- Haskell-Cafe - Haskell.org

Typeable and Dynamic
by oleg＠okmij.org 04 Nov '08

04 Nov '08

minh thu asked a tricky question, about writing > extract :: Typeable a => TypeRep -> Dynamic -> a The question here is what determines the type 'a'. One answer is that 'a' is determined from the context, e.g., (extract tr dyn) + 1.0 fixes 'a' to be an Int. In that case, extract is equivalent to `read' (indeed, String is a primitive sort of Dynamic). We do not need any argument TypeRep though as we obtain 'a' from the context. fromDynamic is sufficient there. One can also construe the question to be asking about writing an `inverse' of typeOf. Whereas, typeOf :: Typeable a => a -> TypeRep can give the TypeRep for any (Typeable) type, undefinedOf :: Typeable a => TypeRep -> a could give (an undefined) value for a given TypeRep. Now, the _type_ 'a' is determined by the _value_ of TypeRep: seemingly we need dependent types. To write function of exactly that signature, we need Template Haskell. Oftentimes, we can get away with a weaker function: > data Dyn = forall a. Typeable a => Dyn a > reflect :: TypeRep -> Dyn to be used to implement dynApply, dynFst, dynSnd, dynHead and other operations on Dynamics. Perhaps the following message may help then http://www.haskell.org/pipermail/haskell-cafe/2007-December/036820.html

2 1

Problem while compiling ghc 6.8
by Magicloud 04 Nov '08

04 Nov '08

Hi, I got my ghc 6.8 by `darcs get --partial http://darcs.haskell.org/ghc-6.8/ghc`, and after `darcs-all get`, `sh boot`, `configure`, without any problem, I started to make it. Well, when compiling libraries/stm, it reports "Control/Concurrent/STM/TVar.hs:22:8: Not in scope: `readTVarIO'. I tried to reget the source without '--partial', still the same.

1 0

huge single file syncronization
by Alberto G. Corona 04 Nov '08

04 Nov '08

I need to backup my ubuntu-VMWare image frequently (5 GBits) . I need to know if exist such a utility (in haskell or not) for single file syncronization. I don´t want to reinvent te weel, but I think that it is a few lines of Haskell using the Diff package or something similar.

3 2

Array bug?
by Andrew Coppin 04 Nov '08

04 Nov '08

Consider the following GHCi session: GHCi, version 6.8.2: http://www.haskell.org/ghc/ :? for help Loading package base ... linking ... done. Prelude> :m Data.Array.IO Prelude Data.Array.IO> t <- newArray ((0,0),(5,4)) 0 :: IO (IOUArray (Int,Int) Int) Loading package array-0.1.0.0 ... linking ... done. Prelude Data.Array.IO> getBounds t ((0,0),(5,4)) Prelude Data.Array.IO> writeArray t (10,10) 5 *** Exception: Error in array index Prelude Data.Array.IO> writeArray t (7,3) 5 *** Exception: Error in array index Prelude Data.Array.IO> writeArray t (3,7) 5 Prelude Data.Array.IO> So the array has 0 <= x <= 5 and 0 <= y <= 4, and writing to (10,10) or (7,3) throws an exception. However, writing to (3,7) triggers no exception - despite being clearly out of range. Judging by the behaviour of the large, complex program I was debugging when I stumbled upon this, the coordinates "wrap round" to the next column. (!!) Obviously, writing to non-existent coordinates and not getting an exception is a Very Bad Thing. I was counting on writeArray (and readArray) to detect out-of-range coordinates so I could fix my code. But as you can see, it doesn't actually work as advertised. You have *no idea* how long I spent trying to track this bug down! >_< Is this a known bug? Is it likely to be fixed any time soon? (I'm guessing the bug is as simple is converting indicies to integers and then checking the integers are in-range, rather than the underlying index type.)

9 14

Re: [Haskell] ANNOUNCE: RefSerialize-0.2.1
by Alberto G. Corona 04 Nov '08

04 Nov '08

I uploadad RefSerialize<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/RefSerialize> to Hackage . Read, Show and Data.Binary do not check for repeated references to the same data address. As a result, the data is serialized multiple times when serialized. This is a waste of space in the filesystem and also a waste of serialization time. but the worst consequence is that, when the serialized data is read, it allocates multiple copies in memory for the same object referenced multiple times. Because multiple referenced data is very typical in a pure language such is Haskell, this means that the resulting data loose the beatiful economy of space and processing time that referential transparency permits. This package allows the serialization and deserialization of large data structures without duplication of data, with the result of optimized performance and memory usage. It is also useful for debugging purposes. There are automatic derived instances for instances of Read/Show, lists and strings. the deserializer contains a almos complete set of Parsec.Token parsers for deserialization. Every instance of Show/Read is also a instance of Data.RefSerialize The serialized string has the form "expr( var1, ...varn) where var1=value1,..valn=valueN " so that the string can ve EVALuated. See demo.hs and tutorial. I presumably will add a entry in haskell-web.blogspot.com To develop: -derived instances for Data.Binary -serialization to/from ByteStings I wrote this module because I needed to serialize lists of verisions of the same data with slight modifications between each version. This is a short tutorial (in tutorial.txt) runW applies showp, the serialization parser of the instance Int for the RefSerialize class Data.RefSerialize>let x= 5 :: Int Data.RefSerialize>runW $ showp x "5" every instance of Read and Show is an instance of RefSerialize. rshowp is derived from showp, it labels the serialized data with a variable name Data.RefSerialize>runW $ rshowp x " v8 where {v8= 5; }" Data.RefSerialize>runW $ rshowp [2::Int,3::Int] " v6 where {v6= [ v9, v10]; v9= 2; v10= 3; }" while showp does a normal show serialization Data.RefSerialize>runW $ showp [x,x] "[5, 5]" rshowp variables are serialized memory references: no piece of data that point to the same addrees is serialized but one time Data.RefSerialize>runW $ rshowp [x,x] " v9 where {v6= 5; v9= [ v6, v6]; }" This happens recursively Data.RefSerialize>let xs= [x,x] in str = runW $ rshowp [xs,xs] Data.RefSerialize>str " v8 where {v8= [ v10, v10]; v9= 5; v10= [ v9, v9]; }" the rshowp serialized data is read with rreadp. The showp serialized data is read by readp Data.RefSerialize>let xss= runR rreadp str :: [[Int]] Data.RefSerialize>print xss [[5,5],[5,5]] this is the deserialized data the deserialized data keep the references!! pointers are restored! That is the whole point! Data.RefSerialize>varName xss !! 0 == varName xss !! 1 True rShow= runW rshowp rRead= runR rreadp Data.RefSerialize>rShow x " v11 where {v11= 5; }" In the definition of a referencing parser non referencing parsers can be used and viceversa. Use a referencing parser when the piece of data is being referenced many times inside the serialized data. by default the referencing parser is constructed by: rshowp= insertVar showp rreadp= readVar readp but this can be redefined. See for example the instance of [] in RefSerialize.hs This is an example of a showp parser for a simple data structure. data S= S Int Int deriving ( Show, Eq) instance Serialize S where showp (S x y)= do xs <- rshowp x -- rshowp parsers can be inside showp parser ys <- rshowp y return $ "S "++xs++" "++ys readp = do symbol "S" -- I included a (almost) complete Parsec for deserialization x <- rreadp y <- rreadp return $ S x y there is a mix between referencing and no referencing parser here: Data.RefSerialize>putStrLn $ runW $ showp $ S x x S v23 v23 where {v23= 5; } (I corrected some errors in this file here)

2 2

Fwd: [Haskell-cafe] Re: [Haskell] ANNOUNCE: RefSerialize-0.2.1
by Alberto G. Corona 04 Nov '08

04 Nov '08

I forgot to cc to haskell-cafe: ---------- Forwarded message ---------- From: Alberto G. Corona <agocorona(a)gmail.com> Date: 2008/11/2 Subject: Re: [Haskell-cafe] Re: [Haskell] ANNOUNCE: RefSerialize-0.2.1 To: Bulat Ziganshin <Bulat.Ziganshin(a)gmail.com> * SerTH is a binary serialization library for Haskell. It supports serializing cyclic datatypes in a fast binary format. SerTH uses template haskell for deriving the serializing interface for new datatypes. *Too bad...I did not know it. Not even many people in the #haskell channel, where i discussed about how badly a functionality such that is needed. It restores the references when data is deserialized?. My package is text oriented and the serialization is readable and eval-uable, so can be used also for debugging purposes. I use System.Mem.StableName. for it. 2008/11/2 Bulat Ziganshin <bulat.ziganshin(a)gmail.com> Hello Alberto, > > Sunday, November 2, 2008, 5:02:10 PM, you wrote: > > Read, Show and Data.Binary do not check for repeated references to > > the same data address. > > afair, SerTH does it, using GHC's internal address compare function > > what way to check for copies you use? > > > -- > Best regards, > Bulat mailto:Bulat.Ziganshin@gmail.com > >

1 0

Cairo build fail on OS X Leapord
by Jefferson Heard 04 Nov '08

04 Nov '08

Installing gtk2hs from MacPorts on a clean mac: 2 -I/usr/X11R6/include svgcairo/Graphics/Rendering/Cairo/SVG.chs:201:2: Couldn't match expected type `()' against inferred type `CInt' Expected type: Render () Inferred type: Render CInt In the expression: liftIO $ (\ (SVG arg1) (Cairo arg2) -> withForeignPtr arg1 $ \ argPtr1 -> rsvg_handle_render_cairo argPtr1 arg2) svg cr In the expression: do cr <- ask liftIO $ (\ (SVG arg1) (Cairo arg2) -> withForeignPtr arg1 $ \ argPtr1 -> rsvg_handle_render_cairo argPtr1 arg2) svg cr make[1]: *** [svgcairo/Graphics/Rendering/Cairo/SVG.o] Error 1 rm svgcairo/Graphics/Rendering/Cairo/SVG.hs make: *** [all] Error 2 Error: Status 1 encountered during processing. -- I try to take things like a crow; war and chaos don't always ruin a picnic, they just mean you have to be careful what you swallow. -- Jessica Edwards

2 3

Arch Haskell News: Nov 02 2008
by Don Stewart 03 Nov '08

03 Nov '08

News about the Haskell packages for Arch Linux. Highlights, * 672 Haskell packages now supported in Arch Linux, up 33 from two weeks ago. Noteworthy, * haskell-tcache-0.5.3: “A Transactional data cache with configurable persistence” * haskell-yampa-0.9.2.3: “Library for programming hybrid systems.” * haskell-network-bytestring-0.1.1.3: “Fast and memory efficient low-level networking” * haskell-checkers-0.1.1: “Check properties on standard classes and data structures.” * haskell-coreerlang-0.0.1: “Facilities for manipulating Core Erlang source code: an abstract syntax, parser and pretty-printer.” Full update list, http://archhaskell.wordpress.com/2008/11/03/arch-haskell-news-nov-02-2008/ -- Don How's your favourite distro doing? If its not up to scratch, talk to someone.

1 0

Re: [Haskell-cafe] ANNOUNCE: Graphalyze-0.5 and SourceGraph-0.3
by Ivan Lazar Miljenovic 03 Nov '08

03 Nov '08

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Sun, 2 Nov 2008 22:43:27 -0500 "Gwern Branwen" <gwern0(a)gmail.com> wrote: > Darn! I was really hoping to analyze my XMonadContrib modules which use > CPP. :( > > Come now, is it really so intractable? Why not try a dumb, but simple > and understandable approach - like dropping everything inside CPP > sections, and analysing the remainder? If it's clearly stated in the > docs, I don't think any user could really blame you. If they insist, > you could always add a flag like --strict-cpp ('So you prefer no > results to somewhat wrong results? FINE.') The main reason I haven't is due to lack of time... as it was, these last few fix-ups were only done last-minute whilst I was waiting for my supervisor to read through my draft (and mainly fixed what I perceived as _real_ bugs, not just adding functionality). Though, to be honest I didn't think about performing sanitizing in that fashion... Of course, if you really want that functionality you can add it ;-) - -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) iEYEARECAAYFAkkOdBkACgkQfEfFJ9JhvyhjYgCggEcRquF+BmZSCkVpxt3dY1sT pI4AnjV5em0zVrTxHQtdf2J6ibOZ121d =qd3I -----END PGP SIGNATURE-----

1 0

ANNOUNCE: zlib and bzlib 0.5 releases
by Duncan Coutts 03 Nov '08

03 Nov '08

I'm pleased to announce updates to the zlib and bzlib packages. The releases are on Hackage: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/zlib http://hackage.haskell.org/cgi-bin/hackage-scripts/package/bzlib What's new ========== What's new in these releases is that the extended API is slightly nicer. The simple API that most packages use is unchanged. In particular, these functions have different types: compressWith :: CompressParams -> ByteString -> ByteString decompressWith :: DecompressParams -> ByteString -> ByteString The CompressParams and DecompressParams types are records of compression/decompression parameters. The functions are used like so: compressWith defaultCompressParams { ... } decompressWith defaultDecompressParams { ... } There is also a new parameter to control the size of the first output buffer. This lets applications save memory when they happen to have a good estimate of the output size (some apps like darcs know this exactly). By getting a good estimate and (de)compressing into a single-chunk lazy bytestring this lets apps convert to a strict bytestring with no extra copying cost. Future directions ================= The simple API is very unlikely to change. The current error handling for decompression is not ideal. It just throws exceptions for failures like bad format or unexpected end of stream. This is a tricky area because error streaming behaviour does not mix easily with error handling. On option which I use in the iconv library is to have a data type describe the real error conditions, something like: data DataStream = Chunk Strict.ByteString Checksum DataStream | Error Error -- for some suitable error type | End Checksum With suitable fold functions and functions to convert to a lazy ByteString. Then people who care about error handling and streaming behaviour can use that type directly. For example it should be trivial to convert to an iterator style. People have also asked for a continuation style api to give more control over dynamic behaviour like flushing the compression state (eg in a http server). Unfortunately this does not look easy. The zlib state is mutable and while this can be hidden in a lazy list, it cannot be hidden if we provide access to intermediate continuations. That is because those continuations can be re-run whereas a lazy list evaluates each element at most once (and with suitable internal locking this is even true for SMP). Background ========== The zlib and bzlib packages provide functions for compression and decompression in the gzip, zlib and bzip2 formats. Both provide pure functions on streams of data represented by lazy ByteStrings: compress, decompress :: ByteString -> ByteString This makes it easy to use either in memory or with disk or network IO. For example a simple gzip compression program is just: > import qualified Data.ByteString.Lazy as ByteString > import qualified Codec.Compression.GZip as GZip > > main = ByteString.interact GZip.compress Or you could lazily read in and decompress .gz file using: > content <- GZip.decompress <$> ByteString.readFile file General ======= Both packages are bindings to the corresponding C libs, so they depend on those external C libraries (except on Windows where we build a bundled copy of the C lib source code). The compression speed is as you would expect since it's the C lib that is doing all the work. The zlib package is used in cabal-install to work with .tar.gz files. So it has actually been tested on Windows. It works with all versions of ghc since 6.4 (though it requires Cabal-1.2). The darcs repos for the development versions live on code.haskell.org. I'm very happy to get feedback on the API, the documentation or of course any bug reports. Duncan

3 3

Poll: Do you need to be able to build darcs from source on GHC 6.6?
by Jason Dagit 03 Nov '08

03 Nov '08

Hello, I would like to find out if any darcs users who build from the source are still using ghc 6.6? If you are such a user, please let me know. Thanks, Jason

11 25

Re: [Haskell-cafe] number of references to a variable
by wren ng thornton 03 Nov '08

03 Nov '08

Alberto G. Corona wrote: > * "Certainly a worthy research goal, but probably not what you had in mind > :)" > > *Not at all, My interest on that was on to improve RefSerialize. Although > the Clean people has done a superb job on optimization. By the way, I'm not > sure if uniqueness is the cause of his performance. I tested Haskell code > generated using Maybe with and without monad instance and the monad does not > impose any overhead at all. Oh, I wasn't saying that monads impose any overhead. Rather, the Clean folks aren't fans of monads and so they use uniqueness typing in order to provide the same kind of solution to IO while retaining functional purity. GHC's implementation of IO is actually very similar under the hood to what Clean does, though that's not necessarily true of other monads. Even though they seem to intersect at IO, the ideas of monads and linear logics are orthogonal. The big optimization trick with linear logic is, since you know when some object is uniquely referenced, you know when it's safe to destructively update it in situ. For example, you can reverse a spine-unique list in linear time with zero space (modulo registers) by just inverting the spine pointers as you traverse it. Since it's uniquely referenced, noone else will notice so referential transparency is preserved. Doing it this way saves on allocation costs and on garbage collection. There are certainly other ways to use the information that some object is held only by a single reference, but Clean's optimizations are the first that leap to my mind. -- Live well, ~wren

1 0

is there a way to pretty print a module?
by Anatoly Yakovenko 03 Nov '08

03 Nov '08

is there a way to pretty print a module? like: module Main where import Language.Haskell.TH main = do print $ pprint Main

6 8

number of references to a variable
by Alberto G. Corona 03 Nov '08

03 Nov '08

Is there a way to know the number of memory references for a variable?. The runtime must know it but i do not know if this available for the program trough any low level trick Thanks

6 6

Syntax question: class (Monad m) => MonadReader r m | m -> r where
by Mauricio 03 Nov '08

03 Nov '08

Hi, I've reading Control.Monad.Reader source code and arrived here: class (Monad m) => MonadReader r m | m -> r where I can't understand that syntax. Since this is not a 'data' line, what is the '|' supposed mean? Thanks, Maurício

4 5

Need help with VXML again (fun deps and forall types)
by Marc Weber 02 Nov '08

02 Nov '08

Some time I've announced that I'm working on VXML, a validating xml library. The use case which makes trouble is elem+ (one or more) <!ELEMENT root (a|b|(c,d+))*> This example is encoded in this way: root -> St 1 id :1 endable : True a -> St 1 b -> St 1 c -> St 12 id :11 endable : True (a|b|c) -> St 1 d -> St 11 id :12 endable : False d -> St 11 to be read as: When creating a new root element start with state 1, then expect one of a,b,c subelemnts. If subelement c is added continue with state 12. The element may not be finalized (endable false because a "d" is expected). Following that we end in a loop at state 11 which is endable when only adding more d subelemnts. in VXML it looks like this print $ fStr $ runRoot $ vdo -- forceElements c e d e -- first, result has state 12 A d e -- second, result has state 11 X d e -- thrd, result has state 11 d e -- fourth, result has state 11 Y -- ... Now I'd like to do something convinient such as foldr1 (>>) print $ [1..10] I've called the corresponding function in VXML vxmlgtgt because it can be used like a monad and even do notation is supported using the vdo cpp macro rebinding (>>), (>>=) and return. Obviously I can only use foldr from X up to Y because A has a different return type. If you download the latest version of the library (git clone git://mawercer.de/vxml; git checkout fc160ab # is master branch ) you see that it actually works quite fine -- helper function: vxmlSeqPlus_ (f,fl) = f `vxmlgtgt` (foldr1 vxmlgtgt fl) -- usage example from testSimple.hs, note that both (d e) have different types vxmlSeqPlus_ ((d e), replicate 9 (d e)) d is actually a function creating the d element requiring a function as first argument which adds attrubutes and subelemnts (e is a nop here) This all makes d having a type which looks rather complicated: el*: the result type (String only in the current implementation) data VXML st el_ st2 el2_ st3 el3_ a = VXML { runVVXML :: (PT st el_ -> PT st2 el2_) -- [1] -> (a, PT st el_ -> PT st3 el3_) -- [2] } [1] : st -> st2 : The function which is passed [2] : st -> st3 : The type of function which is returned taking a function modyfiying the parent and adding "d" resulting in st3 (st3 is either State12 in A, or State11 in Y talking about the example given above) Its even getting more interesting now: Because I'd like to use different result types (String, ByteString, ...) I've used a type var to represent that type. I've called them el el2 el3 etc. When finally creating the document by using runRoot the result types propagates through the xml tree by functional dependencies. An example is the AddElT class which actually does add a subelement: class AddElT est el_ estc elc_ est2 el2_ | est estc -> est2 -- result state is determined by parent and child element state , est est2 estc el2_ -> el_ -- the result type of child and parent privious sibling are determined by the el2_ return type and the element states , est est2 estc el2_ -> elc_ where addElT :: PT est el_ -> PT estc elc_ -> PT est2 el2_ The instance has constraints like this determining el_ elc_ and st2 instance ( , DetermineElAddEl (NYV (Element elType AttrsOk st hchs)) el2 cest2 elc2 (NYV (Element elType AttrsOk st2 HTrue)) el3 , Consume st (Elem celType) st2 [..] ) => AddElT [..] Determining states form leafs to the root then propagating String or ByteString result type form the root to the leaf depending on states works fine until I start trying to use shortcut for the foldr1 example above. Instead of vxmlSeqPlus_ ((d e), replicate 9 (d e)) I'd like to write this. Of course the lamba here is polymorphic because it must return State 12 the first time and State 11 in the following cases. vxmlMapSeqPlus_ (\_ -> d e) [1..10] -- Ex I It's implementation is straight forward: vxmlMapSeqPlus_ f (x:xs) = vxmlSeqPlus_ (f x, map f xs) vxmlMapSeqPlus_ _ [] = error "vxmlSeqPlus has been called with empty list" My attempt to assign a type looks like this: vxmlMapSeqPlus_ :: ( VXMLMonad m st el st2 el2 st3 el3 st3 el3 , VXMLMonad m st el st3 el3 st3 el3 st3 el3 ) => (forall st' elA st'' elB . t -> m st el st' elA st'' elB ()) -> [t] -> m st el st2 el2 st3 el3 () vxmlMapSeqPlus_ f (x:xs) = vxmlSeqPlus_ (f x , map f xs) vxmlMapSeqPlus_ _ [] = error "vxmlSeqPlus has been called with empty list" where class VXMLMonad m st el_ st2 el2_ st3 el3_ st4 el4_ where vxmlgtgt :: m st el_ st2 el2_ st3 el3_ a -> m st el_ st3 el3_ st4 el4_ b -> m st el_ st2 el2_ st4 el4_ b vxmlgtgt a b = vxmlbind a $ const b vxmlbind :: m st el_ st2 el2_ st3 el3_ a -> (a -> m st el_ st3 el3_ st4 el4_ b) -> m st el_ st2 el2_ st4 el4_ b However when compiling the example (Ex I) there are a bunch of errors telling me that ghc can't find the matching instances caused by missing specialization of st.. That is ghc does no longer determine the resulting state based on parent and previous childs. Without state it can't propagate the el type ... You can see both examples in testSimple.hs vxmlSeqPlus_ ((d e), replicate 9 (d e)) vxmlMapSeqPlus_ (\n -> d e ) [1..10] So my question is: The second line does work fine, the first one dosen't. How to write vxmlMapSeqPlus_ so that I can compile the example? vxmlMapSeqPlus_ (\n -> d e ) [1..10] (d e) `vxmlgtgt` (foldr1 vxmlgtgt $ map (const $ d e) [2..10]) If you want to try this with ghc older than 6.10 you'll have to rewrite the vdo notation using vxmlbind and vxmlgtgt.. Do you have any idea how to make this work as expected? That's the last issue preventing me from trying to use it in real life projects. Sincerly Marc Weber

1 0

Newbie on instance of Monad
by Mauricio 02 Nov '08

02 Nov '08

Hi, After a lot of thinking, I can't get what I am doing wrong in this code: ------ data ( RandomGen g ) => RandomMonad g a = RandomMonad (g -> a) instance Monad (RandomMonad g) where return = RandomMonad . const RandomMonad f1 >>= f2 = RandomMonad f3 where f3 a = f2f1 a (next a) RandomMonad f2f1 = f2 . f1 ------ I get this error message: Could not deduce (RandomGen g) from the context (Monad (RandomMonad g)) arising from a use of `RandomMonad' at src/encherDB.hs:10:11-21 Possible fix: add (RandomGen g) to the context of the type signature for `return' In the first argument of `(.)', namely `RandomMonad' In the expression: RandomMonad . const In the definition of `return': return = RandomMonad . const but I'm not smart enough to understand what it means. Thanks a lot, Maurício

3 4

Memory efficiency questions for real-time graphics
by T Willingham 02 Nov '08

02 Nov '08

As my first Haskell exposure, I've been working through Real World Haskell. I am considering converting some of my C++ graphics libraries to Haskell. I've done a fair amount of googling on the subject, however I haven't quite been able to find clear answers to some of following issues. (1) Using an OpenGL vertex array (a contiguous chunk of memory which is handed to the graphics card) is important. I see the source code of Frag does this, so it looks like we're good. Check. (2) In-place modification of the vertex array is important. Every vertex changes on each frame update. And we always want more vertices. (3) Growing and shrinking the vertex array efficiently is important. Here the behavior of C++ std::vector happens to be ideal. When growing, extend the array in-place if possible (using reserved space if any), otherwise allocate a new chunk ("amortized constant time"). When shrinking, do nothing but record the smaller size; the unused memory chunk is reserved for possible future growth. (4) Doing little to no allocations each frame update is important. In the current C++ version, zero allocations occur during a normal frame update. When the vertex array changes, that is the only allocation which happens. To give a context for all of this, I am applying a non-linear transformation to an object on every frame. (Note: non-linear, so a matrix transform will not suffice.) The object is described by a certain function, and is generated from a 3D domain grid. The user can change the resolution of the grid on the fly, while the object is moving. (Hence the need for grow/shrink efficiency.) Given that (1) is out of the way, what's the best I expect from Haskell concerning (2)-(4)? Thanks, T. Willingham

5 11

An irritating Parsec problem
by Andrew Coppin 02 Nov '08

02 Nov '08

I like Parsec. I use it for everything. But it does have one irritating problem. Consider the following parser: expressions = many1 expression Suppose this is the top-level parser for my language. Now suppose the user supplies an expression with a syntax error half way through it. What I *want* to happen is for an error to be raised. What *actually* happens is that Parsec just ignores all input after that point. So if "+" is not a valid token, but the user writes x = 1; y = 2; z = 3 + z; w = 4; then what my program receives back is "x = 1; y = 2; z = 3", as if everything parsed successfully. But actually it has ignored half the input! o_O Does anybody know how to fix this irratiting quirk? I can see why it happens, but not how to fix it.

6 11

Haskell Weekly News: Issue 91 - November 1, 2008
by Brent Yorgey 02 Nov '08

02 Nov '08

--------------------------------------------------------------------------- Haskell Weekly News http://sequence.complete.org/hwn/20081101 Issue 91 - November 01, 2008 --------------------------------------------------------------------------- Welcome to issue 91 of HWN, a newsletter covering developments in the [1]Haskell community. Announcements blas version 0.6. Patrick Perry [2]announced a [3]new version of the Haskell BLAS bindings, now with support for the ST monad! darcs hacking sprint #1 (report). Eric Y. Kow [4]summarized the [5]progress made during the darcs hacking sprint last weekend. Looks like exciting stuff! Much more detail and links can be found in Eric's original email. LAST CALL: Haskell Communities and Activities Report. Janis Voigtlaender [6]is extending the submission deadline for the 15th edition of the Haskell Community and Activities Report by a few days. If you haven't already, please [7]write an entry for your new project or update your old entry. Data.TCache 0.5.1. Alberto G. Corona [8]announced the release of [9]Data.TCache, which implements a transactional cache with configurable persistence. It tries to simulate Hibernate for Java or Rails for Ruby; the main difference is that transactions are done in memory trough STM. multirec-0.1. Andres Loeh [10]announced the release of the [11]multirec package, which provides a mechanism to talk about fixed points of systems of datatypes that may be mutually recursive. On top of this representations, generic functions such as the fold or the Zipper can then be defined. Making 'Super Nario Bros.' in Haskell. Korcan Hussein [12]linked to a [13]super mario brothers clone which was [14]written in Haskell! Chart-0.9. Tim Docker [15]announced the 0.9 release of the [16]Chart library, a library for drawing 2D charts. Publication of InputYourData.com + Project Announcement. Enzo Haussecker [17]announced the publication of [18]InputYourData.com, an online tool, written in Haskell, for financial, mathematical and scientific calculations. Enzo also described an idea to create a similar website where web applications are created by the user. If you are intrigued by this project and have substantial experience in designing Haskell-based web applications, please send Enzo your resume and a brief summery of why you are interested. Blog noise [19]Haskell news from the [20]blogosphere. * Mark Jason Dominus: [21]Atypical Typing. Mark describes his OOPSLA talk about Haskell's type system. * Eric Kow (kowey): [22]official darcs blog!. * Ben Moseley: [23]2 Minute intro to Associated Types / Type Families. * Ivan Lazar Miljenovic: [24]Honours + LXDE. Ivan discusses the status of his Haskell-oriented Mathematics Honours thesis. * Jason Dagit: [25]Darcs Hacking Sprint - Summary from Portland Team. * Eric Kow (kowey): [26]darcs hacking sprint - Team Brighton Day 2. * Dan Piponi (sigfpe): [27]Operads and their Monads. Quotes of the Week * lispy: I just wanted to make sure that this was illegal first * quicksilver: it doesn't entirely help that SQL is a series of broken standards layered over very poor decisions by large corporations * Baughn: SingInTime> hello world <Baughn> SingInTime: Type mismatch: Expected type: IRC [a], inferred type: IO () About the Haskell Weekly News New editions are posted to [28]the Haskell mailing list as well as to [29]the Haskell Sequence and [30]Planet Haskell. [31]RSS is also available, and headlines appear on [32]haskell.org. To help create new editions of this newsletter, please see the information on [33]how to contribute. Send stories to byorgey at cis dot upenn dot edu. The darcs repository is available at darcs get [34]http://code.haskell.org/~byorgey/code/hwn/ . References 1. http://haskell.org/ 2. http://article.gmane.org/gmane.comp.lang.haskell.cafe/47117 3. http://quantile95.com/2008/10/31/ann-blas-bindings-for-haskell-version-06/ 4. http://article.gmane.org/gmane.comp.lang.haskell.cafe/47114 5. http://blog.darcs.net/2008/10/darcs-hacking-sprint-1-report.html 6. http://article.gmane.org/gmane.comp.lang.haskell.cafe/47078 7. http://www.haskell.org/pipermail/haskell/2008-October/020651.html 8. http://article.gmane.org/gmane.comp.lang.haskell.cafe/47016 9. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/TCache 10. http://article.gmane.org/gmane.comp.lang.haskell.general/16574 11. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/multirec 12. http://article.gmane.org/gmane.comp.lang.haskell.general/16572 13. http://uk.youtube.com/watch?v=gVLFGQGRsDw 14. http://svn.coderepos.org/share/lang/haskell/nario/ 15. http://article.gmane.org/gmane.comp.lang.haskell.general/16570 16. http://dockerz.net/software/chart.html 17. http://article.gmane.org/gmane.comp.lang.haskell.general/16550 18. http://inputyourdata.com/ 19. http://planet.haskell.org/ 20. http://haskell.org/haskellwiki/Blog_articles 21. http://blog.plover.com/talk/atypical-typing.html 22. http://koweycode.blogspot.com/2008/10/official-darcs-blog.html 23. http://nattermorphisms.blogspot.com/2008/10/2-minute-intro-to-associated-ty… 24. http://ivanmiljenovic.wordpress.com/2008/10/29/honours-lxde/ 25. http://blog.codersbase.com/2008/10/28/darcs-hacking-sprint-summary-from-por… 26. http://koweycode.blogspot.com/2008/10/darcs-hacking-sprint-team-brighton-da… 27. http://sigfpe.blogspot.com/2008/10/operads-and-their-monads.html 28. http://www.haskell.org/mailman/listinfo/haskell 29. http://sequence.complete.org/ 30. http://planet.haskell.org/ 31. http://sequence.complete.org/node/feed 32. http://haskell.org/ 33. http://haskell.org/haskellwiki/HWN 34. http://code.haskell.org/~byorgey/code/hwn/

1 0

ANN: blas version 0.6
by Patrick Perry 02 Nov '08

02 Nov '08

New version of BLAS bindings out. Now with support for the ST monad! This breaks backwards compatibility, unfortunately. More info (and some sample code) here: http://quantile95.com/2008/10/31/ann-blas-bindings-for-haskell-version-06/ Also, if you want to help, please let me know. There is plenty of work to do. Patrick

2 1

Why 'round' does not just round numbers ?
by L.Guo 01 Nov '08

01 Nov '08

Hi all: I just read about definitions of Prelude [1], and noticing that. In 6.4.6 Coercions and Component Extraction, it discribes like this: "round x returns the nearest integer to x, the even integer if x is equidistant between two integers." I think this is unresonable. then try it in GHC 6.8.3. Prelude> round 3.5 4 Prelude> round 2.5 2 Is there any explanation about that ? [1] The Haskell 98 Report: Predefined Types and Classes http://haskell.org/onlinereport/basic.html Regards -------------- L.Guo 2008-10-27

23 50

darcs hacking sprint #1 (report)
by Eric Y. Kow 01 Nov '08

01 Nov '08

Dear Haskellers, I thought some of you might be interested in our report from the darcs hacking sprint, held on 25-26 October. See also the blog version of it at http://blog.darcs.net/2008/10/darcs-hacking-sprint-1-report.html (it has photos). So how did that darcs hacking sprint go? Well, we had a lot of fun and we got a lot of work done, so I think we can safely say that it was a great success! What next? The sprint participants found themselves with a lot of good work started that we simply couldn't put down, so we have continued hacking into the week, turning many of our good starts into more concrete progress. There is still a lot of work to do so we want to make sure we keep that momentum going! The big challenge right now is to get all of the patches reviewed and merged back into darcs.net. Unfortunately, this is creating a delay in the usual patch review process as we clear our backlog. In the meantime, please continue sending your patches! Thanks very much to David Roundy for his advice before the sprint and cheerful handling of this patch influx; Galois, the University of Brighton and Université de Paris 7 for graciously hosting our three venues; and especially to everybody who participated or joined #darcs to cheer us on :-) The next sprint will be held in conjunction with the Haskell Hackathon, March 2009 in Utrecht, Netherlands. So see you in six months! Overview -------- Total sprint patches : 234 Patches produced - during the sprint itself : 178 - as follow-up work : 56 Patches sent and - accepted into darcs.net : 43 - awaiting review : 191 ("during" defined as 25-27 October 2008 at 08:00 UTC) Site reports ------------ * Team Portland: - report: http://lists.osuosl.org/pipermail/darcs-users/2008-October/015082.html - pictures: http://blog.codersbase.com/2008/10/28/darcs-hacking-sprint-summary-from-por… * Team Brighton: - report: http://lists.osuosl.org/pipermail/darcs-users/2008-October/015122.html - pictures: http://koweycode.blogspot.com/2008/10/darcs-hacking-sprints-some-pictures.h… - pictures: http://koweycode.blogspot.com/2008/10/darcs-hacking-sprint-team-brighton-da… * Team Paris: - report: http://lists.osuosl.org/pipermail/darcs-users/2008-October/015215.html What we worked on ----------------- Warm up tasks ============= * Warn the user when the patch name looks like a command line option - http://bugs.darcs.net/issue395 - Participants: Reinier Lamers (Team Paris) - Status: Accepted! * Warn when tags are too short (length name <2) - http://bugs.darcs.net/issue1000 - Participants: Christian Kellerman - Status: Accepted! Optimisations ============= * Solved stack overflow when doing whatsnew on very large lines - http://bugs.darcs.net/issue1017 - Participants: Ganesh Sittampalam (Team Brighton) - Status: awaiting review * Smarter slurpies for faster directory lookups - http://bugs.darcs.net/issue711 - Participants: Ganesh Sittampalam (Team Brighton) - Status: awaiting review * Avoiding lstats in darcs whatsnew - http://bugs.darcs.net/issue390 - Participants: Reinier Lamers (Team Paris) - Status: needs tweaking * Bytestring optimisations - Participants: Don Stewart (Team Portland) - Status: awaiting review Performance-related features ============================ * Filecache to improve darcs annotate and darcs changes performance - Participants: Benedikt Schmidt - Status: still hacking! * Packs - http://wiki.darcs.net/index.html/Packs_Specification - Participants: Nicolas Pouillard, Florent Becker (Team Paris) - Status: plan is fleshed out; implementation started in branch * "Chunky" hunk representation - Participants: Ian Lynagh (Team Brighton) - Status: needs volunteer to start porting from camp to darcs * Global cache: enabled by default and more portable - http://bugs.darcs.net/issue839 - Participants: Simon Michael - Status: Accepted! * Networking performance (Team Paris) - Used tcpdump to examine network performance problems - New issues filed: * http://bugs.darcs.net/issue1167 - darcs-transfer mode versions * http://bugs.darcs.net/issue1168 - ssh pipelining * http://bugs.darcs.net/issue1170 - Nagle's algorithm - Participants: Team Paris - Status: needs implementation! Improved Windows support ======================== * Bugs fixed: - newline endings on Windows for HTTP module. - http://bugs.darcs.net/issue774 - fix character echo on win32. - http://bugs.darcs.net/issue1023 - bracket file writing to prevent windows permission errors. - http://bugs.darcs.net/issue784 - fix file handle leak and check for exceptions on process running. * Participants: Salvatore Insalaco * Status: Accepted! Infrastructure and cleanups =========================== * Code cleanups - Added language pragmas in all files - Removed OldFastPackedString - Replaced FastPackedStrings api in favor of Data.ByteString api - Participants: Don Stewart and Jason Dagit (Team Portland) - Status: awaiting review * Documentation cleanups - Use .lhs only for truly literate files - Migrate .tex to reST in preparation for user manual overhaul - Participants: Trent Buck - Status: awaiting review * Cabalisation - Participants: Duncan Coutts (Team Portland) * Makefile simplifications and cleanups (for doc) - Participants: Trent Buck * Makefile improvements (make ci, make darcs_p) - Participants: Simon Michael, Eric Kow (Team Brighton) - Status: make ci is accepted! make darcs_p awaiting review * Benchmarking suite - Participants: Eric Kow (Team Brighton) - Status: usable as of Wednesday, needs visualisation Camp ==== * http://projects.haskell.org/camp * Progress... - developed "chunky" hunk representation and tests! - got libcurl working under Windows with Cabal - primitive interactive patch selection implemented - Repository type rather than FilePath for repos * Participants: Ian Lynagh (Team Brighton) -- Eric Kow <http://www.nltg.brighton.ac.uk/home/Eric.Kow> PGP Key ID: 08AC04F9

1 0

Re: [darcs-users] Poll: Do you need to be able to build darcs from source on GHC 6.6?
by Juliusz Chroboczek 31 Oct '08

31 Oct '08

> Also, note that Lenny has 6.8, and it is scheduled to become stable Real > Soon Now. That's irrelevant. Lenny going stable will not cause my servers to automatically get upgraded. FWIW, the experimental server is scheduled to switch to lenny in the summer of 2009. There is no ETA for the production servers, which tend to be managed more conservatively still. Juliusz

3 2

Cabal packaging problem - Build-Depends name for Network.Curl.Download?
by Brian Troutwine 31 Oct '08

31 Oct '08

Hello all, I'm having a small bit of trouble using cabal to package a program I'm calling aule. I cannot build the program using cabal but can compile it using ghc directly. Here's my aule.config: Name: Aule Version: 0.2.0 Cabal-Version: >= 1.2 Build-type: Simple Author: Brian L. Troutwine Maintainer: goofyheadedpunk(a)gmail.com Stability: alpha Executable aule Build-Depends: base, network, bytestring, download-curl Main-Is: Main.hs Hs-Source-Dirs: src ghc-options: -Wall -O2 If I decend into src/ the result is as follows. blt@doritos:~/aule/src $ ghc -Wall -O2 --make Main.hs [1 of 1] Compiling Main ( Main.hs, Main.o ) Linking Main ... If I attempt to use cabal the result is the following. blt@doritos:~/aule $ runhaskell Setup.hs configure --prefix=$HOME Configuring Aule-0.2.0... Setup.hs: At least the following dependencies are missing: download-curl -any I've attempted variations on the download-curl name, as well. Also, download-curl was install using the nifty cabal-install tool. I run Ubuntu 8.04 with ghc 6.8.2. Thanks, Brian

2 1

Re: Problems with Windows
by Felix Martini 31 Oct '08

31 Oct '08

Hi John, You don't have to compile hsc2hs yourself. It is part of the standard GHC installation. Cabal should be able to find it. You can check if it does by running runghc Setup.hs configure -v when configuring a package. Compiling network-2.2.0.0 against parsec-3.0.0 with msys/mingw worked fine for me. So if Cabal cannot find hsc2hs you could reinstall GHC or otherwise try to compile network-2.2.0.0 with msys. Regards, Felix

1 0

LAST CALL: Haskell Communities and Activities Report
by Janis Voigtlaender 30 Oct '08

30 Oct '08

Dear Haskellers, It is not yet too late to contribute to the 15th edition of the HC&A Report. In fact, I will wait for a few more days. If you haven't already, please write an entry for your new project or update your old entry. Please mail your entries to hcar(a)haskell.org in plain text or LaTeX format. More information can be found in the original Call for Contributions at http://www.haskell.org/pipermail/haskell/2008-October/020651.html I look forward to receiving your contributions. Thanks a lot, Janis (current editor) -- Dr. Janis Voigtlaender http://wwwtcs.inf.tu-dresden.de/~voigt/ mailto:voigt@tcs.inf.tu-dresden.de

1 0

RE: [Haskell] Making 'Super Nario Bros.' in Haskell‏
by Eli Ford 30 Oct '08

30 Oct '08

That’s great -- easy to follow, even though I can’t read the comments. ^^ It’s not possible for actors to ‘watch’ each other in this system, correct? For instance, if one actor holds a reference to another, it will keep that old version of the actor alive, but it won’t see when the actor moves. This game doesn’t seem to need actors that watch each other, but it’s very common in games. I’ve been using IORefs for that purpose, but I like how pure the Mario game is. Is there a better way than IORefs? ________________________________ From: haskell-bounces(a)haskell.org [mailto:haskell-bounces@haskell.org] On Behalf Of Korcan Hussein Sent: Wednesday, October 29, 2008 4:57 PM To: haskell(a)haskell.org Subject: [Haskell] Making 'Super Nario Bros.' in Haskell‏ Hi I haven't seen this posted any where so I'm sorry in advance if this has been mentioned already but I came across this recent video on youtube: http://uk.youtube.com/watch?v=gVLFGQGRsDw it's a mario clone written in haskell with a link to source code repository (http://svn.coderepos.org/share/lang/haskell/nario/) I thought that it maybe useful to some people. Trustworthiness: Vendor reliability: Privacy: Child safety: ________________________________ For the best free wallpapers from MSN Click here! <http://wallpapers.msn.com/?ocid=%5bB001MSN42A0716B%5d>

2 3

Hugs GraphicsUtils "legacy" code
by Galchin, Vasili 30 Oct '08

30 Oct '08

Hello, What is the suggested migration path from the Hugs GraphicsUtils to contemporary Haskell?? Thanks, Vasili

2 2

[Somewhat OT] Speed
by Andrew Coppin 30 Oct '08

30 Oct '08

Hi guys. This isn't specifically to do with Haskell, but... does anybody have any idea roughly how fast various CPU operations are? For example, is integer arithmetic faster or slower than floating-point? Is addition faster or slower than multiplication? How much slower are the trigonometric functions? etc. Does using 8-bit integers make arithmetic any faster than using wider values? Does anybody have a good resource for this kind of information?

9 11

Problems with Windows
by John Van Enk 30 Oct '08

30 Oct '08

Hello All, I'm trying to reinstall network-2.2.0.0 against Parsec 3 in Windows. Well, this is really hard/impossible to do. Here's what I've done so far: 1) After bashing my face against my desk for a while, I got cabal-install installed in windows. 2) cabal install network --reinstall 3) This freaks out because I don't have hsc2hs installed, but it doesn't tell me that, it just complains about something having to do with sizeof. 4) I figure out that I need hsc2hs installed, and i put cabal-install to use fetching it for me. 5) cabal-install fails because hsc2hs needs the process and directory packages, but they aren't exposed by the cabal file (at least in the version sitting on hackage, I assume this is the right one to use). 6) I give up on using cabal-install to get hsc2hs, so i download the targz for hsc2hs directly. 7) I fix the .cabal file to include process and directory 8) runhaskell Setup configure: >runhaskell Setup configure Configuring hsc2hs-0.67.20061107... Warning: No 'build-type' specified. If you do not need a custom Setup.hs or ./configure script then use 'build-type: Simple'. 9) runhaskell Setup build: Everything works fine. 10) runhaskell Setup install: Everything works fine. 11) Go back to try and install network-2.2.0.0 again with cabal-install. 12) Gets past the sizeof/hsc2hs errors, but then chokes on spaces in build path names: Preprocessing library network-2.2.0.0... gcc.exe: Files\Haskell\parsec-2.1.0.1\ghc-6.8.3: No such file or directory linking dist\build\Network\BSD_hsc_make.o failed command was: C:\ghc\ghc-6.8.3\gcc.exe -BC:\ghc\ghc-6.8.3\gcc-lib -IC:\ghc\ghc-6.8.3\include\mingw -LC:\Program Files\Haskell\parsec-2.1.0.1\ghc-6.8.3 -LC:\ghc\ghc-6.8.3/lib\base-3.0.2.0 -lwsock32 -lmsvcrt -lkernel32 -luser32 -lshell32 -LC:\ghc\ghc-6.8.3 -LC:\ghc\ghc-6.8.3/gcc-lib -lm -lgmp -lwsock32 dist\build\Network\BSD_hsc_make.o -o dist\build\Network\BSD_hsc_make.exe cabal: Error: some packages failed to install: network-2.2.0.0 failed during the building phase. The exception was:exit: ExitFailure 1 13) And this is where I finally gave up and came here. Does any one have any insight into: 1) Why cabal doesn't check for hsc2hs during a configure 2) How I can rebuild network-2.2.0.0 on my Windows box without sacrificing a goat to Bill Gates/GHC Gods? Thanks. /jve

1 1

Re: [Haskell] How to get the binary respentation of the Int/Double.
by Ryan Ingram 30 Oct '08

30 Oct '08

Actually, this is a good question, at least as relating to floating point values. Is there a primitive to view the machine representation of floats? I'm thinking of functions like: reinterpretFloatAsWord :: Float -> Word32 reinterpretWordAsFloat :: Word32 -> Float reinterpretDoubleAsWord :: Double -> Word64 reinterpretWordAsDouble :: Word64 -> Double There are decodeFloat and encodeFloat in the RealFloat class, but these seem to be a bit heavy for inner-loop usage, especially when you are just going to paste the values back together into a word immediately anyways. Are the precision of Float and Double specified by the standard? There's actually lots of nice tricks you can do with these functions; for example, if you know you have a floating point value between 0 and 2^23-1, you can convert it to integer with a floating point add and an integer mask: > magic = 0x00800000 :: Float -- 2^23 > magicMask = 0x007fffff :: Word32 -- 2^23 - 1 > fastFloatToInt23 :: Float -> Word32 > fastFloatToInt23 x = reinterpretFloatAsWord (x + magic) .&. magicMask The add sets the exponent of the float to +23 and arranges it so the low bit of the float corresponds to "1", rounding if necessary. Then you can interpret the result as an integer and mask off the exponent and sign bit from the float, leaving you with just the integer value. This relies on the representation of IEEE single-precision floats, of course. These sorts of tricks come have in handy when working on graphics code; often I've found myself wanting to index into an array with the nearest value after some floating point computation. Texture mapping hardware does this conversion all the time, for example, and sometimes it's useful to emulate that behavior in software. -- ryan On Tue, Oct 28, 2008 at 10:08 AM, Brandon S. Allbery KF8NH <allbery(a)ece.cmu.edu> wrote: > On 2008 Oct 28, at 10:38, haihualin wrote: >> >> I am wondering how to get the binary respentation of the Int/Double. >> So I can save the integer as the binary data so that the C program can >> read it from the file. > > > The Binary package on Hackage (http://hackage.haskell.org) allows you to > serialize Haskell data in any form including C-compatible binary output. > > -- > brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery(a)kf8nh.com > system administrator [openafs,heimdal,too many hats] allbery(a)ece.cmu.edu > electrical and computer engineering, carnegie mellon university KF8NH > > > _______________________________________________ > Haskell mailing list > Haskell(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell >

3 2

How to use lib compat-base3 in ghc 6.10?
by Magicloud 30 Oct '08

30 Oct '08

Hi, Xmonad needs Data.Generics from base3. And I found out that there is a "compat-base3" in ghc 6.10, which has Data.Generics. But `ghc -v` reports that base-3.0.3.0 is hidden. So I wonder how could I compile Xmonad with ghc 6.10? Thanks.

2 1

Re: [darcs-users] Poll: Do you need to be able to build darcs from source on GHC 6.6?
by Matthias Kilian 29 Oct '08

29 Oct '08

On Wed, Oct 29, 2008 at 12:11:22PM +1100, Trent W. Buck wrote: > To my mind, the benefit is negligible, because: > > Then we still have OpenBSD users. > > means we can't drop GHC 6.6 support. Also, note that Lenny has 6.8, > and it is scheduled to become stable Real Soon Now. Ok, it all depends on when the next release of darcs will be ready and when I (or someone else) gets ghc-6.8 or 6.10 done for OpenBSD (yes, I'm working on this, even after I dropped maintainership from our ghc port). I *hope* to get a working ghc-6.10 port for OpenBSD to the end of this year, and I guess that's a short enough timeline that darcs could drop 6.6 support if it's really necessary. Ciao, Kili

1 0

Fwd: [Haskell-cafe] ANNOUNCE: Data.TCache 0.5.1
by Alberto G. Corona 29 Oct '08

29 Oct '08

---------- Forwarded message ---------- From: Alberto G. Corona <agocorona(a)gmail.com> Date: 2008/10/29 Subject: Re: [Haskell-cafe] ANNOUNCE: Data.TCache 0.5.1 To: Joachim Breitner <mail(a)joachim-breitner.de> I developed it in 2006. At this time I think that Happs did not used STM. I do not know Happs.State very well. The main difference is that it is far far simple (only a handfull of methods exported) it is configurable and permit the full semantic of TVars without loosing content persistence. Also, the query is based on let´s say patterns. A pattern is a partilally filled object. enough to deduce the key. the interface is very natural. For example: withResources [ User{ name= "Alberto"} , Product{ id="Playstation"} buyIt where buyIt [Just user, Just product]= [user{due= due user +price product}, product{ stock= stock product -1]] buyIt _ = error "either the user or the product not found" Just prod <- getResource Product{ id="Playstation"} bla bla bla 2008/10/29 Joachim Breitner <mail(a)joachim-breitner.de> > Hi, > > Am Dienstag, den 28.10.2008, 23:26 +0100 schrieb Alberto G. Corona : > > Data.Tcache is a transactional cache with configurable persistence. It > > tries to simulate Hibernate for Java or Rails for Ruby. The main > > difference is that transactions are done in memory trough STM. There > > are transactional cache implementations for some J2EE servers like > > JBOSS. > > > > TCache uses STM . It can atomically apply a function to a list of > > cached objects. The resulting objects go back to the cache > > (withResources). It also can retrieve these objects (getResources). > > Persistence can be syncronous (syncCache) or asyncronous, wtih > > configurable time between cache writes and configurable cache > > clearance strategy. the size of the cache can be configured too . All > > of this can be done trough clearSyncCacheProc. Even the TVar variables > > can be accessed directly (getTVar) to acceess all the semantic of > > atomic blocks while maintaining the persistence of the TVar updates. > > > > Persistence can be defined for each object.: Each object must have a > > defined key, a default filename path (if applicable). Persistence is > > pre-defined in files, but the readResource writeResource and > > delResource methods can be redefined to persist in databases or > > whatever. > > Interesting. Without much deep knowledge, this sounds similar to > HAppS.State. Where are the differences? > > Greetings, > Joachim > > -- > Joachim "nomeata" Breitner > mail: mail(a)joachim-breitner.de | ICQ# 74513189 | GPG-Key: 4743206C > JID: nomeata(a)joachim-breitner.de | http://www.joachim-breitner.de/ > Debian Developer: nomeata(a)debian.org > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > >

1 0

Re: Poll: Do you need to be able to build darcs from source on GHC 6.6?
by trentbuck＠gmail.com 29 Oct '08

29 Oct '08

"Trent W. Buck" <trentbuck(a)gmail.com> writes: > On Wed, Oct 29, 2008 at 12:39:28PM +0900, Stephen J. Turnbull wrote: >> Trent W. Buck writes: >> >> > In an ideal world, we just make sure it builds with the latest tools, >> > and let the users of stable distros worry about telling us if it >> > breaks against whatever versions they care about. >> >> This is very disappointing coming from (some) developers of *version >> control software*! You'd think they, of all software developers, >> would be sympathetic to the need to, well, control versions! > > Let me clarify that the above are my *personal* opinions, and I'm not > really involved in the Darcs Haskell code -- just the surrounding > build and documentation infrastructure. > > I'm speaking more from my role as a Debian maintainer and user than as > a member of the Darcs comunity. Actually, even more than that I'm speaking as someone who for years tried to keep shell scripts portable and POSIX clean and working even on ten-year-old versions of Solaris... before deciding that I was investing waaaaay too much time testing on those systems considering approximately zero of my users ran them. So I said "fuck it, I'll use bash and assume GNU coreutils, and if it breaks on someone's system, they'll tell me."

1 0

Re: [darcs-users] Poll: Do you need to be able to build darcs from source on GHC 6.6?
by David Roundy 29 Oct '08

29 Oct '08

On Wed, Oct 29, 2008 at 12:11:22PM +1100, Trent W. Buck wrote: > > Thus I think the version/upgrade matrix is handy so we can > > plan/schedule when it is safe to drop support. > > In an ideal world, we just make sure it builds with the latest tools, > and let the users of stable distros worry about telling us if it > breaks against whatever versions they care about. No, in the idea world we'd try to be supportive of our contributors and maintainers by not requiring that they install the latest tools. -- David Roundy http://www.darcs.net

2 1

computational overhead of the "data" declarations
by Daryoush Mehrtash 29 Oct '08

29 Oct '08

I Haskell School of Expression (p172), it says: A newtype declaration is just like a data declaration, except that it can > only be used to defined data types with single constructor. The new data > type is different from the analogous one created by a data declaration, in > that there is no computational overhead in having the constructor.... You > can think of a newtype as defining a "new type" with exactly the same > structure, behaviour, and performance as the underlying type. > What is (or where do you see) the computational overhead of the "data" declrations?

5 5

ANNOUNCE: Data.TCache 0.5.1
by Alberto G. Corona 29 Oct '08

29 Oct '08

I uploaded TCache to hackage.org. Data.Tcache is a transactional cache with configurable persistence. It tries to simulate Hibernate for Java or Rails for Ruby. The main difference is that transactions are done in memory trough STM. There are transactional cache implementations for some J2EE servers like JBOSS. TCache uses STM . It can atomically apply a function to a list of cached objects. The resulting objects go back to the cache (withResources). It also can retrieve these objects (getResources). Persistence can be syncronous (syncCache) or asyncronous, wtih configurable time between cache writes and configurable cache clearance strategy. the size of the cache can be configured too . All of this can be done trough clearSyncCacheProc. Even the TVar variables can be accessed directly (getTVar) to acceess all the semantic of atomic blocks while maintaining the persistence of the TVar updates. Persistence can be defined for each object.: Each object must have a defined key, a default filename path (if applicable). Persistence is pre-defined in files, but the readResource writeResource and delResource methods can be redefined to persist in databases or whatever. There is a sample.hs that explain the main features.

2 1

Functional MetaPost in 5 Steps
by Jared Updike 29 Oct '08

29 Oct '08

I'm interested in using Functional MetaPost on Mac OS X (or FreeBSD). I'm looking for a tutorial like: http://haskell.org/haskellwiki/Haskell_in_5_steps but for FMP. I can't even get a simple example to show up in a PDF file: ------------------- import FMP ... (see full code below) myPicture = text "Hello World" main = do print $ emit $ metaPost 1 myPicture params ---------- When run, this emits MetaPost, which, after running through my shell script, below, won't show up in my PDF... (this same TeX file will show an .eps figure I made with PyX, the Python equivalent of FMP, when I change includegraphics to use that file instead of test.1) What am I missing? If I can get this working I will gladly write the FMP 5 Step Tutorial. I like the idea of using FMP but I can't for the life of me understand why running a toy example is so non-trivial. (Not to mention undocumented... the manual and tutorials are very compelling but they don't mention how to get a viewable PDF out of any of the otherwise enticing examples.) Jared. Relevant almost working code: Test.hs: ------------------- import FMP params = Parameters { prolog = "verbatimtex\n\ \\\documentclass{article}\n\ \\\begin{document}\n\ \etex\n\n\ \input boxes\n\ \input FuncMP\n\n", epilog= "\n\n\\end", defaultDX= 3, defaultDY= 3, textDX= 2, textDY= 2, newmp= True, funcmpRTS= "IGNORE", --"+RTS -H40m -K3M -RTS", funcmpBin= "IGNORE", -- "~/FuncMP-1.2/FuncMP", mpBin= "IGNORE" -- "MPINPUTS=:~/FuncMP-1.2 TEX=latex mpost " } myPicture = text "blah" main = do print $ emit $ metaPost 1 myPicture params ---------- test.tex: ----------- \documentclass[12pt]{article} \usepackage[dvipdfm]{graphicx} \begin{document} \section*{Heading} \begin{figure} \begin{center} \includegraphics{test.1} \end{center} \end{figure} \end{document} --------------- shell script: ------ #!/bin/sh ghc --make Test.hs && \ ./Test > test.mp && \ mpost test.mp && \ latex test.tex && \ latex test.tex && \ dvipdfm test.dvi && \ open test.pdf # MacOS X runs my pdf in preview -----------

3 2

strange ghc output
by brad clawsie 29 Oct '08

29 Oct '08

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 i have a small program i have been using routinely that has stopped working. the last alteration of my install configuration was to upgrade the haskell-feed package as arch linux recommended. here is the error i get: - ----- $ runghc newspage.hs GHCi runtime linker: fatal error: I found a duplicate definition for symbol fps_minimum whilst processing object file /usr/lib/bytestring-0.9.1.3/ghc-6.8.2/HSbytestring-0.9.1.3.o This could be caused by: * Loading two different object files which export the same symbol * Specifying the same object file twice on the GHCi command line * An incorrect `package.conf' entry, causing some object to be loaded twice. GHCi cannot safely continue in this situation. Exiting now. Sorry. - ----- i have reinstalled the haskell-bytestring package, to no avail. here is the actual code i am trying to run: http://hpaste.org/11514#a0 its fairly straightforward. any clues? thanks - brad -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iEYEARECAAYFAkkF8ScACgkQxRg3RkRK91OosgCfeZIA378PleCnaxwymabNz97F TXAAnRzOhL4zQ9n9RG1oDp146a1b4ajK =qtCU -----END PGP SIGNATURE-----

4 5

using ghc as a library
by Anatoly Yakovenko 28 Oct '08

28 Oct '08

so I am trying to figure out how to use ghc as a library. following this example, http://www.haskell.org/haskellwiki/GHC/As_a_library, i can load a module and examine its symbols: module Main where import GHC import GHC.Paths ( libdir ) import DynFlags ( defaultDynFlags ) import System.Environment import Data.Maybe import Outputable main = do args <- getArgs let file = head $ args rv <- defaultErrorHandler defaultDynFlags $ do runGhc (Just libdir) $ do dflags <- getSessionDynFlags setSessionDynFlags dflags target <- guessTarget file Nothing setTargets [target] load LoadAllTargets gr <- getModuleGraph mi <- getModuleInfo $ ms_mod $ head $ gr return $ fromJust $ mi print $ showSDoc $ ppr $ modInfoInstances $ rv print $ showSDoc $ ppr $ modInfoExports $ rv given Test.hs: module Test where hello = "hello" world = "world" one = 1 two = 2 i get this output: $ ./Main ./Test.hs "[]" "[Test.hello, Test.one, Test.two, Test.world]" which is what i expect. My question is, how do manipulate the symbols exported by Test? Is there a way to test the types? lets say i wanted to sum all the numbers and concatenate all the strings in Test.hs, how would i do that?

3 8

Re: [Haskell-cafe] Haskell syntax inside QuasiQuote
by Matt Morrow 28 Oct '08

28 Oct '08

> Is there a simple way to do this, i.e. using existing libraries? Yes indeed. I'll be traveling over the next two days, and am shooting for a fully functional hackage release by mid next week. > What I need is a Haskell expression parser which outputs values of type > Language.Haskell.TH.Syntax.QExp, but I can't see one available in the TH > libraries, or in the haskell-src(-exts) libraries. My strategy is to use the existing haskell-src-exts parser, then translate that AST to the TH AST. Once I've got settled in one place, I'll follow up with a brain dump :) > Cheers, > Reiner Matt

3 6

Cabal and GHCi
by Reiner Pope 28 Oct '08

28 Oct '08

Hi, Is there a way to use GHCi with code which is cabal-buildable but not "ghc --make"-able? The emacs haskell-mode makes a pretty good guess by :cd-ing into the directory with the .cabal file; however, if there is a different source-dir this doesn't work so well. A number of more advanced cabal features are even harder to handle. Cheers, Reiner

2 2

What's this algebraic structure called?
by Richard O'Keefe 28 Oct '08

28 Oct '08

Is there a special name for an operator monoid where the structure that's acted on is an Abelian group?

2 5

Problems building HOC
by Colin Fleming 28 Oct '08

28 Oct '08

Hi all, I'm trying to get HOC to build because I'd like to take Yi for a spin and see how it works. I followed the instructions in the Yi README, but I can't get HOC to build. It seems like HOC is under pretty heavy development right now, so maybe this is something transient. I didn't build libffi because according to the Yi docs that's not required on Leopard. HOC built and installed ok, however it failed on the bindings generation step - I've pasted the full compile output below. Am I doing something daft? I'm an (almost) total Haskell newbie so this is entirely possible... I'm using GHC 6.8.2 from MacPorts, and OSX 10.5.5. Thanks for any help! Cheers, Colin ~/dev/haskell/hoc/Bindings> bash make-bindings-macos.sh --user *** Processing Framework Foundation *** NSObjCRuntime.h:139:32: NSIntegerMax undefined [ ] NSObjCRuntime.h:139:32: Couldn't handle enum value for NSNotFound ] NSPropertyList.h:13:55: kCFPropertyListImmutable undefined ] NSPropertyList.h:13:55: Couldn't handle enum value for NSPropertyListImmutable ] NSPropertyList.h:14:71: kCFPropertyListMutableContainers undefined ] NSPropertyList.h:14:71: Couldn't handle enum value for NSPropertyListMutableContainers NSPropertyList.h:16:1: kCFPropertyListMutableContainersAndLeaves undefined ] NSPropertyList.h:16:1: Couldn't handle enum value for NSPropertyListMutableContainersAndLeaves NSPropertyList.h:20:65: kCFPropertyListOpenStepFormat undefined ] NSPropertyList.h:20:65: Couldn't handle enum value for NSPropertyListOpenStepFormat NSPropertyList.h:21:65: kCFPropertyListXMLFormat_v1_0 undefined ] NSPropertyList.h:21:65: Couldn't handle enum value for NSPropertyListXMLFormat_v1_0 NSPropertyList.h:23:1: kCFPropertyListBinaryFormat_v1_0 undefined NSPropertyList.h:23:1: Couldn't handle enum value for NSPropertyListBinaryFormat_v1_0 NSNumberFormatter.h:39:57: kCFNumberFormatterNoStyle undefined******* ] NSNumberFormatter.h:39:57: Couldn't handle enum value for NSNumberFormatterNoStyle NSNumberFormatter.h:40:67: kCFNumberFormatterDecimalStyle undefined NSNumberFormatter.h:40:67: Couldn't handle enum value for NSNumberFormatterDecimalStyle NSNumberFormatter.h:41:69: kCFNumberFormatterCurrencyStyle undefined NSNumberFormatter.h:41:69: Couldn't handle enum value for NSNumberFormatterCurrencyStyle NSNumberFormatter.h:42:67: kCFNumberFormatterPercentStyle undefined NSNumberFormatter.h:42:67: Couldn't handle enum value for NSNumberFormatterPercentStyle NSNumberFormatter.h:43:73: kCFNumberFormatterScientificStyle undefined NSNumberFormatter.h:43:73: Couldn't handle enum value for NSNumberFormatterScientificStyle NSNumberFormatter.h:45:1: kCFNumberFormatterSpellOutStyle undefined NSNumberFormatter.h:45:1: Couldn't handle enum value for NSNumberFormatterSpellOutStyle NSNumberFormatter.h:189:73: kCFNumberFormatterPadBeforePrefix undefined NSNumberFormatter.h:189:73: Couldn't handle enum value for NSNumberFormatterPadBeforePrefix NSNumberFormatter.h:190:71: kCFNumberFormatterPadAfterPrefix undefined NSNumberFormatter.h:190:71: Couldn't handle enum value for NSNumberFormatterPadAfterPrefix NSNumberFormatter.h:191:73: kCFNumberFormatterPadBeforeSuffix undefined NSNumberFormatter.h:191:73: Couldn't handle enum value for NSNumberFormatterPadBeforeSuffix NSNumberFormatter.h:193:1: kCFNumberFormatterPadAfterSuffix undefined NSNumberFormatter.h:193:1: Couldn't handle enum value for NSNumberFormatterPadAfterSuffix NSNumberFormatter.h:200:67: kCFNumberFormatterRoundCeiling undefined NSNumberFormatter.h:200:67: Couldn't handle enum value for NSNumberFormatterRoundCeiling NSNumberFormatter.h:201:63: kCFNumberFormatterRoundFloor undefined NSNumberFormatter.h:201:63: Couldn't handle enum value for NSNumberFormatterRoundFloor NSNumberFormatter.h:202:61: kCFNumberFormatterRoundDown undefined NSNumberFormatter.h:202:61: Couldn't handle enum value for NSNumberFormatterRoundDown NSNumberFormatter.h:203:57: kCFNumberFormatterRoundUp undefined NSNumberFormatter.h:203:57: Couldn't handle enum value for NSNumberFormatterRoundUp NSNumberFormatter.h:204:69: kCFNumberFormatterRoundHalfEven undefined NSNumberFormatter.h:204:69: Couldn't handle enum value for NSNumberFormatterRoundHalfEven NSNumberFormatter.h:205:69: kCFNumberFormatterRoundHalfDown undefined NSNumberFormatter.h:205:69: Couldn't handle enum value for NSNumberFormatterRoundHalfDown NSNumberFormatter.h:207:1: kCFNumberFormatterRoundHalfUp undefined NSNumberFormatter.h:207:1: Couldn't handle enum value for NSNumberFormatterRoundHalfUp NSDecimal.h:49:1: problem parsing struct 61% [*************** ] NSDateFormatter.h:40:53: kCFDateFormatterNoStyle undefined*************** ] NSDateFormatter.h:40:53: Couldn't handle enum value for NSDateFormatterNoStyle NSDateFormatter.h:41:59: kCFDateFormatterShortStyle undefined NSDateFormatter.h:41:59: Couldn't handle enum value for NSDateFormatterShortStyle NSDateFormatter.h:42:61: kCFDateFormatterMediumStyle undefined NSDateFormatter.h:42:61: Couldn't handle enum value for NSDateFormatterMediumStyle NSDateFormatter.h:43:57: kCFDateFormatterLongStyle undefined NSDateFormatter.h:43:57: Couldn't handle enum value for NSDateFormatterLongStyle NSDateFormatter.h:45:1: kCFDateFormatterFullStyle undefined NSDateFormatter.h:45:1: Couldn't handle enum value for NSDateFormatterFullStyle NSCalendar.h:16:47: kCFCalendarUnitEra undefined 79% [******************* ] NSCalendar.h:16:47: Couldn't handle enum value for NSEraCalendarUnit NSCalendar.h:17:49: kCFCalendarUnitYear undefined NSCalendar.h:17:49: Couldn't handle enum value for NSYearCalendarUnit NSCalendar.h:18:51: kCFCalendarUnitMonth undefined NSCalendar.h:18:51: Couldn't handle enum value for NSMonthCalendarUnit NSCalendar.h:19:47: kCFCalendarUnitDay undefined NSCalendar.h:19:47: Couldn't handle enum value for NSDayCalendarUnit NSCalendar.h:20:49: kCFCalendarUnitHour undefined NSCalendar.h:20:49: Couldn't handle enum value for NSHourCalendarUnit NSCalendar.h:21:53: kCFCalendarUnitMinute undefined NSCalendar.h:21:53: Couldn't handle enum value for NSMinuteCalendarUnit NSCalendar.h:22:53: kCFCalendarUnitSecond undefined NSCalendar.h:22:53: Couldn't handle enum value for NSSecondCalendarUnit NSCalendar.h:23:49: kCFCalendarUnitWeek undefined NSCalendar.h:23:49: Couldn't handle enum value for NSWeekCalendarUnit NSCalendar.h:24:55: kCFCalendarUnitWeekday undefined NSCalendar.h:24:55: Couldn't handle enum value for NSWeekdayCalendarUnit NSCalendar.h:25:69: kCFCalendarUnitWeekdayOrdinal undefined NSCalendar.h:25:69: Couldn't handle enum value for NSWeekdayOrdinalCalendarUnit NSCalendar.h:70:61: kCFCalendarComponentsWrap undefined NSCalendar.h:70:61: Couldn't handle enum value for NSWrapCalendarComponents NSCalendar.h:93:1: NSIntegerMax undefined NSCalendar.h:93:1: Couldn't handle enum value for NSUndefinedDateComponent NSByteOrder.h:9:45: CFByteOrderUnknown undefined NSByteOrder.h:9:45: Couldn't handle enum value for NS_UnknownByteOrder Parsing Objective-C header files: 100% [*************************] Building initial entities: 100% [*************************] Resolving cross-references: 100% [*************************] Converting types: 100% [*************************] Zapping unconvertable entities: 100% [*************************] Filling in additional instance declarations: 100% [*************************] Combining duplicate entities: 100% [*************************] Resolving name conflicts: 100% [*************************] Eliminating redundant instances: 100% [*************************] Writing binding modules: 100% [*************************] Writing Foundation.hs: 100% [*************************] Writing Foundation.pi: 100% [*************************] done. ~/dev/haskell/hoc/Bindings/Generated/HOC-Foundation ~/dev/haskell/hoc/Bindings/Generated Configuring HOC-Foundation-1.0... Preprocessing library HOC-Foundation-1.0... Building HOC-Foundation-1.0... [ 2 of 154] Compiling Foundation.NSProxy[boot] ( Foundation/NSProxy.hs-boot, dist/build/Foundation/NSProxy.o-boot ) [ 3 of 154] Compiling Foundation.NSObject[boot] ( Foundation/NSObject.hs-boot, dist/build/Foundation/NSObject.o-boot ) [ 4 of 154] Compiling Foundation.NSPort[boot] ( Foundation/NSPort.hs-boot, dist/build/Foundation/NSPort.o-boot ) [ 5 of 154] Compiling Foundation.NSScanner[boot] ( Foundation/NSScanner.hs-boot, dist/build/Foundation/NSScanner.o-boot ) [ 6 of 154] Compiling Foundation.NSScriptCommand[boot] ( Foundation/NSScriptCommand.hs-boot, dist/build/Foundation/NSScriptCommand.o-boot ) [ 7 of 154] Compiling Foundation.NSScriptCommandDescription[boot] ( Foundation/NSScriptCommandDescription.hs-boot, dist/build/Foundation/NSScriptCommandDescription.o-boot ) [ 8 of 154] Compiling Foundation.NSScriptObjectSpecifiers[boot] ( Foundation/NSScriptObjectSpecifiers.hs-boot, dist/build/Foundation/NSScriptObjectSpecifiers.o-boot ) [ 9 of 154] Compiling Foundation.NSSet[boot] ( Foundation/NSSet.hs-boot, dist/build/Foundation/NSSet.o-boot ) [ 10 of 154] Compiling Foundation.NSStream[boot] ( Foundation/NSStream.hs-boot, dist/build/Foundation/NSStream.o-boot ) [ 11 of 154] Compiling Foundation.NSString[boot] ( Foundation/NSString.hs-boot, dist/build/Foundation/NSString.o-boot ) [ 12 of 154] Compiling Foundation.NSTimeZone[boot] ( Foundation/NSTimeZone.hs-boot, dist/build/Foundation/NSTimeZone.o-boot ) [ 13 of 154] Compiling Foundation.NSTimer[boot] ( Foundation/NSTimer.hs-boot, dist/build/Foundation/NSTimer.o-boot ) [ 14 of 154] Compiling Foundation.NSURL[boot] ( Foundation/NSURL.hs-boot, dist/build/Foundation/NSURL.o-boot ) [ 15 of 154] Compiling Foundation.NSValue[boot] ( Foundation/NSValue.hs-boot, dist/build/Foundation/NSValue.o-boot ) [ 16 of 154] Compiling Foundation.NSXMLNode[boot] ( Foundation/NSXMLNode.hs-boot, dist/build/Foundation/NSXMLNode.o-boot ) [ 17 of 154] Compiling Foundation.NSXMLDTDNode[boot] ( Foundation/NSXMLDTDNode.hs-boot, dist/build/Foundation/NSXMLDTDNode.o-boot ) [ 18 of 154] Compiling Foundation.NSXMLDocument[boot] ( Foundation/NSXMLDocument.hs-boot, dist/build/Foundation/NSXMLDocument.o-boot ) [ 19 of 154] Compiling Foundation.NSXMLElement[boot] ( Foundation/NSXMLElement.hs-boot, dist/build/Foundation/NSXMLElement.o-boot ) [ 23 of 154] Compiling Foundation.NSNotification[boot] ( Foundation/NSNotification.hs-boot, dist/build/Foundation/NSNotification.o-boot ) [ 24 of 154] Compiling Foundation.NSMethodSignature[boot] ( Foundation/NSMethodSignature.hs-boot, dist/build/Foundation/NSMethodSignature.o-boot ) [ 25 of 154] Compiling Foundation.NSLocale[boot] ( Foundation/NSLocale.hs-boot, dist/build/Foundation/NSLocale.o-boot ) [ 26 of 154] Compiling Foundation.NSInvocation[boot] ( Foundation/NSInvocation.hs-boot, dist/build/Foundation/NSInvocation.o-boot ) [ 27 of 154] Compiling Foundation.NSIndexSet[boot] ( Foundation/NSIndexSet.hs-boot, dist/build/Foundation/NSIndexSet.o-boot ) [ 28 of 154] Compiling Foundation.NSGeometry ( Foundation/NSGeometry.hs, dist/build/Foundation/NSGeometry.o ) Loading package base ... linking ... done. Loading package array-0.1.0.0 ... linking ... done. Loading package bytestring-0.9.0.1 ... linking ... done. Loading package containers-0.1.0.1 ... linking ... done. Loading package old-locale-1.0.0.0 ... linking ... done. Loading package old-time-1.0.0.0 ... linking ... done. Loading package filepath-1.1.0.0 ... linking ... done. Loading package directory-1.0.0.0 ... linking ... done. Loading package mtl-1.1.0.0 ... linking ... done. Loading package fgl-5.4.1.1 ... linking ... done. Loading package parsec-3.0.0 ... linking ... done. Loading package pretty-1.0.0.0 ... linking ... done. Loading package packedstring-0.1.0.0 ... linking ... done. Loading package template-haskell ... linking ... done. Loading package unix-2.3.0.0 ... linking ... done. Loading package HOC-1.0 ... linking ... done. Foundation/NSGeometry.hs:36:8: Not in scope: data constructor `NSRect' Foundation/NSGeometry.hs:36:16: Not in scope: data constructor `NSPoint' Foundation/NSGeometry.hs:36:30: Not in scope: data constructor `NSSize' Foundation/NSGeometry.hs:37:8: Not in scope: data constructor `NSRect' Foundation/NSGeometry.hs:37:16: Not in scope: data constructor `NSPoint' Foundation/NSGeometry.hs:37:30: Not in scope: data constructor `NSSize' Foundation/NSGeometry.hs:38:8: Not in scope: data constructor `NSRect' Foundation/NSGeometry.hs:38:16: Not in scope: data constructor `NSPoint' Foundation/NSGeometry.hs:38:30: Not in scope: data constructor `NSSize' Foundation/NSGeometry.hs:39:8: Not in scope: data constructor `NSRect' Foundation/NSGeometry.hs:39:16: Not in scope: data constructor `NSPoint' Foundation/NSGeometry.hs:39:30: Not in scope: data constructor `NSSize' Foundation/NSGeometry.hs:40:8: Not in scope: data constructor `NSRect' Foundation/NSGeometry.hs:40:16: Not in scope: data constructor `NSPoint' Foundation/NSGeometry.hs:40:30: Not in scope: data constructor `NSSize' Foundation/NSGeometry.hs:41:8: Not in scope: data constructor `NSRect' Foundation/NSGeometry.hs:41:16: Not in scope: data constructor `NSPoint' Foundation/NSGeometry.hs:41:30: Not in scope: data constructor `NSSize' Foundation/NSGeometry.hs:42:9: Not in scope: data constructor `NSRect' Foundation/NSGeometry.hs:42:17: Not in scope: data constructor `NSPoint' Foundation/NSGeometry.hs:42:31: Not in scope: data constructor `NSSize' Foundation/NSGeometry.hs:43:10: Not in scope: data constructor `NSRect' Foundation/NSGeometry.hs:43:18: Not in scope: data constructor `NSPoint' Foundation/NSGeometry.hs:43:32: Not in scope: data constructor `NSSize'

1 0

Re: [Haskell] IORef sharing
by Bulat Ziganshin 28 Oct '08

28 Oct '08

Hello Rodney, Tuesday, October 28, 2008, 1:27:26 AM, you wrote: > Now I define an IORef and a couple of counters that share > the IORef, >> iio :: IO (IORef Int) >> iio = newIORef 0 >> ic1 = do { io <- iio ; count io 0 } >> ic2 = do { io <- iio ; count io 0 } > So apparently my mental picture of an IORef as a pointer > to a value is wrong. I need a new mental picture. What's > going on here? this part is right. but "iio = newIORef 0" doesn't define IORef, instead it defines *operation* that creates new IORef and returns it then ic1 and ic2 are *operations* that performs iio, creating new IORef on each call, and then use this new IORef in further operation look at http://haskell.org/haskellwiki/IO_inside -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com

1 0

Problem with haddock 2.3.0
by Leonidas Fegaras 28 Oct '08

28 Oct '08

You have received a secure message. Read your secure message by opening the attachment, securedoc.html. You will be prompted to open (view) the file or save (download) it to your computer. For best results, save the file first, then open it in a Web browser. To access from a mobile device, forward this message to mobile(a)res.cisco.com to receive a mobile login URL. If you have concerns about the validity of this message, contact the sender directly. First time users - will need to register after opening the attachment. Help - https://res.cisco.com/websafe/help?topic=RegEnvelope About Cisco Registered Email Service - https://res.cisco.com/websafe/about">https://res.cisco.com/websafe/about

1 0

Problem with haddock 2.3.0
by Fegaras, Leonidas 28 Oct '08

28 Oct '08

You have received a secure message. Read your secure message by opening the attachment, securedoc.html. You will be prompted to open (view) the file or save (download) it to your computer. For best results, save the file first, then open it in a Web browser. To access from a mobile device, forward this message to mobile(a)res.cisco.com to receive a mobile login URL. If you have concerns about the validity of this message, contact the sender directly. First time users - will need to register after opening the attachment. Help - https://res.cisco.com/websafe/help?topic=RegEnvelope About Cisco Registered Email Service - https://res.cisco.com/websafe/about">https://res.cisco.com/websafe/about

2 1

Re: [Haskell-cafe] Why 'round' does not just round numbers ?
by Janis Voigtlaender 28 Oct '08

28 Oct '08

Felipe Lessa wrote: > On Mon, Oct 27, 2008 at 8:15 AM, Janis Voigtlaender > <voigt(a)tcs.inf.tu-dresden.de> wrote: > >>That is of course true (and was the topic of heated discussion with my >>fourth grade math teacher), but does not explain 2.5 -> 2. > > > If you round to odd instead of round to even, then 4.5 rounds to 5, Well, of course I did not learn to round to odd. I learned to round .5 to above, but not to do repeated rounding. So we would never have either of > 2.45 -> 2.4 -> 2 > 2.45 -> 2.5 -> 3 as you suggest. Instead, always in one go: 2.45 -> 2 Because of the 4, whereas any digit following it would be ignored: 2.4x -> x In fact, by your explanation, you would have: 3.46 -> 3.5 -> 4 Which is most odd. 3.46 is definitely closer to 3 than to 4. -- Dr. Janis Voigtlaender http://wwwtcs.inf.tu-dresden.de/~voigt/ mailto:voigt@tcs.inf.tu-dresden.de

7 11