December 2005 - Haskell-Cafe

Re: Haskell Speed
by Isaac Gouy 27 Dec '05

27 Dec '05

Branimir Maksimovic wrote: > Of course, first example uses [String] instead of Data.HashTable > as other languages do. Imagine C program does not use > hash,rather list, how it will perform:) And the author comments his program -- This is a purely functional solution to the problem. -- An alternative which keeps a mutable table of occurences would -- be faster. We'll be happy to also show a Haskell program that uses Data.HashTable - first, someone needs to contribute that program. > I didn't look further after that. Ideal - you may criticize without the risk that others will criticize what you do. __________________________________ Yahoo! for Good - Make a difference this year. http://brand.yahoo.com/cybergivingweek2005/

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Re: Haskell Speed
by Isaac Gouy 27 Dec '05

27 Dec '05

Jared Updike wrote: > What that means is the results are completely subject to > (1) how good the submission for that tests was Contribute faster more-elegant programs http://shootout.alioth.debian.org/gp4/faq.php#contribute >(2) the choice of tests in the first place Suggest better tests http://shootout.alioth.debian.org/gp4/faq.php#newbench > (3) startup times for loading the binaries into memory (GHC > makes big binaries that are arguably much faster if you do > things in "daemon" mode, for example). Is that just speculation? (Erlang is an application server starting-up and that really is noticeable.) -snip- > it is pretty much a game created to make C win---it already > wins! Which C do you mean - gcc, Intel C, Tiny C? And, no! It is not a game created to make C win (although it is a game). And, no! C does not already win all the games - astonishingly it doesn't even "win" the basic loop and array test nsieve. __________________________________________ Yahoo! DSL Something to write home about. Just $16.99/mo. or less. dsl.yahoo.com

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Re: Haskell Speed
by Isaac Gouy 27 Dec '05

27 Dec '05

Simon Marlow wrote: > Also, I would like to draw your attention to the fact that GHC > wipes the floor with nearly everyone in the concurrency > benchmark SmartEiffel is so much faster that I'm still trying to figure out if it's doing something different :-) Be interesting to see GHC on the other concurrency benchmark... http://shootout.alioth.debian.org/benchmark.php?test=chameneos&lang=all > Seriously, it's very difficult to draw any meaningful > conclusions from these benchmarks. Is it any easier to draw meaningful conclusions about the relative performance of programming languages from some other benchmarks? __________________________________________ Yahoo! DSL Something to write home about. Just $16.99/mo. or less. dsl.yahoo.com

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Database mailing list?
by John Goerzen 27 Dec '05

27 Dec '05

Greetings, It seems there are a lot of people working on database-related things in Haskell. HaskellDB, wxHaskell, HDBC, HSQL, etc. I'm wondering if it would make sense to have a haskell-db mailing list to help coordinate efforts? (Or even just to help manage development on these projects without cluttering more general lists) -- John

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Tutorial uploaded
by Daniel Carrera 27 Dec '05

27 Dec '05

Hi all, I've finished a first draft of what I call "First steps in Haskell". It's intended to be the very first thing a new user sees when they decide to try out Haskell. http://www.haskell.org/hawiki/FirstSteps?action=show It's a bit longer than I'd like, but I don't inmediately see anything I can take out without losing something valuable (given the purpose of this document). Thoughts and comments? Cheers, Daniel. -- /\/`) http://oooauthors.org /\/_/ http://opendocumentfellowship.org /\/_/ \/_/ I am not over-weight, I am under-tall. /

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Re: [Haskell-cafe] Proper way to write this
by Donn Cave 27 Dec '05

27 Dec '05

Quoth Pupeno <pupeno(a)pupeno.com>: | I have this piece of code: What do you think about this? may_ = maybe (return ()) (\ _ -> f) stopDaytimeServer dts = do may_ (killServer (ss dts)) (streamPort dts) may_ (killServer (ds dts)) (dgramPort dts) | PS: I have a worse case: I don't think it will be too much worse. I would not try to combine the struct updates, in the "both" case -- it doesn't buy you anything, and pulls you into duplication you don't want. Donn Cave, donn(a)drizzle.com | stopDaytimeServer dts = | case dts of | DaytimeServer {streamPort = Just _, dgramPort = Just _} -> do | killServer (ss dts) | killServer (ds dts) | DaytimeServer {streamPort = Just _, dgramPort = Nothing} -> do | killServer (ss dts) | DaytimeServer {streamPort = Nothing, dgramPort = Just _} -> do | killServer (ds dts) | -- | Having a 'DaytimeServer', run it according to its specifications. | runDaytimeServer :: DaytimeServer -> IO DaytimeServer | runDaytimeServer dts = | case dts of | DaytimeServer {streamPort = Just _, dgramPort = Just _} -> do | ss <- runDgramDaytimeServer dts | ds <- runStreamDaytimeServer dts | return dts{ss = ss, ds = ds} | DaytimeServer {streamPort = Just _, dgramPort = Nothing} -> do | ss <- runStreamDaytimeServer dts | return dts{ss = ss} | DaytimeServer {streamPort = Nothing, dgramPort = Just _} -> do | ds <- runDgramDaytimeServer dts | return dts{ds = ds}

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Re[2]: [Haskell-cafe] binary IO
by Bulat Ziganshin 27 Dec '05

27 Dec '05

Hello Pupeno, Tuesday, December 27, 2005, 6:03:50 PM, you wrote: >> you must use `openBitAligned` to open bit-aligned stream over Handle, >> and use `flushBits` at the end of writing. there is much more >> features, ask me about what you need P> Well, it seems I am seeing a bit of light here :) P> I have a couple of questions: P> - Is it possible to serialize from and to a Ptr ? Because TCP gives me a P> Handle, but UDP just gives me a Ptr with the packet and I'll turn the TCP P> into a Ptr as well. reading: h <- openMemory ptr size bh <- openBitAligned h a <- get bh b <- get bh .... -- you don't need to close/flush/free resources at the end writing: h <- createMemoryStream 64 -- replace 64 with initial buffer size you need -- the buffer will be extended if more data -- will be written bh <- openBitAligned h put_ bh a put_ bh b ... flushBits bh but currently there is no way to get data from this buffer :) just see structure of SimpleMemoryStream (created by createMemoryStream) and extract these data yourself - something like: copyMemToHandle mem handle = do let (Mem buf' pos' end') = mem buf <- readPtr buf' pos <- readPtr pos' hPutBuf handle buf (pos-:buf) P> - Is it possible to serialize from and to a Ptr ? Because TCP gives me a P> Handle, but UDP just gives me a Ptr with the packet and I'll turn the TCP P> into a Ptr as well. btw, you don't need to "convert" anything, my library works with Handle and memory buffers in the same way. so just parse data directly from the original source P> - Is it possible to specify the endiannes ? I need to read everything as P> big-endian. my library works in network format which is what you used in ptrToWord16BE. if you need another format - you can either define and use new low-level functions: getWord16LE h = do w1 <- vGetByte h w2 <- vGetByte h return $! ((w2 `shiftL` 8) .|. w1) or define these functions and use them in defining instances of Binary class: instance Binary Word16 where put_ = putWord16LE get = getWord16LE instance Binary Word32 where put_ = putWord32LE get = getWord32LE .... and then just read Word16/Word32/... types. the second solution needs to edit Binary.hs -- Best regards, Bulat mailto:bulatz@HotPOP.com

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binary IO
by Dominic Steinitz 27 Dec '05

27 Dec '05

It might also be worth looking at the networking code in House given the intended application is parsing network packets. See http://www.cse.ogi.edu/~hallgren/House/kernel/pfe.cgi?Net.PacketParsing, for example. Dominic.

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Re: [Haskell-cafe] Re: Haskell Speed
by Branimir Maksimovic 26 Dec '05

26 Dec '05

Paul Moore wrote: > On 25 Dec 2005 12:24:38 +0100, Peter Simons <simons(a)cryp.to> wrote: > >>Paul Moore writes: >> >> > It would be interesting to see standalone code for wcIOB >> > (where you're allowed to assume that any helpers you >> > need, like your block IO library, are available from the >> > standard library). This would help in comparing the >> > "obviousness" of the two approaches. >> >>A simple version of the program -- which doesn't need any >>3rd party modules to compile -- is attached below. My guess >>is that this approach to I/O is quite obvious, too, if you >>have experience with system programming in C. > > > Hmm, I can't honestly believe that you feel that your code is as > "obvious" as the original. I'm not unfamiliar with monads and state, > and I know C well, but it took me a significant amount of time to > decipher your code (even knowing what it was intended to do), whereas > I knew what the original was doing instantly. > > >>IMHO, the main point of the example in the article is that >> >> wc :: String -> (Int, Int, Int) >> wc file = ( length (lines file) >> , length (words file) >> , length file >> ) >> >>is a crapy word-counting algorithm. > > > Dunno. It's certainly not a bad (executable!) definition of the > problem. My point is that Haskell allows me to write *very* clear > "executable pseudocode", but that code is not a good starting point > for writing production-quality code. this program counts two times length of lists of strings formed by lines, and words and third time counts again length of file. This is not just word counting program, it creates two additional lists, which are not used anywhere but to count :) While it is certainly expressive, in terms of programing is pointless. No one would write such a code for word counting. Here is what I would write in Haskell, same logic as in C++ (i don;t know standard lib ): module Main where import IO import Char main = do s <- hGetContents stdin putStrLn $ show $ wc s wc :: String -> (Int , Int , Int) wc strs = wc' strs (0,0,0) where wc' [] res = res wc' (s:str) (lns, wrds, lngth ) | s == '\n' = wc' str (lns+1,wrds, lngth+1) | isAlpha s = wc'' str (lns, wrds+1,lngth+1) | otherwise = wc' str (lns,wrds, lngth+1) wc'' [] res = res wc'' (s:str) (lns,wrds,lngth) = if isAlphaNum s then wc'' str (lns,wrds,lngth+1) else wc' str (lns,wrds, lngth+1) Greetings, Bane.

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Functions with side-effects?
by Daniel Carrera 26 Dec '05

26 Dec '05

Hi all, I'm a Haskell newbie and I don't really understand how Haskell deals with functions that really must have side-effects. Like a rand() function or getLine(). I know this has something to do with monads, but I don't really understand monads yet. Is there someone who might explain this in newbie terms? I don't need to understand the whole thing, I don't need a rand() function right this minute. I just want to understand how Haskell separates purely functional code from non-functional code (I understand that a rand() function is inevitably not functional code, right?) Cheers, Daniel. -- /\/`) http://oooauthors.org /\/_/ http://opendocumentfellowship.org /\/_/ \/_/ I am not over-weight, I am under-tall. /

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