- Haskell-Cafe - Haskell.org

Problem about hidden package again.
by Magicloud Magiclouds 12 Nov '09

12 Nov '09

Hi, Today, when I compiled gtk2hs, I got this: cairo/Graphics/Rendering/Cairo.hs.pp:264:0: Failed to load interface for `Data.Array.Base': it is a member of the hidden package `array-0.2.0.0' Use -v to see a list of the files searched for. As usual, I searched for the resolvement. No luck. And seems like this problem (not particularly to this package) is very common. I wonder how to resolve it? -- 竹密岂妨流水过山高哪阻野云飞

3 5

(state) monad and CPS
by jean-christophe mincke 12 Nov '09

12 Nov '09

Hello, I would like to get some advice about state monad (or any other monad I guess) and CPS. Let's take a simple exemple (see the code below) 'walk' is a function written in CPS that compute the number of nodes & leaves in a tree. It use a counter which is explicitly passed through calls. 'walk2' is does the same using the state monad but is not written in CPS Is it possible to write a function 'walk3' written in CPS and using the state monad? Thank you Regards J-C module M where import Control.Monad.State data Node = Node (Node, Int, Node) |Leaf Int |Empty deriving (Show) walk Empty acc k = k acc walk (Leaf _) acc k = k (acc+1) walk (Node (l, _, r)) acc k = let k1 acc = walk r acc k in walk l (acc+1) k1 nb = Node (Leaf 1, 2, Leaf 3) nd = Node (nb, 4, Empty) nh = Node (Empty, 8, Leaf 9) ng = Node (Leaf 6, 7, nh) ne = Node (nd, 5, ng) r = walk ne 0 id walk2 Empty = return () walk2 (Leaf _ ) = do acc <- get put (acc+1) return () walk2 (Node (l, _, r)) = do acc <- get put (acc+1) walk2 l walk2 r return () r2 = runState (walk2 ne) 0

6 7

lambda-bot installation problem: gentoo trickery problem
by Евгений Пермяков 12 Nov '09

12 Nov '09

When I try cabal-install lambdabot (gentoo linux/amd64, ghc installed with portage), it runs fine until compiler tries to link readline package (some template haskell?). The problem caused by dirty trick, used in gentoo: the /usr/lib64/libreadline is a fake with script, redirecting ld to /lib64 . GHC is not redirected but simply fails with message "can't load .so/.DLL for: readline (/usr/lib64/libreadline.so: invalid ELF header)". So, the question is: is there any workaround? Copying library look like an option, but it is very, very dirty one. Is there a way to say ghc, which libreadline.so it should load?

2 1

Static Linking Problem
by MightyByte 12 Nov '09

12 Nov '09

I am trying to statically compile a simple haskell program so I can use it on a Linux computer without haskell and it's associated libraries. Here is a small example program that illustrates my problem: > module Main where > import Network.Fancy > main = do > withDgram (IP "127.0.0.1" 1234) (flip send "Hello network\n") After a bit of googling, I came to the conclusion that I needed to compile it with "ghc --make -static -optl-static Foo.hs". Using only "-static" or "-optl-static" by themselves did not generate a statically linked binary. But when I compile with both those parameters I get a bunch of linker errors: /home/mightybyte/.cabal/lib/network-fancy-0.1.4/ghc-6.10.4/libHSnetwork-fancy-0.1.4.a(Fancy.o): In function `s6ks_info': (.text+0x3068): warning: Using 'getaddrinfo' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking /usr/lib/ghc-6.10.4/libffi.a(closures.o): In function `init_mparams': (.text+0x3e): undefined reference to `pthread_mutex_lock' /usr/lib/ghc-6.10.4/libffi.a(closures.o): In function `init_mparams': (.text+0x52): undefined reference to `pthread_mutex_unlock' /usr/lib/ghc-6.10.4/libffi.a(closures.o): In function `init_mparams': (.text+0xd3): undefined reference to `pthread_mutex_init' /usr/lib/ghc-6.10.4/libffi.a(closures.o): In function `ffi_closure_free': (.text+0x59c): undefined reference to `pthread_mutex_lock' etc... I've tried this on both Fedora and Arch Linux and I get the same error. Anyone know how to solve this problem?

4 5

"Least common supertype"?
by Sean Leather 12 Nov '09

12 Nov '09

Is there a name for the following concept? Can you point me to any references on it? Suppose I have the following two functions ... > swap1 :: (Int, Char) -> (Char, Int) > swap2 :: (Char, Int) -> (Int, Char) ... and, for some reason, I think I can unify these into a single function. I think, hmm, given that the structure is that same, let's do a first pass: > swap? :: (a, b) -> (c, d) But then I go back to the input types to confirm that this will work, and, alas, it will not, because there are similarities that I missed. This is way too general. I need to ensure that what's an Int stays an Int and likewise for Char. > swap! :: (a, b) -> (b, a) And now I have found a type that is more general than swap1 and swap2 and yet not so general that the shared constraints are left out. This seems somewhat analogous to the least common multiple. Another example is the following: > showFloat :: Float -> String > showBool :: Bool -> String We could say the more general type is ... > show? :: a -> String ... but then we lose the implied constraint that we must know something about 'a' to produce a string. So, we add back such some such constraint: > show! :: (Show a) => a -> String Of course, with all of this, it may not be clear what to do about the definitions of the functions, but I'm curious if there's a name for the concept from a type perspective. Thanks, Sean

7 8

Wrestling the inliner beast
by Bryan O'Sullivan 12 Nov '09

12 Nov '09

I did a little bit of Data.Text benchmarking the other day, and I was shocked to find that decoding a UTF-8 stream proceeded at a sedate 3MB/sec. On investigation, the culprit was that I'd marked both the outer function and the inner (a loop) as INLINE. Because the inner loop was marked as INLINE, GHC wasn't inlining critically important leaf functions into it, so I was getting clobbered to death by boxing and unboxing. Leaving the outer function marked as INLINE, but taking the INLINE off the inner function, seems to cause *both* to get inlined as I originally hoped. This behaviour is all rather mysterious to me. The old "Secrets of the Inliner" paper is very much out of date now, but short of reading the source, I don't know where else to look to turn my voodoo folk intuition into something more solid. Is this all going to change in 6.12 anyway?

1 0

Help Haskell driving Medical Instruments
by Philippos Apolinarius 12 Nov '09

12 Nov '09

Recently, I received as gift medical instruments designed by one of my father former students. There is a description of these instruments on my web page. Here is the address: http://www.discenda.org/med/ By the way, I am not that guy that appears in a picture wearing emg sensors. That said, the instruments and everything else are programmed in Clean. Then I have a new opportunity of translating Clean programs to Haskell and test them in a real application application. Of course, I simplified the programs to see how they work. The medical instruments have on-board computers, that record signals (electromyograms, electroencephalograms, electrocardiograms, end-tydal CO2 partial pressure and temperature), pre-process them and send them to the main computer. The main-computer recognizes patterns in the signals, and use the result to drive a wheelchair, or to call a doctor. On my page you wil find more complete explanations and pictures of the instruments. For ready reference, here is my address: http://www.discenda.org/med/ I decided start my translation work from the most simple programs, the graphical interface and the communication protocol. After substituting a Haskell program for the Clean original, I discovered that the system did not work anymore if I exited the Haskell program. In few words, after leaving the Haskell program without turning off the computer or the sensors, and entering the Haskell program again, Haskell failed to communicate with the sensors. I did what I always do in such a situation: I simplified the program until I reduced it to a few lines. I discovered that Haskell failed to close the serial port. There is a serial to UART-0 driver that allows me to plug the serial cable to a USB port, that both feeds the sensors, and permit communication. I fixed the bug by passing a useless integer argument to the function used to close the port. Since I don't like this kind of patch (useless arguments), I would like to know why the original program does not work, and also I would appreciate if someone could suggest a way to get rid of the argument whose sole job is force Haskell to close the port. The GUI is based on the Small JAPI biding, fixed and incremented with text processing components. Here is the fixed Haskell program: import Gui.Binding import Gui.Types import Gui.Constants import SER.IAL import Control.Monad import Data.Char main = do rv <- j_start frame <- j_frame "Sensors" exit_button <- j_button frame "Exit" j_setpos exit_button 50 50 j_setsize exit_button 80 30 fld <- j_textfield frame 30 j_setpos fld 50 100 j_show frame opencport(4) waitForFrameAction frame fld exit_button let r = closecport 7 {- without the argument, closecport does not work -} print r return j_quit waitForFrameAction :: Frame -> Object -> Object -> IO Bool waitForFrameAction frame f b = do obj <- j_nextaction again <- if obj == event b then return False else do {- nm <- j_gettext f 200 -} tx <- sendMessage 1 "t" let tp= filter (> ' ') tx rx <- sendMessage 1 "x" let rd= filter (> ' ') rx let x = hex2dec rd let tt= (fromIntegral x)*209.0/1024 - 67.5 j_settext f ((show tt)++" ==> "++tp) return True if not again then return True else waitForFrameAction frame f b hex2dec :: String -> Int hex2dec h= sum (zipWith (*) (map (16^) [3,2,1,0]) [digitToInt c | c <- h]) convert d r s0= (fromIntegral (hex2dec d))*r/1024.0- s0 As I told before, let r = closecport 7 did not work until I gave it an argument. Here is the interface between the C-side, and the Haskell-side of the program: {-# LANGUAGE ForeignFunctionInterface #-} module SER.IAL where import Control.Monad import Foreign import Foreign.C.Types import Foreign.C foreign import ccall "rs232.h opencport" opencport :: CInt -> IO () foreign import ccall "rs232.h closecport" closecport :: CInt -> CInt foreign import ccall "rs232.h rdrs232" c_sendmsg :: CInt -> CString -> CString sendMessage :: Int -> String -> IO String sendMessage n msg = withCString msg $ \str -> peekCString (c_sendmsg (fromIntegral n) str) Originally, I had the following line (that did not work properly): foreign import ccall "rs232.h closecport" closecport :: IO () You will find below the C-program. The original program (that did not work) had the following definition for closecport: int closecport() { CloseComport(); return 3; } This deffinition (that did not work) was replaced by the following one: int closecport(int n) { CloseComport(); return n; } Here is the complete C program: #include "serial.h" #include <string.h> #include <stdio.h> /* Possible baudrates on a normal pc: 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400, 57600, 115200 */ #define BAUD "baud=9600 data=8 parity=N stop=1" HANDLE Cport; char comports[16][10]={"\\\\.\\COM1", "\\\\.\\COM2", "\\\\.\\COM3", "\\\\.\\COM4", "\\\\.\\COM5", "\\\\.\\COM6", "\\\\.\\COM7", "\\\\.\\COM8", "\\\\.\\COM9", "\\\\.\\COM10", "\\\\.\\COM11", "\\\\.\\COM12", "\\\\.\\COM13", "\\\\.\\COM14", "\\\\.\\COM15", "\\\\.\\COM16"}; int OpenComport(int comport_number) { if(comport_number>15) { printf("illegal comport number\n"); return(1); } Cport = CreateFileA(comports[comport_number], GENERIC_READ|GENERIC_WRITE, 0, /* no share */ NULL, /* no security */ OPEN_EXISTING, 0, /* no threads */ NULL); /* no templates */ if(Cport==INVALID_HANDLE_VALUE) { printf("unable to open comport\n"); return(1); } DCB port_settings; memset(&port_settings, 0, sizeof(port_settings)); /* clear the new struct */ port_settings.DCBlength = sizeof(port_settings); if(!BuildCommDCBA(BAUD, &port_settings)) { printf("unable to set comport dcb settings\n"); CloseHandle(Cport); return(1); } if(!SetCommState(Cport, &port_settings)) { printf("unable to set comport cfg settings\n"); CloseHandle(Cport); return(1); } COMMTIMEOUTS Cptimeouts; Cptimeouts.ReadIntervalTimeout = MAXDWORD; Cptimeouts.ReadTotalTimeoutMultiplier = 10; Cptimeouts.ReadTotalTimeoutConstant = 10; Cptimeouts.WriteTotalTimeoutMultiplier = 10; Cptimeouts.WriteTotalTimeoutConstant = 10; if(!SetCommTimeouts(Cport, &Cptimeouts)) { printf("unable to set comport time-out settings\n"); CloseHandle(Cport); return(1); } return(0); } int PollComport(unsigned char *buf, int size) { int n; if(size>4096) size = 4096; /* added the void pointer cast, otherwise gcc will complain about */ /* "warning: dereferencing type-punned pointer will break strict aliasing rules" */ ReadFile(Cport, buf, size, (LPDWORD)((void *)&n), NULL); return(n); } int RdByte(unsigned char* m) { int n; ReadFile(Cport, m, 1, (LPDWORD)((void *)&n), NULL); return(n); } int SendByte(unsigned char byte) { int n; WriteFile(Cport, &byte, 1, (LPDWORD)((void *)&n), NULL); if(n<0) return(1); return(0); } int SendBuf(unsigned char *buf, int size) { int n; if(WriteFile(Cport, buf, size, (LPDWORD)((void *)&n), NULL)) { return(n); } return(-1); } int CloseComport(void) { CloseHandle(Cport); return(0); } int IsCTSEnabled(void) { int status; GetCommModemStatus(Cport, (LPDWORD)((void *)&status)); if(status&MS_CTS_ON) return(1); else return(0); } int cprintf(const char *text) /* sends a string to serial port */ { while(*text != 0) SendByte(*(text++)); return(0); } int opencport(int p) { OpenComport(p-1); return 3; } int closecport(int n) { CloseComport(); return n; } char* rdrs232(int n, char* msg) { char *str; char mm; int i, j; for (j=0; j<n; j++) { SendByte(msg[j]); } str = (char *) malloc(16000); i=0; mm=0; while (mm != 10) { RdByte(&mm); str[i]= mm; i= i+1; } if (i>0 && str[0]==0) { str[0]= ' ';} return(str); } Finally, here is the serial.h file: #ifndef rs232_INCLUDED #define rs232_INCLUDED #ifdef __cplusplus extern "C" { #endif #include <stdio.h> #include <string.h> #ifdef __linux__ #include <termios.h> #include <sys/ioctl.h> #include <unistd.h> #include <fcntl.h> #include <sys/types.h> #include <sys/stat.h> #include <limits.h> #else #include <windows.h> #endif int OpenComport(int); int PollComport(unsigned char *, int); int SendByte(unsigned char); int SendBuf(unsigned char *, int); int CloseComport(void); int cprintf(const char *); int IsCTSEnabled(void); char *topa(int n); int opencport(int p); int closecport(int n); char* rdrs232(int n, char* msg); #ifdef __cplusplus } /* extern "C" */ #endif #endif __________________________________________________________________ Make your browsing faster, safer, and easier with the new Internet Explorer® 8. Optimized for Yahoo! Get it Now for Free! at http://downloads.yahoo.com/ca/internetexplorer/

4 8

ANNOUNCE: simple-observer-0.0.1, a simple implementation of the observer design pattern
by Andy Gimblett 12 Nov '09

12 Nov '09

Hi all, Further to earlier discussion on this topic, I've just released a first version of this package to hackage: http://hackage.haskell.org/package/simple-observer It is a fairly simple implementation of subject/observer which I've recently used to good effect in an GUI written using wxHaskell. Here's a blog post discussing it further and giving a simple example of use: http://gimbo.org.uk/blog/2009/11/12/simple-observers-in-haskell/ Many thanks for the earlier comments, even if they haven't resulted in any changes (yet?). Best regards, -Andy

1 0

Re: [Haskell-cafe] looking for a good algorithm
by Tillmann Vogt 11 Nov '09

11 Nov '09

Hong Yang schrieb: > The question is more about algorithm than Haskell. But I am going to code in > Haskell which I am still learning. > > Suppose I have a large table, with hundreds of columns and thousands of > rows. But not every cell has a value (of String, or Int, or Double type). > > I want to shuffle the rows to maximize the number of columns whose first 100 > rows have at least one number, given a list of preferred column names since > there is no guarantee that every number column will have at least one number > in its first 100 rows after shuffling. > > Can someone provide a good algorithm for this problem? (I do not have any > background in algorithms.) You can assume I already know which columns are > of Int or Double type. I would say it depends on the distribution of values in the table. If there are rows with a lot of values and rows with few values, then I would first sort the rows after the number of cells with values. If you look at all the columns and the number of values for each row is unique then it would be perfectly solved. With a list of preferred columns and also a uniform distribution the problem might be hard (NP-complete?), but these hard problems can often be approximated, i.e with simulated annealing, which in short is switching two rows repeatedly as long as the result improves. > > This is not a homework. > Thanks, > > Hong > > > ------------------------------------------------------------------------ > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe

3 2

Tabla de calculo de dolares viajero CADIVI
by Hector Guilarte 11 Nov '09

11 Nov '09

Tabla del operador cambiario para determinar cuantos dolares te tocan por viaje en el 2009... Saquen sus propias conclusiones... Además de la tabla, miren los bloqueos de ciertas transacciones de abajo... Increíble La reenvío como me llegó... **

1 0

What's the deal with Clean?
by Deniz Dogan 11 Nov '09

11 Nov '09

Recently there has been a lot of discussion on this list about the programming language Clean and converting Clean programs to Haskell. Reading the Wikipedia article on the language, I can't really see any major difference between that and Haskell, except for the monads vs. uniqueness types. So what's the deal with Clean? Why is it preferable to Haskell? Why is it not? -- Deniz Dogan

27 59

a problem defining a monad instance
by Petr Pudlak 11 Nov '09

11 Nov '09

Hi all, (This is a literate Haskell post.) I've encountered a small problem when trying to define a specialized monad instance. Maybe someone will able to help me or to tell me that it's impossible :-). To elaborate: I wanted to define a data type which is a little bit similar to the [] monad. Instead of just having a list of possible outcomes of a computation, I wanted to have a probability associated with each possible outcome. A natural way to define such a structure is to use a map from possible values to numbers, let's say Floats: > module Distribution where > > import qualified Data.Map as M > > newtype Distrib a = Distrib { undistrib :: M.Map a Float } Defining functions to get a monad instance is not difficult. "return" is just a singleton: > dreturn :: a -> Distrib a > dreturn k = Distrib (M.singleton k 1) Composition is a little bit more difficult, but the functionality is quite natural. (I welcome suggestions how to make the code nicer / more readable.) However, the exact definition is not so important. > dcompose :: (Ord b) => Distrib a -> (a -> Distrib b) -> Distrib b > dcompose (Distrib m) f = Distrib $ M.foldWithKey foldFn M.empty m > where > foldFn a prob umap = M.unionWith (\psum p -> psum + prob * p) umap (undistrib $ f a) The problem is the (Ord b) condition, which is required for the Map functions. When I try to define the monad instance as > instance Monad Distrib where > return = dreturn > (>>=) = dcompose obviously, I get an error at (>>=): Could not deduce (Ord b) from the context. Is there some way around? Either to somehow define the monad, or to achieve the same functionality without using Map, which requires Ord instances? Thanks a lot, Petr

8 8

Hoogle is great but ...
by zaxis 11 Nov '09

11 Nov '09

http://www.haskell.org/hoogle/ is VERY great for haskeller. However, i feel hoogle should be improved by providing more examples as : isInfixOf :: Eq a => [a] -> [a] -> Bool The isInfixOf function takes two lists and returns True iff the first list is contained, wholly and intact, anywhere within the second. Example: isInfixOf "Haskell" "I really like Haskell." -> True isInfixOf "Ial" "I really like Haskell." -> False The Example code will be helpful for programmer to understand its definition. Sincerely! -- View this message in context: http://www.nabble.com/Hoogle-is-great-but-...-tp26046410p26046410.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

8 8

Fair diagonals
by Martijn van Steenbergen 11 Nov '09

11 Nov '09

Dear café, I am looking for a function that does an N-dimensional diagonal traversal. I want the traversal to be fair: the sum of the indices of the produced combinations should be non-decreasing. Let me illustrate with an example. The type of a 2-dimensional traversal would look like this: > diag2 :: [a] -> [b] -> [(a, b)] The first two arguments are the two half-axes of the grid and the result is a fair diagonal traversal of all the points. For example: >> diag2 [1,2,3] [4,5,6,7] > [(1,4),(2,4),(1,5),(3,4),(1,6),(2,5),(1,7),(3,5),(2,6),(2,7),(3,6),(3,7)] Of course the function should work on infinite lists: >> diag2 [1..] [1..] > [(1,1),(2,1),(1,2),(3,1),... Or a combination of finite and infinite lists: >> diag2 [1,2] [1..] > [(1,1),(2,1),(1,2),(1,3),(2,2),(1,4),... Notice that in each case the sum of the pairs (which can seen as indices in these particular examples) are non-decreasing: >> let sums = map (uncurry (+)) >> sums $ diag2 [1,2,3] [4,5,6,7] > [5,6,6,7,7,7,8,8,8,9,9,10] >> sums $ diag2 [1..] [1..] > [2,3,3,4,4,4,5,5,5,5,6,... >> sums $ diag2 [1,2] [1..] > [2,3,3,4,4,5,5,6,6,7,7,... Similarly for 3 dimensions the type would be: > diag3 :: [a] -> [b] -> [c] -> [(a, b, c)] For N dimensions we have to sacrifice some generality and ask all axes to be of the same type and produce lists instead of tuples, but I'm perfectly happy with that: > diagN :: [[a]] -> [[a]] I have implemented diag2 and diag3 [1] but noticed that the function bodies increase in size exponentially following Pascal's triangle and have no clue how to generialize to N dimensions. Can you help me write diagN? Bonus points for the following: * An infinite number of singleton axes produces [origin] (and finishes computing), e.g. forall (infinite) xs. diagN (map (:[]) xs) == map (:[]) xs * For equal indices, the traversal biases to axes that are occur early in the input (but I don't know how to formalize this). * The implementation shows regularity and elegance. Many thanks, Martijn. [1] http://hpaste.org/fastcgi/hpaste.fcgi/view?id=11515

9 15

Working with multiple projects
by Tony Morris 11 Nov '09

11 Nov '09

I have two projects that I intend to put on hackage soon. One depends on the other. I have "cabaled" both. I am wondering how others work with this kind of set up where changes are made to both libraries as they work. -- Tony Morris http://tmorris.net/

5 5

ANN: haskell-mode 2.6
by Svein Ove Aas 11 Nov '09

11 Nov '09

Fellow haskellers: Haskell-mode 2.6 has been released. * By web: http://projects.haskell.org/haskellmode-emacs/ * By darcs: http://code.haskell.org/haskellmode-emacs/ This is mainly a bugfix release; to anyone using haskell-indentation, the big news will be that it no longer under some circumstances hands you a parse error and refuses to insert a newline, or backspace. It still gives you a parse error. It just tries its best to proceed anyway. There are also some new features, courtesy of Alex Ott: More font-lock symbols, and a hayoo function. In the case of the font-lock symbols, your mileage may vary on how nice the picked ones are. Mine certainly does. As such, I'm announcing open season on font-lock symbols: Comment to your heart's desire, and I'll use whatever you decide on for the next official release. The tab-cycle implementation is thanks to ivanm, whose random comments can trigger hours and hours of work. I'll just quote from the NEWS file now: === Changes since 2.5.1 * haskell-indentation: Pressing tab in the rightmost position now moves to the leftmost, by default with a warning. * Typo fix: One haskell-indentation variable had ended up in the haskell-ntation customize group. * haskell-hoogle aliased to hoogle, haskell-hayoo aliased to hayoo * Courtesy of Alex Ott: - Additional unicode symbols for font-lock-symbols: () == /= >= <= !! && || sqrt - M-x haskell-hayoo search added, opens using browse-url - Bug-fix for inferior-haskell-type * If haskell-indentation errors out, it now fail-safes to inserting a literal newline or deleting one character, for return and backspace respectively. -- Svein Ove Aas

4 9

Problems with Language.Haskell.Interpreter and errors
by Martin Hofmann 11 Nov '09

11 Nov '09

Hi, The API of Language.Haskell.Interpreter says, that 'runInterpreter' runInterpreter :: (MonadCatchIO m, Functor m) => InterpreterT m a -> m (Either InterpreterError a) returns 'Left' in case of errors and 'GhcExceptions from the underlying GHC API are caught and rethrown as this'. What kind of errors do a generate here, why are they not caught by runInterpreter and how can I catch them? I assumed to get a 'Left InterpreterError' from the first and an error in MonadCatchIO in the second. > :m +Language.Haskell.Interpreter > let estr1 = "let lst [a] = a; lst _ = error \"foo\" in lst []" > let estr1 = "let lst [a] = a; in lst []" > runInterpreter (setImportsQ [("Prelude", Nothing)] >> eval estr1 ) Right "*** Exception: foo > runInterpreter ( eval estr2) Right "*** Exception: <interactive>:1:101-111: Non-exhaustive patterns in function lst Thanks a lot

2 7

caba install with external gcc toolchain not the ghc-bundled one
by Daniel Kahlenberg 11 Nov '09

11 Nov '09

Hello friends, I have a question regarding one thing I can't get my head around: First my problem is, that wanted to install 'bindings-common' here on my Windows machine. Usually that is no problem with the help of the glorious cabal. Now, 'bindings-common' needs a higher version of gcc than the one bundled with ghc-6.10.4 to build as the developer told me, so I install the gcc version 4.4.0 by mingw and try to give the needed options to 'cabal install bindings-common...' - '--with-gcc=... --with-ld=...' etc. - At the same time I log everything cabal is putting to the outside world when doing the tasks for building the 'binding-commons': For this sake I use the '--build-log=...' option of 'cabal install' and at the same time pipe what gets shown on the terminal with 'tee' as well as verbosity level 3 for 'cabal install'. So far nothing new... But the package isn't built, so I wonder what the transcript is saying and have a look at the two generated log files, stating that the one generated by 'tee' tells me another linker (the one coming with the ghc-6.10.4 bundle) than I thought to have specified is actually used. An excerpt from the tee built log file: *** Linker: E:\programme\ghc\ghc-6.10.4\gcc -BE:\programme\ghc\ghc-6.10.4\gcc-lib/ ... Configured with: ../gcc-3.4.5-20060117-3/configure --with-gcc ... Thread model: win32 gcc version 3.4.5 (mingw-vista special r3) (Sorry if I'm mis-interpreting something here) While the log file resulting from the '--build-log' cabal install option has nothing suspicious in it telling me to (plan to?) use exactly what I specified by options. A little excerpt from that log file: ("e:\\programme\\ghc\\ghc-6.10.4\\bin\\hsc2hs.exe",["--cc=e:/programme/ghc/mingw-gcc4/bin/gcc.exe","--ld=e:/programme/ghc/mingw-gcc4/bin/gcc.exe","--cflag=-Be:/programme/ghc/mingw-gcc4/lib/","--cflag=-Ie:/programme/ghc/mingw4-gcc/include","--cflag=-Le:/programme/ghc/mingw-gcc4/lib","--lflag=-Be:/programme/ghc/mingw-gcc4/lib/","--lflag=-Ie:/programme/ghc/mingw4-gcc/include","--lflag=-Le:/programme/ghc/mingw-gcc4/lib","--cflag=-D__GLASGOW_HASKELL__=610","--cflag=-Isrc","--cflag=-Ie:/programme/ghc/mingw-gcc4/include","--cflag=-D_ISOC99_SOURCE","--lflag=-Le:/programme/ghc/mingw-gcc4/lib","--cflag=-Ie:\\programme\\ghc\\ghc-6.10.4\\base-4.1.0.0\\include","--cflag=-Ie:\\programme\\ghc\\ghc-6.10.4/include","--lflag=-Le:\\programme\\ghc\\ghc-6.10.4\\base-3.0.3.1","--lflag=-Le:\\programme\\ghc\\ghc-6.10.4\\syb-0.1.0.1","--lflag=-Le:\\programme\\ghc\\ghc-6.10.4\\base-4.1.0.0","--lflag=-lwsock32","--lflag=-luser32","--lflag=-lshell32","--lflag=-Le:\\programme\\ghc\\ghc-6.10.4\\integer-0 .1.0.1","--lflag=-Le:\\programme\\ghc\\ghc-6.10.4\\ghc-prim-0.1.0.0","--lflag=-Le:\\programme\\ghc\\ghc-6.10.4","--lflag=-Le:\\programme\\ghc\\ghc-6.10.4/gcc-lib","--lflag=-lm","--lflag=-lffi","--lflag=-lgmp","--lflag=-lwsock32","-o","H:\\.homedir\\hugsdata\\build\\Bindings\\C\\Ctype.hs","src\\Bindings\\C\\Ctype.hsc"]) ... Using ld given by user at: e:/programme/ghc/mingw-gcc4/bin/ld.exe So now my question is: Can anybody give me a good hint or tell me how I would, aside from using hard links or other file system related tasks, specify the external compiler, linker or gcc-toolchain to be used by 'cabal install' (or in consequence by 'ghc')? Cheers and thanks for your Daniel searching for ghc in path. found ghc at e:\programme\ghc\ghc-6.10.4\bin\ghc.exe ("e:\\programme\\ghc\\ghc-6.10.4\\bin\\ghc.exe",["--numeric-version"]) e:\programme\ghc\ghc-6.10.4\bin\ghc.exe is version 6.10.4 looking for package tool: ghc-pkg near compiler in e:\programme\ghc\ghc-6.10.4\bin found package tool in e:\programme\ghc\ghc-6.10.4\bin\ghc-pkg.exe ("e:\\programme\\ghc\\ghc-6.10.4\\bin\\ghc-pkg.exe",["--version"]) e:\programme\ghc\ghc-6.10.4\bin\ghc-pkg.exe is version 6.10.4 ("e:\\programme\\ghc\\ghc-6.10.4\\bin\\ghc.exe",["--supported-languages"]) Reading installed packages... ("e:\\programme\\ghc\\ghc-6.10.4\\bin\\ghc-pkg.exe",["dump","--global"]) ("e:\\programme\\ghc\\ghc-6.10.4\\bin\\ghc-pkg.exe",["dump","--package-conf=h:\\.homedir\\ghc\\i386-mingw32-6.10.4\\package.conf"]) Reading available packages... Resolving dependencies... selecting bindings-common-1.3.3 (hackage) and discarding bindings-common-0.1, 0.1.1, 0.1.2, 0.1.3, 0.1.4, 0.2, 0.2.1, 0.2.2, 0.2.3, 0.2.4, 0.2.5, 0.2.6, 1.0, 1.1, 1.2, 1.3, 1.3.1 and 1.3.2 selecting base-3.0.3.1 (installed) and 4.1.0.0 (installed) and discarding syb-0.1.0.0 and 0.1.0.1 selecting ghc-prim-0.1.0.0 (installed) selecting integer-0.1.0.1 (installed) selecting rts-1.0 (installed) selecting syb-0.1.0.1 (installed) In order, the following would be installed: bindings-common-1.3.3 (new package) bindings-common-1.3.3 has already been downloaded. Extracting C:\Dokumente und Einstellungen\Zyx\Anwendungsdaten\cabal\packages\hackage.haskell.org\bindings-common\1.3.3\bindings-common-1.3.3.tar.gz to c:\DOKUME~1\Zyx\LOKALE~1\Temp\bindings-common-1.3.31176... Using external setup method with build-type Simple Creating h:\.homedir\hugsdata\setup (and its parents) Using Cabal library version 1.6.0.3 Using h:\.homedir\hugsdata\setup\setup.hs as setup script. Setup script is out of date, compiling... ("e:\\programme\\ghc\\ghc-6.10.4\\bin\\ghc.exe",["-v","--make","h:\\.homedir\\hugsdata\\setup\\setup.hs","-o","h:\\.homedir\\hugsdata\\setup\\setup.exe","-odir","h:\\.homedir\\hugsdata\\setup","-hidir","h:\\.homedir\\hugsdata\\setup","-i","-ic:\\DOKUME~1\\Zyx\\LOKALE~1\\Temp\\bindings-common-1.3.31176\\bindings-common-1.3.3","-no-user-package-conf","-package-conf","h:\\.homedir\\ghc\\i386-mingw32-6.10.4\\package.conf","-package","Cabal-1.6.0.3"]) Glasgow Haskell Compiler, Version 6.10.4, for Haskell 98, stage 2 booted by GHC version 6.10.1 Using package config file: E:\programme\ghc\ghc-6.10.4\package.conf Using package config file: h:\.homedir\ghc\i386-mingw32-6.10.4\package.conf Using package config file: h:\.homedir\ghc\i386-mingw32-6.10.4\package.conf hiding package base-3.0.3.1 to avoid conflict with later version base-4.1.0.0 hiding package regex-base-0.72.0.2 to avoid conflict with later version regex-base-0.93.1 hiding package parsec-2.1.0.1 to avoid conflict with later version parsec-3.0.1 hiding package QuickCheck-1.2.0.0 to avoid conflict with later version QuickCheck-2.1.0.2 wired-in package ghc-prim mapped to ghc-prim-0.1.0.0 wired-in package integer mapped to integer-0.1.0.1 wired-in package base mapped to base-4.1.0.0 wired-in package rts mapped to rts-1.0 wired-in package haskell98 mapped to haskell98-1.0.1.0 wired-in package syb mapped to syb-0.1.0.1 wired-in package template-haskell mapped to template-haskell-2.3.0.1 wired-in package dph-seq mapped to dph-seq-0.3 wired-in package dph-par mapped to dph-par-0.3 Hsc static flags: -static *** Chasing dependencies: Chasing modules from: *H:\.homedir\hugsdata\setup\setup.hs Stable obj: [] Stable BCO: [] Ready for upsweep [NONREC ModSummary { ms_hs_date = Mon Nov 9 14:45:34 Westeuropäische Normalzeit 2009 ms_mod = main:Main, ms_imps = [Distribution.Simple] ms_srcimps = [] }] compile: input file H:\.homedir\hugsdata\setup\setup.hs Created temporary directory: C:\DOKUME~1\Zyx\LOKALE~1\Temp\/ghc2388_0 *** Checking old interface for main:Main: [1 of 1] Compiling Main ( H:\.homedir\hugsdata\setup\setup.hs, H:\.homedir\hugsdata\setup\Main.o ) *** Parser: *** Renamer/typechecker: *** Desugar: Result size = 8 *** Simplify: Result size = 6 Result size = 6 *** Tidy Core: Result size = 6 writeBinIface: 1 Names writeBinIface: 28 dict entries *** CorePrep: Result size = 6 *** Stg2Stg: *** CodeGen: *** CodeOutput: *** Assembler: E:\programme\ghc\ghc-6.10.4\gcc -BE:\programme\ghc\ghc-6.10.4\gcc-lib/ -IE:\programme\ghc\ghc-6.10.4\include/mingw -IH:\.homedir\hugsdata\setup -c C:\DOKUME~1\Zyx\LOKALE~1\Temp\/ghc2388_0/ghc2388_0.s -o h:\.homedir\hugsdata\setup\Main.o *** Deleting temp files: Deleting: C:\DOKUME~1\Zyx\LOKALE~1\Temp\/ghc2388_0/ghc2388_0.s Upsweep completely successful. *** Deleting temp files: Deleting: link: linkables are ... LinkableM (Mon Nov 9 14:45:34 Westeuropäische Normalzeit 2009) main:Main [DotO h:\.homedir\hugsdata\setup\Main.o] Linking h:\.homedir\hugsdata\setup\setup.exe ... *** Windres: E:\programme\ghc\ghc-6.10.4\bin/windres --preprocessor="E:\programme\ghc\ghc-6.10.4\gcc" "-BE:\programme\ghc\ghc-6.10.4\gcc-lib/" "-IE:\programme\ghc\ghc-6.10.4\include/mingw" "-E" "-xc" "-DRC_INVOKED" --use-temp-file --input=C:\DOKUME~1\Zyx\LOKALE~1\Temp\/ghc2388_0/ghc2388_0.rc --output=C:\DOKUME~1\Zyx\LOKALE~1\Temp\/ghc2388_0/ghc2388_0.o --output-format=coff *** Linker: E:\programme\ghc\ghc-6.10.4\gcc -BE:\programme\ghc\ghc-6.10.4\gcc-lib/ -IE:\programme\ghc\ghc-6.10.4\include/mingw -v -o h:\.homedir\hugsdata\setup\setup.exe -DDONT_WANT_WIN32_DLL_SUPPORT h:\.homedir\hugsdata\setup\Main.o C:\DOKUME~1\Zyx\LOKALE~1\Temp\/ghc2388_0/ghc2388_0.o -Lh:\.homedir\.cabal\Cabal-1.6.0.3\ghc-6.10.4 -LE:\programme\ghc\ghc-6.10.4\process-1.0.1.1 -LE:\programme\ghc\ghc-6.10.4\pretty-1.0.1.0 -LE:\programme\ghc\ghc-6.10.4\directory-1.0.0.3 -LE:\programme\ghc\ghc-6.10.4\old-time-1.0.0.2 -LE:\programme\ghc\ghc-6.10.4\old-locale-1.0.0.1 -LE:\programme\ghc\ghc-6.10.4\filepath-1.1.0.2 -LE:\programme\ghc\ghc-6.10.4\Win32-2.2.0.0 -LE:\programme\ghc\ghc-6.10.4\bytestring-0.9.1.4 -LE:\programme\ghc\ghc-6.10.4\containers-0.2.0.1 -LE:\programme\ghc\ghc-6.10.4\array-0.2.0.0 -LE:\programme\ghc\ghc-6.10.4\syb-0.1.0.1 -LE:\programme\ghc\ghc-6.10.4\base-4.1.0.0 -LE:\programme\ghc\ghc-6.10.4\integer-0.1.0.1 -LE:\programme\ghc\ghc-6.10.4\ghc-prim-0.1.0.0 -LE:\programme\ghc\ghc-6.10.4 -LE:\programme\ghc\ghc-6.10.4/gcc-lib -lHSCabal-1.6.0.3 -lHSprocess-1.0.1.1 -lHSpretty-1.0.1.0 -lHSdirectory-1.0.0.3 -lHSold-time-1.0.0.2 -lHSold-locale-1.0.0.1 -lHSfilepath-1.1.0.2 -lHSWin32-2.2.0.0 -luser32 -lgdi32 -lwinmm -ladvapi32 -lHSbytestring-0.9.1.4 -lHScontainers-0.2.0.1 -lHSarray-0.2.0.0 -lHSsyb-0.1.0.1 -lHSbase-4.1.0.0 -lwsock32 -luser32 -lshell32 -lHSinteger-0.1.0.1 -lHSghc-prim-0.1.0.0 -lHSrts -lm -lffi -lgmp -lwsock32 -u _ghczmprim_GHCziTypes_Izh_static_info -u _ghczmprim_GHCziTypes_Czh_static_info -u _ghczmprim_GHCziTypes_Fzh_static_info -u _ghczmprim_GHCziTypes_Dzh_static_info -u _base_GHCziPtr_Ptr_static_info -u _base_GHCziWord_Wzh_static_info -u _base_GHCziInt_I8zh_static_info -u _base_GHCziInt_I16zh_static_info -u _base_GHCziInt_I32zh_static_info -u _base_GHCziInt_I64zh_static_info -u _base_GHCziWord_W8zh_static_info -u _base_GHCziWord_W16zh_static_info -u _base_GHCziWord_W32zh_static_info -u _base_GHCziWord_W64zh_static_info -u _base_GHCziStable_StablePtr_static_info -u _ghczmprim_GHCziTypes_Izh_con_info -u _ghczmprim_GHCziTypes_Czh_con_info -u _ghczmprim_GHCziTypes_Fzh_con_info -u _ghczmprim_GHCziTypes_Dzh_con_info -u _base_GHCziPtr_Ptr_con_info -u _base_GHCziPtr_FunPtr_con_info -u _base_GHCziStable_StablePtr_con_info -u _ghczmprim_GHCziBool_False_closure -u _ghczmprim_GHCziBool_True_closure -u _base_GHCziPack_unpackCString_closure -u _base_GHCziIOBase_stackOverflow_closure -u _base_GHCziIOBase_heapOverflow_closure -u _base_ControlziExceptionziBase_nonTermination_closure -u _base_GHCziIOBase_blockedOnDeadMVar_closure -u _base_GHCziIOBase_blockedIndefinitely_closure -u _base_ControlziExceptionziBase_nestedAtomically_closure -u _base_GHCziWeak_runFinalizzerBatch_closure -u _base_GHCziTopHandler_runIO_closure -u _base_GHCziTopHandler_runNonIO_closure -u _base_GHCziConc_runHandlers_closure -u _base_GHCziConc_ensureIOManagerIsRunning_closure Reading specs from E:/programme/ghc/ghc-6.10.4/gcc-lib/specs Configured with: ../gcc-3.4.5-20060117-3/configure --with-gcc --with-gnu-ld --with-gnu-as --host=mingw32 --target=mingw32 --prefix=/mingw --enable-threads --disable-nls --enable-languages=c,c++,f77,ada,objc,java --disable-win32-registry --disable-shared --enable-sjlj-exceptions --enable-libgcj --disable-java-awt --without-x --enable-java-gc=boehm --disable-libgcj-debug --enable-interpreter --enable-hash-synchronization --enable-libstdcxx-debug Thread model: win32 gcc version 3.4.5 (mingw-vista special r3) E:/programme/ghc/ghc-6.10.4/gcc-lib/collect2.exe -Bdynamic -o h:\.homedir\hugsdata\setup\setup.exe -u _ghczmprim_GHCziTypes_Izh_static_info -u _ghczmprim_GHCziTypes_Czh_static_info -u _ghczmprim_GHCziTypes_Fzh_static_info -u _ghczmprim_GHCziTypes_Dzh_static_info -u _base_GHCziPtr_Ptr_static_info -u _base_GHCziWord_Wzh_static_info -u _base_GHCziInt_I8zh_static_info -u _base_GHCziInt_I16zh_static_info -u _base_GHCziInt_I32zh_static_info -u _base_GHCziInt_I64zh_static_info -u _base_GHCziWord_W8zh_static_info -u _base_GHCziWord_W16zh_static_info -u _base_GHCziWord_W32zh_static_info -u _base_GHCziWord_W64zh_static_info -u _base_GHCziStable_StablePtr_static_info -u _ghczmprim_GHCziTypes_Izh_con_info -u _ghczmprim_GHCziTypes_Czh_con_info -u _ghczmprim_GHCziTypes_Fzh_con_info -u _ghczmprim_GHCziTypes_Dzh_con_info -u _base_GHCziPtr_Ptr_con_info -u _base_GHCziPtr_FunPtr_con_info -u _base_GHCziStable_StablePtr_con_info -u _ghczmprim_GHCziBool_False_closure -u _ghczmprim_GHCziBool_True_closure -u _base_GHCziPack_unpackCString_closure -u _base_GHCziIOBase_stackOverflow_closure -u _base_GHCziIOBase_heapOverflow_closure -u _base_ControlziExceptionziBase_nonTermination_closure -u _base_GHCziIOBase_blockedOnDeadMVar_closure -u _base_GHCziIOBase_blockedIndefinitely_closure -u _base_ControlziExceptionziBase_nestedAtomically_closure -u _base_GHCziWeak_runFinalizzerBatch_closure -u _base_GHCziTopHandler_runIO_closure -u _base_GHCziTopHandler_runNonIO_closure -u _base_GHCziConc_runHandlers_closure -u _base_GHCziConc_ensureIOManagerIsRunning_closure E:/programme/ghc/ghc-6.10.4/gcc-lib/crt2.o E:/programme/ghc/ghc-6.10.4/gcc-lib/crtbegin.o -Lh:\.homedir\.cabal\Cabal-1.6.0.3\ghc-6.10.4 -LE:\programme\ghc\ghc-6.10.4\process-1.0.1.1 -LE:\programme\ghc\ghc-6.10.4\pretty-1.0.1.0 -LE:\programme\ghc\ghc-6.10.4\directory-1.0.0.3 -LE:\programme\ghc\ghc-6.10.4\old-time-1.0.0.2 -LE:\programme\ghc\ghc-6.10.4\old-locale-1.0.0.1 -LE:\programme\ghc\ghc-6.10.4\filepath-1.1.0.2 -LE:\programme\ghc\ghc-6.10.4\Win32-2.2.0.0 -LE:\programme\ghc\ghc-6.10.4\bytestring-0.9.1.4 -LE:\programme\ghc\ghc-6.10.4\containers-0.2.0.1 -LE:\programme\ghc\ghc-6.10.4\array-0.2.0.0 -LE:\programme\ghc\ghc-6.10.4\syb-0.1.0.1 -LE:\programme\ghc\ghc-6.10.4\base-4.1.0.0 -LE:\programme\ghc\ghc-6.10.4\integer-0.1.0.1 -LE:\programme\ghc\ghc-6.10.4\ghc-prim-0.1.0.0 -LE:\programme\ghc\ghc-6.10.4 -LE:\programme\ghc\ghc-6.10.4/gcc-lib -LE:/programme/ghc/ghc-6.10.4/gcc-lib h:\.homedir\hugsdata\setup\Main.o C:\DOKUME~1\Zyx\LOKALE~1\Temp\/ghc2388_0/ghc2388_0.o -lHSCabal-1.6.0.3 -lHSprocess-1.0.1.1 -lHSpretty-1.0.1.0 -lHSdirectory-1.0.0.3 -lHSold-time-1.0.0.2 -lHSold-locale-1.0.0.1 -lHSfilepath-1.1.0.2 -lHSWin32-2.2.0.0 -luser32 -lgdi32 -lwinmm -ladvapi32 -lHSbytestring-0.9.1.4 -lHScontainers-0.2.0.1 -lHSarray-0.2.0.0 -lHSsyb-0.1.0.1 -lHSbase-4.1.0.0 -lwsock32 -luser32 -lshell32 -lHSinteger-0.1.0.1 -lHSghc-prim-0.1.0.0 -lHSrts -lm -lffi -lgmp -lwsock32 -lmingw32 -lgcc -lmoldname -lmingwex -lmsvcrt -luser32 -lkernel32 -ladvapi32 -lshell32 -lmingw32 -lgcc -lmoldname -lmingwex -lmsvcrt E:/programme/ghc/ghc-6.10.4/gcc-lib/crtend.o link: done *** Deleting temp files: Deleting: C:\DOKUME~1\Zyx\LOKALE~1\Temp\/ghc2388_0/ghc2388_0.o C:\DOKUME~1\Zyx\LOKALE~1\Temp\/ghc2388_0/ghc2388_0.rc *** Deleting temp dirs: Deleting: C:\DOKUME~1\Zyx\LOKALE~1\Temp\/ghc2388_0 h:\.homedir\hugsdata\setup\setup.exe configure --verbose=3 --builddir=h:\.homedir\hugsdata --ghc --prefix=h:\.homedir\.cabal --datadir=h:\.homedir\.cabal --configure-option=CC=e:\programme\mingw-gcc4\bin\gcc.exe --user --package-db=h:\.homedir\ghc\i386-mingw32-6.10.4\package.conf --extra-include-dirs=e:/programme/ghc/mingw-gcc4/include --extra-lib-dirs=e:/programme/ghc/mingw-gcc4/lib --constraint=base ==3.0.3.1 --with-gcc=e:\programme\ghc\mingw-gcc4\bin\gcc.exe --with-ld=e:\programme\ghc\mingw-gcc4\bin\ld.exe --gcc-option=-v --gcc-option=-Wall Redirecting build log to {handle: h:\.homedir\hugsdata\build-bindings-common-1.3.3-ghc-6.10.4.log} Using external setup method with build-type Simple Creating h:\.homedir\hugsdata\setup (and its parents) Using Cabal library version 1.6.0.3 Using h:\.homedir\hugsdata\setup\setup.hs as setup script. h:\.homedir\hugsdata\setup\setup.exe build --verbose=3 --builddir=h:\.homedir\hugsdata Redirecting build log to {handle: h:\.homedir\hugsdata\build-bindings-common-1.3.3-ghc-6.10.4.log} cabal.exe: Error: some packages failed to install: bindings-common-1.3.3 failed during the building phase. The exception was: exit: ExitFailure 1

1 0

help with Haskell performance
by Gokul P. Nair 11 Nov '09

11 Nov '09

Hi all, The task I'm trying to accomplish: Given a log file containing several lines of white space delimited entries like this: [Sat Oct 24 08:12:37 2009] [error] GET /url1 HTTP/1.1]: Requested URI does not exist [Sat Oct 24 08:12:37 2009] [error] GET /url2 HTTP/1.0]: Requested URI does not exist [Sat Oct 24 08:12:37 2009] [error] GET /url1 HTTP/1.1]: Requested URI does not exist [Sat Oct 24 12:12:37 2009] [error] GET /url1 HTTP/1.1]: Requested URI does not exist filter lines that match the string " 08:", extract the 6th, 7th and 8th words from that line, group all lines that have the the same resulting string, do a count on them and sort the result in descending order of counts and print it out. So in the example above we'd end up with an output like this: ("GET /url1 HTTP/1.1]:", 2) ("GET /url2 HTTP/1.0]:", 1) Seems pretty straightforward, so I wrote a simple perl script to achieve this task (see the bottom of this email). The input file is 335 MB in size and contains about 2 million log line entires in it. The perl script does a pretty decent job and finishes in about 3 seconds. Now the interesting part. I decided to implememt this in Haskell (being my favorite language and all) and ended up with the following code: --- begin haskell code --- import Text.Regex.Posix ( (=~) ) import qualified Data.List as List import qualified Data.Map as Map import qualified Data.ByteString.Lazy.Char8 as LB main = do contents <- LB.readFile "log_file" putStr . unlines . map ( show . (\(x, y) -> ((LB.unpack x), y)) ) . -- create a Map grouping & counting matching tokens and sort based on the counts List.sortBy (\(_, x) (_, y) -> y `compare` x) . Map.toList . Map.fromListWith (+) . filtertokens . LB.lines $ contents where filtertokens = foldr (\x acc -> if (f x) then ((g x) : acc) else acc) [] -- filter lines starting with " 08:" where f = (=~ " 08:") . LB.unpack -- extract tokens 6, 7 & 8 and create an association list like so ("GET /url2 HTTP/1.0]:", 1) g line = flip (,) 1 . LB.unwords . map (xs !!) $ [6, 7, 8] where xs = LB.words line --- end haskell code --- This haskell implementation takes a whopping 27 seconds to complete! About 9 times slower than the perl version! I'm using ghc 6.10.4, compiling with -O2 and even went to the extent of fusing an adjacent map and filter using a foldr like so: map f (filter g) => foldr ( if g x then f x ... ), fusing adjacents maps etc. Still the same result. I really hope I'm missing some obvious optimization that's making it so slow compared to the perl version, hence this email soliciting feedback. Thanks in advance. P.S. For reference, here's my corresponding perl implementation: --- start perl code --- #!/usr/bin/perl use strict; use warnings FATAL => 'all'; my %urls; open(FILE, '<', $ARGV[0]); while(<FILE>) { if (/ 08:/) { my @words = split; my $key = join(" ", ($words[6], $words[7], $words[8])); if (exists $urls{$key}) { $urls{$key}++ } else { $urls{$key} = 1 } } } for (sort { $urls{$b} <=> $urls{$a} } keys %urls) { print "($_, $urls{$_})\n" } --- end perl code ---

6 7

Re: [Haskell-cafe] Help to solve simple problem !
by Eduard Sergeev 11 Nov '09

11 Nov '09

Aneto wrote: > > compress :: Eq a => [a] -> [(a, Int)] > If you have string "AAABCCC" it transforms it to : {A, 3} {B,1} {C,3} > Basically you need to "group" equal elements of the list first and then transform every group (which is a list of equal elements) to the tuple of (first_element , the_ length_of_the_group). All necessary functions can be found in Prelude and Data.List: import Data.List compress :: Eq a => [a] -> [(a, Int)] compress xs = map (\g -> (head g, length g)) (group xs) PS You can express it somehow nicer with arrows thought: import Data.List import Control.Arrow compress :: Eq a => [a] -> [(a, Int)] compress = map (head &&& length) <<< group -- View this message in context: http://old.nabble.com/Help-to-solve-simple-problem-%21-tp26249028p26294356.… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

1 0

Cabal HackORama -- how to handle par and pseq on stable platforms
by John D. Ramsdell 10 Nov '09

10 Nov '09

I am writing a Cabal file for an application that uses par and pseq. I want to support both modern distributions of GHC and the version that comes with Ubuntu Hardy Heron, a Long Term Support version of Ubuntu that will be retired in April 2011. It provides GHC 6.8.2 with Cabal 1.2.3.0 and no parallel package. You might be interested in my solution to supporting both releases. I did the obvious in my Cabal file. A defined a flag as follows: -- Disable with -f-par option during configuration. Flag Par Description: Enable use of the parallel construct par Default: True The description of the executable includes: if flag(par) Cpp-Options: -DHAVE_PAR GHC-Options: -threaded Build-Depends: parallel The C preprocessor is used to toggle between a parallel version of map and the usual one. #if defined HAVE_PAR parMap :: (a -> b) -> [a] -> [b] parMap _ [] = [] parMap f (x:xs) = par y (pseq ys (y:ys)) where y = f x ys = parMap f xs #else parMap :: (a -> b) -> [a] -> [b] parMap = map #endif Here is what makes this cabal file sweet. Cabal 1,2,3.0 supports flags, but ignores the Default specification. It assumes the default value of every flag is False. Thus, for both modern versions of GHC and the one on Hardy Heron, no user supplied flags are required during configuration. John

1 0

Re: [Haskell-cafe] Help to solve simple problem !
by Ezra Lalonde 10 Nov '09

10 Nov '09

The following program should work: =======compress.hs============= toList :: (Eq a) => [a] -> [[a]] toList [] = [] toList x = start : toList end where (start, end) = span (==(head x)) x toTuple :: [a] -> (a, Int) toTuple x = (head x, length x) compress :: Eq a => [a] -> [(a, Int)] compress x = map toTuple $ toList x ============================= The important thing to understand here, is the "span" function from the Prelude, and apply it recursively. *Main> span (=='A') "AAABCC" ("AAA","BCC") *Main> span (=='h') "hhhaskell" ("hhh","askell") I've used a function "toList" to separate each part of the string into a separate element of a list: *Main> toList "AAABCC" ["AAA","B","CC"] *Main> toList "EEEZZZRRAAAA!!" ["EEE","ZZZ","RR","AAAA","!!"] >From there, "toTuple" takes the first letter of the string, and puts it with its length in a tuple: *Main> toTuple "EEE" ('E',3) *Main> toTuple "EEEEE" ('E',5) Because of how it's defined, we also get the following: *Main> toTuple "Ezra" ('E',4) But that won't matter if we only use it after "toList", as in "compress". Also, I've used your type signature for my solution, not your example output; if you want it to be displayed like that, you'll have to write your own function for printing. This solution is probably not optimal, but it's a start. Hope that helps, Ezra Aneto wrote: > > Hi ! I am beginner in Haskell and have problems with this problem: > compress :: Eq a => [a] -> [(a, Int)] > If you have string "AAABCCC" it transforms it to : {A, 3} {B,1} {C,3} > > Could you help me with it ? > Thank you in advance ! > -- View this message in context: http://old.nabble.com/Help-to-solve-simple-problem-%21-tp26249028p26292205.… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

1 0

ICFP 2010: Call for papers
by Wouter Swierstra 10 Nov '09

10 Nov '09

===================================================================== Call for Papers ICFP 2010: International Conference on Functional Programming Baltimore, Maryland, 27 -- 29 September 2010 http://www.icfpconference.org/icfp2010 ===================================================================== Important Dates (at 14:00 UTC) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Submission: 2 April 2010 Author response: 24 -- 25 May 2010 Notification: 7 June 2010 Final papers due: 12 July 2010 Scope ~~~~~ ICFP 2010 seeks original papers on the art and science of functional programming. Submissions are invited on all topics from principles to practice, from foundations to features, from abstraction to application. The scope includes all languages that encourage functional programming, including both purely applicative and imperative languages, as well as languages with objects or concurrency. Particular topics of interest include * Language Design: type systems; concurrency and distribution; modules; components and composition; metaprogramming; relations to object-oriented or logic programming; interoperability * Implementation: abstract machines; compilation; compile-time and run-time optimization; memory management; multi-threading; exploiting parallel hardware; interfaces to foreign functions, services, components or low-level machine resources * Software-Development Techniques: algorithms and data structures; design patterns; specification; verification; validation; proof assistants; debugging; testing; tracing; profiling * Foundations: formal semantics; lambda calculus; rewriting; type theory; monads; continuations; control; state; effects * Transformation and Analysis: abstract interpretation; partial evaluation; program transformation; program calculation; program proof * Applications and Domain-Specific Languages: symbolic computing; formal-methods tools; artificial intelligence; systems programming; distributed-systems and web programming; hardware design; databases; XML processing; scientific and numerical computing; graphical user interfaces; multimedia programming; scripting; system administration; security; education * Functional Pearls: elegant, instructive, and fun essays on functional programming The conference also solicits Experience Reports, which are short papers that provide evidence that functional programming really works or describe obstacles that have kept it from working in a particular application. Abbreviated instructions for authors ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ By 2 April 2010, 14:00 UTC, submit an abstract of at most 300 words and a full paper of at most 12 pages (6 pages for an Experience Report), including bibliography and figures. The deadline will be strictly enforced and papers exceeding the page limits will be summarily rejected. Authors have the option to attach supplementary material to a submission, on the understanding that reviewers may choose not to look at it. A submission will be evaluated according to its relevance, correctness, significance, originality, and clarity. It should explain its contributions in both general and technical terms, clearly identifying what has been accomplished, explaining why it is significant, and comparing it with previous work. The technical content should be accessible to a broad audience. Functional Pearls and Experience Reports are separate categories of papers that need not report original research results and must be marked as such at the time of submission. Detailed guidelines on both categories are on the conference web site. Each submission must adhere to SIGPLAN's republication policy, as explained on the web at http://www.acm.org/sigplan/republicationpolicy.htm. Proceedings will be published by ACM Press. Authors of accepted submissions are expected to transfer the copyright to the ACM. Presentations will be videotaped and released online if the presenter consents by signing an additional permission form at the time of the presentation. Formatting: Submissions must be in PDF format printable in black and white on US Letter sized paper and interpretable by Ghostscript. If this requirement is a hardship, make contact with the program chair at least one week before the deadline. Papers must adhere to the standard ACM conference format: two columns, nine-point font on a ten-point baseline, with columns 20pc (3.33in) wide and 54pc (9in) tall, with a column gutter of 2pc (0.33in). A suitable document template for LATEX is available from SIGPLAN at http://www.acm.org/sigs/sigplan/authorInformation.htm. Submission: Submissions will be accepted electronically at a URL to be named later. Improved versions of a paper may be submitted at any point before the submission deadline using the same web interface. Author response: Authors will have a 48-hour period, starting at 14:00 UTC on 24 May 2010, to read and respond to reviews. Special Journal Issue: There will be a special issue of the Journal of Functional Programming with papers from ICFP 2010. The program committee will invite the authors of select accepted papers to submit a journal version to this issue. Organization ~~~~~~~~~~~~ Conference Chair Paul Hudak, Yale University Program Chair Stephanie Weirich, University of Pennsylvania Program Committee: Umut Acar, Max Planck Institute for Software Systems Zena Ariola, University of Oregon James Cheney, University of Edinburgh Peter Dybjer, Chalmers University of Technology Robert Bruce Findler, Northwestern University Andy Gill, Kansas University Fritz Henglein, University of Copenhagen Michael Hicks, University of Maryland, College Park Patricia Johann, University of Strathclyde Andres Löh, Utrecht University Simon L. Peyton Jones, Microsoft Research Didier Rémy, INRIA Paris-Rocquencourt John Reppy, University of Chicago Manuel Serrano, INRIA Sophia-Antipolis Matthieu Sozeau, Harvard University

1 0

Calling all Haskellers in Huntsville, Alabama, or surrounding areas!
by Jake McArthur 10 Nov '09

10 Nov '09

Shae Errisson, myself, Greg Bacon, and some other locals who I think might not have as big a presence online are starting a user's group in Huntsville, AL. Please join the Google group / mailing list [1] if you are interested! [1] http://groups.google.com/group/alabamahaskell - Jake McArthur

1 0

pattern match failure as control structure
by Dan Mead 10 Nov '09

10 Nov '09

hey all, is there something special about pattern match exceptions? i'm attempting to catch pattern match failures to use as control for a production system. so i want to be able to do something like catch (head []) (\e -> print "that theres pattern fail!" ) any suggestions?

3 4

Sending patches to ghc related repositories
by Maurício CA 10 Nov '09

10 Nov '09

Hi, all, I just tried to send a patch to a ghc tool. I see in hackage that the maintainer e-mail is 'cvs-fptools(a)haskell.org' (package is hsc2hs). I tried sending darcs patch to this e-mail, but it's refused as it's not on that server allowed e-mails table. The patch isn't really important, just a documentation typo, but I'm curious about what is the proper way to do it. Thanks, Maurício

1 0

is proof by testing possible?
by muad 10 Nov '09

10 Nov '09

Is it possible to prove correctness of a functions by testing it? I think the tests would have to be constructed by inspecting the shape of the function definition. -- View this message in context: http://www.nabble.com/is-proof-by-testing-possible--tp25860155p25860155.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

15 31

filter using foldr point-free?
by damodar kulkarni 10 Nov '09

10 Nov '09

Hi, We can define filter using foldr as under: filter1 p = foldr (\x xs -> (if (p x) then (x:xs) else xs)) [] Can we define filter using foldr but in pointfree style? Thanks -DM

2 1

ANN: acme-dont
by Gracjan Polak 10 Nov '09

10 Nov '09

Hello fellow haskellers, While reading reddit in the morning today: http://www.reddit.com/r/programming/comments/a26fe/dont/ I was shocked and surprised to see that Haskell lacks a very important feature present in Perl. It appeared that Haskell cannot not do monadic actions! I decided to act as fast as possible. Luckily, monads enable us to create control flow constructs on enterprise level. I'm proud to present the Acme.Dont module, that implements the indispensable don't monadic action. http://hackage.haskell.org/package/acme-dont-1.0 With special apologies to Luke Palmer that it took the Haskell community 7.5 years to catch up with Perl. Thanks go to Damian Conway. Have fun! Gracjan

4 4

Exciting job opportunity
by siki 09 Nov '09

09 Nov '09

Principal investment firm based in Manhattan is looking for an outstanding software developer to maintain and develop proprietary accounting and portfolio management systems. You should have at least a bachelor’s degree in computer science from a top university and impeccable coding style. This is a high-impact, high-visibility job opportunity where successful candidates will be entrusted with a lot of responsibility for products that have a direct effect on the P&L of the firm and influences our workflow. This is a very small hedge fund with me being the only developer right now. The next hire will have a very direct say into how this side of our business progresses from here. We are a growth oriented firm that values people who take a craftsman’s pride in their work. We always like to take a contrarian view of things and value experimenting and using often overlooked technologies. That is one of the main reasons why we currently started using Haskell in developing our quantitative models. We are looking for a canditate who shows strong analytical, organizational, and communication skills. Attention to detail is essential, i.e. we fully document everything we do and pay a lot of attention to coding style. The majority of our existing code was written in Java, so candidates must have at least some experience with Java and related technologies. Experience working with SQL would be desired as well. Background in accounting is not necessary but is definitely a plus. Please send your CV and cover letter to recruitment at karamaan.com, or reply to this post if you have any questions. Thanks -- View this message in context: http://old.nabble.com/Exciting-job-opportunity-tp26275652p26275652.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

1 0

Type-indexed expressions with fixpoint
by Brent Yorgey 09 Nov '09

09 Nov '09

Hi all, This email is literate Haskell. I'm struggling to come up with the right way to add a fixpoint constructor to an expression language described by a type-indexed GADT (details below). Any suggestions, comments, or pointers welcome. > {-# LANGUAGE KindSignatures, GADTs #-} Consider the following type-indexed GADT, which encodes descriptions of polymorphic regular types: > data U :: (* -> *) -> * where > Unit :: U None > Var :: U Id > (:+:) :: U f -> U g -> U (Sum f g) > (:*:) :: U f -> U g -> U (Prod f g) > > data None a = None > data Id a = Id a > data Sum f g a = Inl (f a) | Inr (g a) > data Prod f g a = Prod (f a) (g a) Given u :: U f, thanks to the type indexing, we can write the following function to enumerate all the shapes of a given size described by u: > enumShapes :: Int -> U f -> [f ()] > enumShapes 0 Unit = [None] > enumShapes _ Unit = [] > enumShapes 1 Var = [Id ()] > enumShapes _ Var = [] > enumShapes n (f :+: g) = map Inl (enumShapes n f) ++ map Inr (enumShapes n g) > enumShapes n (f :*: g) = [ Prod x y | x <- enumShapes n f, y <- enumShapes n g ] But of course this isn't very interesting without adding a least fixpoint constructor. That is, I'd like to have something like data U :: (* -> *) -> * where Unit :: U None Var :: U Id (:+:) :: U f -> U g -> U (Sum f g) (:*:) :: U f -> U g -> U (Prod f g) Mu :: ??? enumShapes n (Mu ...) = ... But I am quite at a loss as far as expressing the type of Mu. If the GADT wasn't type-indexed, I'd just use HOAS, i.e. Mu :: (U -> U) -> U; but since Haskell doesn't have type-level lambdas, I don't see how to make that work. Suggestions greatly appreciated! Pointing out that I am looking at this in the wrong way (if you think such is the case) would be highly appreciated as well. thanks, -Brent

1 0

Observer pattern in Haskell?
by Andy Gimblett 09 Nov '09

09 Nov '09

Hi all, I've been doing some GUI programming recently, using wx. To help manage dependencies between state and UI elements, I looked for a Haskell version of the Observer design pattern, and I found an implementation written by Bastiaan Heeren of ou.nl [1]. It pretty much did what I wanted, though I made a few changes along the way. Since this seems to be of general use (ie beyond wx), I've proposed to Bastiaan that I package it up for release on hackage, and he's happy for me to do so. Before I do so, I thought I'd ask for comments. The code is on github: http://github.com/gimbo/observer.hs where we have: Control.Observer - a typeclass for observable objects. Control.Observer.Synchronous - an implementation based on IORefs. This is essentially the same as Bastiaan's original, except I've changed the names, split it into two modules, commented it, added one or two small things, and Cabalised it. I've also made a branch where Control.Observer.Synchronous uses MVars instead of IORefs, in an attempt to achieve thread safety: http://github.com/gimbo/observer.hs/blob/threadsafeSync/Control/Observer/Sy… Now, before I make a hackage release: 0. Is this completely insane, in a Haskell setting? Are there better ways to do this that aren't laden with OO-worldview baggage? 1. Does anyone have any comments, on either version? 2. In particular, is the MVar version sensible? I'm aiming for mutual exclusion between threads. I _think_ I've got it, but I'm perhaps not familiar enough with the semantics of MVar to be certain. Advice appreciated. If it _is_ sensible, then is there any reason not to just use this, and discard the IORef version? The current implementation is synchronous, in that any observer functions are called immediately and synchronously (and in the same thread as the change of subject value). I'm pondering extending the package with an asynchronous version where the update just trips a flag, and the observer function picks this up later - possibly in another thread. The idea there is to help in cases where certain operations have to be in a particular thread. But this will mean a change to the typeclass too, I guess - or the addition of another one for observers themselves. Again, any thoughts? Thanks! -Andy [1] http://www.cs.uu.nl/wiki/bin/view/Afp0607/ExerciseWXHaskell

4 9

classes question
by Paul Tokarev 09 Nov '09

09 Nov '09

Hi. I am using Hugs 98 I have that piece of code: class PlusTimes a where plus :: a -> a -> a instance PlusTimes Int where plus x y = x + y when I run : "plus 2 3" I get this error: ERROR - Unresolved overloading *** Type : (Num a, PlusTimes a) => a *** Expression : plus 2 3 What am I doing wrong? Thanks. -- View this message in context: http://old.nabble.com/classes-question-tp26271257p26271257.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

3 5

strict mapM implementation correctness
by Paolo Losi 09 Nov '09

09 Nov '09

Hi all, while coding recently I came across the need for a strict mapM (that I indicidently use for m = MaybeT IO). I implementented this with the following simple code (it works for my use case): mapM' :: Monad m => (a-> m b) -> [a] -> m [b] mapM' _ [] = return [] mapM' f (x:xs) = do y <- f x ys <- y `seq` mapM' f xs return (y:ys) Now a couple of questions: 1. is it so "rare" to need such a beast? Why there isn't anything like that in standard libraries? 2. Is my implementation correct? 3. I've seen that mapM is implemented in base via sequence (which is in turn based on foldr). Is that any specific reason to prefer base implementation to mine? Thanks! Pao

1 0

O'Haskell
by shengwang 09 Nov '09

09 Nov '09

Hi, Somebody has idea, how to achieve reactive in O'Haskell? Shawn Wang _________________________________________________________________ MSN十年回馈，每位用户可免费获得价值25元的卡巴斯基反病毒软件2010激活码，快来领取！ http://kaba.msn.com.cn/?k=1

2 1

cabal install on Windows
by Jian Fan 09 Nov '09

09 Nov '09

Does cabal install --user or --prefix work on Windows at all? I tried: cabal install colour --user cabal install --user colour etc and all failed because install try to install at c:Program Files which I don't have permission writing. I have: cabal-install version 0.6.2 using version 1.6.0.3 of the Cabal library The Glorious Glasgow Haskell Compilation System, version 6.10.4 Thanks Jian ~ ~ ~ ~ ~ ~

3 2

cabal with non-default cc1
by Daniel Kahlenberg 09 Nov '09

09 Nov '09

Hello friends, I want a package which can't be built with the version of gcc coming with the current release of ghc, so I installed a sufficient version of gcc and called cabal with the parameters that should override it's default settings (see the failure.log, line 112). But I have the impression(*) that the remaining process doesn't use my settings related to the version of cc1 to use but still uses the one coming with ghc (6.10.4). Can you help further? Cheers Daniel * See: "*** Assembler:", "*** Linker:" searching for ghc in path. found ghc at e:\programme\ghc\ghc-6.10.4\bin\ghc.exe ("e:\\programme\\ghc\\ghc-6.10.4\\bin\\ghc.exe",["--numeric-version"]) e:\programme\ghc\ghc-6.10.4\bin\ghc.exe is version 6.10.4 looking for package tool: ghc-pkg near compiler in e:\programme\ghc\ghc-6.10.4\bin found package tool in e:\programme\ghc\ghc-6.10.4\bin\ghc-pkg.exe ("e:\\programme\\ghc\\ghc-6.10.4\\bin\\ghc-pkg.exe",["--version"]) e:\programme\ghc\ghc-6.10.4\bin\ghc-pkg.exe is version 6.10.4 ("e:\\programme\\ghc\\ghc-6.10.4\\bin\\ghc.exe",["--supported-languages"]) Reading installed packages... ("e:\\programme\\ghc\\ghc-6.10.4\\bin\\ghc-pkg.exe",["dump","--global"]) ("e:\\programme\\ghc\\ghc-6.10.4\\bin\\ghc-pkg.exe",["dump","--package-conf=h:\\.homedir\\ghc\\i386-mingw32-6.10.4\\package.conf"]) Reading available packages... Resolving dependencies... selecting bindings-common-1.3.3 (hackage) and discarding bindings-common-0.1, 0.1.1, 0.1.2, 0.1.3, 0.1.4, 0.2, 0.2.1, 0.2.2, 0.2.3, 0.2.4, 0.2.5, 0.2.6, 1.0, 1.1, 1.2, 1.3, 1.3.1 and 1.3.2 selecting base-3.0.3.1 (installed) and 4.1.0.0 (installed) and discarding syb-0.1.0.0 and 0.1.0.1 selecting ghc-prim-0.1.0.0 (installed) selecting integer-0.1.0.1 (installed) selecting rts-1.0 (installed) selecting syb-0.1.0.1 (installed) In order, the following would be installed: bindings-common-1.3.3 (new package) bindings-common-1.3.3 has already been downloaded. Extracting C:\Dokumente und Einstellungen\Zyx\Anwendungsdaten\cabal\packages\hackage.haskell.org\bindings-common\1.3.3\bindings-common-1.3.3.tar.gz to c:\DOKUME~1\Zyx\LOKALE~1\Temp\bindings-common-1.3.31176... Using external setup method with build-type Simple Creating h:\.homedir\hugsdata\setup (and its parents) Using Cabal library version 1.6.0.3 Using h:\.homedir\hugsdata\setup\setup.hs as setup script. Setup script is out of date, compiling... ("e:\\programme\\ghc\\ghc-6.10.4\\bin\\ghc.exe",["-v","--make","h:\\.homedir\\hugsdata\\setup\\setup.hs","-o","h:\\.homedir\\hugsdata\\setup\\setup.exe","-odir","h:\\.homedir\\hugsdata\\setup","-hidir","h:\\.homedir\\hugsdata\\setup","-i","-ic:\\DOKUME~1\\Zyx\\LOKALE~1\\Temp\\bindings-common-1.3.31176\\bindings-common-1.3.3","-no-user-package-conf","-package-conf","h:\\.homedir\\ghc\\i386-mingw32-6.10.4\\package.conf","-package","Cabal-1.6.0.3"]) Glasgow Haskell Compiler, Version 6.10.4, for Haskell 98, stage 2 booted by GHC version 6.10.1 Using package config file: E:\programme\ghc\ghc-6.10.4\package.conf Using package config file: h:\.homedir\ghc\i386-mingw32-6.10.4\package.conf Using package config file: h:\.homedir\ghc\i386-mingw32-6.10.4\package.conf hiding package base-3.0.3.1 to avoid conflict with later version base-4.1.0.0 hiding package regex-base-0.72.0.2 to avoid conflict with later version regex-base-0.93.1 hiding package parsec-2.1.0.1 to avoid conflict with later version parsec-3.0.1 hiding package QuickCheck-1.2.0.0 to avoid conflict with later version QuickCheck-2.1.0.2 wired-in package ghc-prim mapped to ghc-prim-0.1.0.0 wired-in package integer mapped to integer-0.1.0.1 wired-in package base mapped to base-4.1.0.0 wired-in package rts mapped to rts-1.0 wired-in package haskell98 mapped to haskell98-1.0.1.0 wired-in package syb mapped to syb-0.1.0.1 wired-in package template-haskell mapped to template-haskell-2.3.0.1 wired-in package dph-seq mapped to dph-seq-0.3 wired-in package dph-par mapped to dph-par-0.3 Hsc static flags: -static *** Chasing dependencies: Chasing modules from: *H:\.homedir\hugsdata\setup\setup.hs Stable obj: [] Stable BCO: [] Ready for upsweep [NONREC ModSummary { ms_hs_date = Mon Nov 9 14:45:34 Westeuropäische Normalzeit 2009 ms_mod = main:Main, ms_imps = [Distribution.Simple] ms_srcimps = [] }] compile: input file H:\.homedir\hugsdata\setup\setup.hs Created temporary directory: C:\DOKUME~1\Zyx\LOKALE~1\Temp\/ghc2388_0 *** Checking old interface for main:Main: [1 of 1] Compiling Main ( H:\.homedir\hugsdata\setup\setup.hs, H:\.homedir\hugsdata\setup\Main.o ) *** Parser: *** Renamer/typechecker: *** Desugar: Result size = 8 *** Simplify: Result size = 6 Result size = 6 *** Tidy Core: Result size = 6 writeBinIface: 1 Names writeBinIface: 28 dict entries *** CorePrep: Result size = 6 *** Stg2Stg: *** CodeGen: *** CodeOutput: *** Assembler: E:\programme\ghc\ghc-6.10.4\gcc -BE:\programme\ghc\ghc-6.10.4\gcc-lib/ -IE:\programme\ghc\ghc-6.10.4\include/mingw -IH:\.homedir\hugsdata\setup -c C:\DOKUME~1\Zyx\LOKALE~1\Temp\/ghc2388_0/ghc2388_0.s -o h:\.homedir\hugsdata\setup\Main.o *** Deleting temp files: Deleting: C:\DOKUME~1\Zyx\LOKALE~1\Temp\/ghc2388_0/ghc2388_0.s Upsweep completely successful. *** Deleting temp files: Deleting: link: linkables are ... LinkableM (Mon Nov 9 14:45:34 Westeuropäische Normalzeit 2009) main:Main [DotO h:\.homedir\hugsdata\setup\Main.o] Linking h:\.homedir\hugsdata\setup\setup.exe ... *** Windres: E:\programme\ghc\ghc-6.10.4\bin/windres --preprocessor="E:\programme\ghc\ghc-6.10.4\gcc" "-BE:\programme\ghc\ghc-6.10.4\gcc-lib/" "-IE:\programme\ghc\ghc-6.10.4\include/mingw" "-E" "-xc" "-DRC_INVOKED" --use-temp-file --input=C:\DOKUME~1\Zyx\LOKALE~1\Temp\/ghc2388_0/ghc2388_0.rc --output=C:\DOKUME~1\Zyx\LOKALE~1\Temp\/ghc2388_0/ghc2388_0.o --output-format=coff *** Linker: E:\programme\ghc\ghc-6.10.4\gcc -BE:\programme\ghc\ghc-6.10.4\gcc-lib/ -IE:\programme\ghc\ghc-6.10.4\include/mingw -v -o h:\.homedir\hugsdata\setup\setup.exe -DDONT_WANT_WIN32_DLL_SUPPORT h:\.homedir\hugsdata\setup\Main.o C:\DOKUME~1\Zyx\LOKALE~1\Temp\/ghc2388_0/ghc2388_0.o -Lh:\.homedir\.cabal\Cabal-1.6.0.3\ghc-6.10.4 -LE:\programme\ghc\ghc-6.10.4\process-1.0.1.1 -LE:\programme\ghc\ghc-6.10.4\pretty-1.0.1.0 -LE:\programme\ghc\ghc-6.10.4\directory-1.0.0.3 -LE:\programme\ghc\ghc-6.10.4\old-time-1.0.0.2 -LE:\programme\ghc\ghc-6.10.4\old-locale-1.0.0.1 -LE:\programme\ghc\ghc-6.10.4\filepath-1.1.0.2 -LE:\programme\ghc\ghc-6.10.4\Win32-2.2.0.0 -LE:\programme\ghc\ghc-6.10.4\bytestring-0.9.1.4 -LE:\programme\ghc\ghc-6.10.4\containers-0.2.0.1 -LE:\programme\ghc\ghc-6.10.4\array-0.2.0.0 -LE:\programme\ghc\ghc-6.10.4\syb-0.1.0.1 -LE:\programme\ghc\ghc-6.10.4\base-4.1.0.0 -LE:\programme\ghc\ghc-6.10.4\integer-0.1.0.1 -LE:\programme\ghc\ghc-6.10.4\ghc-prim-0.1.0.0 -LE:\programme\ghc\ghc-6.10.4 -LE:\programme\ghc\ghc-6.10.4/gcc-lib -lHSCabal-1.6.0.3 -lHSprocess-1.0.1.1 -lHSpretty-1.0.1.0 -lHSdirectory-1.0.0.3 -lHSold-time-1.0.0.2 -lHSold-locale-1.0.0.1 -lHSfilepath-1.1.0.2 -lHSWin32-2.2.0.0 -luser32 -lgdi32 -lwinmm -ladvapi32 -lHSbytestring-0.9.1.4 -lHScontainers-0.2.0.1 -lHSarray-0.2.0.0 -lHSsyb-0.1.0.1 -lHSbase-4.1.0.0 -lwsock32 -luser32 -lshell32 -lHSinteger-0.1.0.1 -lHSghc-prim-0.1.0.0 -lHSrts -lm -lffi -lgmp -lwsock32 -u _ghczmprim_GHCziTypes_Izh_static_info -u _ghczmprim_GHCziTypes_Czh_static_info -u _ghczmprim_GHCziTypes_Fzh_static_info -u _ghczmprim_GHCziTypes_Dzh_static_info -u _base_GHCziPtr_Ptr_static_info -u _base_GHCziWord_Wzh_static_info -u _base_GHCziInt_I8zh_static_info -u _base_GHCziInt_I16zh_static_info -u _base_GHCziInt_I32zh_static_info -u _base_GHCziInt_I64zh_static_info -u _base_GHCziWord_W8zh_static_info -u _base_GHCziWord_W16zh_static_info -u _base_GHCziWord_W32zh_static_info -u _base_GHCziWord_W64zh_static_info -u _base_GHCziStable_StablePtr_static_info -u _ghczmprim_GHCziTypes_Izh_con_info -u _ghczmprim_GHCziTypes_Czh_con_info -u _ghczmprim_GHCziTypes_Fzh_con_info -u _ghczmprim_GHCziTypes_Dzh_con_info -u _base_GHCziPtr_Ptr_con_info -u _base_GHCziPtr_FunPtr_con_info -u _base_GHCziStable_StablePtr_con_info -u _ghczmprim_GHCziBool_False_closure -u _ghczmprim_GHCziBool_True_closure -u _base_GHCziPack_unpackCString_closure -u _base_GHCziIOBase_stackOverflow_closure -u _base_GHCziIOBase_heapOverflow_closure -u _base_ControlziExceptionziBase_nonTermination_closure -u _base_GHCziIOBase_blockedOnDeadMVar_closure -u _base_GHCziIOBase_blockedIndefinitely_closure -u _base_ControlziExceptionziBase_nestedAtomically_closure -u _base_GHCziWeak_runFinalizzerBatch_closure -u _base_GHCziTopHandler_runIO_closure -u _base_GHCziTopHandler_runNonIO_closure -u _base_GHCziConc_runHandlers_closure -u _base_GHCziConc_ensureIOManagerIsRunning_closure Reading specs from E:/programme/ghc/ghc-6.10.4/gcc-lib/specs Configured with: ../gcc-3.4.5-20060117-3/configure --with-gcc --with-gnu-ld --with-gnu-as --host=mingw32 --target=mingw32 --prefix=/mingw --enable-threads --disable-nls --enable-languages=c,c++,f77,ada,objc,java --disable-win32-registry --disable-shared --enable-sjlj-exceptions --enable-libgcj --disable-java-awt --without-x --enable-java-gc=boehm --disable-libgcj-debug --enable-interpreter --enable-hash-synchronization --enable-libstdcxx-debug Thread model: win32 gcc version 3.4.5 (mingw-vista special r3) E:/programme/ghc/ghc-6.10.4/gcc-lib/collect2.exe -Bdynamic -o h:\.homedir\hugsdata\setup\setup.exe -u _ghczmprim_GHCziTypes_Izh_static_info -u _ghczmprim_GHCziTypes_Czh_static_info -u _ghczmprim_GHCziTypes_Fzh_static_info -u _ghczmprim_GHCziTypes_Dzh_static_info -u _base_GHCziPtr_Ptr_static_info -u _base_GHCziWord_Wzh_static_info -u _base_GHCziInt_I8zh_static_info -u _base_GHCziInt_I16zh_static_info -u _base_GHCziInt_I32zh_static_info -u _base_GHCziInt_I64zh_static_info -u _base_GHCziWord_W8zh_static_info -u _base_GHCziWord_W16zh_static_info -u _base_GHCziWord_W32zh_static_info -u _base_GHCziWord_W64zh_static_info -u _base_GHCziStable_StablePtr_static_info -u _ghczmprim_GHCziTypes_Izh_con_info -u _ghczmprim_GHCziTypes_Czh_con_info -u _ghczmprim_GHCziTypes_Fzh_con_info -u _ghczmprim_GHCziTypes_Dzh_con_info -u _base_GHCziPtr_Ptr_con_info -u _base_GHCziPtr_FunPtr_con_info -u _base_GHCziStable_StablePtr_con_info -u _ghczmprim_GHCziBool_False_closure -u _ghczmprim_GHCziBool_True_closure -u _base_GHCziPack_unpackCString_closure -u _base_GHCziIOBase_stackOverflow_closure -u _base_GHCziIOBase_heapOverflow_closure -u _base_ControlziExceptionziBase_nonTermination_closure -u _base_GHCziIOBase_blockedOnDeadMVar_closure -u _base_GHCziIOBase_blockedIndefinitely_closure -u _base_ControlziExceptionziBase_nestedAtomically_closure -u _base_GHCziWeak_runFinalizzerBatch_closure -u _base_GHCziTopHandler_runIO_closure -u _base_GHCziTopHandler_runNonIO_closure -u _base_GHCziConc_runHandlers_closure -u _base_GHCziConc_ensureIOManagerIsRunning_closure E:/programme/ghc/ghc-6.10.4/gcc-lib/crt2.o E:/programme/ghc/ghc-6.10.4/gcc-lib/crtbegin.o -Lh:\.homedir\.cabal\Cabal-1.6.0.3\ghc-6.10.4 -LE:\programme\ghc\ghc-6.10.4\process-1.0.1.1 -LE:\programme\ghc\ghc-6.10.4\pretty-1.0.1.0 -LE:\programme\ghc\ghc-6.10.4\directory-1.0.0.3 -LE:\programme\ghc\ghc-6.10.4\old-time-1.0.0.2 -LE:\programme\ghc\ghc-6.10.4\old-locale-1.0.0.1 -LE:\programme\ghc\ghc-6.10.4\filepath-1.1.0.2 -LE:\programme\ghc\ghc-6.10.4\Win32-2.2.0.0 -LE:\programme\ghc\ghc-6.10.4\bytestring-0.9.1.4 -LE:\programme\ghc\ghc-6.10.4\containers-0.2.0.1 -LE:\programme\ghc\ghc-6.10.4\array-0.2.0.0 -LE:\programme\ghc\ghc-6.10.4\syb-0.1.0.1 -LE:\programme\ghc\ghc-6.10.4\base-4.1.0.0 -LE:\programme\ghc\ghc-6.10.4\integer-0.1.0.1 -LE:\programme\ghc\ghc-6.10.4\ghc-prim-0.1.0.0 -LE:\programme\ghc\ghc-6.10.4 -LE:\programme\ghc\ghc-6.10.4/gcc-lib -LE:/programme/ghc/ghc-6.10.4/gcc-lib h:\.homedir\hugsdata\setup\Main.o C:\DOKUME~1\Zyx\LOKALE~1\Temp\/ghc2388_0/ghc2388_0.o -lHSCabal-1.6.0.3 -lHSprocess-1.0.1.1 -lHSpretty-1.0.1.0 -lHSdirectory-1.0.0.3 -lHSold-time-1.0.0.2 -lHSold-locale-1.0.0.1 -lHSfilepath-1.1.0.2 -lHSWin32-2.2.0.0 -luser32 -lgdi32 -lwinmm -ladvapi32 -lHSbytestring-0.9.1.4 -lHScontainers-0.2.0.1 -lHSarray-0.2.0.0 -lHSsyb-0.1.0.1 -lHSbase-4.1.0.0 -lwsock32 -luser32 -lshell32 -lHSinteger-0.1.0.1 -lHSghc-prim-0.1.0.0 -lHSrts -lm -lffi -lgmp -lwsock32 -lmingw32 -lgcc -lmoldname -lmingwex -lmsvcrt -luser32 -lkernel32 -ladvapi32 -lshell32 -lmingw32 -lgcc -lmoldname -lmingwex -lmsvcrt E:/programme/ghc/ghc-6.10.4/gcc-lib/crtend.o link: done *** Deleting temp files: Deleting: C:\DOKUME~1\Zyx\LOKALE~1\Temp\/ghc2388_0/ghc2388_0.o C:\DOKUME~1\Zyx\LOKALE~1\Temp\/ghc2388_0/ghc2388_0.rc *** Deleting temp dirs: Deleting: C:\DOKUME~1\Zyx\LOKALE~1\Temp\/ghc2388_0 h:\.homedir\hugsdata\setup\setup.exe configure --verbose=3 --builddir=h:\.homedir\hugsdata --ghc --prefix=h:\.homedir\.cabal --datadir=h:\.homedir\.cabal --configure-option=CC=e:\programme\mingw-gcc4\bin\gcc.exe --user --package-db=h:\.homedir\ghc\i386-mingw32-6.10.4\package.conf --extra-include-dirs=e:/programme/ghc/mingw-gcc4/include --extra-lib-dirs=e:/programme/ghc/mingw-gcc4/lib --constraint=base ==3.0.3.1 --with-gcc=e:\programme\ghc\mingw-gcc4\bin\gcc.exe --with-ld=e:\programme\ghc\mingw-gcc4\bin\ld.exe --gcc-option=-v --gcc-option=-Wall Redirecting build log to {handle: h:\.homedir\hugsdata\build-bindings-common-1.3.3-ghc-6.10.4.log} Using external setup method with build-type Simple Creating h:\.homedir\hugsdata\setup (and its parents) Using Cabal library version 1.6.0.3 Using h:\.homedir\hugsdata\setup\setup.hs as setup script. h:\.homedir\hugsdata\setup\setup.exe build --verbose=3 --builddir=h:\.homedir\hugsdata Redirecting build log to {handle: h:\.homedir\hugsdata\build-bindings-common-1.3.3-ghc-6.10.4.log} cabal.exe: Error: some packages failed to install: bindings-common-1.3.3 failed during the building phase. The exception was: exit: ExitFailure 1

1 0

Re: [Haskell-cafe] Haskell image libraries
by Pierre-Etienne Meunier 09 Nov '09

09 Nov '09

there is also a binding for libGD on hackage : http://hackage.haskell.org/package/gd And, of course, you can improve it, or write a binding to a more complete library. Or, even better, write a mix between http://www.libpng.org/pub/png/pngdocs.html and http://hackage.haskell.org/package/binary

1 0

WinGHCi stuck in a loop
by Henk-Jan van Tuyl 09 Nov '09

09 Nov '09

L.S., I changed the options in WinGHCi and now WinGHCi is stuck in a loop each time I start it; how can I edit the options? I cannot find them in the registry. -- Met vriendelijke groet, Henk-Jan van Tuyl -- http://Van.Tuyl.eu/ http://members.chello.nl/hjgtuyl/tourdemonad.html --

2 1

Re: [Haskell] ANNOUNCE: control-monad-exception 0.5 with monadic call traces
by Henning Thielemann 09 Nov '09

09 Nov '09

Jose Iborra schrieb: > Folks, > > I'm happy to announce a new release of control-monad-exception with > monadic call traces, > available in Hackage. Grab it now while it is still online! > > Monadic stack traces are described in detail in a blog post [1]. > > In short, what this means for your code is the ability to generate > errors like this: > > 500 Internal Server Error > The CGI server failed with the following error: > DeleteException (BmPK 2009-10-26 19:39:51.031297 UTC "Testing RPO") > in deleteBenchmarkFromPK, > NarradarBenchmarkDB(src/NarradarBenchmarkDB.hs): (186, 44) > deleteBenchmarkFromPK, > NarradarBenchmarkDB(src/NarradarBenchmarkDB.hs): (186, 25) > deleteBenchmarkFromPK, > NarradarBenchmarkDB(src/NarradarBenchmarkDB.hs): (184, 17) > deleteBenchmarkFromPK, > NarradarBenchmarkDB(src/NarradarBenchmarkDB.hs): (180, 90) > deleteTests, NarradarBenchmarkCGI(src/NarradarBenchmarkCGI.hs): > (108, 3) > deleteTests, NarradarBenchmarkCGI(src/NarradarBenchmarkCGI.hs): > (106, 20) > cgiMain, NarradarBenchmarkCGI(src/NarradarBenchmarkCGI.hs): (52, 33) > cgiMain, NarradarBenchmarkCGI(src/NarradarBenchmarkCGI.hs): (52, 30) > cgiMain, NarradarBenchmarkCGI(src/NarradarBenchmarkCGI.hs): (50, 9) > cgiMain, NarradarBenchmarkCGI(src/NarradarBenchmarkCGI.hs): (46, 11) Sure, this is a nice functionality. But isn't it about debugging, not exception handling? Internal Server Error means to me, the server has a bug, thus we want to know, how to reproduce it, thus the stack trace. For handling expected irregularites, what exceptions are, you would not need that, right?

6 8

Area from [(x,y)] using foldl
by michael rice 09 Nov '09

09 Nov '09

Here's an (Fortran) algorithm for calculating an area, given one dimensional arrays of Xs and Ys. I wrote a recursive Haskell function that works, and one using FOLDL that doesn't. Why would Haskell be "expecting" (t, t) out of ((*) (xold-x) (yold+y))? Michael ==================== AREA = 0.0 XOLD = XVERT(NVERT) YOLD = YVERT(NVERT) DO 10 N = 1, NVERT X = XVERT(N) Y = YVERT(N) AREA = AREA + (XOLD - X)*(YOLD + Y) XOLD = X YOLD = Y 10 CONTINUE AREA = 0.5*AREA ==================== area :: [(Double,Double)] -> Double area ps = abs $ (/2) $ area' (last ps) ps where area' _ [] = 0 area' (x0,y0) ((x,y):ps) = (x0-x)*(y0+y) + area' (x,y) ps *Main> let p = [(0.0,0.0),(1.0,0.0),(1.0,1.0),(0.0,1.0),(0.0,0.0)] *Main> area (last p) p 1.0 *Main> ==================== area :: [(Double,Double)] -> Double area p = foldl (\ (xold,yold) (x,y) -> ((*) (xold-x) (yold+y))) 0 ((last p):p) Prelude> :l area [1 of 1] Compiling Main ( area.hs, interpreted ) area.hs:29:40: Occurs check: cannot construct the infinite type: t = (t, t) Expected type: (t, t) Inferred type: t In the expression: ((*) (xold - x) (yold + y)) In the first argument of `foldl', namely `(\ (xold, yold) (x, y) -> ((*) (xold - x) (yold + y)))' Failed, modules loaded: none. Prelude>

4 11

bit of help with n-ary please...
by spot135 09 Nov '09

09 Nov '09

Hi, Ok what im trying to do is replace an element in an n-ary and display the completed tree. So this is what ive got so far. data Tree a = Empty |Leaf a|Branch a [Tree a] deriving (Show) replace :: Eq a=>a->a->Tree a -> (Tree a) replace x y Empty = Element x replace x y (Leaf z) | x==z = (Leaf y) -- | otherwise = replace x y (Branch z lis) | x==z = (Branch y lis) |otherwise = replaceA x y clis replaceA :: Eq a=> a->a->[Tree a]->(Tree a) replaceA _ _ [] = Empty -- run out replaceA x y (h:r) |Q suc = suc |otherwise = replaceA x y r where suc=replace x y h Q :: a -> Bool Q a = True Q a = False Theres two main problems i am having. One is I'm not sure what should be the "otherwise" in the leaf function. Another problem is it doesn't show the whole tree just the part after the replacement. If you think this is complete bull I'll quite happily start over if somebody could give me some insight into what is the best way of tackling this problem is. Many thanks in advance spot -- View this message in context: http://old.nabble.com/bit-of-help-with-n-ary-please...-tp26258006p26258006.… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

6 9

Urgent: Please suggest me for Flow Caml Compiler
by Akshay Dave 08 Nov '09

08 Nov '09

Hello, I undertsand that this is Haskell cafe discussion forum. But I would highly appreciate if anyone can tell me where can I get Compiler and editor for FLow Caml ( it's a ML based language)) as I am not able to find it on net :(. Thanks in Adavnce! Akshay _________________________________________________________________ Hotmail: Trusted email with Microsoft's powerful SPAM protection. http://clk.atdmt.com/GBL/go/177141664/direct/01/ http://clk.atdmt.com/GBL/go/177141664/direct/01/

2 1

getting ready to sprint! darcs: 14-15 Nov, Portland/Vienna
by Eric Kow 08 Nov '09

08 Nov '09

Hi everybody, We're less than one week away from the third Darcs Hacking Sprint, taking place in Portland and in Vienna on 14-15 November. Everybody is welcome (Haskell and Darcs newbies included), but please do let us know if you're thinking of attending! Preflight checklist ------------------- We've got our work cut out for us, so we want to make sure that we can hit the ground running. Here are three things each participant can do to help: 1. Request a code.haskell.org account http://community.haskell.org/admin/ 2. Build Darcs (install the Haskell Platform if needed) cabal install darcs darcs get --lazy http://darcs.net darcs cd darcs cabal install 3. Tell Eric your code.haskell.org login This is so that I can add you to the Darcs group Vienna Friday ------------- There's going to be quite a few of us arriving in Vienna on Friday. I propose we meet up at the Hostel Ruthensteiner, say at 11:00 for morning arrivals and 16:30 for those of us getting there in the afternoon. Perhaps we could walk around a bit, have a nice relaxed chat, find some food :-) http://www.hostelruthensteiner.com/ Meetings -------- There are few things we'll be talking about over the sprint (eg, darcs 2.4, SVN integration, filecache). If you're interested in joining in, please put your name down on the wiki so that we can work out a rough schedule. http://wiki.darcs.net/Sprints/2009-11 Nothing formal. Maybe just lunch and me scribbling in a notebook. Or maybe Darcs Hackers gesticulating wildly in front a white board. See you there -------------- That's all for now. Please shout if you have any questions or last minute comments. Otherwise, I'm really excited about this and looking forward to seeing you all this weekend! -- Eric Kow <http://www.nltg.brighton.ac.uk/home/Eric.Kow> PGP Key ID: 08AC04F9

1 0

Haskell image libraries
by Max Rabkin 08 Nov '09

08 Nov '09

Haskellers, To add image support to fdo-notify, I need an image type. Looking through Hackage, I didn't find any image library with the following features: * Load from a variety of formats (at least PNG and JPG, I'd say) * Efficient per-pixel access, or a way to dump the image into a ByteString as a bitmap (I need to serialise them into the protocol's bitmap format) Preferably, it should be possible to construct images programmatically too. Is there really no such library? It would be nice to have something like a Haskell equivalent of the Python Imaging Library, which is the de facto standard image library in Python and supports just about every type of operation on images you could ask for. Regards, Max

7 7

Re: [Haskell-cafe] Is () a 0-length tuple?
by Matthew Gruen 08 Nov '09

08 Nov '09

Forgot to cc haskell-cafe. Trying again: ---------- Forwarded message ---------- From: Matthew Gruen <wikigracenotes(a)gmail.com> Date: Sat, Nov 7, 2009 at 2:16 PM Subject: Re: [Haskell-cafe] Is () a 0-length tuple? To: Pasqualino Titto Assini <tittoassini(a)gmail.com> On Sat, Nov 7, 2009 at 2:00 PM, Pasqualino "Titto" Assini <tittoassini(a)gmail.com> wrote: > The syntax is similar, but what else is? > > In JavaScript there is a "null" value, that is the only value of the null type. > > Isn't () the same thing? The only value of the unary type? > > Best, > > titto > > Pasqualino "Titto" Assini, Ph.D. > http://quicquid.org/ In JavaScript's case, there is not a null type. The null value belongs to the 'object' type, whereas the undefined value belongs to the 'undefined' type. This is all a lot less useful when you realize that JavaScript has a dynamic type system. But this is JSON, not JavaScript. In JSON, arrays, objects, strings, and numbers can be any number of values. Booleans can be two values. Null can only be one value. Personally, I think a better mapping for () would be JSNull, since both have only one value in normal form. However, there is not necessarily any natural mapping between Haskell values and JSON values. The library tries to provide as many as possible, including (), which it happens to map to JSArray [] instead of JSNull. As long as the library is internally consistent, though, it should be fine.

2 3

call for help: FOSDEM devroom
by Ganesh Sittampalam 08 Nov '09

08 Nov '09

Hi, I'm thinking of trying to get a devroom for haskell.org at the next FOSDEM, which is Saturday-Sunday February 6th-7th 2010 in Brussels: http://www.fosdem.org/2010/call-developer-rooms The idea would be to try to introduce Haskell to people at FOSDEM who were interested, and thus help build our ties with We'd try to have a few introductory talks about Haskell, and some demos etc. It would probably also make sense to talk about/demo darcs at the same time. Apparently there's a lot of demand so it's a bit of a long shot, and I expect we'd only get one day, which is probably all we'd need. To make this work, we'll need several reasonably experienced Haskellers to turn up to help out with the talks, demos and talking to people in general. I've got a couple of people interested already but need more. So, please could you let me know, preferably within the next week, whether you would be interested in coming along and helping. You can email me directly or on-list as you prefer. The deadline for actually making the application for the devroom is 22nd November. Cheers, Ganesh

1 0

virus/trojan in bamse package?
by Daniel van den Eijkel 08 Nov '09

08 Nov '09

hi, my Avira antivirus program says that there is a trojan in the bamse-0.9.5 package. I downloaded the hackage-torrent a week ago, and Avira says "TR/Crypt.CFI.Gen" is in bamse. To be sure, I downloaded bamse-0.9.5 from hackage today, and now avira says less specificly that there are "some viruses and/or unwanted programs" inside. Since I have some trojan trouble for a few days now, bamse might be the reason for that, but I am not sure. Maybe it is a false alarm, I can't determine this. (bamse is a framework for building Windows Installer, so it might contain code that looks like a virus or alike wrongly?) Does anybody know if this is really a virus/trojan? Best regards, Daniel

2 2

Small Japi binding for GHC
by Philippos Apolinarius 08 Nov '09

08 Nov '09

JAPI is by far my favorite GUI library. Since every machine has Java RE installed, JAPI offers GUI with a very small footprint. Besides this, it is very easy to code, and delivers GUI programs that are hardly larger than console applications. I use Jorlano's version of JAPI, coded for Java 2, which is very cool. I study Computer Science in a small college, and I always handle my homework in JAPI. When I took functional programming one year ago, the language chosen by Professor Lopes was Clean, that has a GUI. However, I feel that JAPI is much easier than ObjectIO; therefore, I used JAPI for my homework. So, I searched for JAPI bindings for Haskell. The only library I found was something called Small Japi binding for GHC. The package is incomplete, and bug ridden. I wonder whether the author fixed the bugs, completed the package, and added more examples. I would appreciate if people could send me links to a complete Japi binding for GHC. In the mean time, I fixed the bugs of Small Japi Binding, and added a few important components (j_textfield, j_settext, j_gettext, j_button, etc.) Of course, a link to a more recent version of the official binding will save me a lot of work. __________________________________________________________________ Looking for the perfect gift? Give the gift of Flickr! http://www.flickr.com/gift/

2 3

Re: [Haskell-cafe] Haskell image libraries
by Andrew Coppin 08 Nov '09

08 Nov '09

Max Rabkin wrote: > On Sun, Nov 8, 2009 at 5:09 PM, Max Rabkin <max.rabkin(a)gmail.com> wrote: > >> On Sun, Nov 8, 2009 at 4:58 PM, Andrew Coppin >> <andrewcoppin(a)btinternet.com> wrote: >> >>> Try AC-EasyRaster-GTK. >>> >> Thanks, I'll give that a try >> > > Having downloaded it, I must admit I was a bit put off by seeing things like > init_system :: IO () > process_event :: IO () > wait_event :: IO () > main_loop :: IO () > in an image library. > > But it's the best we've got right now, so I've got a couple questions: > is it safe to call init_system more than once? And what do I need the > event-handling functions for, if anything? > If all you want to do is load/save images and do pixel I/O on them, you can completely ignore process_event, wait_event, main_loop, etc. All you need to do is make sure you call init_system at the start of your program. (You see the ib_display function? If you want *that* to work properly, you need to run the GTK event loop, which is what these event-related functions are all about. If you're not trying to display the image on screen, you can ignore all that.) I should probably make the documentation clearer...

1 0