic-coding/ 114. http://blog.moertel.com/articles/2007/02/22/a-simple-directory-tree-printer… 115. http://www.randomhacks.net/articles/2007/02/22/bayes-rule-and-drug-tests 116. http://mikeburrell.wordpress.com/2007/02/25/combinator-parsing/ 117. http://sigfpe.blogspot.com/2007/02/monads-for-vector-spaces-probability.html 118. http://sigfpe.wordpress.com/2007/03/04/monads-vector-spaces-and-quantum-mec… 119. http://printf.wordpress.com/2007/02/27/haskell-functional-programming-langu… 120. http://conway.rutgers.edu/~ccshan/wiki/blog/posts/Monad_transformers.html 121. http://gbacon.blogspot.com/2007/02/my-first-monadic-program.html 122. http://shaurz.wordpress.com/2007/03/03/forth-as-a-haskell-dsl-or-lambda-the… 123. http://changelog.complete.org/posts/587-A-better-environment-for-shell-scri… 124. http://www.randomhacks.net/articles/2007/03/03/smart-classification-with-ha… 125. http://common-lisp.net/project/patty/patty.html Quotes of the Week * sleepingsquirrel: Programming in Haskell is like having an interactive conversation with a teleportation machine. You tell it you want to go to some place warm and sandy. The machine complains about ambiguous constraints. So you tell it that there should be plenty of free tropical fruit drinks. It carps 'Inferred location less polymorphic than expected'. Whoops, free flowing that is... After a few more iterations, there's a little puff of smoke, and at the sound of the chimes, you discover you're now on the beach in Tahiti. And although you've used the machine many times before, you can't help but be impressed that it usually 'Just works' most of the time. * jmillikin: If I had to work on code with performance requirements, Haskell would be my choice (followed by C++). Haskell has functional goodness with the ability to break into imperative mode, and C++ gives me direct memory management with a few functional pieces. * Cale: It ought to be called simonPerformIO, and only used if your first name is Simon * monochrom: m a -> (a -> m b) -> m b is much more to the point than 'mumble computation mumble computation' * mwc: There's a time when your brain doesn't get the monads. Then something violent and irreversable happens and you hate every other language for not having monads Code Watch Wed Feb 28 05:07:14 PST 2007. Simon Marlow. [126]Remove vectored returns. We recently discovered that they aren't a win any more, and just cost code size. 126. http://article.gmane.org/gmane.comp.lang.haskell.cvs.ghc/19418 Wed Feb 21 09:04:01 PST 2007. simonpj. [127]Allow GADT syntax for newtypes 127. http://article.gmane.org/gmane.comp.lang.haskell.cvs.ghc/19344 About the Haskell Weekly News Each week, new editions are posted to [128]the Haskell mailing list as well as to [129]the Haskell Sequence and [130]Planet Haskell. [131]RSS is also available, and headlines appear on [132]haskell.org. Headlines are available as [133]PDF. To help create new editions of this newsletter, please see the [134]contributing information. Send stories to dons at cse.unsw.edu.au. The darcs repository is available at darcs get [135]http://www.cse.unsw.edu.au/~dons/code/hwn 128. http://www.haskell.org/mailman/listinfo/haskell 129. http://sequence.complete.org/ 130. http://planet.haskell.org/ 131. http://sequence.complete.org/node/feed 132. http://haskell.org/ 133. http://www.cse.unsw.edu.au/~dons/code/hwn/archives/20070305.pdf 134. http://haskell.org/haskellwiki/HWN 135. http://www.cse.unsw.edu.au/~dons/code/hwn

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Announcing harchive: Backup and restore software in Haskell.
by David Brown 04 Mar '07

04 Mar '07

Announcing release 0.1 of "harchive", a program for backing up and restoring data. I've included a brief feature list below. The code is available in darcs at: http://www.davidb.org/darcs/harchive/ The connection isn't all that fast, so if it gets too busy, I'll move it somewhere else. This software is in a very early stage, but is at the point where others may be interested in looking at it. It does demonstrate that Haskell (at least GHC) is indeed useful for this kind of low-level seeming task. Thanks, David Brown Harchive version 0.1. - Implemented, with support for the following. - Client/server model. The backup is stored in a file pool with the hpool program. The hfile program can access this pool over tcp (no authentication or encryption, so be careful). - Stores data from multiple backups and multiple machines in a content addressible store. Duplicated data even on separate machines will not take additional space. Collisions can be made arbitrarily improbable by choice of hash function size (not easily changeable, in the current code, though). - Pool manager uses Sqlite3 specific capabilities to get efficient storage of the pool index. Sqlite3 is a custom binding to Sqlite3 to take advantage of these capabilities. - Uses openssl's sha1 library. Wouldn't be difficult to use a different library (there are license issues with openssl). Generally the program's performance is bound by the speed of hashing and/or the speed of data compression. - Uses Duncan Coutts' zlib library to get good zlib speed. - Linux dependent. Uses the output of '/sbin/blkid' to map devices to UUIDs of the filesystems to get persistent, and unique identifiers for each filesystem. - Has a primitive status display ('-v') during backup. - Able to backup and restore directories/filesystems. Restore semantics are as accurate as I can get them without extra strange semantics. - Multithreaded backup. Allows backup to run at high speed, even while waiting for cache responses from the server. Does not need to be built with '-threaded'. - Restore is reasonably simple. It tends to get tested less, so it is beneficial to move complexity to the backup side.

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