- Haskell-Cafe - Haskell.org

ANN: shelltestrunner 0.8 released
by Simon Michael 09 Apr '10

09 Apr '10

I'm pleased to announce a new release of shelltestrunner, a tool which aims to make testing command-line programs easy. Thanks to Bernie Pope for contributing features and valuable feedback. Example: $ cabal install shelltestrunner ... $ cat - >a.test # a simple test - run cat, provide stdin, check stdout cat <<< 1 2 >>> 1 2 $ shelltest a.test a.test: [OK] Test Cases Total Passed 1 1 Failed 0 0 Total 1 1 Release notes: 2010/4/9 0.8 * rename executable to shelltest. The package might also be renamed at some point. * better built-in help * shell tests now include a full command line, making them more readable and self-contained. The --with option can be used to replace the first word with something else, unless the test command line begins with a space. * we also accept directory arguments, searching for test files below them, with two new options: --execdir execute tested command in same directory as test file --extension=EXT file extension of test files (default=.test) home: http://hackage.haskell.org/package/shelltestrunner repo: http://joyful.com/repos/shelltestrunner

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GSoC Project: A Haddock + Pandoc documentation tool
by ViaToR (Alvaro V.) 09 Apr '10

09 Apr '10

Hello, I just finished writing my GSoC proposal and I want to have some feedback from the community. I'll try to be brief (this is not the proposal). The project is about creating a new documentation tool for Haskell projects, like Sphinx[1] for Python or Scribble[2] for Scheme. We have Haddock, which is a great tool. It can take the sources of a project and generate a useful API reference. But the reference is just a fragment of the whole project documentation. So, Haddock can only do a part of what Sphinx can do. But we have another tool, Pandoc, that takes files of whatever markup language and transform it to another format. And this is the more general-purposed part of Sphinx that is missing in Haddock. So we have the tools for creating documentation as useful as other systems, we just need the glue and several improvements. To achieve this project, first I'll have to use Haddock as an API. Currently, the Haddock API is rudimentary and highly experimental, so I would have to extend and test it. Then I would have to write a Haddock backend which would generate the reference in an internal independent pandoc format [3]. Finally I would have to write a new command-line program that would manage the projects or I would have to add Pandoc support in Haddock command-line program or Haddock support in Pandoc. IMHO, I think that will be better a new command-line program, everyone with its own purpose. I created an example of what would be a library documented with this system [4]. The file contains a configuration file a la cabal, a reST file (It could be markdown) and the html output. I tried to represent that the html output for the reference have to be almost the same that generates Haddock (css may differ). Note that all the entries of the Haddock reference are first-citizens entities in the documentation, so you can refer to the entries, render one entry, all or by groups (there are examples in the reST file). I am looking forward your impressions and suggestions. Thanks to Simon Marlow, David Waern and Conal Elliott for their suggestions and help. Thanks you all. [1] http://sphinx.pocoo.org/ [2] http://docs.plt-scheme.org/scribble/ [3] http://hackage.haskell.org/packages/archive/pandoc/1.5.1.1/doc/html/Text-Pa… [4] http://bitbucket.org/viator/doc-example/get/tip.zip

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Can Haskell enforce the dimension?
by Haihua 09 Apr '10

09 Apr '10

Hi, In C++, template can be used to enforce the dimension. For example, F=m*a is OK and F=m*t will issue a compile time error. Is there a way to do this in Haskell? Thanks, Haihua

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mapM for vectors
by Khudyakov Alexey 09 Apr '10

09 Apr '10

Hello I found that there is no monadic map for vector. It's possible to define to define such map using conversion to list, but I suppose it's not efficient. I didn't make any measurements. > mapM' :: Monad m => (a -> m b) -> V.Vector a -> m (V.Vector b) > mapM' f = return . V.fromList <=< mapM f . V.toList Any suggestions about implementation of such function? Specifically I want to use Random monad. -- Khudyakov Alexey

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Re: [Haskell-cafe] ANN: darcsum.el 1.2 released
by Jose A. Ortega Ruiz 09 Apr '10

09 Apr '10

Simon Michael <simon(a)joyful.com> writes: > Unfortunately it will still hang if darcs emits something it can't > parse. An emacs process-filter is used to drive an interactive darcs > command, like an expect script. The process-filter can receive darcs > output in random chunks, so it's hard to distinguish a parse failure > from partial output, unless the output has a recognisable prefix, > which some of it does not (eg darcs amend's.) I'm not sure what a more > robust way to drive darcs looks like. Maybe i'm not understanding the problem, but cannot you just accumulate the output in an auxiliary variable and parse the ouput as a whole once the darcs process finishes? Thanks a lot for working on darcsum, btw! jao -- There are two ways to write error-free programs; only the third one works. - Alan Perlis, Epigrams in Programing

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Type constrain in instance?
by Louis Zhuang 09 Apr '10

09 Apr '10

Hi, I got an issue when playing haskell's type system, partically parametic class/instance have no way to specify constrains of their parameters. for example, i want to data struct to chain functions and their derivatives so we can have combined function and derivations, as following import qualified Control.Category as Cat data ChainableFunction a b = CF { cfF :: (a->b), cfDeriv :: (a->b) } class Module a b wher4e (*>) :: a -> b -> b instance Cat.Category CF where id :: (Num a) -- GHC dis-allow this id = CF id (const 1) (.) :: (Num a, Num b, Num c, Module a b, Module b c) => CF a b -> CF b c -> CF a c -- GHC disallow this either (.) (CF f f') (CF g g') = CF (g.f) (\a -> f' a *> g' (f a)) However GHC only has kinds for class/instance like (*->*->*) so we are forced to allow all possible types in instance code. I'm not sure if I'm modelling things correctly or is there another way to do the same thing? Cheers, Louis

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transliteration with Haskell iconv?
by Eric Kow 09 Apr '10

09 Apr '10

Hi all, I'd like transliterate a UTF-8 text to ASCII. With iconv(1), I would do iconv -f UTF-8 -t ASCII//TRANSLIT foo I've tried using Duncan's iconv library, but it seems to give me more question marks than iconv(1) would, which seems odd if it's the same library underneath. In other words, transliterating Aonach Mòr is a mountain in the Highlands of Scotland. On va boire un petit café si ça te dit. gives me with iconv(1) Aonach Mor is a mountain in the Highlands of Scotland. On va boire un petit cafe si ca te dit. but with my attempts at using Codec.Text.IConv and examples/hiconv -f utf-8 -t ascii --transliterate, I get Aonach M?r is a mountain in the Highlands of Scotland. On va boire un petit caf? si ?a te dit. Anybody run into this and know what to do? Thanks! PS. I'm on Ubuntu 9.04 if it makes any difference... -- Eric Kow <http://www.nltg.brighton.ac.uk/home/Eric.Kow> PGP Key ID: 08AC04F9

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Call for Contributions - Haskell Communities and Activities Report, May 2010 edition
by Janis Voigtländer 09 Apr '10

09 Apr '10

Dear all, I would like to collect contributions for the 18th edition of the ================================================================ Haskell Communities & Activities Report http://www.haskell.org/communities/ Submission deadline: 1 May 2010 (please send your contributions to hcar at haskell.org, in plain text or LaTeX format) ================================================================ This is the short story: * 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! * If you are interested in an existing project related to Haskell that has not previously been mentioned in the HCAR, please tell me, so that I can contact the project leaders and ask them to submit an entry. * Feel free to pass on this call for contributions to others that might be interested. More detailed information: The Haskell Communities & Activities Report is a bi-annual overview of the state of Haskell as well as Haskell-related projects over the last, and possibly the upcoming six months. If you have only recently been exposed to Haskell, it might be a good idea to browse the November 2009 edition -- you will find interesting topics described as well as several starting points and links that may provide answers to many questions. Contributions will be collected until the submission deadline. They will then be compiled into a coherent report that is published online as soon as it is ready. As always, this is a great opportunity to update your webpages, make new releases, announce or even start new projects, or to talk about developments you want every Haskeller to know about! Looking forward to your contributions, Janis (current editor) FAQ: Q: What format should I write in? A: The required format is a LaTeX source file, adhering to the template that is available at: http://haskell.org/communities/05-2010/template.tex There is also a LaTeX style file at http://haskell.org/communities/05-2010/hcar.sty that you can use to preview your entry. If you do not know LaTeX, then use plain text. If you modify an old entry that you have written for an earlier edition of the report, you should already have received your old entry as a template (provided I have your valid email address). Please modify that template, rather than using your own version of the old entry as a template. Q: Can I include images? A: Yes, you are even encouraged to do so. Please use .jpg format, then. Q: How much should I write? A: Authors are asked to limit entries to about one column of text. This corresponds to approximately one page, or 40 lines of text, with the above style and template. A general introduction is helpful. Apart from that, you should focus on recent or upcoming developments. Pointers to online content can be given for more comprehensive or "historic" overviews of a project. Images do not count towards the length limit, so you may want to use this opportunity to pep up entries. There is no minimum length of an entry! The report aims for being as complete as possible, so please consider writing an entry, even if it is only a few lines long. Q: Which topics are relevant? A: All topics which are related to Haskell in some way are relevant. We usually had reports from users of Haskell (private, academic, or commercial), from authors or contributors to projects related to Haskell, from people working on the Haskell language, libraries, on language extensions or variants. We also like reports about distributions of Haskell software, Haskell infrastructure, books and tutorials on Haskell. Reports on past and upcoming events related to Haskell are also relevant. Finally, there might be new topics we do not even think about. As a rule of thumb: if in doubt, then it probably is relevant and has a place in the HCAR. You can also ask the editor. Q: Is unfinished work relevant? Are ideas for projects relevant? A: Yes! You can use the HCAR to talk about projects you are currently working on. You can use it to look for other developers that might help you. You can use it to write "wishlist" items for libraries and language features you would like to see implemented. Q: If I do not update my entry, but want to keep it in the report, what should I do? A: Tell the editor that there are no changes. The old entry will be reused in this case, but it might be dropped if it is older than a year, to give more room and more attention to projects that change a lot. Do not resend complete entries if you have not changed them.

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Re: Asynchronous exception wormholes kill modularity
by Simon Marlow 09 Apr '10

09 Apr '10

On 08/04/2010 21:20, Tyson Whitehead wrote: > On March 26, 2010 15:51:42 Isaac Dupree wrote: >> On 03/25/10 12:36, Simon Marlow wrote: >>> I'd also be amenable to having block/unblock count nesting levels >>> instead, I don't think it would be too hard to implement and it wouldn't >>> require any changes at the library level. >> >> Wasn't there a reason that it didn't nest? >> >> I think it was that operations that block-as-in-takeMVar, for an >> unbounded length of time, are always supposed to C.Exception.unblock and >> in fact be unblocked within that operation. Otherwise the thread might >> never receive its asynchronous exceptions. > > If I'm understanding correctly here, it would be nice if you could just go > > unmask :: IO a -> IO a > > and always have asynchronous exceptions on for the duration of IO a. > > One solution might be if unmask always enabled asynchronous exception, but, in > a masked context, stopped them from propagating beyond the boundary of the IO > a action by re-queueing them be re-raised when next allowed. > > Of course you've then got the problem of umask having to produce a valid value > even when IO a was aborted, so you would have to go with something like > > unmask :: a -> IO a -> IO a > > where the first a gets returned if the IO a computation gets aborted by an > exception. The original problem code would then go from I haven't seen anyone else asking for this kind of design, and it's quite different to both what we have now and the new proposal. What advantages would this have, do you think? Cheers, Simon

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Performance question
by Arnoldo Muller 09 Apr '10

09 Apr '10

Hello! I am trying to implement a binary search function that returns the index of an exact or the (index + 1) where the item should be inserted in an array if the item to be searched is not found (I am not trying to insert data in the array) . Right now, the bottleneck of my program is in binarySearch', the function must be called a few billion times. Do you have any ideas on how to improve the performance of this function? import Data.Array.IArray type IntArray a = Array Int a -- The array must be 0 indexed. binarySearch :: Ord a => a -> IntArray a -> Int binarySearch query array = let (low, high) = bounds array in binarySearch' query array low high binarySearch' :: Ord a => a -> IntArray a -> Int -> Int -> Int binarySearch' query array !low !high | low <= high = let ! mid = low + ((high - low) `div` 2) ! midVal = array ! mid in next mid midVal | otherwise = -(low + 1) where next mid midVal | midVal < query = binarySearch' query array (mid + 1) high | midVal > query = binarySearch' query array low (mid - 1) | otherwise = mid Thank you! Arnoldo Muller

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Announce: hothasktags
by Luke Palmer 09 Apr '10

09 Apr '10

Hi, I'd like to draw attention to a little script I wrote. I tend to use qualified imports and short names like "new" and "filter". This makes hasktags pretty much useless, since it basically just guesses which one to go to. hothasktags is a reimplementation of hasktags that uses haskell-src-exts to analyze the import structure to generate (scoped) tags pointing to the right definition. I'm pretty addicted to it, since it provides the only functionality I miss from visual studio :-). VIm only for now, since I don't know if emacs tags format supports scoped tags. I am aware that it is not perfect -- patches and bug reports welcome. http://hackage.haskell.org/package/hothasktags Luke

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Suitable structure to represents lots of similar lists
by Dan Piponi 09 Apr '10

09 Apr '10

I have a situation where I have a bunch of lists and I'll frequently be making new lists from the old ones by applying map and filter. The map will be applying a function that's effectively the identity on most elements of the list, and filter will be using a function that usually gives True. This means that there is potential for a large amount of sharing between these lists that could be exploited, something that ordinary lists would do badly. Does anyone have a recommendation for a pure functional data structure for this case? (It reminds me a bit of my own antidiagonal type, but that's not well adapted to the highly dynamic situation I'm describing.) -- Dan

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Why haskell.org down again?
by Andy Stewart 09 Apr '10

09 Apr '10

Hi all, haskell.org down again? Hardware not stable? Attack? Can't we avoid haskell.org off? -- Andy

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Nested unsafePerformIO?
by DavidA 09 Apr '10

09 Apr '10

Hi, I am having difficulty debugging a troublesome stack overflow, which I think might be related to calling unsafePerformIO from within the IO monad. So I have the following code: import System.Random import System.IO.Unsafe import Data.Time.Clock timedIterateIO :: Int -> (a -> a) -> a -> IO a timedIterateIO durationSecs f x = do t0 <- getCurrentTime timedIterateIO' t0 x where duration' = fromIntegral durationSecs timedIterateIO' t0 x = do let y = f x t <- getCurrentTime let d = diffUTCTime t t0 if d >= duration' then return y else timedIterateIO' t0 y f x = unsafePerformIO $ do m <- randomRIO (1,2) return (m+x) The idea of the timedIterateIO function is that it should repeatedly apply f to x until a specified duration is up. The use case is for game search, where I want to keep searching until time is up, and then play the best move I've found at that point. So the following works: *Main> timedIterateIO 1 (+1) 0 45580 (1.01 secs, 360357840 bytes) The following also seems to work: *Main> unsafePerformIO $ timedIterateIO 1 f 0 67866 (1.25 secs, 394938540 bytes) Now, in the real use case, I have another function, g let's say. It is similar to f, in that it uses unsafePerformIO internally to get random numbers. It's proven to work under normal circumstances, for example: *Main> (!! 100) $ iterate g x works, and completes in around a second. However, the following doesn't work, failing with a stack overflow: *Main> unsafePerformIO $ timedIterateIO 1 g x Any ideas? Thanks, David

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LLVM study SoC proposal
by Marco Túlio Gontijo e Silva 09 Apr '10

09 Apr '10

Hi. I wrote a(nother) SoC proposal for studying LLVM performance, compared with the Native Code Generator back-end. It's available at: http://www2.dcc.ufmg.br/laboratorios/llp/wiki/doku.php?id=marco_soc2 I know the deadline is now near, but I'd be happy to hear comments about it and update it before 19:00 UTC. Thanks. -- marcot http://wiki.debian.org/MarcoSilva

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HDBC-ODBC and SqlValues
by Tim Docker 09 Apr '10

09 Apr '10

I'm experimenting with haskell and relational databases. I have successfully coupled unixodbc + freetds + hdbc-odbc, and can make trivial queries. However, I'm surprised at the result types: $ ghci GHCi, version 6.10.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. Prelude> c <- Database.HDBC.ODBC.connectODBC "DSN=xxxxx;UID=xxxxx;PWD=xxxx" Loading package syb ... linking ... done. Loading package base-3.0.3.1 ... linking ... done. Loading package array-0.2.0.0 ... linking ... done. Loading package containers-0.2.0.1 ... linking ... done. Loading package bytestring-0.9.1.4 ... linking ... done. Loading package old-locale-1.0.0.1 ... linking ... done. Loading package old-time-1.0.0.2 ... linking ... done. Loading package mtl-1.1.0.2 ... linking ... done. Loading package utf8-string-0.3.5 ... linking ... done. Loading package time-1.1.4 ... linking ... done. Loading package convertible-1.0.9 ... linking ... done. Loading package HDBC-2.2.4 ... linking ... done. Loading package HDBC-odbc-2.2.3.0 ... linking ... done. Prelude> Database.HDBC.quickQuery c "select 1+3" [] [[SqlByteString "4"]] Prelude> Why do I see an SqlByteString returned, rather than a numeric type? Taking a closer look at the HDBC-ODBC implementation it would appear that data will always be returned as SqlByteString, or as SqlNull. Is this the intended behaviour, or just a sign of an incomplete implementation of the ODBC driver? It would certainly seem possible for the ODBC driver to return more specific types. Tim

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Haskell.org re-design
by Christopher Done 08 Apr '10

08 Apr '10

This is a post about re-designing the whole Haskell web site. We got a new logo but didn't really take it any further. For a while there's been talk about a new design for the Haskell web site, and there are loads of web pages about Haskell that don't follow a theme consistent with Haskell.org's, probably because it doesn't really have a proper theme. I'm not a designer so take my suggestion with a grain of salt, but something that showed pictures of the latest events and the feeds we currently have would be nice. The feeds let you know that the community is busy, and pictures tell you that we are human and friendly. Anyway, I came up with something to kick off a discussion: http://haskell.org/haskellwiki/Image:Haskell-homepage-idea.png It answers the basic questions: - What's Haskell? - Where am I on the site? (Answered by a universally recognised tab menu) - What's it like? - How do I learn it? - Does it have an active community? - What's going on in the community? What are they making? - This language is weird. Are they human? -- Yes. The picture of a recent event can fade from one to another with jQuery. The colours aren't the most exciting, but someone who's a professional designer could do a proper design. But I like the idea of the site being like this; really busy but not scarily busy. Subsections of the site could use the header and footer and heading theme, but have a completely different primary-content layout. Probably sub-sections would need a left-nav. Keeping the design simple like this also makes it easy to theme the current Wiki to fit in with it seamlessly. Personally I don't have a problem with the existing site, functionally. It has all the stuff I want to look at. The only stuff that I had issue with as a newbie was finding The One Book I Should Read and The One Download I Should Get. The current site is starting to address this with a "Download Haskell" button. However, looking at it as a marketing site, it does look pretty lame and messy, and it gives you that impression of Haskell. So if people who own the site are going to redesign it, I thought I'd contribute a bit. Anyway, please contribute your ideas. (Again, I'm not a designer, so you don't need to pick at the aesthetics, a real designer can sort that out.) Cheers!

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Re: [Haskell-cafe] GSOC Haskell Project
by Mihai Maruseac 08 Apr '10

08 Apr '10

I have submitted my proposal to the gsoc site taking care to include all the feedback that was given either publicly or privately both from people on haskell-cafe, on #haskell or from my country. This is the last call for feedback before the submission period is ended. One last chance to improve the application.

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Re: [Haskell-cafe] Correct way to record state in OpenGL?
by Mark Spezzano 08 Apr '10

08 Apr '10

I sort of understand what people are getting at. My basic question is now, given that I have a bunch of parameters that represent state should I bundle up ALL of these parameters in one data type (DemoState, say) and have ONE IORef variable that references the lot, or have an IORef for each piece of state, separately. What are the disadvantages of each approach? Also, is reading and writing to an IORef expensive computationally? Thanks, Mark On 05/04/2010, at 2:25 AM, Tobias Brandt wrote: > HOpenGL uses Data.StateVar. One can define the following function: > > newStateVar :: a -> IO (StateVar a) > newStateVar val = do > ref <- newIORef val > let readAction = readIORef ref > let writeAction = \newVal -> writeIORef ref newVal > return (makeStateVar readAction writeAction) > > Now one can use StateVar consistent with HOpenGL: > > create: foo <- newStateVar bar > read: get foo > write foo $= baz > > On 4 April 2010 11:03, Mark Spezzano <mark.spezzano(a)chariot.net.au> wrote: > Hi > > What is the correct way to record "custom" state when using OpenGL? > > By this, I refer to, say, properties of a square--say it's x,y coordinates as it moves across the screen. This requires that the program keep track of the object's state as it moves. These coordinates are _not_ part of the OpenGL state machine, so is the correct way to use the State monad? > > If so--or if not so--how would I proceed to keep track of the state of my objects as they move about the screen? Maybe the HOpenGL implementation comes with such state-tracking devices? > > Please post code snippets if necessary. > > Thanks in advance, > > Mark Spezzano > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >

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Seeking advice about monadic traversal functions
by Darryn Reid 08 Apr '10

08 Apr '10

Hi, I hope that this is an appropriate place to post this question; I initially posted to Haskell-beginners since that seemed appropriate to my knowledge level. Brent Yorgey kindly suggested I should post here instead. Just for a little background: I'm an experienced computer scientist and mathematician but am very new to Haskell (I love it, I might add, but have much to learn). I've coded a (fairly) general rewriting traversal - I suspect the approach might be generalisable to all tree-like types, but this doesn't concern me much right now. My purpose is for building theorem provers for a number of logics, separating the overall control mechanism from the specific rules for each logic. The beauty of Haskell here is in being able to abstract the traversal away from the specific reduction rules and languages of the different logics. I have paired down the code here to numbers rather than modal formulas for the sake of clarity and simplicity. My question is two-fold: 1. Does my representation of the traversal seem good or would it be better expressed differently? If so, I'd appreciate the thoughts of more experienced Haskell users. 2. I cannot really see how to easily extend this to a queue-based breadth-first traversal, which would give me fairness. I'm sure others must have a good idea of how to do what I'm doing here except in breadth-first order; I'd appreciate it very much if someone could show me how to make a second breadth-first version. Thanks in advance for any help! Darryn. start of code. ------------------------------------------------------------------------- import Control.Monad import Control.Monad.Identity -- Tableau is a tree containing formulas of type a, in -- Fork (disjunctive) nodes and Single (conjunctive) nodes. -- Paths from root to Nil each represent an interpretation. data Tableau a = Nil -- End of a path | Single a (Tableau a) -- Conjunction | Fork (Tableau a) (Tableau a) -- Disjunction deriving (Eq, Show) -- 'Cut' directs the traversal to move back up the tree rather than into -- the current subtree, while 'Next' directs the traversal to proceed -- into the subtree. data Action = Cut | Next deriving (Eq, Show) -- The type of the rewrite function to perform at each node in -- the traversal of the tree. The Rewriter returns the new -- subtree to replace the existing subtree rooted at the -- traversal node, and a direction controlling the traversal -- to the next node. type Rewriter m a = Tableau a -> m (Tableau a, Action) -- The traversal function, depth-first order. rewrite :: (Monad m) => Rewriter m a -> Tableau a -> m (Tableau a) rewrite rf t = do (t', d) <- rf t rewrite' rf d t' -- Worker function for traversal, really its main body. rewrite' :: (Monad m) => Rewriter m a -> Action -> Tableau a -> m (Tableau a) rewrite' rf Cut t = return t rewrite' rf Next Nil = return Nil rewrite' rf Next (Single x t1) = do t1' <- rewrite rf t1 return (Single x t1') rewrite' rf Next (Fork t1 t2) = do t1' <- rewrite rf t1 t2' <- rewrite rf t2 return (Fork t1' t2') -- Some examples to test the code with: -- ghci> let t0 = (Single 2 (Single 3 Nil)) -- ghci> let t1 = (Single 1 (Fork t0 (Fork (Single 4 Nil) (Single 5 Nil)))) -- ghci> let t2 = (Fork (Single 10 Nil) (Single 11 Nil)) -- ghci> let t3 = (Fork (Single 3 Nil) (Single 3 Nil)) -- Running "test4 t1 t2" produces the expected result; running -- "test4 t1 t3" does not terminate, because this endlessly -- generates new patterns that match the substitution condition: test4 :: (Num t) => Tableau t -> Tableau t -> Tableau t test4 tab tab' = runIdentity (rewrite rf tab) where rf (Single 3 Nil) = return (tab', Next) rf t = return (t, Next) -- Running "test5 t1 t3", however, does terminate because the "Cut" -- prevents the traversal from entering the newly spliced subtrees -- that match the pattern. test5 :: (Num t) => Tableau t -> Tableau t -> Tableau t test5 tab tab' = runIdentity (rewrite rf tab) where rf (Single 3 Nil) = return (tab', Cut) rf t = return (t, Next) ------------------------------------------------------------------------- end of code.

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ANNOUNCE: Hac phi 2010
by Chris Casinghino 08 Apr '10

08 Apr '10

Greetings, I am very pleased to officially announce Hac phi 2010, a Haskell hackathon/get-together to be held May 21-23 at the University of Pennsylvania in Philadelphia. The hackathon will officially kick off at 2:30 Friday afternoon, and go until 5pm on Sunday (with breaks for sleep, of course). Last year's Hac phi was a lot of fun, and many people have already expressed interest in coming back this year. I want to stress that everyone is welcome---you do not have to be a Haskell guru to attend! Helping hack on someone else's project could be a great way to increase your Haskell-fu. If you plan on coming, please officially register [1]. Registration, travel, lodging and many other details can be found on the Hac phi wiki [2]. Note that we're in a different space this year and may have to cap attendance, so register early. We're also looking for a few people interested in giving short (15-20 min.) talks, probably on Saturday afternoon. Anything of interest to the Haskell community is fair game---a project you've been working on, a paper, a quick tutorial. If you'd like to give a talk, add it on the wiki [3]. Hope to see you in Philadelphia! -The Hac φ team [1] http://haskell.org/haskellwiki/Hac_φ/Register [2] http://haskell.org/haskellwiki/Hac_φ [3] http://haskell.org/haskellwiki/Hac_φ/Talks

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multi-ghc: Managing Multiple GHC Distributions
by Sean Leather 08 Apr '10

08 Apr '10

I created a few tools to help me manage multiple GHC distributions in a Bash shell environment. Perhaps it's useful to others. http://github.com/spl/multi-ghc Feedback welcome. I'd also like to know if something similar exists. Regards, Sean

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Traypoweroff questions
by Luis Cabellos 08 Apr '10

08 Apr '10

Hi, I just put an application into hackage http://hackage.haskell.org/package/traypoweroff. I made this application to allow a tray icon in xmonad to poweroff and reboot my computer. But I dislike two things I made. The first one is the use of */sbin/poweroff* and */sbin/reboot* with system call. I feel than i should be a better way to do the poweroff or the reboot. err <- system "sudo /sbin/reboot" The second issue is, the user need to put into sudoers the permission to execute reboot and poweroff. The use of *sudo* seems a little awkward. I'll like a cleaner installation without force user touch configuration files. myuser ALL=(ALL) NOPASSWD: /sbin/poweroff Thanks for the help, Luis Cabellos p.d: I'll add suspend with pm-suspend command in the next version BTW

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GHC LLVM ARM Cross Compilation
by Nathaniel Neitzke 08 Apr '10

08 Apr '10

I saw the Google Summer of Code project for using LLVM to cross compile for other architectures such as ARM. Professionally I write embedded Linux code that targets ARM processors such as the TI DaVinci DM355 and am very intrigued by the potential use of Haskell for future projects. If I was interested in attempting to add support for LLVM ARM cross-compilation, are there any thoughts on what parts would have to be modified to do so? Or has work already been conducted in this area? ~Nathan

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what are the safety conditions for unsafeIOToST
by Nicolas Frisby 08 Apr '10

08 Apr '10

I haven't been able to find it via Google or Haddock. An old message suggests is was just a matter of exceptions? I only want to use the IO for generating Data.Uniques to pair with STRefs in order to make a map of them. I'm guessing this would be a safe use since it's exception free (... right?). Thanks!

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ANNOUNCE: JSONb-1.0.0
by Jason Dusek 07 Apr '10

07 Apr '10

A new release of JSONb, taking advantage of the latest Attoparsec. http://hackage.haskell.org/package/JSONb-1.0.0 Thanks to Grant Monroe for help with the numerics parser. -- Jason Dusek

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lhaskell.vim: syntax highlighting fix for pragmas and comments in TeX mode
by Tomas Janousek 07 Apr '10

07 Apr '10

Hello cafe :-), you're the maintainer of lhaskell.vim and I'm sending you a patch that fixes the highlighting of curly brackets and anything between them. (Who's supposed to send it to vim maintainer? Me, or cafe?) Regards, -- Tomáš Janoušek, a.k.a. Liskni_si, http://work.lisk.in/

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libraries [was GUI haters]
by gladstein＠gladstein.com 07 Apr '10

07 Apr '10

As a working engineer, one of my greatest frustrations is my inability to use Haskell in the workplace. The unfortunate fact is that my media industry clients use mostly Windows, some Macs, and no linux except for servers. The core system works everywhere, but many contributed libraries don't. GUIs are the big showstopper. One of the reasons Java won out over Common Lisp is that it had huge libraries. Franz's libraries were superb but few in number. One diehard Lisp user converted his lab to Java because "Java gives you everything you want, for free." That languages are distinct from their libraries escapes a lot of people; they see each language as a package. I met a COBOL programmer recently (I'm not making this up) that was looking into Java. He didn't see how people could use it, he said, because it had "thousands of commands". I'll stop whining now.

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Metaprogramming in Haskell vs. Ocaml
by aditya siram 07 Apr '10

07 Apr '10

Hi all, I would like to learn a little bit more about metaprogramming in Haskell. And I'm also wondering why metaprogramming is used much more in Ocaml than in Haskell. Camlp4 (Ocaml's metaprogramming facility) doesn't seem to much more powerful that Template Haskell. The former is celebrated in its community as a killer feature of the language and its use is encouraged by numerous accessible tutorials. The latter however is down-played and not as well documented. Seeing that the languages are parallel in many ways is there some reason for this? Is metaprogramming less useful in Haskell? Is it worth learning? thanks ... -deech

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Established names for a couple of list functionals?
by Stephen Tetley 07 Apr '10

07 Apr '10

Hello all Having traversals with special behaviour for the first or last element is useful for my current work: -- first element special -- anacrusisMap :: (a -> b) -> (a -> b) -> [a] -> [b] anacrusisMap _ _ [] = [] anacrusisMap f g (a:as) = f a : map g as -- last element special -- cabooseMap :: (a -> b) -> (a -> b) -> [a] -> [b] cabooseMap _ _ [] = [] cabooseMap f g (a:as) = step a as where step x [] = [g x] step x (y:ys) = f x : step y ys *Overlay1> anacrusisMap (+1) id [1..10] [2,2,3,4,5,6,7,8,9,10] *Overlay1> cabooseMap id (+1) [1..10] [1,2,3,4,5,6,7,8,9,11] My question (trivial, but still...) - is there any prior art naming these functions? For the record, my name derivation is: + anacrusis - musical term, the pickup notes before the first bar in a score. + caboose - there was discussion on Haskell-Cafe a couple of months ago about a list data type with a distinguished terminal type. Caboose is the name I remember. Thanks Stephen

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Network: buffering troubles
by Yves Parès 07 Apr '10

07 Apr '10

Hello, I have isolated a problem when using (lazy) ByteStrings through the network (GHC 6.12.1, Ubuntu 9.10 32bits): Here is my client: http://old.nabble.com/file/p28162932/Client.hs Client.hs And my server: http://old.nabble.com/file/p28162932/Server.hs Server.hs The server holds until the client closes the connection, even if I flush the handle on the client side after writing or even if I turn off buffering on both sides. ----- Yves Parès Live long and prosper -- View this message in context: http://old.nabble.com/Network%3A-buffering-troubles-tp28162932p28162932.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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hsql repository
by Daniil Elovkov 07 Apr '10

07 Apr '10

Hello I've looked at hsql-* packages at hackage and found that they have progressed to 1.8.1. However, as always there is no hsql-oracle on hackage. It was usually found in the repository. But I can't find where the repository is. Places, like code.haskell.org and htoolkit.sourceforge.net seem to have the older 1.7 version. Can somebody point me to the repository? Is there any chance that hsql-oracle compiles with new hsql? Thanks Daniil Elovkov

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Break Function Using Lazy Pairs
by aditya siram 07 Apr '10

07 Apr '10

Hi all, For the past couple of weeks I've been trying to understand tying-the-knot style programming in Haskell. A couple of days ago, Heinrich Apfelmus posted the following 'break' function as part of an unrelated thread: break [] = ([],[]) break (x:xs) = if x == '\n' then ([],xs) else (x:ys,zs) where (ys,zs) = Main.break xs I've stepped through the code manually to see if I understand and I'm hoping someone will tell me if I'm on the right track: -- break "hi\nbye" = -- let f1 = (break "i\nbye") -- = let f2 = (break "\nbye") -- = ([],"bye") -- ('i' : fst f2, snd f2) => ('i' : [], "bye") -- ('h' : fst f1, snd f1) => ('h' : 'i' : [], "bye") -- => ("hi","bye") -deech

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Crypto: PC1 - Cipher?
by Günther Schmidt 07 Apr '10

07 Apr '10

Hello, does anyone know what the PC1-cipher is and if there is a Haskell implementation? Günther

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Re: HXT Namespaces and XPath
by Uwe Schmidt 07 Apr '10

07 Apr '10

Hi Mads, > In HXT, namespace prefixes bound by an XML document are valid in the > context of an XPath. How do avoid that? > > An example program will clarify: > > simpleXml :: String > simpleXml = "<soap:Body xmlns:soap=\"http://www.w3.org/2003/05/soap-envelope\"/>" > > nsEnv :: [(String, String)] > nsEnv = [ ("s" , "http://www.w3.org/2003/05/soap-envelope") ] > > evalXPath :: String -> String -> [XmlTree] > evalXPath xpath xml = > runLA ( xread > >>> propagateNamespaces > >>> getXPathTreesWithNsEnv nsEnv xpath > ) xml > > Here: > > evalXPath "//s:Body" simpleXml == > evalXPath "//soap:Body" simpleXml > > Even though I only mentions the prefix "s" (and not "soap") in the > function nsEnv. When working with namespaces in XML, the prefixes are not longer significant. After namespace propagation every name in the XML document is identified by a qualified name. This is a pair consisting of the namespace URI and the local part. The prefixes become irrelevant. A namespace aware XPath expression needs a namespace environment, as given in the example, to construct these qualified names for the names in the XPath expression. So the results of both evalXPath calls in your example must be the same. > I do not want the XPath to see prefixes declared in the xml-document, as > it means that two semantically similar XML documents can get different > results when applied to the same XPath. If you intend, that the prefixes are significant, then you should not work with namespace propagation. If namespaces are not propagated, all names occurring in the document are taken as they are. That means "s:Body" is different from "soap:Body". For solving your tasks there could be 2 ways: 1. don't use namespaces, no propagateNamespaces, no getXPathTreesWithNsEnv, use the prefixes instead. Disadvantage: the prefixes become significant. If prefixes change, the semantics changes. 2. Use propagateNamespaces and getXPathTreesWithNsEnv, but select all nodes via the namespace URIs, not via the prefixes. If you want to output the manipulated XML parts and use standard prefixes for the namespaces, then use the namespace manipulation functions in http://hackage.haskell.org/packages/archive/hxt/latest/doc/html/Text-XML-HX… Cheers, Uwe

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[haskell.org Google Summer of Code] Student Applications Due Friday!
by Edward Kmett 07 Apr '10

07 Apr '10

This is a friendly reminder that student applications for the summer of code are due to Google by Friday, April 9th. http://socghop.appspot.com/document/show/gsoc_program/google/gsoc2010/timel… That is just *3 days* from now! Keep in mind that while we've been tracking general interest in different projects through the trac, the application doesn't count unless you submit it to Google at http://socghop.appspot.com/gsoc/program/home/google/gsoc2010 While all details of the application do not need to be finalized, as much of the information from http://hackage.haskell.org/trac/summer-of-code/wiki/StudApply2010 as possible should probably be included in your application. If you are stuck and having a hard time thinking of ideas, I highly recommend the excellent guide that Don Stewart posted recently: http://donsbot.wordpress.com/2010/04/01/the-8-most-important-haskell-org-gs… I'd also recommend taking a look through the trac at http://hackage.haskell.org/trac/summer-of-code/report/1 to gauge interest. Please email me if you have any questions or concerns. -Edward Kmett

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Why does Haskell not infer most general type?
by Job Vranish 07 Apr '10

07 Apr '10

Is haskell supposed to always infer the most general type (barring extensions)? I found a simple case where this is not true: f _ = undefined where _ = y :: Int -> Int y x = undefined where _ = f x Haskell infers the types of 'y' and 'f' as: f :: Int -> a y :: Int -> Int This confused me at first, but after thinking about it a while it seemed to make sense. But then my friend John pointed out that you can add type sigs for 'f' and 'y': f :: a -> b y :: a -> b and have it still typecheck! This thoroughly confused me. Why does haskell not infer the most general type for these functions? Is it a limitation of the algorithm? a limitation of the recursive let binding? Any insight would be appreciated :) - Job

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GSOC Haskell Project
by Mihai Maruseac 06 Apr '10

06 Apr '10

Hi, I'd like to introduce my idea for the Haskell GSOC of this year. In fact, you already know about it, since I've talked about it here on the haskell-cafe, on my blog and on reddit (even on #haskell one day). Basically, what I'm trying to do is a new debugger for Haskell, one that would be very intuitive for beginners, a graphical one. I've given some examples and more details on my blog [0], [1], also linked on reditt and other places. This is not the application, I'm posting this only to receive some kind of feedback before writing it. I know that it seems to be a little too ambitious but I do think that I can divide the work into sessions and finish what I'll start this summer during the next year and following. [0]: http://pgraycode.wordpress.com/2010/03/20/haskell-project-idea/ [1]: http://pgraycode.wordpress.com/2010/03/24/visual-haskell-debugger-part-2/ Thanks for your attention, -- Mihai Maruseac

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HXT error handling
by Mads Lindstrøm 06 Apr '10

06 Apr '10

Hi I am trying to use HXT to evaluate XPath expressions. The XPath expressions are not specified by myself, but by users of my program. However, the idea behind HXT's error handling confuses me. Maybe somebody can enlighten me. This program fragment: evalXPath :: String -> String -> [XmlTree] evalXPath xpath xml = runLA ( xread >>> propagateNamespaces >>> getXPathTrees xpath ) xml seems to work fine, except when it comes to error handling. If the xml-string is malformed, the error is simply ignored and the evalXPath-function just returns an empty list. I can understand what happens. 'getXPathTrees xpath' tries to match the xpath to a XmlTree which represents a parse error, and it therefore never matches anything. What I do not understand, is when this behavior would be desirable. Or why do the error in 'xread' not propagate throughout the arrow, similar to how: foobar :: Either String Int foobar = do _ <- fail "Some failure" return 2 the error in 'foobar' would propagate and 'foobar = Left "Some failure"'. What if the xpath-parameter contains an invalid XPath expression? Well, then the output depends upon both the xpath and the xml -parameters. That is: length (evalXPath "/...../" " <foo/> ") == 3 whereas length (evalXPath "/...../" "<foo/>") == 1 Which just seems strange to me. If we add a getText to evalXPath: evalXPath :: String -> String -> [String] evalXPath xpath xml = runLA ( xread >>> propagateNamespaces >>> getXPathTrees xpath >>> getText -- added here ) xml Then an error in the xpath-parameter will be hidden by the getText function, similar to how 'getXPathTrees xpath' ignores errors in the xread function. Again, I understand what happens, I just cannot see why it is designed as it is. What I really would like was functions like: parseStr :: (Monad m) => String -> m XmlTrees parseStr xml = case Parsec.xread xml of (x:xs) -> if (Dom.isError x) then fail "Could not parse tree" else return (x:xs) [] -> fail "No XML tree resultet from parsing XML" And a similar function for the XPath. This could also speed up my program, as I would not parse the same XPath again and again. A stand-alone function to parse an XPass expression, would also make it easy to create a Template Haskell parse-xpath-function, that gave compile-time error messages and increased performance for XPath expression know at compile-time. Regards, Mads Lindstrøm

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[OT?] Haskell-inspired functions for BASH
by Patrick LeBoutillier 06 Apr '10

06 Apr '10

Hi all, I've been studying Haskell for about a year now, and I've really come to like it. In my daily work I write a lot of BASH shell scripts and I thought I'd try add some of the haskell features and constructs to BASH to make my scripting life a bit easier. So I've been working on a small BASH function library that implements some basic functional programming building blocks. Note: There is no actual Haskell code involved here. I put up the full manpage here: http://hpaste.org/fastcgi/hpaste.fcgi/view?id=24564 Source is here: http://svn.solucorp.qc.ca/repos/solucorp/bashkell/trunk/trunk/ All this is very prototypical, but here is an example of some of the stuff I've got so far (map, filter, foldr): $ ls data 1.txt 2.txt # basic map, argument goes on the command line $ ls -d data/* | map basename 1.txt 2.txt # map with lambda expression $ ls -d data/* | map '\f -> basename $f .txt' 1 2 # simple filter, also works with lambda $ ls -d data/* | map basename | filter 'test 1.txt =' 1.txt # sum $ ls -d data/* | map '\f -> basename $f .txt' | foldr '\x acc -> echo $(($x + $acc))' 0 3 Basically I'm looking for a bit of feedback/info: - Does anyone know if there are already similar projets out there? - Does anyone find this interesting? - Any other comment/suggestion/feedback - Where's a good place to promote such a project? Thanks a lot, Patrick LeBoutillier -- ===================== Patrick LeBoutillier Rosemère, Québec, Canada

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How do I use ByteString?
by Günther Schmidt 06 Apr '10

06 Apr '10

Hi all, I've never found an easy way to deal with ByteStrings. I'm using the RSA library and it en- and decodes Data.ByteString.Lazy.ByteString. I initially start with Strings, ie. [Char], but there is no function to convert the 2 back and forth. There is however a function which takes [Word8] to BytesString and back. It all wouldn't be so confusing if there weren't several versions of ByteString in several modules to choose from. And a number of libraries requiring different types of ByteString. I am sure the designers of the bytestring package had good reason for this design, is there also a webpage which explains which one to use and under what circumstances? Günther

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FRP, arrows and loops
by Maciej Piechotka 06 Apr '10

06 Apr '10

Hello. I'm trying to understand the FRP (by implementing FRP system on my own) and I think I'm slowly getting it. 1. How to interpret ArrowLoop? I have two possible implementations: type RunSF a = a Dynamic () data SF a b c = SF (a (Dynamic, b, RunSF, Set Unique) (c, Set Unique, SF a b c)) (...) instance ArrowLoop (SF a) where loop (SF f) = loop' f undefined where loop' g d = proc (dyn, b, r, s) -> do ((c, d'), s, g') <- g <- (dyn, (b, d), r, s) returnA -< (c, s, loop' g' d') instance ArrowLoop a => ArrowLoop (SF a) where loop (SF f) = SF $! proc (d, b, r, s) -> do rec ((c, d), s, f') <- f -< (d, (b, d), r, s) returnA -< (c, s, loop f') Since the first is not unlike ArrayCircuit from arrays I guess second one but I'm not quite sure. 2. Why there is no ArrowIO in arrows? I.e. class Arrow a => ArrowIO a where liftAIO :: Kleisli IO b c -> a b c (possibly class Arrow a => ArrowST a where liftAST :: Kleisli ST b c -> a b c ) 3. Why switch is needed? How to interpret switch with current continuation? I think switch is equivalent to ArrowChoice but do I miss something? Regards

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Data Structures GSoC
by Nathan Hunter 06 Apr '10

06 Apr '10

Hello. I am hoping to take on the Data Structures project proposed two years ago by Don Stewart here<http://hackage.haskell.org/trac/summer-of-code/ticket/1549>, this summer. Before I write up my proposal to Google, I wanted to gauge the reaction of the Haskell community to this project. Particularly: -What Data Structures in the current libraries are in most dire need of improvement? -How necessary do you think a Containers Library revision is? -Should I attempt to build on the work Jamie Brandon did with Map as generalised tries, or is that beyond the scope of this project I am very excited to work with functional data structures, and I would greatly appreciate any input. -Nathan Hunter

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Haskell JSON requests from your blog, roll your own Try Haskell!
by Christopher Done 05 Apr '10

05 Apr '10

For those interested, http://chrisdone.com/posts/2010-04-05-haskell-json-service-tryhaskell.html I've updated the Haskell JSON service I whipped up a month ago and made it much simpler, written some sample code for how to include this in your blog or tutorials. It supports the JSONP way of making requests, so you can use it from any domain. Thanks to that, Try Haskell can now be run by anyone who has the HTML/JavaScript code and an internet connection, which is nice. Lowers the barrier a bit for people who'd like to write interactive tutorials but can't be bothered messing around with FastCGI and a web server. Don't worry about using it too much, it's on a Linode account with 200GB of bandwidth a month. AJAX requests really won't use that up. ;) I hope someone uses it on a tutorial. *Hint hint* BONUS. Hope you guys find it useful!

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Re: Hackage accounts and real names
by Hein Hundal 05 Apr '10

05 Apr '10

I don't like using my real name on line unless I am 100% sure that I want my statements recorded for all time and available to anyone. Using a pseudonym allows me to be more honest in my opinions and it allows me to join groups without wondering how my membership in that group will be viewed in 20 years. Simply put, if you don't want much input from me or people that think like I do about anonymity, then, go ahead and require a real name.

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Where are the haskell elders?
by Günther Schmidt 05 Apr '10

05 Apr '10

Hi all, I notice that posts from the Haskell elders are pretty rare now. Only every now and then we hear from them. How come? Günther

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Haskell on Debian
by Alex Rozenshteyn 05 Apr '10

05 Apr '10

I tend to install haskell packages from apt whenever possible. One such package is "unix", which appears to come provided by the ghc6 debian package. I'm trying to cabal install lambdabot and getting the following: $ cabal install lambdabot Resolving dependencies... Configuring lambdabot-4.2.2.1... Preprocessing executables for lambdabot-4.2.2.1... Building lambdabot-4.2.2.1... Main.hs:11:7: Could not find module `System.Posix.Signals': It is a member of the hidden package `unix-2.4.0.0'. Perhaps you need to add `unix' to the build-depends in your .cabal file. Use -v to see a list of the files searched for. cabal: Error: some packages failed to install: lambdabot-4.2.2.1 failed during the building phase. The exception was: ExitFailure 1 I have a feeling this has something to do with the interaction between cabal and apt... Does anyone have any advice for fixing this issue other than just adding "unix" to the lambdabot.cabal file? -- Alex R

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Integers v ints
by Jens Blanck 05 Apr '10

05 Apr '10

I was wondering if someone could give me some references to when and why the choice was made to default integral numerical literals to Integer rather than to Int in Haskell. Also, if you are aware of similar discussions in other languages. I'd like to use this information to make an analogous case for defaulting real numerical literals (well, the literals are likely to be in scientific notation, i.e., floating point) to some data type of computable reals rather than to floating point Double. Jens

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Hackage and popular packages: 2010 Q1 report
by Don Stewart 05 Apr '10

05 Apr '10

Hackage 2010 Q1 report http://donsbot.wordpress.com/2010/04/03/the-haskell-platform-q1-2010-report/ After the big move of Hackage from monk to the new abbot server, here's the first report on which packages are popular, and how Hackage is doing in general. -- Don

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ANN: spec2code
by Greg Fitzgerald 05 Apr '10

05 Apr '10

After 5 years of R&D, I’m proud to announce the spec2code compiler. With spec2code, developers no longer need to acknowledge the mundane details of programming, such as memory allocation, bounds-checking, byte ordering, inheritance models or performance tuning. spec2code uses the latest techniques in compiler optimization to derive a deterministic implementation from only a high-level specification. For example, an optimal quicksort is derived from the following specification. sort :: Ord a => [a] -> (b | ordered b) sort = undefined ordered :: Ord a => [a] -> Bool ordered [] = True ordered [_] = True ordered (x1:x2:xs) = x2 > x1 && ordered (x2:xs) Read as, “the function 'sort' takes a list of orderable list items, and returns a list for which each list item is greater to the one preceding it.” How does it work? By telling the compiler about the logical properties of how its output relates to its input, the compiler is sufficiently constrained to apply its genetic algorithm. It iterates over the specification with all known optimization techniques, algebraically reducing the program to an underlying machine model. The compiler uses static analysis and complexity theory in conjunction with the machine model to order implementations by their performance characteristics and choose the optimal one. Conceptually, the first phase orders algorithms by complexity, using "average case", "worst case" and "memory consumption": [MergeSort (n*log n) (n*log n) n, QuickSort (n*log n) (n*n) (log n), InsertionSort (n*n) (n*n) 1, BubbleSort (n*n) (n*n) 1 ] After choosing a high-level algorithm, spec2code does the usual low-level optimizations via LLVM to map the algorithm to optimal native code. Does it scale? Absolutely, spec2code is not confined to specifications for which optimized algorithms are already known. spec2code can be used to implement operation systems, device drivers, build systems, package management tools, and even do your shirt laundry. spec2code will change your job from programmer to specification author, giving you more time for meetings, managing email, and browsing the web. Say goodbye to those dirty Perl scripts, broken C code, and ultimately, your job. spec2code is the future of programming and the beginning of the end of mankind. Looking forward to obsoleting you soon, Greg

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