[Haskell-cafe] #haskell irc channel reaches 400 users
A small announcement :) 5 1/2 years after its inception, under the guiding hand of Shae Erisson (aka shapr), the #haskell IRC channel[1] on freenode has finally reached 400 users! To chart the growth, we can note that the channel was founded in late 2001, and had slow growth till 2006, reaching 200 users in January of that year. Since then growth in the user base has been far more rapid, reaching 300 users in Dec 2006, and 400 users now, in August 2007. This puts the channel at around the 13th largest community of the 5500 freenode channels. For comparision, a sample of the state of the other language communities: #php 485 #perl472 ##c++457 ##c 445 #python 430 #ruby-lang 420 #haskell 411 #lisp246 ##java 236 ##javascript 226 #perl6 144 #scheme 139 #erlang 118 #lua 105 #ocaml58 You can see the growth of the channel over here: http://www.cse.unsw.edu.au/~dons/irc If you've not dropped by the channel yet, feel free to come and chat, and toss around some lambdas! :) Cheers, Don 1. http://www.haskell.org/haskellwiki/IRC_channel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How can I pass IOUArrays to FFI functions?
ryani.spam: Your code is broken in a most evil and insidious way. Interesting. This is for a toy project, so I'm not too worried, but lets say I wanted to do this correctly and I was set on using IOUArray for some reason. (The Haskell wiki claims that StorableArray is slower; is that actually the case?) Which of the following fixes would work now? Which has the lowest probability of not working in the future? 1) Declare f to take Addr# and don't construct a Ptr Word32 I suspect this would be enough unless the GC changed to some sort of continous GC which can happen even without an allocation 2) Declare f to take MutableByteArray# Is this good enough to make the collector happy? 3) Something else I haven't thought of? If there was no other option, and StorableArray wasn't slower, and I was working on a real project, I'd probably wrap my own around ForeignPtr like Data.ByteString. Yeah, we have ForeignPtr arrays and Foreign.Array /exactly/ for calling to C safely. I don't know why people suggest all these other dodgy solutions, when there's one that's guaranteed by the FFI spec to work. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] GHC optimisations
phil:
On Mon, Aug 20, 2007 at 09:57:38PM +0100, Simon Peyton-Jones wrote:
GHC does some constant folding, but little by way of strength
reduction, or using shifts instead of multiplication. It's pretty
easy to add more: it's all done in a single module. Look at
primOpRules in the module PrelRules.
Patches welcome! But please also supply test-suite tests that check
the correctness of the rules.
Sucking another example out of comp.lang.functional:
This:
import System
f :: Int - Int - Int
f s n = if n 0 then f (s+n) (n-1) else s
main = do
[n] - getArgs
putStrLn $ show $ f 0 (read n)
is 3-4x slower than this:
#include stdio.h
#include stdlib.h
#include assert.h
int f(int s, int n) {
return n 0 ? f(s+n, n-1) : s;
}
int main(int argc, char *argv[]) {
assert(argc == 2);
printf(%d\n, f(0, strtol(argv[1],0,0)));
}
The generated assembler suggests (if I've read it correctly) that gcc
is spotting that it can replace the tail call with a jump in the C
version, but for some reason it can't spot it for the Haskell version
when compiling with -fvia-C (and neither does ghc itself using
-fasm). So the haskell version ends up pushing and popping values on
and off the stack for every call to f, which is a bit sad.
That doesn't sound quite right. The C version should get a tail call ,
with gcc -O2, the Haskell version should be a tail call anyway.
Let's see:
C
$ gcc -O t.c -o t
$ time ./t 10
zsh: segmentation fault (core dumped) ./t 10
./t 10 0.02s user 0.22s system 5% cpu 4.640 total
Turning on -O2
$ time ./t 10
-243309312
./t 10 1.89s user 0.00s system 97% cpu 1.940 total
And GHC:
$ ghc -O2 A.hs -o A
$ time ./A 10
-243309312
./A 10 3.21s user 0.01s system 97% cpu 3.289 total
So, what, 1.6x slower than gcc -O2
Seems ok without any tuning.
-- Don
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Re: [Haskell-cafe] Parsing binary data.
dot: On Sun, 19 Aug 2007, Peter Cai wrote: My duty is writing a network server which talks to another server through a binary based private protocol. Haskell needs something like Erlang's bit syntax. http://erlang.org/doc/reference_manual/expressions.html#6.16 http://erlang.org/doc/programming_examples/bit_syntax.html#4 The IP header example in the latter is a brilliant real-world example. It has recently been upgraded to support arbitrary bit streams. See http://www.it.uu.se/research/group/hipe/papers/padl07.pdf Yes, we've looked at this in the context of Data.Binary. Rather than extending the core syntax, on option is to use Template Haskell, http://hackage.haskell.org/cgi-bin/hackage-scripts/package/BitSyntax-0.3 Another is to just use monad and pattern guards, which give quite reasonable syntax. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Norvig's Sudoku Solver in Haskell
chaddai.fouche: For the translation of the above OCaml code, there is not much to do, in fact it is mostly functional, and so easily translated in Haskell code, note that I add a code to handle input of the form 4.8.5.3..7..2.6.8.4..1...6.3.7.5..2.1.4.., to resolve it and print a solution : Spencer Janssen also wrote a rather elegant translation, which you can find on hpaste.org import Data.List import Data.Ord n = 3 :: Int invalid (i, j) (i', j') = i == i' || j == j' || i `div` n == i' `div` n j `div` n == j' `div` n select p n p' ns | invalid p p' = filter (/= n) ns | otherwise= ns add p n sols = sortBy (comparing (length . snd)) $ map f sols where f (p', ns) = (p', select p n p' ns) search [] = [[]] search ((p, ns):sols) = [(p, n):ss | n - ns, ss - search $ add p n sols] You can see the development here, http://hpaste.org/2348 -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hawiki articles
lemming:
On Mon, 3 Sep 2007, Derek Elkins wrote:
On Mon, 2007-09-03 at 14:57 +0200, Henning Thielemann wrote:
In the current Haskell Wiki (haskell.org/haskellwiki) I found references
to articles of the old Hawiki (haskell.org/hawiki), like OnceAndOnlyOnce
and SeparationOfConcerns. Are the files still available somewhere?
HaWiki was taken down for the not unreasonable reason that, since it is
no longer being updated, there is a decent chunk of out-dated and thus
misleading information on it. Unfortunately there is a ridiculously
large amount extremely good information on it that never got ported and
frankly never is going to be ported (for good and bad reasons).
... and there was unfortunately no support in porting the stuff. I guess
some simple program (perl -p -e 's/{{{/hask/g' :-) could have simplified
a lot. Its however more difficult for me to do this via the web interface,
than for the people who have access to the bare files.
The problem was the licensing. Only pages whose authors were known, and
who gave permission to license the work freely, were ported. And only
some of those pages actually got moved.
Clearly making HaWiki live again would be a bad idea; haskellwiki is
being used now for a reason. However, having it up in stasis as it
was with some prominent indication on each page that it is out of
date/no longer updated/obsolete or whichever term suits you fancy should
effectively solve the problem. It should be possible and probably even
desirable to distill the pages into static HTML documents so that
MoinMoin would not be needed, if that is an issue.
Since it is easier to port Wiki code than HTML code, I propose copying all
hawiki pages as they are to haskellwiki in a directory like DEPRECATED.
From there people can go on moving pages into the space of current pages.
This would also allow to track where pages came from Hawiki.
We can't do that, due to the licensing issues. Details here:
http://haskell.org/haskellwiki/HaWiki_migration
-- Don
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Re: [Haskell-cafe] Serial Communications in Haskell
mmitar: Hi! Of course, I don't know how to call Windows API functions from Haskell, and I have no idea how to hook things to the IO library so that I can use a Handle for a serial port. I'm looking for some advice on how to proceed. You can check how I did this in my Lego Mindstorms NXT interface, pre-beta version: http://www.forzanka.si/files/NXT.tgz It is for UNIX (POSIX?) systems but I had similar problems so I had to use FFI (foreign function interface) to setup a link. You will probably just have to replace that with Windows API calls. I hope. That's really cool! I hope you can upload this to hackage soon. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANNOUNCE: xmonad 0.3
The xmonad dev team is pleased to announce the 0.3 release of xmonad. xmonad: a tiling window manager http://xmonad.org About: xmonad is a tiling window manager for X. Windows are arranged automatically to tile the screen without gaps or overlap, maximising screen use. All features of the window manager are accessible from the keyboard: a mouse is strictly optional. xmonad is written and extensible in Haskell. Custom layout algorithms, and other extensions, may be written by the user in config files. Layouts are applied dynamically, and different layouts may be used on each workspace. Xinerama is fully supported, allowing windows to be tiled on several screens. Features: * Very stable, fast, small and simple. * Automatic window tiling and management * First class keyboard support: a mouse is unnecessary * Full support for tiling windows on multi-head displays * Full support for floating windows * XRandR support to rotate, add or remove monitors * Per-workspace layout algorithms * Per-screens custom status bars * Easy, powerful customisation and reconfiguration * Large extension library * Extensive documentation and support for hacking Since xmonad 0.2, the following notable features and bug fixes have appeared: New features: * floating layer support: transients windows are not tiled by default, and windows may be dragged to and from a traditional floating layer (which allows mouse-resizing, and overlapping windows). * improved Xinerama support: workspace switching reuses multiple displays more effectively. * huge new extension library. Over 50 extensions to xmonad have been contributed by users, and are available all in a standard library, with documentation. More information, screenshots, documentation and community resources are available from: http://xmonad.org Xmonad is available from hackage, and via darcs. Happy hacking! The Xmonad Team: Spencer Janssen Don Stewart Jason Creighton Xmonad has also received contributions from at least: Alec Berryman Andrea Rossato Chris Mears Daniel Wagner David Glasser David Lazar David Roundy Hans Philipp Annen Joachim Fasting Joe Thornber Kai Grossjohann Karsten Schoelzel Michael Sloan Miikka Koskinen Neil Mitchell Nelson Elhage Nick Burlett Peter De Wachter Robert Marlow Sam Hughes Shachaf Ben-Kiki Shae Erisson Simon Peyton Jones Stefan O'Rear as well as many others on the IRC channel and mailing list. Thanks to everyone! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Efficient way to edit a file
briqueabraque: Hi, I need to edit big text files (5 to 500 Mb). But I just need to change one or two small lines, and save it. What is the best way to do that in Haskell, without creating copies of the whole files? I'd think maybe a lazy bytestring would be ok. Something like: import Data.ByteString.Lazy.Char8 B.putStr . B.unlines . B.map edit . B.lines = B.getContents in the darcs version of Data.ByteString, here, http://www.cse.unsw.edu.au/~dons/fps.html Let me know how you go, it would make a good benchmark. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Efficient way to edit a file
dons: briqueabraque: Hi, I need to edit big text files (5 to 500 Mb). But I just need to change one or two small lines, and save it. What is the best way to do that in Haskell, without creating copies of the whole files? I'd think maybe a lazy bytestring would be ok. Something like: import Data.ByteString.Lazy.Char8 B.putStr . B.unlines . B.map edit . B.lines = B.getContents in the darcs version of Data.ByteString, here, http://www.cse.unsw.edu.au/~dons/fps.html Let me know how you go, it would make a good benchmark. Oh, of course, if you actually don't want to copy the file, you'll need to strictly read the input file, in order to write over it safely. - Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Efficient way to edit a file
dons: briqueabraque: Hi, I need to edit big text files (5 to 500 Mb). But I just need to change one or two small lines, and save it. What is the best way to do that in Haskell, without creating copies of the whole files? Thinking further, since you want to avoid copying on the disk, you need to be able to keep the edited version in memory. So the strict bytestring would be best, for example: import System.Environment import qualified Data.ByteString.Char8 as B main = do [f] - getArgs B.writeFile f . B.unlines . map edit . B.lines = B.readFile f where edit :: B.ByteString - B.ByteString edit s | (B.pack Instances) `B.isPrefixOf` s = B.pack EDIT | otherwise = s Edits a 100M file in $ ghc -O -funbox-strict-fields A.hs -package fps $ time ./a.out /home/dons/data/100M ./a.out /home/dons/data/100M 1.54s user 0.76s system 13% cpu 17.371 total You could probably tune this further. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Newbie request
gphilip.newsgroups:
I am trying to learn Haskell. As an exercise, I wrote a
function to create a binary tree in level-order. I am attaching
the code. I am sure there are a number of places where
the code could be improved. Could you please point these out?
There's a highly efficient example here, not exactly a beginner's
example, but perhaps useful:
http://shootout.alioth.debian.org/gp4/benchmark.php?test=binarytreeslang=ghcid=2
--
BinTree.lhs : Implementation of a binary tree. createTree
accepts a sequence and builds a binary tree in level-order.
--
module BinTree where
--
A binary tree either
1. is empty, or
2. consists of three distinct binary trees : a root node, a left
subtree, and a right subtree.
--
data Tree a = Empty | Tree {rootNode::a, left::(Tree a),
right::(Tree a)} deriving (Eq, Show)
Too many parens, perhaps? Those (Tree a)'s look unnecessary.
--
Count the number of nodes in a binary tree, using the simple
recursive definition of the count.
--
countNodes :: Tree a - Integer
countNodes Empty = 0
countNodes (Tree rootNode left right) = 1 + countNodes left
+ countNodes right
--
Insert a single element into the proper place in the tree, as
per level-order.
--
insert :: Eq a = Tree a - a - Tree a
insert tree x = if tree == Empty
then Tree x Empty Empty
else if (left tree) == Empty
then Tree (rootNode tree) (Tree x Empty
Empty) (right tree)
else if (right tree) == Empty
then Tree (rootNode tree) (left tree)
(Tree x Empty Empty)
else if countNodes (left tree) =
countNodes (right tree)
then Tree (rootNode tree)
(insert (left tree) x) (right tree)
else Tree (rootNode tree)
(left tree) (insert (right tree) x)
Logic looks too convoluted. Perhaps use guards and pattern matching:
insert Empty x = Tree x Empty Empty
insert (Tree root Empty r) x = Tree root (Tree x Empty Empty) r
insert (Tree root l Empty) x = Tree root l (Tree x Empty Empty)
insert (Tree root l r) x
| countNodes l = countNodes r = Tree root (insert l x) r
| otherwise= Tree root l (insert r x)
Seems inefficent to recalculate countNodes each time though.
--
Use insert to create a tree from a sequence.
--
createTree :: Eq a = [a] - Tree a
createTree [] = Empty
createTree (x:xs) = foldl insert (insert Empty x) xs
Pretty good.
Cheers,
Don
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Re: [Haskell-cafe] HCAR
stefan: Tashdid, does anyone know what happened to HCAR? or HWN? I guess the May ;) 2006 edition of HCAR will appear soon. I'm not sure about what happened to HWN the last couple of weeks, though, but I think that Donald is just quite busy these days. Yep, that's the case. Expect an issue tomorrow though. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] what do you think of haskell ? (yes, it's a bit general ...:)
noteed: i want to process 4k pictures (and not just one pixel fater one)... for example. if there is a better solution than array, i'm eager to know it! Try Data.ByteString. 4G can be feasible :) -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Binary IO
m4d.skills: Greetings, I am considering writing -in Haskell of course - a small program to translate binary files to human readable text. The trouble is that I can find no easily digestible tutorial style info on how to do binary IO in Haskell. I have read about some of the libraries that people have created to do binary IO, but the documentation wasn't sufficient to get me started (perhaps because I'm a bit dense, and also relatively new to Haskell). What I would like is to see a short example showing some code that reads from a binary file. I would also like to know what the most widely used library for doing binary IO in Haskell is. I would greatly appreciate it if someone could post a small example or two illustrating how to do binary IO in Haskell using the most widely used binary IO lib (if there is such a thing). Failing that, I would appreciate a link to some Haskell code that does binary IO that I could study. Lastly, if there is a good tutorial on doing binary IO in Haskell then I would appreciate a link to that as well. Thanks in advance, Jeff Lasslett Here's a howto: http://www.haskell.org/hawiki/BinaryIo Look for the instance Binary code. That's where you set up your binary parsers for each Haskell type. lso, these day,s you can do a fair bit of binary hacking with Data.ByteString, without the Binary class layer over the top. Hope that helps. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A question about stack overflow
hankgong: Hi, all I'm just a newbie for Haskell and functional programming world. The idea I currently read is quite different and interesting. I have one general question about the recursively looping style. For example: myMax [ ] = error empty list myMax [x] = x myMax [x:xs] = if x= (myMax xs) then x else (myMax xs) I just list out this kind of very simple program. However, if the list size if a big number such as 1000, the Does it mean that the functional programming is lacking of scalability? I do know that we can manually change the stack size for it. But that's not a good solution according to my opinion. No, your code is just really inefficient (think about how many times its traversing the list). Try rewriting it as a simple accumulating pass over the list, carrying the largest element you've seen so far. mymax [] = undefined mymax (x:xs) = f x xs where f x [] = x f x (y:ys) | y x = f y ys | otherwise = f x ys However, 'f' is just a foldl inlined: import Data.List mymax [] = undefined mymax (x:xs) = foldl' (\a b - if b a then b else a) x xs And the lambda is just 'max': import Data.List mymax [] = undefined mymax (x:xs) = foldl' max x xs Now, we already check for the empty list, so avoid checking again: import Data.List mymax [] = undefined mymax xs = foldl1' max xs And that'll do. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] New Benchmark Under Review: Magic Squares
Perhaps you could post a new entry page on our shootout wiki?
http://www.haskell.org/hawiki/ShootoutEntry
This makes it easier for people to keep contributing.
Cheers,
Don
daniel.is.fischer:
Am Sonntag, 2. Juli 2006 01:58 schrieb Brent Fulgham:
We recently began considering another benchmark for the shootout,
namely a Magic Square via best-first search. This is fairly
inefficient, and we may need to shift to another approach due to the
extremely large times required to find a solution for larger squares.
A slightly less naive approach to determining the possible moves dramatically
reduces the effort, while Josh Goldfoot's code did not finish within 4 1/2
hours on my machine, a simple modification (see below) reduced runtime for
N = 5 to 4.3 s, for N = 6 to 86.5 s.
Unfortunately, the squares are now delivered in a different order, so my
programme would probably be rejected :-(
I thought the Haskell community might be interested in the
performance we have measured so far (see http://
shootout.alioth.debian.org/sandbox/fulldata.php?
test=magicsquaresp1=java-0p2=javaclient-0p3=ghc-0p4=psyco-0
Interestingly, Java actually beats the tar out of GHC and Python for
N=5x5 (and I assume higher, though this already takes on the order of
2 hours to solve on the benchmark machine). Memory use in GHC stays
nice and low, but the time to find the result rapidly grows.
I was hoping for an order of magnitude increase with each increase in
N, but discovered that it is more like an exponential...
Thanks,
-Brent
Modified code, still best-first search:
import Data.Array.Unboxed
import Data.List
import System.Environment (getArgs)
main :: IO ()
main = getArgs = return . read . head = msquare
msquare :: Int - IO ()
msquare n = let mn = (n*(n*n+1)) `quot` 2
grd = listArray ((1,1),(n,n)) (repeat 0)
unus = [1 .. n*n]
ff = findFewestMoves n mn grd unus
ini = Square grd unus ff (2*n*n)
allSquares = bestFirst (successorNodes n mn) [ini]
in putStrLn $ showGrid n . grid $ head allSquares
data Square = Square { grid :: UArray (Int,Int) Int
, unused :: [Int]
, ffm :: ([Int], Int, Int, Int)
, priority :: !Int
} deriving Eq
instance Ord Square where
compare (Square g1 _ _ p1) (Square g2 _ _ p2)
= case compare p1 p2 of
EQ - compare g1 g2
ot - ot
showMat :: [[Int]] - ShowS
showMat lns = foldr1 ((.) . (. showChar '\n')) $ showLns
where
showLns = map (foldr1 ((.) . (. showChar ' ')) . map shows)
lns
showGrid :: Int - UArray (Int,Int) Int - String
showGrid n g = showMat [[g ! (r,c) | c - [1 .. n]] | r - [1 .. n]]
bestFirst :: (Square - [Square]) - [Square] - [Square]
bestFirst _ [] = []
bestFirst successors (front:queue)
| priority front == 0 = front : bestFirst successors queue
| otherwise = bestFirst successors $ foldr insert queue (successors front)
successorNodes n mn sq
= map (place sq n mn (r,c)) possibilities
where
(possibilities,_,r,c) = ffm sq
place :: Square - Int - Int - (Int,Int) - Int - Square
place (Square grd unus _ _) n mn (r,c) k
= Square grd' uns moveChoices p
where
grd' = grd//[((r,c),k)]
moveChoices@(_,len,_,_) = findFewestMoves n mn grd' uns
uns = delete k unus
p = length uns + len
findFewestMoves n mn grid unus
| null unus = ([],0,0,0)
| otherwise = (movelist, length movelist, mr, mc)
where
openSquares = [(r,c) | r - [1 .. n], c - [1 .. n], grid ! (r,c) ==
0]
pm = possibleMoves n mn grid unus
openMap = map (\(x,y) - (pm x y,x,y)) openSquares
mycompare (a,_,_) (b,_,_) = compare (length a) (length b)
(movelist,mr,mc) = minimumBy mycompare openMap
possibleMoves n mn grid unus r c
| grid ! (r,c) /= 0 = []
| otherwise = intersect [mi .. ma] unus -- this is the difference that
-- does it: better bounds
where
cellGroups
| r == c r + c == n + 1 = [d1, d2, theRow, theCol]
| r == c = [d1, theRow, theCol]
| r + c == n + 1 = [d2, theRow, theCol]
| otherwise = [theRow, theCol]
d1 = diag1 grid n
d2 = diag2 grid n
theRow = gridRow grid n r
theCol = gridCol grid n c
lows = scanl (+) 0 unus
higs = scanl (+) 0 $ reverse unus
rge cg = let k = count0s cg - 1
lft = mn - sum cg
in (lft - (higs!!k),lft - (lows!!k))
(mi,ma) = foldr1 mima $ map rge cellGroups
mima (a,b) (c,d) = (max a c, min b d)
gridRow grid n r = [grid ! (r,i) | i - [1 .. n]]
gridCol grid n c = [grid ! (i,c) | i - [1 .. n]]
diag1 grid n = [grid ! (i,i) |
Re: [Haskell-cafe] Clever generic ByteString hack?
duncan.coutts: On Wed, 2006-07-05 at 05:58 -0500, John Goerzen wrote: Hi, In MissingH, I have a bunch of little functions that operate on lists. Some, like uniq (which eliminates duplicate elements in a list), operate on (Eq a = [a]) lists. Others, like strip (which eliminates whitespace at the start and end), operate on Strings only. Most functions of both types would be useful on ByteStrings and lazy ByteStrings. Most of these functions are written in terms of Data.List functions or list primitives that have equivolents in Data.ByteString. So, my question is: is there a clever hack available to me so that I could have 1 version of each function, and have it work on all three different types of input? I'd rather avoid having 3 versions, that are exactly the same except for imports. People sometimes talk about doing a type class to cover string like modules. What functions are you thinking of btw? We may want to include them in the ByteString modules anyway (possibly directly rather than in terms of other functions, to take advantage of tricks with the representation). Spencer Janssen is actually working on such a class (String) to deal with this, initially to support [a] and Word8 and Unicode bytestrings, as part of his Summer of Code project. Note also that we have the Foldable and Monoid classes, which support parts of a String interface. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re[2]: Haskell performance in heavy numerical computations
bulat.ziganshin: Hello Simon, Monday, July 10, 2006, 1:12:13 PM, you wrote: numerical speed is poor in ghc 6.4, according to my tests. it's 10-20 times worse than of gcc. afair, the mandelbrot benchmark of Great Language Shootout proves this - despite all optimization attempts, GHC entry is still 5-10 times slower than gcc/ocaml/clean ones We average 1.3x slower than C in the shootout. Thanks to Don Stewart for the following stats... as i once wrote, most of shootout benchmarks depends on the libs. for example, multi-threading benchmark is much faster on GHC than on GCC because former has user-level threads support pre-included and for later the external libs should be used (testing policy prohibits using of additional libs) The numerical floating-point-intensive benchmarks: mandelbrot 2.7x C(Clean 1.7x, OCaml 2.4x, C++ 2.6x) n-body 2.1x C(Clean 0.9x, OCaml 1.3x, C++ 1.4x) that is the benchmarks that i had in mind http://shootout.alioth.debian.org/gp4/benchmark.php?test=mandelbrotlang=all the same benchmark with N=600 and Sempron processor: http://shootout.alioth.debian.org/debian/benchmark.php?test=mandelbrotlang=all here GHC is 10x slower than GCC and more than 5 times compared to Clean and Ocaml. i think that this is the real computing speed difference while with N=2000 C/Ocaml/Clean programs was really limited by memory speed. Ah! In this case, on the debian, the benchmark has been compiled _without_ -fexcess-precision, that's what's causing the big slow down. We had to turn it on, on the gp4, but it seems the flag wasn't propagated to the debian/sempron builds for some reason. Looks like the ghc/mandelbrot benchmarks just needs to be rerun with -fexcess-precision in this case. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Defining show for a function type.
johan.gronqvist: I am a haskell-beginner and I wish to write a Forth-like interpreter. (Only for practice, no usefulness.) I would like use a list (as stack) that can contain several kinds of values. data Element = Int Int | Float Float | Func : Machine - Machine | ... Now I would like to have this type be an instance of the class Show, so that I can see what the stack contains in ghci. Here's an interesting, I think, show for functions that we use in lambdabot's Haskell interpreter environment: module ShowQ where import Language.Haskell.TH import System.IO.Unsafe import Data.Dynamic instance (Typeable a, Typeable b) = Show (a - b) where show e = '' : (show . typeOf) e ++ instance Ppr a = Show (Q a) where show e = unsafePerformIO $ runQ e = return . pprint which generates results like: dons:: toUpper lambdabot:: Char - Char dons:: \x - x+1::Int lambdabot:: Int - Int dons:: map lambdabot:: Add a type signature Note that also the standard libraries come with Text.Show.Functions -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Why is there no splitBy in the list module?
simonmarhaskell: I guess the problem with the splitWith thing is that it's a slippery path that leads right up to full-on parsers. Exactly, and this is why we didn't reach a concensus last time. Would someone like to make a concrete proposal (with code!) for 2-3 functions we could reasonably add to Data.List? No parsers! I vote for this, currently implemented in Data.ByteString: -- | split on characters split:: Char - String - [String] -- | split on predicate * splitBy :: (Char - Bool) - String - [String] and -- | split on a string tokens :: String - String - [String] Question over whether it should be: splitBy (=='a') aabbaca == [,,bb,c,] or splitBy (=='a') aabbaca == [bb,c] I argue the second form is what people usually want. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Type-Level Naturals Like Prolog?
jawarren: Thank you to everyone for the responses. I guess what I should have clarified is that I know how Peano numbers are *normally* encoded in the type language (I am very familiar with the HList library), but I would like to know why the type language appears to require data structures to do so while [Idealised] Prolog has none. Niklas Broberg helpfully corrected my Prolog: That is not a valid encoding of peano numbers in prolog, so I think that's where your problems stem from. :-) % defining natural numbers natural(zero). natural(s(X)) :- natural(X). % translate to integers toInt(zero, 0). toInt(s(X), N) :- toInt(X, Y), N is Y + 1. Thank you. I can now more precisely state that what I'm trying to figure out is: what is 's', a predicate or a data structure? If it's a predicate, where are its instances? If not, what is the difference between the type language and Prolog such that the type language requires data structures? It shouldn't actually require new data structures, just new types (with no inhabiting values). such as, data Zero data Succ a So there are no values of this type (other than bottom). That is, you can just see 'data' here as a way of producing new types to play with in the type checker. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] irc channel stats
While we're in a period of reflection, pondering the history of haskell, I've prepared some graphs of activity on the IRC channel. Summary: its growing much as the mailing lists are, with more than 5000 users over the past 5 years. Full details here, http://www.cse.unsw.edu.au/~dons/irc/ Another interesting note is that lambdabot's get more and more verbose over time, as it provides further features. It's turning into an ide of sorts. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why Haskell?
marco-oweber: 2) Recompiling binaries (necessary in order to link in foreign object code into GHCi) is slow using GHC. Moreover I have to restart GHCi if I want to reload a changed DLL (unless there is a way to unload a DLL in GHCi). It also requires jumping around between several console windows to get the job done. (I'm not using an IDE does one exist?) There are several. (I know of one using visual studio and eclipsefp).. It should|nt be a problem to find them.. But I still prefer vim :) Concerning switching between several console windows... Perhaps try something like mrxvt which has several tabs to run more than one shell. You can then use key combinations to switch.. (I haven't used mrxvt on cygwin yet but I've read that it runs there) Marc Or use a more efficient window manager, i.e. ion or wmii let you navigate entirely from the keyboard, as if you were inside an editor. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Universal machines in Haskell
Now the ICFP contest is now over, several of the entrants have been interested in seeing if we can't write a decent universal machine (the 'hardware' of this year's contest), in Haskell. This is an interesting problem for Haskell, since the spec encourages the use of mutable variables and mutable arrays, as well as a bit of IO. Getting C-like performance from Haskell, for this problem, is a bit of a challenge, and highlights some corners in our libraries. So, we're collecting any UMs in Haskell, with the goal to breed some good solutions, and learn a bit about writing low level machines in Haskell. The website is here, http://www.cse.unsw.edu.au/~dons/um.html If you wrote a Haskell UM, or a faster C UM, free to submit it! Just mail me a darcs repo url, a source module url, or the source itself. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Monad Imparative Usage Example
kaveh.shahbazian:
Haskell is the most powerfull and interesting thing I'v ever
encountered in IT world. But with an imparative background and lack of
understanding (because of any thing include that maybe I am not that
smart) has brought me problems. I know this is an old issue. But
please help it.
Question : Could anyone show me a sample of using a monad as a
statefull variable?
For example see this code in C# :
//
public class Test
{
int var;
static void Fun1() { var = 0; Console.Write(var); }
static void Fun2() { var = var + 4; Console.Write(var); }
static void Main() { Fun1(); Fun2(); var = 10; Console.Write(var
= + var.ToString()); }
}
//
I want to see this code in haskell.
Ok, here you go. A state monad on top of IO, storing just your variable. Its
even 'initialised' to undefined at the start :)
import Control.Monad.State
main = execStateT (do f1; f2; put 10) undefined
f1 = do
let v = 0
put v
liftIO $ print v
f2 = do
v - get
let v' = v + 4
put v'
liftIO $ print v'
Running:
$ runhaskell A.hs
0
4
10
Of course, there are many other ways to do this, too.
-- Don
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Re: [Haskell-cafe] Monad Imparative Usage Example
kaveh.shahbazian: Monad Imparative Usage Example Thanks for your replies. I have not haskell on this computer and I will try this solutions tonight. I must notice that IO computations is not the point here. My target is to have this code for mutable variable 'var'. Still not entirely clear what your goal in the translation is. The most Haskell way would be to emulate a mutable variable with a state monad, but you seem to want an actual named mutable variable? So here's an example, like Seb's, where we create a mutable variable (in the IO monad) and mutate it all over the place. This uses similar scoping to your original code. For fun we use MVars instead of IORefs. import Control.Concurrent.MVar main = do var - newEmptyMVar let write = withMVar var print f1 = do putMVar var 0 write f2 = do modifyMVar_ var (return.(+4)) write f1 f2 swapMVar var 10 write Produces: $ runhaskell A.hs 0 4 10 Of course, if you're learning Haskell, you should probably try to /avoid/ mutable variables for a while. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] fast image processing in haskell?
bulat.ziganshin: Hello Chris, Saturday, August 5, 2006, 3:47:19 AM, you wrote: in Haskell before blitting the data (whilst also retaining some semblance of functional programming...) the best way to optimize Haskell program (with current technologies) is to rewrite it in strict imperative manner: Strict, very often, since we get unboxed types out of ghc. Imperative, not always (and will be less so with Data.ByteString -- since we don't need to drop into IO to get peek/poke). -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A problem with Show
zdenes: Hello, I made a simple datatype called Pair and I'd like to make it an instance of Show class. But when I try to do that I run into troubles: data Pair a b = Pair a b instance Show a b = Show (Pair a b) where show (Pair a b) = show a ++ _ ++ show b In Hugs I get this error: Haskell does not support multiple parameter classes When I run it in ghci I get a kind error Show is applied to too many type arguments in the instance declaration for Show (Pair a b) Am I jsut using wrong syntax or is it not possible to do? Missing some parens and a comma: data Pair a b = Pair a b instance (Show a, Show b) = Show (Pair a b) where show (Pair a b) = show a ++ _ ++ show b $ hugs A.hs Main show (Pair 'x' ()) 'x'_() Alternately: data Pair a b = Pair a b deriving Show -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Need a good book on Haskell
Also, we have a large library of research papers here: http://www.haskell.org/haskellwiki/Research_papers mvanier: A good follow-up is The Haskell School of Expression by Paul Hudak. Eventually, though, you're going to have to start reading research papers, which is where most of the cutting-edge stuff is. Phil Wadler's papers (available from his web site, just google it) are a good place to start, as are Simon Peyton-Jones' papers. Mike Johan Tibell wrote: I've read Haskell: The Craft of Functional Programming on a course on functional programming at Chalmers (I also took the advanced course) and now I'm looking for some more reading material. Are there any other good Haskell books? Is there a Pick Axe, Camel or Dragon Book for Haskell? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How can we detect and fix memory leak due to lazyness?
kyagrd:
On 8/7/06, Spencer Janssen [EMAIL PROTECTED] wrote:
Forcing evaluation using (==) is a bit of a hack. Luckily, we have a
better function to force evaluation: seq (which has type a - b - b).
seq x y evaluates x to weak head normal form before returning
y.
Let's try another feature of Haskell to force evaluation: strict data
fields. A ! in front of a field in a data declaration signifies
strictness. In the example below, whenever we construct a value with
TT, the second argument is evaluated.
\begin{code}
data TT a b = TT a !b
\end{code}
Perhaps your instances will work correctly with this data declaration?
Surely I've tried that.
Unfortunately seq and the strict data declaration is not helpful in general.
They are only helpful on base values such as Int or Bool.
What they do is just making sure that it is not a thunk.
That is if it was a list it would just evaluate to see the cons cell
but no further.
Someone wrote a deepSeq module for forcing deep evaluation, which is
like doing self equality strictness hack like x==x.
However, we should be able to locate what is the source of the memory
leak to apply such strictness tricks.
The key is to profile. Compile the code, with optimisations on, with
-prof -auto-all, then run the resulting program with +RTS -p -RTS.
This will identify costly and timely functions.
You can then refine the search further with {-# SCC line1 #-} pragmas,
next to expressoins you want to check the cost of.
-- Don
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Re: [Haskell-cafe] Re:Re: Why Haskell
hthiel.char: And just from a PR point of view, Haskell does project a cutting edge image. Anyway... Maybe this is our brand! Be on the cutting edge of programming language development -- use Haskell Bored of your language? Try something new. Try Haskell! Same old syntax? Same old bugs? Think different. Think Haskell -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] beginner's haskell question
jens-theisen-tmp01: Hello, as a haskell newbie I'm wondering about the following question. Are there options to popular haskell implementations or other means (haskell lint?) to check for incomplete patterns at compile time for some? I can't see a reason why this shouldn't be possible or even a relatively simple thing to implement. Cheers, Jens You might just want to always use: -Wall -Werror to get the full range of extended warnings and checks. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why Not Haskell?
robdockins: On Aug 8, 2006, at 5:36 PM, Albert Lai wrote: Brian Hulley [EMAIL PROTECTED] writes: Also, the bottom line imho is that Haskell is a difficult language to understand, and this is compounded by the apparent cleverness of unreadable code like: c = (.) . (.) when a normal person would just write: c f g a b = f (g a b) All mainstream languages are also difficult to understand, with similarly clever, unreadable code. Let's have a fun quiz! Guess the mainstream languages in question: [snip] 2. What language allows you to test primality in constant runtime? That is, move all the work to compile time, using its polymorphism. GHC-Haskell (with enough extensions enabled)? We're most of the way there already with type arithmetic. I bet putting together a nieve primality test would be pretty doable. In fact, I suspect that GHC's type-checker is turing-complete with MPTCs, fundeps, and undecidable instances. I've been contemplating the possibility of embedding the lambda calculus for some time (anybody done this already?) http://haskell.org/haskellwiki/Type_arithmetic#A_Really_Advanced_Example_:_Type-Level_Lambda_Calculus also http://haskell.org/haskellwiki/Type_arithmetic#An_Advanced_Example_:_Type-Level_Quicksort -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Flags
Maduser: I have started to program in Haskell. Now I want programm something like flags. It's a set of flags. It sould be possible to convert the Flag as Int/String (the bit combination). I have written this: import Data.Set as Set type Flags = Set Flag data Flag = Flag1 | Flag2 | Flag3 deriving(Eq, Ord, Enum, Show) flagToInt :: Flags - Int flagToInt flags = flag1 + flag2 + flag3 where flag1 = if member Flag1 flags then 1 else 0 flag2 = if member Flag2 flags then 2 else 0 flag3 = if member Flag3 flags then 4 else 0 but this seems to me to be inelegant. Can somebody help me making it better, please. Something like: type Flags = [Flag] data Flag = Flag1 | Flag2 | Flag3 deriving (Eq, Ord, Enum, Show) flagToInt :: Flags - Int flagToInt = sum . map ((2 ^) . fromEnum) Perhaps? -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A restricted subset of CPP included in a revision of Haskell 98
brianlsmith: Hi, I find it strange that right now almost every Haskell program directly or indirectly (through FPTOOLS) depends on CPP, yet there is no effort to replace CPP with something better or standardize its usage in Haskell. According to the Note also cpphs, http://www.cs.york.ac.uk/fp/cpphs/ -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Description of Haskell extensions used by FPTOOLS
brianlsmith: Is there any design document for the FPTOOLS libraries or some description of language features that are (allowed to be) used in them? There's a list of extensions used at the bottom of this page: http://hackage.haskell.org/trac/haskell-prime/wiki/HaskellExtensions I am going to be taking some significant time off from my normal jobs in the upcoming months. During part of that time, I would like to do some work to improve the Haskell toolchain. This involves creating or improving tools that parse and analyze Haskell code. My goal is to have these tools support enough of Haskell to be able to handle at least the most important libraries used by Haskell programmers. In particular, this includes all or most of the libraries in FPTOOLS. Plus, I want these tools to operate on Darcs as it is an obvious poster-child for Haskell. Thus, I need to support Haskell 98 plus all the extensions being used in Darcs and FPTOOLS as of approx. March, 2007 (as I intened to start working again at that time). Cool! It would be very nice if there was some document that described Haskell 98 plus all the extensions being used in Darcs and FPTOOLS as of March, 2007. Besides being useful to me, it would be a useful guide for potential contributors to FPTOOLS. Darcs may also use GADTs then (not in the standard libs). Better check with the darcs src. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Useful: putCharLn {inspire by the Int-[Char] thread
yumagene: On 8/19/06, Henk-Jan van Tuyl [EMAIL PROTECTED] wrote: Or you could use: putStrLn [head This and that] Gotta say I really like this ... running the head function inside of the list... Okay so I can really learn something here... what would that look like in raw monadic notation? using bind and such notation... = etc.. hey, mention was made of lists being monads.. so Perhaps: putStrLn . return . head $ This and that -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Re[2]: class [] proposal Re: [Haskell-cafe] One thought: Num to 0as ? to list?
tomasz.zielonka: On Wed, Aug 23, 2006 at 01:28:57PM +0100, Malcolm Wallace wrote: The lengths people will go to in making things difficult for the reader, just to save a few characters is truly amazing. Remember, the code will be read many more times than it is written. IMHO, the various proposed sugar adds nothing helpful, and just muddies understanding. Seconded. If someone just wants to type less characters, the he/she can omit most of type signatures. I haven't used any IDE for Haskell (like VisualHaskell), but it would be nice if it could fill the missing type signatures automatically. In cases when monomorphism restriction kicks in, it could also present the type that would be inferred with MR turned off. I use the following script from vim to infer top level type declarations for me. I've found it particularly useful for understanding others' code: #!/bin/sh # input is a top level .hs decls FILE=$* DECL=`cat` ID=`echo $DECL | sed 's/^\([^ ]*\).*/\1/'` echo :t $ID | ghci -v0 -cpp -fglasgow-exts -w $FILE echo $DECL Saved to 'typeOf', you can bind it from vim with: :map ty :.!typeOf %^M in your .vimrc So, from vim the following source: f (x,y,z) a b = y + a + b hit, 'ty' and its replaced with: f :: forall b c a. (Num b) = (a, b, c) - b - b - b f (x,y,z) a b = y + a + b I imagine it would be possible to bind from emacs with little effort. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] question on traversing syntax tree
xiongyf04: I am writing a compiler using Haskell. After the compiler parses program, the program is stored into an syntax tree stucture defined blew: .. data Exp = Plus Exp Term | Minus Exp Term | Term Term deriving Show data Term = Times Term Factor | Div Term Factor | Factor Factor deriving Show .. This is just part of the definition. The full tree contains much more definition than this. Now I want to adjust the syntax-tree. However, I don't need to adjust all the data types, but a small subset of the syntax tree. e.g. I might adjust the Times data like the following, but not modify the rest of the syntax tree: transformTerm (Times t f) = Times t (FactorInt 100) However, in order to apply the modification like this, I have to write a series of function to traverse the tree until I get to the Term data type. e.g. I have to define: transformExp (Plus e t) = Plus (transformExp e) (transformTerm t) transformExp (Minus e t) = Minus (transformExp e)(transformTerm t) transformTerm (Term t) = ... This is tedious and error-prone. I want to know if there some means in Haskell to write a single generic function to traverse the syntax tree and only stop on the Term data type. Can anyone tell me something about it? Thanks a lot. The Scrap Your Boilerplate series covers this, as does several other works on generics in Haskell. Here's a good place to start: http://www.cs.vu.nl/boilerplate/ also, http://www.informatik.uni-bonn.de/~loeh/SYB0.html http://www.informatik.uni-bonn.de/~loeh/SYB1.html -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Exercise in point free-style
haskell: Hello, I was just doing Exercise 7.1 of Hal Daum?'s very good Yet Another Haskell Tutorial. It consists of 5 short functions which are to be converted into point-free style (if possible). It's insightful and after some thinking I've been able to come up with solutions that make me understand things better. But I'm having problems with one of the functions: func3 f l = l ++ map f l Looks pretty clear and simple. However, I can't come up with a solution. Is it even possible to remove one of the variables, f or l? If so, how? The solution is to install lambdabot ;) Point free refactoring: lambdabot pl func3 f l = l ++ map f l func3 = ap (++) . map Find the type: lambdabot type ap (++) . map forall b. (b - b) - [b] - [b] Get some free theorems: lambdabot free f :: (b - b) - [b] - [b] f . g = h . f = map f . f g = f h . map f :) -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Exercise in point free-style
haskell: Julien Oster wrote: But I'm having problems with one of the functions: func3 f l = l ++ map f l While we're at it: The best thing I could come up for func2 f g l = filter f (map g l) is func2p f g = (filter f) . (map g) Which isn't exactly point-_free_. Is it possible to reduce that further? Similarly: lambdabot pl func2 f g l = filter f (map g l) func2 = (. map) . (.) . filter :) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why does this program eat RAM?
jeremy.shaw: At Tue, 5 Sep 2006 03:03:51 + (UTC), John Goerzen wrote: I have the below program, and I'm trying to run it on an input of about 90MB. It eats RAM like crazy, and I can't figure out why. I have not looked in detail at your code -- but it could simply be the fact that String requires gobs of memory to store a string. If you forced all 90MB into memory at once, I would expect it to take almost of gig of RAM. (Around a 10-11 fold increase in size). I suspect this line could be forcing the whole thing into memory: wordfreq = map (\x - (head x, length x)) . group . sort because sort can not return the first element until it has looked at all the elements in the list to determine which one should be first. If you fold a Data.Map or associative list over the word-list, then you could probably get the lazy behaviour you expect. A quick hack up to use Data.ByteString uses a lot less ram, though profiling still shows 95% of time spent in the building the Map. import System.Environment import Data.Char import Data.List import qualified Data.Map as Map import qualified Data.ByteString.Char8 as B import Data.ByteString (ByteString) wordfreq inp = Map.toList $ foldl' k m inp where m = Map.empty :: Map.Map ByteString Int k n w = Map.insertWith f w 1 n f _ x = let y = x + 1 in y `seq` y freqsort (w1, c1) (w2, c2) | c1 == c2 = compare w1 w2 | otherwise = compare c2 c1 showit (w, c) = B.join (B.singleton ' ') [B.pack(show c), w] main :: IO () main = do args - getArgs B.interact $ B.unlines . map showit . take (read . head $ args) . sortBy freqsort . wordfreq . B.words -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] User data type with operator contructors only
kolar: Hello all, my question probably comes from not reading manual properly. But, why is it not possible to have something like: infixr 5 : data Stack a = a : (Stack a) | :|| And if yes, how can I do that? I know that lists are a hack in Haskell, infixr 5 : data Stack a = a : (Stack a) | (:||) test = 7 : 8 : 2 : (:||) Not ideal, though, I suppose. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] how do you debug programs?
mnislaih: Hi Tamas There are several ways to debug a Haskell program. The most advanced ones are based in offline analysis of traces, I think Hat [1] is the most up-to-date tool for this. There is a Windows port of Hat at [5]. Another approach is to simply use Debug.Trace. A more powerful alternative for this approach is Hood [2]. Even if it hasn't been updated in some time, Hood works perfectly with the current ghc distribution. Even more, Hugs has it already integrated [3]. You can simply import Observe and use observations directly in your program. For instance: import Observe f' = observe f f f a b = And then in hugs the expression: f' 1 2 would output what you want. Finally, the GHCi debugger project [4] aims to bring dynamic breakpoints and intermediate values observation to GHCi in a near future. Right now the tool is only available from the site as a modified version of GHC, so unfortunately you will have to compile it yourself if you want to try it. Pepe, would you like to put up a page on the haskell.org wiki about debugging in Haskell? You could use the above mail as a start :) -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] does the compiler optimize repeated calls?
tpapp: Hi, I have a question about coding and compilers. Suppose that a function is invoked with the same parameters inside another function declaration, eg -- this example does nothing particularly meaningless g a b c = let something1 = f a b something2 = externalsomething (f a b) 42 something3 = externalsomething2 (137 * (f a b)) in ... Does it help (performancewise) to have g a b c = let resultoff = f a b something2 = externalsomething resultoff 42 something3 = externalsomething2 (137 * resultoff) in ... or does the compiler perform this optimization? More generally, if a function is invoked with the same parameters again (and it doesn't involve anything like monads), does does it makes sense (performancewise) to store the result somewhere? on the wiki, http://www.haskell.org/haskellwiki/Performance/GHC#Common_subexpressions -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Heap profiling
bitshifter:
Does anyone know if there is a way around the 20 charachter identifier
limitation when heap profiling? I have a number of identifiers that
indistinguishably break that limit.
Add custom {-# SCC mybetteridentifier #-} pragmas next to the places
with overly long names?
-- Don
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Re: [Haskell-cafe] Slow IO
daniel.is.fischer: Am Dienstag, 12. September 2006 22:26 schrieben Sie: Daniel Fischer wrote: The programme consumed more and more memory (according to top), kswapd started to have a higher CPU-percentage than my programme, programme died, system yelling 'Speicherzugriffsfehler', top displays 'kswapddefunct'. I believe that means my programme demanded more memory than I have available (only 256MB RAM + 800MB swap). Is that a segfault or what is the correct term? That is probably due to (apart from the stupidity of my IO-code) the large overhead of Haskell lists. Most certainly not. I'm pretty sure this is to a bug in your code. Something retains a data structure which is actually unneeded. Probably Apparently. And my money is on a load of lines from the file (of which I need only the first and last Char). a case of foldl where foldl' should be used or a try in Parsec code where it should be left out or a lot of updateWiths to a Map, etc. Or it could be a bad choice of data structure. I bet, it's the map you're using to represent the graph (which you don't even need to represent at all, btw). No foldl nor parsec around. I represent the graph as a UArray (Char,Char) Int (I've switched to Int for the index type, too, when tuning the code), so that shouldn't use much memory (array size is 676). The array is built via accumArray, I hope that's sufficiently efficient (though now I use unsafeAccumArrayUArray, that's faster). How could I solve the problem without representing the graph in some way? Possibly that could be done more efficiently than I do it, but I can't imagine how to do it without representing the graph in some data structure. So the chunk of the file which easily fits into my RAM in ByteString form is too large as a list of ordinary Strings. The chunk of file should never need to fit into RAM. If that's a problem, you also forgot to prime a crucial foldl. Forgive the stupid question, but where if not RAM would the chunk currently processed reside? I agree. Some problems simply require you to hold large strings in memory. And for those, [Char] conks out around 5-10M (try reversing a 10M [Char]). -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] foreach
lemmih: On 9/13/06, Tim Newsham [EMAIL PROTECTED] wrote: I was rewriting some non-haskell code in haskell and came up with this construct: foreach l f = mapM_ f l main = do args - getArgs foreach args (\arg - do foreach [1..3] (\n - do putStrLn ((show n) ++ ) ++ arg) ) ) which is reminiscent of foreach in other languages. Seems fairly useful and I was wondering how hard it would be to add some syntactic sugar to the do construct to make it a little prettier (ie. not require the parenthesis, binding and nested do, as: main = do args - getArgs foreach args arg foreach [1..3] n putStrLn ((show n) ++ ) ++ arg) would this type of transformation be possible with template haskell or does this need stronger support from the parser to pull off? How about: main = do args - getArgs flip mapM_ args $ \arg - flip mapM_ [1..3] $ \n - putStrLn $ show n ++ ) ++ arg Which is, with current Control.Monad: main = do args - getArgs forM_ args $ \arg - forM_ [1..3] $ \n - putStrLn $ show n ++ ) ++ arg I think Tim is looking for an if-then-else real syntax feel to his `foreach' though. I.e. TH or some small preprocessor. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bit string
tomasz.zielonka: On Fri, Sep 15, 2006 at 11:35:45AM +1000, Thomas Conway wrote: My question for all present is: Have I missed either a problem with using Integer, or have I overlooked a better representation? Consider also (UArray Int Bool). In GHC it has an efficient implementation. A _very_ efficient implementation: http://shootout.alioth.debian.org/gp4/benchmark.php?test=nsievelang=all :) -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Microsoftish Haskell
kaveh.shahbazian: Will Haskell become another pet for Microsoft? No. This question doesn't even make sense. are many issues around licensing GHC as you'v seen in this mailing list and I think Haskell already HAS some big problems that prevent others to use it confidently.) Haskell is in wide academic, and commerical use. Just use it, and quit with the FUD. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Microsoftish Haskell
kaveh.shahbazian: Thanks Don I sense the truth in your words. But I expect a more technical view of point. I need it for presenting to other peoples i.e. to whom wanted fom me an overview of Haskell/Using It/Licensing/Libraries/Communities to be provided (BOSS!). Ok. Overview, http://haskell.org/haskellwiki/Introduction Using it, http://haskell.org/haskellwiki/Learning_Haskell Licensing, Compilers and libraries are generally BSD licensed Libraries, http://haskell.org/ghc/docs/latest/html/libraries/ http://haskell.org/haskellwiki/Libraries_and_tools Communities, http://haskell.org/communities/ http://planet.haskell.org/ http://haskell.org/haskellwiki/Mailing_lists http://haskell.org/haskellwiki/IRC_channel All this and more at http://haskell.org -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Optimization problem
ross: On Thu, Sep 14, 2006 at 07:51:59PM +0200, Bertram Felgenhauer wrote: It's a result of thinking about lazy evaluation, and especially lazy patterns (and let bindings) for some time. A wiki article that helped me a lot to understand these is http://www.haskell.org/hawiki/TyingTheKnot I'd like to point out the trustList function there which uses the idea of encoding the structure of a term and its actual values in different arguments, i.e. a blueprint. One view of your device is as separating the shape (blueprint) from the contents, e.g. one can split a finite map type data Map k a = Node !Int k a (Map k a) (Map k a) | Leaf into a pair of types data MapShape k = SNode !Int k (MapShape k) (MapShape k) | SLeaf data MapData a = DNode a (MapData a) (MapData a) | DLeaf ... Nice description. Ross, I added a wiki page for this technique. Would you like to either elaborate on the wiki, or include the text of your email to it? http://haskell.org/haskellwiki/Separating_shape_and_content Cheers, Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Java or C to Haskell
crespi.albert:
I'm trying to write in Haskell a function that in Java would be something
like this:
char find_match (char[] l1, char[] l2, char e){
//l1 and l2 are not empty
int i = 0;
while (l2){
char aux = l2[i];
char[n] laux = l2;
while(laux){
int j = 0;
if(laux[j] = aux) laux[j] = e;
j++;
}
if compare (l1, laux) return aux;
else i++;
}
return '';
}
Yikes!
compare function just compares the two lists and return true if they are
equal, or false if they are not.
it is really a simple function, but I've been thinking about it a lot of
time and I can't get the goal. It works like this:
find_match 4*ha 4*5a 'h' returns '5' (5 matches with the h)
find_match 4*ns 4dhnn k returns '' (no match at all - lists
are different anyway)
That's almost a spec there :)
How about:
import Data.List
findMatch s t c
| Just n - elemIndex c s = Just (t !! n)
| otherwise = Nothing
Using it in GHCi:
findMatch 4*ha 4*5a 'h'
Just '5'
findMatch 4*ns 4dhnn 'k'
Nothing
-- Don
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Re: [Haskell-cafe] Java or C to Haskell
dons:
crespi.albert:
I'm trying to write in Haskell a function that in Java would be something
like this:
char find_match (char[] l1, char[] l2, char e){
//l1 and l2 are not empty
int i = 0;
while (l2){
char aux = l2[i];
char[n] laux = l2;
while(laux){
int j = 0;
if(laux[j] = aux) laux[j] = e;
j++;
}
if compare (l1, laux) return aux;
else i++;
}
return '';
}
Yikes!
compare function just compares the two lists and return true if they are
equal, or false if they are not.
it is really a simple function, but I've been thinking about it a lot of
time and I can't get the goal. It works like this:
find_match 4*ha 4*5a 'h' returns '5' (5 matches with the h)
find_match 4*ns 4dhnn k returns '' (no match at all - lists
are different anyway)
That's almost a spec there :)
Ah, I see I misread the spec :) Time for some tea.
-- Don
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Re: [Haskell-cafe] Java or C to Haskell
mailing_list: On Wed, Sep 20, 2006 at 01:31:22AM -0700, Carajillu wrote: compare function just compares the two lists and return true if they are equal, or false if they are not. it is really a simple function, but I've been thinking about it a lot of time and I can't get the goal. I forgot, obviously, that lists are an instance of the Eq class... so, this is enough: comp l1 l2 = if l1 == l2 then True else False You never stop learning! andrea which you would just write as: comp = (==) and then you'd just use == anyway :) -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ICFP programming contest 2006 results: video stream
Malcolm Wallace has recorded the ICFP programming contest results announcement as video, straight from the ICFP conference in Portland. He's posted it to Google Video, and it's available to download (120M) or stream from Google video, here: http://video.google.com/videoplay?docid=6419094369756184531 Thanks Malcolm! -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [newbie] How to test this function?
br1:
I've written a function that looks similar to this one
getList = find 5 where
find 0 = return []
find n = do
ch - getChar
if ch `elem` ['a'..'e'] then do
tl - find (n-1)
return (ch : tl) else
find n
First, how do I fix the identation of the if then else?
getList = find 5
where find 0 = return []
find n = do
ch - getChar
if ch `elem` ['a'..'e']
then do tl - find (n-1)
return (ch : tl)
else find n
Second, I want to test this function, without hitting the filesystem. In
C++ I would use a istringstream. I couldn't find a function that returns
a Handle from a String. The closer thing that may work that I could find
was making a pipe and convertind the file descriptor. Can I simplify that
function to take it out of the IO monad? How? I thought about
getContents, but that eats all input.
Refactor!
The reason your getList is hard to test, is that you're mixing side
effecting monadic code with pure computations. Let's untangle that, and
then test the the referentially transparent parts simply with
QuickCheck. And remember that since getContents uses lazy IO, it only
eats as much input as you ask it to.
So let's refactor this, partitioning off the side effecting IO code:
getList :: IO [Char]
getList = take5 `fmap` getContents -- a thin IO skin
take5 :: [Char] - [Char]
take5 = take 5 . filter (`elem` ['a'..'e']) -- the actual worker
Now we can test the 'guts' of the algorithm, the take5 function, in
isolation. Let's use QuickCheck. First we need an Arbitrary instance for
the Char type -- this takes care of generating random Chars for us to
test with. I'll restrict it to a range of nice chars just for simplicity:
import Data.Char
import Test.QuickCheck
instance Arbitrary Char where
arbitrary = choose ('\32', '\128')
coarbitrary c = variant (ord c `rem` 4)
So now we can write some simple tests.
An easy one, a [Char] is equal to itself:
*A quickCheck ((\s - s == s) :: [Char] - Bool)
OK, passed 100 tests.
Reversing twice is the identity:
*A quickCheck ((\s - (reverse.reverse) s == s) :: [Char] - Bool)
OK, passed 100 tests.
Ok, so what properties does take5 have? Well, for one, the length of the
string returned by take5 should be 5, no?
*A quickCheck (\s - length (take5 s) == 5)
Falsifiable, after 0 tests:
Ah, but what if the input file is small :) Thanks quickCheck.
Let's modify that then:
*A quickCheck (\s - length (take5 s) = 5)
OK, passed 100 tests.
Ok good. You can probably come up with some more things to check for now.
-- Don
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Re: [Haskell-cafe] [newbie] How to test this function?
dons: br1: Second, I want to test this function, without hitting the filesystem. In C++ I would use a istringstream. I couldn't find a function that returns a Handle from a String. The closer thing that may work that I could find was making a pipe and convertind the file descriptor. Can I simplify that function to take it out of the IO monad? How? I thought about getContents, but that eats all input. Oh, another thing to check would be that the correct characters are returned, such as: *A quickCheck (\s - all (`elem` ['a'..'e']) (take5 s)) OK, passed 100 tests. So for all strings QuickCheck produced, all Chars in the string returned by take5 where elements of ['a'..'e']. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [newbie] How to test this function?
dons: br1: Second, I want to test this function, without hitting the filesystem. In C++ I would use a istringstream. I couldn't find a function that returns a Handle from a String. The closer thing that may work that I could find was making a pipe and convertind the file descriptor. Can I simplify that function to take it out of the IO monad? How? I thought about getContents, but that eats all input. I've summarised this little introduction to QuickCheck on the haskell.org wiki here, http://haskell.org/haskellwiki/Introduction_to_QuickCheck -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Haskell.org down
Just in case it has gone unnoticed, haskell.org seems to have been down for a few hours now. Do we have an admin looking into this? -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Unable to profile program using Data.ByteString.Lazy
lists: Hi folks, I wrote a program that uses some of the Data.ByteString libraries. I'm using GHC 6.4.1 and FPS 0.7. The program compiles and works just fine. But when I try to profile it, by compiling with -prof, I get: Failed to load interface for `Data.ByteString.Lazy': Could not find module `Data.ByteString.Lazy': locations searched: Data/ByteString/Lazy.hi Data/ByteString/Lazy.hi-boot /f/g/lib/fps-0.7/Data/ByteString/Lazy.p_hi Why can it find the module when it's compiling without -prof, but not when it's compiling with it? I would really like to get profiling to work. Probably you didn't build fps with profiling as well? You can rebuild fps with: runhaskell Setup.hs configure -p as the first step. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell.org down
paul.hudak: Thanks Don. I alerted our IT staff this morning, and they seem to have things working again, although here is their final response: The web server had over 150 client connections which exceeded its limit. I restarted the web server and all is well. I'll keep and eye on it and see if someone is trying a denial of server attack, or it could be you need a newer faster machine. :-) So either Haskell is getting really popular (on a Friday night?) or there's something fishy going on. Hmm. Looks like its gone down again? Seems fishy... -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Unable to profile program using Data.ByteString.Lazy
lists: Donald Bruce Stewart wrote: Probably you didn't build fps with profiling as well? You can rebuild fps with: runhaskell Setup.hs configure -p as the first step. -- Don Thanks, I'll try it. Does that mean when I want to optimize my program, I'll need to rebuild fps without profiling? - Lyle If you build a cabalised project with the -p flag to configure, you get both the profiled and normal versions. You won't need to rebuild after that. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Haskell.org down (again)
Something's going on. Haskell.org seems to be down again. That's the 3rd time in 4 days. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Unable to profile program using Data.ByteString.Lazy
lists: Donald Bruce Stewart wrote: Probably you didn't build fps with profiling as well? You can rebuild fps with: runhaskell Setup.hs configure -p as the first step. That worked on my Windows box at home, but on my Linux box at work, I got unrecognized flag -p. You're cabal version is too old then. Try updating either Cabal or GHC. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell.org down (again)
dons: Something's going on. Haskell.org seems to be down again. That's the 3rd time in 4 days. And of course sending this message when the server _was_ down is guaranteed to lead to confusion when it is finally delivered, and the server is _up_. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is Haskell a 5GL?
david.curran: Where are compute languages going? I think multi core, distributed, fault tolerant. So you would end up with a computer of the sort envisioned by Hillis in the 80s with his data parallel programs. The only language that seems even close to this model is Erlang. What am I missing about the ability of Haskell to distribute across processors or a network? Data parallel Haskell is a very active area at the moment, http://www.cse.unsw.edu.au/~chak/project/dph/ Just last week Roman Leshchinskiy was able to get parallel arrays running SMP GHC on a shared memory 40 cpu Sun sparc server :) Also, GPH and its ilk have a long history: http://www.haskell.org/haskellwiki/Research_papers/Parallelism_and_concurrency -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Porting content from the old wiki
The main thing holding up porting of content from the old wiki is licensing. In order to help this, could people who've written for the old wiki, and are happy to have that work moved to the new wiki and relicensed, add their names to the list here: http://haskell.org/haskellwiki/HaWiki_migration Or email me and I'll add the name. Then anyone can move your work over, which should really speed things up. Thanks, Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell performance (again)!
duncan.coutts: On Sun, 2006-10-08 at 15:25 -0700, Jason Dagit wrote: Another good idea when you have a pretty version which is easy to verify for correctness and an ugly version that is harder to verify is to use QuickCheck or SmallCheck and define a property that says both versions are equal for all inputs. Ugly code is notorious for holding bugs, but doing this would help test the ugly code. This is exactly how we tested Data.ByteString and to great effect I think. We uncovered loads of bugs during testing. The few bugs uncovered by our users since it has been released have invariably been in things we didn't have QC properties for. Yes, I agree with this. By checking fast-bug-ugly code against slow-but-obvious code, we were able to catch bugs before Data.ByteString was deployed in the outside world, and before the bugs could hurt anyone. These days, Data.ByteString has some 2000 lines of QC properties, which are run on ever darcs commit. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: What's going on in our courses?
monnier: Last Spring my Functional Programming class implemented a Genetic Algorithm with Neural Networks that learned to play Nim. The students had a really good time--they also learned lots about Functional Programming with Haskell. Part of the final exam was a tournament. This Fall in AI we'll be doing GA's again and Genetic Programming. Is there a list or forum that talks about teaching our students about Haskell? Indeed, I'd be interested as well. I'm actually looking for a good textbook for a concepts of programming language course. All the books I can find tend to emphasize OO or imperative programming too much for my taste. You might want to look at : http://cgi.cse.unsw.edu.au/~cs3161/docs/references.php We use: Bob Harper's book, Programming Languages: Theory and Practice http://www-2.cs.cmu.edu/~rwh/plbook/ and Types and Programming Languages, Benjamin Pierce Cheers, Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: What's going on in our courses?
dons: monnier: Last Spring my Functional Programming class implemented a Genetic Algorithm with Neural Networks that learned to play Nim. The students had a really good time--they also learned lots about Functional Programming with Haskell. Part of the final exam was a tournament. This Fall in AI we'll be doing GA's again and Genetic Programming. Is there a list or forum that talks about teaching our students about Haskell? Also, http://haskell.org/haskellwiki/Haskell_in_education -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] List comparisons and permutation group code
dmhouse: On 21/10/06, Tomasz Zielonka [EMAIL PROTECTED] wrote: Do you also have this experience with Haskell?: when you feel that some code is not ideal, almost always it can be improved. One of the recurring features of the #haskell IRC conversations is something called 'Algorithm Golf' (which is a misnomer and should really be 'Algorithm Tennis'): one person will request an algorithm and anyone interested sets about building their own. The results are then shared using lambdabot's Haskell evaluation feature and collaboratively improved. I also like how when doing true 'golf', with @pl, we find new combinators: http://haskell.org/haskellwiki/Pointfree#Combinator_discoveries Like the owl: ((.)$(.)) I'd recommend hanging out in the channel to anyone. :) I agree, if you're not on #haskell, you're missing out! http://haskell.org/haskellwiki/IRC_channel :) -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Read a single char
briqueabraque: Hi, How can I read a single character from standard output? I would like the user to press a single key and the reading function return imediately after that key is pressed. so you want a function of type: IO Char asking Hoogle (http://haskell.org/hoogle) we get: Prelude. getChar:: IO Char IO. hGetChar :: Handle - IO Char -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Haskell custom search engine
Google now lets us create our own custom search engine pages, so I whipped one up for Haskell, http://www.google.com/coop/cse?cx=015832023690232952875%3Acunmubfghzq also, as a demo, embedded http://www.cse.unsw.edu.au/~dons/search.html Seems to do a reasonable job of targetting just Haskell sites. Feel free to add more Haskell material, or refine the search. In fact, search for mailing list items seems rather easy this way. Neil, I wonder if we could integrate this with Hoogle somehow? -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell custom search engine
bulat.ziganshin: Hello Donald, Wednesday, October 25, 2006, 8:44:48 AM, you wrote: Google now lets us create our own custom search engine pages, so I whipped one up for Haskell, great. and it search mail archives too how about adding it to haskell site, or at least a LARGE link so that everyone will see it. it will be very helpful for strangers/novices My plan was to have the community play with it for a week or so, and tune the results (i.e. volunteer and help refine the searches), and then we can embed it in haskell.org -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Fwd: [Haskell-cafe] Haskell custom search engine
dnavarro: Google now lets us create our own custom search engine pages, so I whipped one up for Haskell, I volunteered. Accepted. Are you planning to add just sites for Haskell-related software, or are research papers included in the scope of this? (Dude, where's my english grammar.) Yes, Haskell research sites would be good, as would working out the 'Refinement' stuff, to give more detailed searches (i.e. search only the research papers) -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell custom search engine
ndmitchell: Hi Neil, I wonder if we could integrate this with Hoogle somehow? If I provide an Ajax'y style API and we put the results in a frame, I'm sure we can give something like top 3 results from hoogle (if they make any sense). That sound a reasonable idea? You should be able to do just that, yes. The code for embedding the search engine on my example page might be a good place to start. I think augmenting hoogle is a in general better than forking two search engines for slightly different problems. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Ruby quiz, Haskell wiki
I've created a page to document haskell solutions to the ruby quiz puzzle series. http://haskell.org/haskellwiki/Haskell_Quiz Those of you working on them, please upload your solutions, and create sub pages for new puzzles as they appear. Cheers, Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] More documentation: how to create a Haskell project
There's been a bit of discussion on irc, lists and privately about about documenting publically the best practice for creating a new Haskell project -- be that a library or an application. Some advice is now available here: http://haskell.org/haskellwiki/How_to_write_a_Haskell_program Suggestions include: * use darcs * use cabal But we could do with more information on: * where to host a haskell project * integration of testsuites * anything about Hackage? * portability issues? So have a look at the page and make some suggestions, so it will be easier for newcomers in the future to create and contribute new projects, that will be readily accesible, useable and adopted by the community. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Documenting subcommunities
As the Haskell community grows and spreads its lambda-tipped tentacles into new domains, I've noticed that some distinct sub-communities are emerging. To try to document and collect information relevant to these groups, some new wiki pages have been created. Alongside the 'traditional' areas of: http://haskell.org/haskellwiki/Haskell_in_research http://haskell.org/haskellwiki/Haskell_in_education There is also a growing number of users of Haskell: http://haskell.org/haskellwiki/Haskell_in_industry http://haskell.org/haskellwiki/Haskell_and_mathematics If you're using Haskell for maths or in industry, and know of some relevant resources, please feel free to add the material to the above pages. Alternatively, if there are subcommunities that are missing a page (hmm, the open source community, perhaps?), then dive in and create a page documenting this. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] More documentation: languages written in Haskell
I noticed today that although we have a list of most applications written in Haskell, nowhere was there collected a page of perhaps our best use case for Haskell: for implementing compilers and interpreters! So here's a new 'libraries and tools' category page: http://haskell.org/haskellwiki/Libraries_and_tools/Compilers_and_interpreters If you know of a compiler or interpreter written in Haskell, (I think at least a few people on this list have written one or two themselves ... ;) please add it to the list. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Tutorial: Writing a Lisp Interpreter In Haskell
People might be interested in a new tutorial that's just appeared in blogspace, by coffeemug (of #haskell): http://www.defmacro.org/ramblings/lisp-in-haskell.html Also, its on reddit, http://programming.reddit.com/info/oj1w/details An enthusiastic view of the language from a newcomer's perspective. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to improve speed? (MersenneTwister is several times slower than C version)
Now, this will be hard to get close the the highly tuned C. Possibly its doable. The main tricks are documented here: http://haskell.org/haskellwiki/Performance/GHC#Unboxed_types Inspecting the Core to ensure the math is being inlined and unboxed will be the most crucial issue, I'd imagine. Then again, an FFI binding to mersenne.c is also a good idea :) -- Don isto.aho: Hi all, On HaWiki was an announcement of MersenneTwister made by Lennart Augustsson. On a typical run to find out 1000th rnd num the output is (code shown below): $ time ./testMTla Testing Mersenne Twister. Result is [3063349438] real0m4.925s user0m4.856s I was exercising with the very same algorithm and tried to make it efficient (by using IOUArray): now a typical run looks like (code shown below): $ time ./testMT Testing Mersenne Twister. 3063349438 real0m3.032s user0m3.004s The original C-version (modified so that only the last number is shown) gives typically $ time ./mt19937ar outputs of genrand_int32() 3063349438 real0m0.624s user0m0.616s Results are similar with 64 bit IOUArray against 64 bit C variant. C seems to work about 5 to 10 times faster in this case. I have tried to do different things but now I'm stuck. unsafeRead and unsafeWrite improved a bit the lazy (STUArray-version) and IOUArray-versions but not very much. I took a look of Core file but then, I'm not sure where the boxed values are ok. E.g. should IOUArray Int Word64 be replaced with something else? Any hints and comments on how to improve the efficiency and make everything better will be appreciated a lot! br, Isto - testMTla.hs (MersenneTwister, see HaWiki) module Main where -- ghc -O3 -optc-O3 -optc-ffast-math -fexcess-precision --make testMTla import MersenneTwister main = do putStrLn Testing Mersenne Twister. let mt = mersenneTwister 100 w = take 1 (drop 999 mt) -- w = take 1 (drop 99 mt) putStrLn $ Result is ++ (show w) - - testMT.hs module Main where -- Compile eg with -- ghc -O3 -optc-O3 -optc-ffast-math -fexcess-precision --make testMT import Mersenne genRNums32 :: MT32 - Int - IO (MT32) genRNums32 mt nCnt = gRN mt nCnt where gRN :: MT32 - Int - IO (MT32) gRN mt nCnt | mt `seq` nCnt `seq` False = undefined gRN mt 1= do (r,mt') - next32 mt putStrLn $ (show r) return mt' gRN mt nCnt = do (r,mt') - next32 mt gRN mt' $! (nCnt-1) main = do putStrLn Testing Mersenne Twister. mt32 - initialiseGenerator32 100 genRNums32 mt32 1000 - - Mersenne.hs (sorry for linewraps) module Mersenne where import Data.Bits import Data.Word import Data.Array.Base import Data.Array.MArray import Data.Array.IO -- import System.Random data MT32 = MT32 (IOUArray Int Word32) Int data MT64 = MT64 (IOUArray Int Word64) Int last32bitsof :: Word32 - Word32 last32bitsof a = a .. 0x -- == (2^32-1) lm32 = 0x7fff :: Word32 um32 = 0x8000 :: Word32 mA32 = 0x9908b0df :: Word32 -- == 2567483615 -- Array of length 624. initialiseGenerator32 :: Int - IO MT32 initialiseGenerator32 seed = do let s = last32bitsof (fromIntegral seed)::Word32 mt - newArray (0,623) (0::Word32) unsafeWrite mt 0 s iG mt s 1 mt' - generateNumbers32 mt return (MT32 mt' 0) where iG :: (IOUArray Int Word32) - Word32 - Int - IO (IOUArray Int Word32) iG mt lastNro n | n == 624= return mt | otherwise = do let n1 = lastNro `xor` (shiftR lastNro 30) new = (1812433253 * n1 + (fromIntegral n)::Word32) unsafeWrite mt n new iG mt new (n+1) generateNumbers32 :: (IOUArray Int Word32) - IO (IOUArray Int Word32) generateNumbers32 mt = gLoop 0 mt where gLoop :: Int - (IOUArray Int Word32) - IO (IOUArray Int Word32) gLoop i mt | i==623 = do wL - unsafeRead mt 623 w0 - unsafeRead mt 0 w396 - unsafeRead mt 396 let y = (wL .. um32) .|. (w0 .. lm32) :: Word32 if even y then unsafeWrite mt 623 (w396 `xor` (shiftR y 1)) else unsafeWrite mt 623 (w396 `xor` (shiftR y 1) `xor` mA32) return mt
Re: [Haskell-cafe] Basic Binary IO
nuno: Hi all! Today i was reading System.IO and didn't manage to understand how it works just by reading it. I looked the internet for some help on this, but only advanced information is available. Can anyone show me how to use openBinaryFile ? Just an example, like opening file somefile and separating it into something that can be edited in the code (like 8 bit words) then go to word nr12 and edit the last bit? http://haskell.org/haskellwiki/Binary_IO For flat lists of bytes, use Data.ByteString, for structured data, try NewBinary. There are other options too, documented above. openBinaryFile just sets the line ending handling on windows. I don't think it does what you think it does. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to improve speed? (MersenneTwister is several times slower than C version)
lemmih: On 11/1/06, isto [EMAIL PROTECTED] wrote: Hi all, On HaWiki was an announcement of MersenneTwister made by Lennart Augustsson. On a typical run to find out 1000th rnd num the output is (code shown below): $ time ./testMTla Testing Mersenne Twister. Result is [3063349438] real0m4.925s user0m4.856s I was exercising with the very same algorithm and tried to make it efficient (by using IOUArray): now a typical run looks like (code shown below): $ time ./testMT Testing Mersenne Twister. 3063349438 real0m3.032s user0m3.004s The original C-version (modified so that only the last number is shown) gives typically $ time ./mt19937ar outputs of genrand_int32() 3063349438 real0m0.624s user0m0.616s Results are similar with 64 bit IOUArray against 64 bit C variant. C seems to work about 5 to 10 times faster in this case. I have tried to do different things but now I'm stuck. unsafeRead and unsafeWrite improved a bit the lazy (STUArray-version) and IOUArray-versions but not very much. I took a look of Core file but then, I'm not sure where the boxed values are ok. E.g. should IOUArray Int Word64 be replaced with something else? Any hints and comments on how to improve the efficiency and make everything better will be appreciated a lot! br, Isto Greetings, Applying a few optimations can make it about 3x faster. 1. Hoist the array out of your loops. (See generateNumbers32, initialiseGenerator32 and genRNums). 2. Don't create too many new MT32 boxes. Most of the time is spent in 'next32' and changing its type to 'IOUArray Int Word32 - Int - IO (Word32, Int)' makes it much faster. 3. Demand more inlining. If you're using GHC, -funfolding-use-threshold=16 will substantially improve the performance. Using 'seq' is generally a bad idea. It can worsen the performance if not used carefully and GHCs strictness analyser is usually good enough. I used the profiler and -ddump-simpl to analyse this program. Donald suggested manual unboxing. However, in this case it won't help much (if at all) since GHC is doing such an excellent job on its own. I wasn't suggesting manual unboxing, more that you should carefully inspect the Core, and tune with bang patterns where necessary. -funfolding-use-threshold=16 is a good idea though. or =100 ;) -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to improve speed? (MersenneTwister is several times slower than C version)
bulat.ziganshin: Hello isto, Thursday, November 2, 2006, 1:16:55 AM, you wrote: I have tried to do different things but now I'm stuck. unsafeRead and unsafeWrite improved a bit the lazy (STUArray-version) and why you think it's a lazy? :) ST monad is just the same as IO monad internally, only types are different (there is also Lazy.ST monad - this is really lazy) 10-20 times difference is typical for GHC programs. ! It's really more like 2-4x. Sometimes better than C. Where's this huge figure coming from Bulat? If you have code that behaves like this, you should report it. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Finding Memory Leaks
mattcbro: Jason Dagit-2 wrote: Do any memory leaks show up if you compile with -caf-all when you profile? Jason ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe It doesn't seem to make any difference, although I do not know what this flag does. I compiled the code using ghc -fglasgow-exts -fffi -prof -auto -caf-all -I. --make leaky.hs cleaky.o and did not see the steady ramp up in memory that one sees with the windows xp performance tool. Hmm, are you missing a -O ? Does that help at all? -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] RFC and Announcement: HLADSPA, LADSPA for Haskell
lemming: On Sun, 5 Nov 2006, Alfonso Acosta wrote: PS1: Big thanks and claps for the people at [EMAIL PROTECTED] . They helped a lot to make this initial release possible. PS2: I would like to get the project hosted at the darcs repository at haskell.org. Do you consider it interesting enough for it? Yes, definitely. Could you also please add some note to http://www.haskell.org/haskellwiki/Libraries_and_tools/Music_and_sound I agree, and would remark for anyone reading: Please add your projects, whether they are applications, libraries, tools, darcs repos, to : http://haskell.org/haskellwiki/Libraries_and_tools *All* Haskell code that's available, and fit to compile should be findable from that page. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Livecoding music in Haskell
Alex McLean has kindly put up a screencast of him creating *music via live coding in Haskell* ! http://doc.gold.ac.uk/~ma503am/alex/haskellmusic And a .avi version of the screencast, playable in mplayer (for those not flash inclined). http://yaxu.org/20/hs.avi The code is running in hs-plugins, and being reloaded on the fly as he edits the source, changing the rhythms that are produced. More on this on Alex's blog: http://doc.gold.ac.uk/~ma503am/alex/ Cool stuff! -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] don't: a 'do' for comonads?
As seen on #haskell, from an idea by Malcolm, 14:42 ?let top'n'tail = (pre++) . (++/pre) 14:42 lambdabot Defined. 14:43 dons L.top'n'tail foo me now 14:43 lambdabot prefoo me now/pre 14:43 mauke that reminds me, haskell needs don't 14:43 dons yes! 14:44 pkhuong- mm. the opposite of do, eh? do for comonads? :) So now a prize to the person who comes up with the best use for the identifier: don't :: ? -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Sistema de Ecuaciones NO lineales
bonobo: On Thu, 9 Nov 2006 02:52 pm, Sebastian Gaviria wrote: hola como estan Quiero preguntar quien puede resolver el sistemas de ecuaciones NO lineales de Newton y el codigo de Jacobi en Haskell me ayudarian mucho al poder implementar ese codigo por Favor es con urgencia tener estos codigos!! muchas gracias !!! Hola Sebastian, Lo siento por mi espa?ol mal. Si esa es una pregunta sobre tarea, por favor lee http://www.haskell.org/haskellwiki/Homework_help Y escribo Haskell como escribo espa?ol :-), as? lo siento, no puedo ayudar. :-( You might try: #haskell.es irc channel http://www.haskell.org/haskellwiki/IRC_channel -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Great language shootout: reloaded
So back in January we had lots of fun tuning up Haskell code for the Great Language Shootout[1]. We did quite well at the time, at one point ranking overall first[2]. After doing all we could with ghc 6.4.2, the Haskell entries have been left for the last 10 months, while we worked on new libraries (bytestring, regex-*). 1. http://shootout.alioth.debian.org/ 2. http://www.cse.unsw.edu.au/~dons/data/haskell_1.html Now the time has come to reload the shootout for another round! GHC 6.6 is on the 'sandbox' debian machine, and will soon be on the other shootout boxes[3], which means we can use: * Data.ByteString * regex-* libraries 3. http://shootout.alioth.debian.org/sandbox/benchmark.php?test=alllang=ghclang2=javaxint#about And thus greatly improve: fannkuch fasta k-nucleotide regex-dna reverse-complement sum-file While we're here we should fix: chameneos And anything else you want to take a look at. A community page has been set up to which you can submit improved entries: http://www.haskell.org/haskellwiki/Great_language_shootout So, install GHC 6.6, read up on Data.ByteString and the new regex libs, and submit faster code to the wiki! Our shootout-interface officer, musasabi, can then commit them to shootout cvs, once consensus is reached on the best code to submit. Let's take back first place! :) -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: don't: a 'do' for comonads?
apfelmus: Donald Bruce Stewart wrote: As seen on #haskell, from an idea by Malcolm, 14:42 ?let top'n'tail = (pre++) . (++/pre) 14:42 lambdabot Defined. 14:43 dons L.top'n'tail foo me now 14:43 lambdabot prefoo me now/pre 14:43 mauke that reminds me, haskell needs don't 14:43 dons yes! 14:44 pkhuong- mm. the opposite of do, eh? do for comonads? :) So now a prize to the person who comes up with the best use for the identifier: don't :: ? -- Don don't :: IO a - a example :: () example = don't (do erase /dev/hda) I like it! -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] don't: a 'do' for comonads?
hjgtuyl: don't :: whatever - (whatever goes in, nothing comes out) So its: don't :: a - Void ? -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Great language shootout: reloaded
igouy2: On 11/10/06, Henk-Jan van Tuyl hjgtuyl at chello.nl wrote: Haskell suddenly dropped several places in the overall socre, when the size measurement changed from line-count to number-of-bytes after gzipping. Maybe it's worth it, to study why this is; Haskell programs are often much more compact then programs in other languages, but after gzipping, other languages do much better. One reason I can think of, is that for very short programs, the import statements weigh heavily. Before this gets out-of-hand, my memory is certainly fallible but as I recall Haskell /did not/ drop several places because size measurement changed from line-count to gzip byte-count. 1) Check the webpage that Don Stewart cached and note the values for the memory use and code-lines multipliers, and note the values for the benchmark weights http://www.cse.unsw.edu.au/~dons/data/haskell_1.html Now go to the computer language shootout website and note the multipliers and benchmark weights. 2) Some Haskell programs were pushed into 'interesting alternative implementations' because they'd strayed so far from the spirit of the benchmark. (It takes a while for people to notice and complain, but eventually they do.) I agree. Breaking the rules was mainly the reason for the drop. Entries like chameneos and fasta. Also, the other language teams kept improving things. Other language (perl, iirc) were affected far worse by the gzipping. gzip is an interesting measurement, and it doesn't hurt Haskell too much either way -- short Haskell programs stay short when compressed. As a result, rewriting verbose entries to ByteString will probably be much more useful :) Btw, Isaac, are we going to have any new parallelism benchmarks? I'd love to try out the SMP runtime ;) -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] best Linux for GHC?
bulat.ziganshin: Hello haskell-cafe, Now i'm consider installation of some Linux version at my box. My friend offered me 3 variants: SuSe, Fedora Core 5, free variant of RedHat (i can't remember its name, may be Ubuntu?) what may be best for GHC-based development? in particular, i want to compile Haskell itself i suspect that it is a really dumb question, and GHC will work great just with any linux i can find :) -- Gentoo or Debian, I suspect, since then you get the #haskell-gentoo team, and Igloo, keeping things up to date :) -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ByteString FFI
donn: How do people like to set up their foreign I/O functions to return ByteStrings? I was a little stumped over this yesterday evening, while trying to write ` recv :: Socket - Int - Int - ByteString ' Doc says `Byte vectors are encoded as strict Word8 arrays of bytes, held in a ForeignPtr, and can be passed between C and Haskell with little effort.' Which sounds perfect - I'm always up for `little effort'! CString doesn't seem like the right thing for socket results, because the data shouldn't be NUL-terminated, and I might want to realloc when the returned data doesn't fill the buffer. I don't see any other Ptr-related function or constructor in the documentation - am I missing something there? And for custom data (not just C strings), if the withCString* functions don't quite fit, you can always pack the foreign Ptr into a ByteString by stepping inside the ByteString constructor: http://www.haskell.org/haskellwiki/Wc#Going_via_C -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ByteString FFI
donn: On Mon, 13 Nov 2006, Donald Bruce Stewart wrote: And for custom data (not just C strings), if the withCString* functions don't quite fit, you can always pack the foreign Ptr into a ByteString by stepping inside the ByteString constructor: http://www.haskell.org/haskellwiki/Wc#Going_via_C That's actually what I tried first, but in this particular situation (ghc-6.4.1 / fps-0.7), PS apparently isn't exported? Right, you'll want to grab the soon-to-be-tagged fps 0.8, which matches that provided with ghc 6.6. It's in the darcs repo. The CStringLen approach works, except that the allocated data doesn't get garbage-collected. Just for the sake of experiment I tried a regular CString with packMallocCString, and that didn't leak nearly as much memory - but still some, in a simple loop where pack doesn't leak anything. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Great language shootout: reloaded
tpledger: Donald Bruce Stewart wrote: [...] While we're here we should fix: chameneos And anything else you want to take a look at. A community page has been set up to which you can submit improved entries: http://www.haskell.org/haskellwiki/Great_language_shootout [...] Well, then! I've put a new chameneos solution up on the wiki, and will wait the recommended couple of days for Community Feedback. Great! One issue is that the pragma is unnecessary (all the good flags are set in the Makefile, so that saves a few gzipped bytes ;) -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
