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Re: [Haskell-cafe] Why the Prelude must die
by Vivian McPhail 03 Apr '07

03 Apr '07

I agree with Sven, but... What I want to push is a 'mathematically sound' numeric prelude. A proper numerical prelude should have bona fide mathematical obects like groups, rings, and fields underlying common numerical classes. It would be edifying to the student who discovered that the particular data type he is using is an inhabitant of a known class and can thus take advantage of known properties, presupplied as class methods. Reasoning and communication about programs, data types, and functions would be enhanced. [Conjecture 1 (2007). Haskell Mathematical Prelude and Mathematicians] If Haskell had a mathematically sound prelude then more mathematicians would use Haskell. Cheers, Vivian > > Message: 1 > Date: Sat, 24 Mar 2007 17:56:11 +0100 > From: Sven Panne <sven.panne(a)aedion.de> > Subject: Re: [Haskell-cafe] Why the Prelude must die > To: haskell-cafe(a)haskell.org > Cc: libraries(a)haskell.org > Message-ID: <200703241756.11121.sven.panne(a)aedion.de> > Content-Type: text/plain; charset="iso-8859-1" > > On Saturday 24 March 2007 03:48, Stefan O'Rear wrote: > > 1. Namespace pollution > > > > The Prelude uses many simple and obvious names. Most > programs don't > > use the whole Prelude, so names that aren't needed take up > namespace > > with no benefit. [...] > > Even though I think that the current Prelude is far from > perfect, one should not forget that is a very solid > foundation of a "common language": If one sees e.g. '(.)' or > 'map', it is immediately clear to everybody what this means, > without having to scan through (perhaps long) import lists. > Of course one could hide some parts of the Prelude etc., but > I think in the long run this only leads to confusion. > Redefining common things, heavy use of tons of self-defined > operators etc. all make maintenance much harder. > > Try reading Lisp code with heavy use of macros or C++ code > with tons of overloadings. This is more like Sudoku solving > than anything else, because there is no "common language" > between the author and the reader anymore. > > And taking away the prelude is a little bit like taking away > 'int', 'double', 'for', 'while' etc. from the C programmer... > > > 11. Committeeism > > > > Because the Prelude has such a wide audience, a strong committee > > effect exists on any change to it. This is the worst kind of > > committeeism, and impedes real progress while polluting the Prelude > > with little-used features such as fail in Monad (as opposed to > > MonadZero) and until. > > Depending on your viewpoint, you can see this as a plus. > Everybody agrees that finalizers are evil, but propose the > removal of that method from java.lang.Object to the Java people. :-) > > My proposal would be to incrementally improve the Prelude, > modularize it a bit more, fix the Num hierarchy, but > basically leave it as it is. > > Cheers, > S. > >

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ANN: HSH 1.2.0
by John Goerzen 03 Apr '07

03 Apr '07

Hi, I'm pleased to announce HSH 1.2.0. Since version 1.0.0 was announced a few days ago, there have been some improvements: * run is now a function with a polymorphic return type. Depending on the value expected, it can return to you a String representing all output, an exit code, a list of lines of output, etc. runS is now removed. * A number of new helper functions in ShellEquivs. Fixes to readlink and readlinkabs there. * New helper functions runIO (to force an IO () context) and runSL (returns a single line of output, \n stripped) * There are now 82 unit tests. Get it at: http://software.complete.org/hsh -- John Goerzen Author, Foundations of Python Network Programming http://www.amazon.com/exec/obidos/tg/detail/-/1590593715

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was Re: ANN: HSH 1.2.0
by Thomas Hartman 03 Apr '07

03 Apr '07

I'm still trying to figure out how to do this on ubuntu. If this winds up being a garden path I'll try on debian next, but at least I'm learning a lot about getting haskell stuff built. Anyway, since I'm on a virtualized linux box, I decided to get a fresh start, unmounted my original OS profile and installed a fresh dapper 6. I then changed /etc/apt/sources.list to be okay for grabbing .debs from feisty. (No longer doing the build from source thing.) apt-get install ghc6, ok from feisty. (Is there another repo that gets all the extra libs at one go?) sudo apt-cache search -o APT::Cache-Limit=25165824 ghc6 | grep -i missing libghc6-hdbc-missingh-dev - Integration of HDBC with MissingH, GHC version libghc6-missingh-dev - Library of utility functions for Haskell, GHC6 package thartman@linodehaskell:~/haskellinstalls/hsh>sudo apt-cache search -o hoorah, my apt cache search command seems ok. sudo apt-cache search -o APT::Cache-Limit=25165824 ghc6 | grep -i hsh thartman@linodehaskell:~/haskellinstalls/hsh> too bad, still no hsh in ubuntu repo. darcs get http://darcs.complete.org/hsh/ (Or should I have used something else?) runghc Setup.hs configure same problems as before. But starting afresh seems to have detangled the issues I was having with packaging confusion. At least now I can apt-get install missingh And some other dependency following is made easier. Finally configure for hsh works. But then thartman@linodehaskell:~/haskellinstalls/hsh>sudo runghc Setup.lhs install Setup.lhs: Warning: The field "hs-source-dir" is deprecated, please use hs-source-dirs. Installing: /usr/local/lib/HSH-1.2.1/ghc-6.6 & /usr/local/bin HSH-1.2.1... Setup.lhs: Error: Could not find module: HSH with any suffix: ["hi"] So, I seem to be stuck at this point. 2007/4/2, Thomas Hartman <tphyahoo(a)gmail.com>: > Well, I guess I spoke to soon. After building ghc6 from feisty as > described above, I tried building missingh and have basically what I > started with. > > Is there something I can tweak to get the above straightened out using > those nice deb packages, or do I have to do all the dependency chasing > involved with building from source? Or is there another way? > > If this is too debian oriented please yell at me and I will ask about > this on a deb/ubuntu forum. > > thanks... > > Note, should have mentioned, after doing as my above post describes, I > installed all the newly generated deb packages with > > dpkg -i *.deb > > **************** > > thartman@linodewhyou:~/haskellInstalls/missingh>runghc Setup.hs configure > Configuring MissingH-0.18.3... > configure: /usr/lib/ghc-6.6/bin/ghc-pkg > configure: Dependency unix-any: using unix-1.0 > Setup.hs: cannot satisfy dependency network-any > > thartman@linodewhyou:~/haskellInstalls/missingh>which runghc > /usr/lib/ghc-6.6/bin/runghc > > # note, definitely the thing I installed today: > thartman@linodewhyou:~/haskellInstalls/missingh>ls -l `which runghc` > -rwxr-xr-x 1 root root 300716 Apr 2 09:17 /usr/lib/ghc-6.6/bin/runghc > thartman@linodewhyou:~/haskellInstalls/missingh> > > # and I installed it from deb ghc6, dpkg recognizes it > > thartman@linodewhyou:~/haskellInstalls/missingh>dpkg -S > /usr/lib/ghc-6.6/bin/runghc > ghc6: /usr/lib/ghc-6.6/bin/runghc > > # it does seem like ghc6 comes with a network package > thartman@linodewhyou:~/learning/haskell>apt-cache showpkg ghc6 | grep -i network > 6.4.1-2ubuntu2 - libghc6-readline-dev libghc6-stm-dev libghc6-hgl-dev > libghc6-x11-dev libghc6-fgl-dev libghc6-mtl-dev libghc6-hunit-dev > libghc6-quickcheck-dev libghc6-network-dev libghc6-haskell-src-dev > libghc6-parsec-dev libghc6-cabal-dev libghc6-unix-dev > libghc6-template-haskell-dev libghc6-haskell98-dev libghc6-base-dev > libghc6-rts-dev ghc haskell-compiler > > # I get lost here. Do I have libghc6-network-dev, or don't I? > > thartman@linodewhyou:~/haskellInstalls/missingh>sudo apt-get install > libghc6-network-dev > Reading package lists... Done > Building dependency tree... Done > Note, selecting ghc6 instead of libghc6-network-dev > ghc6 is already the newest version. > You might want to run `apt-get -f install' to correct these: > The following packages have unmet dependencies: > hat-ghc6: Depends: ghc6 (< 6.4.1+) but 6.6-3 is to be installed > libghc6-cabal-dev: Depends: ghc6 (< 6.4.2) but 6.6-3 is to be installed > E: Unmet dependencies. Try 'apt-get -f install' with no packages (or > specify a solution). > > > > > > > 2007/4/2, Thomas Hartman <tphyahoo(a)gmail.com>: > > > As you have built ghc6.6 from sources I think that you also need to build > > > all haskell libs from sources. So, do > > > > I did this, and got the feeling this would probably work, but is a > > real sad world of dependency chasing with no (clear) end in sight. > > > > So I investigated your second suggestion > > > > > Another way is to take ghc6 and all haskell libs from fiesty. > > > > which to me seems much preferrable. > > > > http://old.pupeno.com/blog/unstable-packages-on-ubuntu/ > > > > Was indispensible in helping me figure out how to do this. > > > > To give some details on this (which is really more apt packaging know > > how than haskell but whatever), I did something like > > > > 1) change /etc/apt/sources.list to add > > > > deb-src http://archive.ubuntu.com/ubuntu/ feisty main restricted > > universe multiverse > > > > note, only add deb-src line here, not deb line, see article above for why. > > > > sudo aptitude install fakeroot (needed utility) > > fakeroot apt-get source --build ghc6 > > -- complains, some dependencies are missing > > > > sudo aptitude install ..... > > install packages with above command, not from source. it's my first > > time using the aptitude command, I wonder if this does the same thing > > as apt-get install, which is what I usually do. Whatever the case... > > > > fakeroot apt-get source --build ghc6 > > > > works :) > > > > 2007/3/21, Max Vasin <max.vasin(a)gmail.com>: > > > >>>>> "Thomas" == Thomas Hartman <tphyahoo(a)gmail.com> writes: > > > > > > Thomas> Furthermore (as the above messages suggest and locate confirms), I > > > Thomas> seem to have mtl already > > > > > > Thomas> I took a wild guess and tried specifying this with ghc -i > > > > > > Thomas> like > > > > > > Thomas> sudo runghc -i/usr/lib/ghc6-mtl-dev Setup.lhs configure > > > Thomas> and sudo runghc -i/usr/lib/ Setup.lhs configure > > > > > > Thomas> but no dice. > > > > > > Thomas> *************** > > > > > > Thomas> thartman@linodewhyou:~/haskellInstalls/hsh$ locate libghc6-mtl-dev > > > Thomas> /home/thartman/libghc6-mtl-dev_1.0-3_i386.deb > > > Thomas> /usr/lib/libghc6-mtl-dev > > > Thomas> /usr/lib/libghc6-mtl-dev/register.sh > > > Thomas> /usr/lib/libghc6-mtl-dev/unregister.sh > > > Thomas> /usr/share/doc/libghc6-mtl-dev > > > Thomas> /usr/share/doc/libghc6-mtl-dev/changelog.Debian.gz > > > Thomas> /usr/share/doc/libghc6-mtl-dev/copyright > > > Thomas> /var/lib/dpkg/info/libghc6-mtl-dev.list > > > Thomas> /var/lib/dpkg/info/libghc6-mtl-dev.md5sums > > > Thomas> /var/lib/dpkg/info/libghc6-mtl-dev.postinst > > > Thomas> /var/lib/dpkg/info/libghc6-mtl-dev.prerm > > > > > > As you have built ghc6.6 from sources I think that you also need to build > > > all haskell libs from sources. So, do > > > > > > $ apt-get source libghc6-mtl-dev > > > $ cd <haskell-mtl-or-whatever-dir-is-named> > > > $ runhaskell Setup.lhs configure > > > $ runhaskell Setup.lhs build > > > $ sudo runhaskell Setup.lhs install > > > > > > Another way is to take ghc6 and all haskell libs from fiesty. > > > > > > -- > > > WBR, > > > Max Vasin. > > > > > > _______________________________________________ > > > Haskell-Cafe mailing list > > > Haskell-Cafe(a)haskell.org > > > http://www.haskell.org/mailman/listinfo/haskell-cafe > > > > > >

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Matlab/BLAS/LAPack and Re: [Haskell-cafe] Mathematics in Haskell Re: Why the Prelude must Die
by Alexander McPhail 03 Apr '07

03 Apr '07

Since I brought this up (search haskell' list) I should probably volunteer to help. If people agree I can coordinate an effort to build a mathematically sound hierarchy. Unfortunately my mathematical knowledge is less than ideal for this purpose (I am actively remedying this at university). However, if there is an administrative burden I volunteer to shoulder it. On a related note I have written a binding to Matlab data files and arrays if anyone is interested, and I am embarking on a project to bind to CBLAS and CLAPack. Vivian > > Jacques Carette wrote: > > > >> perhaps i was mistaken in thinking that there is a group of > >> math-interested haskellers out there discussing, developing, and > >> documenting the area? or perhaps that group needs introductory > >> tutorials presenting its work? > > My guess is that there are a number of people "waiting in > the wings", > > waiting for a critical mass of features to show up before really > > diving in. See http://www.cas.mcmaster.ca/plmms07/ > > for my reasons for being both interested and wary). > > > > Probably the simplest test case is the difficulties that people are > > (still) encountering doing matrix/vector algebra in Haskell. One > > either quickly encounters efficiency issues (although PArr might > > help), or typing issues (though many tricks are known, but not > > necessarily simple). Blitz++ and the STL contributed > heavily to C++ > > being taken seriously by people in the scientific computation > > community. Haskell has even more _potential_, but it is > definitely unrealised potential. > > > > I am one of those mathematicians "waiting in the wings." > Haskell looked > very appealing at first, and the type system seems perfect, > especially for > things like multilinear algebra where currying and duality is > fundamental. > I too was put off by the Num issues though--strange mixture > of sophisticated > category theory and lack of a sensible hierarchy of algebraic objects. > > However, I've decided I'm more interested in helping to fix > it than wait; > so count me in on an effort to make Haskell more > mathematical. For me that > probably starts with the semigroup/group/ring setup, and good > arbitrary-precision as well as approximate linear algebra support. > > -- > > I've been watching this thread for quite a while now, and it seems to > me that there is quite a bit of interest in at least working on a new > Prelude. I've also noticed a 'The Other Prelude' page on the wiki > [http://haskell.org/haskellwiki/The_Other_Prelude] and they seem to > have a start on this. So it seems that we should actually start this, > because people will contribute. Can somebody with good Cabal skills > and maybe access to darcs.haskell.org start a new library for people > to start patching? > > Bryan Burgers > > > > On Apr 2, 2007, at 3:24 PM, Andrzej Jaworski wrote: > > >> I too was put off by the Num issues though--strange mixture of > >> sophisticated > >> category theory and lack of a sensible hierarchy of algebraic > >> objects. > > > > Perhaps we should replace CT with lattice theoretic thinking (e.g. > > functor = monotonic > > function) before cleaning up the type-related mess? > > See: http://citeseer.ist.psu.edu/269479.html > > > >> so count me in on an effort to make Haskell more mathematical. > >> For me that > >> probably starts with the semigroup/group/ring setup, and good > >> arbitrary-precision as well as approximate linear algebra support. > > > > I agree: semigoups like lattices are everywhere. > > Then there could be a uniform treatment of linear algebra, > > polynomial equations, operator > > algebra, etc. So, perhaps haste is not a good advice here? > > > > -Andrzej > >

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Fwd: darcs.haskell.org access for maths hierarchy
by Alexander McPhail 03 Apr '07

03 Apr '07

I have set up a page on the wiki for discussion: http://www.haskell.org/haskellwiki/Haskell_and_mathematics/Hierarchy And about a darcs repo for people to patch against: ---------- Forwarded message ---------- From: Simon Marlow <simonmarhaskell(a)gmail.com> Date: 03-Apr-2007 20:28 Subject: Re: darcs.haskell.org access for maths hierarchy To: Alexander McPhail <haskell.vivian.mcphail(a)gmail.com> Hi there, The plan is to set up a separate server for hosting community projects. Right now we have the server, but we still have to set it up. Hopefully it should be available soon, we'll announce something when it is. Cheers, Simon Alexander McPhail wrote: > Hi, > > There is some movement on the haskell-cafe mailing list to set up a repo > to develop a mathematically sound algebraic class hierarchy. I have > volunteered to coordinate this. > > What is the policy on giving access to darcs.haskell.org > <http://darcs.haskell.org>? > Cheers, > > Vivian > >

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Keeping a symbol table with Parsec
by Joel Reymont 02 Apr '07

02 Apr '07

Folks, Are there any examples of keeping a symbol table with Parsec? I'm translating a parser from OCaml and I do this OUTPUT COLON ID LP NUMERIC_SIMPLE RP { add $3 TypNumOut; SimpleOutputDec ($3, Number) } Meaning that if a keyword Output is followed by ":" and an identifier and then "(NumericSimple)" then add identifier to the symbol table as a Number and box it in a constructor. Then in my lexer I do a lookup to check if I have seen this identifier and if I have seen one of type TypeNumOut I return the token NUM instead of ID. This ensures that I can have rules with the token NUM as opposed to ID everywhere. How would I accomplish the same with Parsec, that is 1) update a symbol table and 2) check identifiers and "return a different token"? Thanks, Joel -- http://wagerlabs.com/

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String to Word64 Conversion
by Dominic Steinitz 02 Apr '07

02 Apr '07

> [Haskell-cafe] String to Word64 Conversion > Ian Sefferman iseff at iseff.com > Sun Apr 1 15:42:07 EDT 2007 > Previous message: [Haskell-cafe] Josephus problem and style > Next message: [Haskell-cafe] Data.ByteStream.Char8.words performance > Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] > I've been spending a lot of time trying to find a clean way to convert > from a String to a Word64 for the Crypto library. > > Specifically, we're trying to encrypt the strings with Blowfish. The > type for the encrypt function is: > > encrypt :: (Integral a) => a -> Word64 -> Word64 > > I assume I would want something like: > toWord64s :: String -> [Word64] > toWord64s = .... > > myEncrypt string = map (Blowfish.encrypt myKey) (toWord64s string) > > I would have to imagine that encrypting strings is a fairly common > thing to do, so a conversion should be trivial, but I can't seem to > find anything on it. I feel like I must be missing something rather > obvious here. Am I? > > Thanks, > Ian Ian, Maybe something like this. I've pretty much taken it from http://darcs.haskell.org/crypto/Data/Digest/SHA1.hs. fromBytes :: (Bits a) => [a] -> a fromBytes input = let dofb accum [] = accum dofb accum (x:xs) = dofb ((shiftL accum 8) .|. x) xs in dofb 0 input blockWord8sIn64 :: [Word8] -> [[Word8]] blockWord8sIn64 = unfoldr g where g [] = Nothing g xs = Just (splitAt 8 xs) getWord64s :: [Word8] -> [Word64] getWord64s = map fromBytes . map (map fromIntegral) . blockWord8sIn64 Don't forget you will need to pad http://www.haskell.org/crypto/doc/html/Codec.Encryption.Padding.html. I don't know what your application is but I suggest NOT using ECB mode which your code suggests you are thinking of doing. The only mode currently supported in the crypto library is CBC but other modes should be trivial to add. Dominic.

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Binary I/O
by Daniel Brownridge 02 Apr '07

02 Apr '07

Hello. I am a Computer Science student attempting to write an emulator using Haskell. One of my main design choices is how to deal with machine code. Clearly it is possible to represent 0's and 1's as ASCII characters, however it strikes me that it would be much nicer to the I/O using raw binary. I don't seem to be able to find much documentation on this. Does anybody know how it's done, or can point me in the direction of some resources. Many thanks Daniel

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Re: [Haskell-cafe] Memory leak in streaming parser
by Oren Ben-Kiki 02 Apr '07

02 Apr '07

On Mon, 2007-04-02 at 13:54 +0100, Malcolm Wallace wrote: > An observation about your state setter functions, ... > You can shorten your code considerably by using the standard named-field > update syntax for exactly this task: > > setDecision :: String -> State -> State > setDecision decision state = state { sDecision = decision } If I do that, the run time insists on the state being "more" evaluated before it changes that specific field. This kills streaming, enforcing each production (including the top one) to be fully parsed before I can access its generated tokens. So the GC won't be hanging on to State objects, but memory still explodes - with unconsumed Token objects. And there's no output from the program until it dies :-( > Not only is it shorter, but it will often be much more efficient, since > the entire structured value is copied once once, then a single field > updated, rather than being re-built piece-by-piece in 15 steps. I know! Is there an efficient way to lazily modify just one field record? > You probably want to be strict in the state component, but not in the > output values of your monad. So as well as replacing > let ... in (finalState, rightResult) > with > let ... in finalState `seq` (finalState, rightResult) > in the (>>=) method in your Monad instance (and in the separate defn of For some strange reason, adding this didn't solve the problem - the GC still refuses to collect the state objects. BTW, forcing the evaluation of the intermediate states (originalState, leftState, rightState etc.) doesn't help either. I have tried to ensure that when '>>=' and '/' will allow the GC to discard old states "as soon as possible", but I'm obviously missing something. Is there a way to get more detailed retainer information than what's available with '-hr'? > you might also need to make all the named fields of your State datatype > strict. If I make any of them strict, streaming goes away :-( Writing a streaming parser in Haskell is turning out to be much harder than I originally expected. Every fix I tried so far either broke streaming (memory blows up due to tokens) or had no effect (memory blows up due to states). I am assuming that there's a magic point in the middle where tokens are consumed and states are GC-ed... but it has eluded me so far. Thanks, Oren Ben-Kiki P.S. I uploaded the package to Hackage. I added a debug-leak production to make it easier to profile this with even less productions involved. ``yes '#' | yaml2yeast -p debug-leak''.

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Memory leak in streaming parser
by Oren Ben-Kiki 02 Apr '07

02 Apr '07

I just created an initial version of a "streaming" parser. This parser is intended to serve as a reference parser for the YAML spec. Efficiency isn't the main concern; the priority was to have it use the BNF productions from the spec without any changes (ok, with tiny, minor, insignificant changes :-) and to allow it to stream large files. I'm happy to say I achieved the first goal, and the parser .hs file simply #includes a file that is, for all intents and purposes, a BNF file. I didn't have as much luck with the second goal. After putting a lot of effort into it, I have got to the point it is "streaming". That is, I can "cat" a large YAML file to the wrapper program and it will "immediately" start spitting out parsed tokens. This took some doing to ensure the resulting token stream is accessible while it is being generated, in the presence of potential parsing failures and, of course, parsing decision points. I must have done "too good a job" converting things to lazy form because, while the parser is streaming, it also hangs on to old state objects for no "obvious" reason. At least it isn't obvious to me after profiling it in any way I could think of and trying to `seq` the "obvious" suspects. Adding a `seq` in the wrong place will of course stop it from being a streaming parser... I'd take it as a kindness if someone who had some deeper knowledge of the Haskell internals would peek at it. It is packaged as Cabal .tar.gz file in http://www.ben-kiki.org/oren/YamlReference - it includes the wrapper program and a regression-test program. To watch it consume all available memory using a very small set of BNF productions, yes '#' | yaml2yeast -p s-l-comments (This basically matches "l-comment*" - each '#\n' is a comment line). You'll get a stream of parsed tokens to stdout and an ever-climbing memory usage in top (or htop). Any advice would be appreciated, Oren Ben-Kiki

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