Re: [Haskell-cafe] Bit streams programs in Haskell
per.gustafsson:
>
> Haskell gurus,
>
> We have made a proposal to extend the Erlang `binary' data type from
> being a sequence of bytes (a byte stream) to being a sequence of bits (a
> bitstream) with the ability to do pattern matching at the bit level.
>
> Our experience in writing efficient (and beautiful) Haskell programs is
> close to (if not below) zero. Also, perhaps our mind might be suffering
> from severe case of strictness and might be completely unable to `think
> lazily'. So, we request your help in noticing obvious NO-NOs and stupid
> mistakes that we might have made. We even welcome completely different
> Haskell programs provided they adhere to the constraint mentioned
> above -- no mutation.
Ok, I rewrote the drop3 program to use packed, unboxed arrays as the
OCaml version does, instead of lazy boxed lists.
It now runs in 3.5s on my linux box, which is around which is around
what the OCaml version does.
$ ghc B.hs
$ ./a.out testdata.drop3
3.617
$ cmp testdata.drop3.haskell testdata.drop3.out
Comparing lazy list IO against packed array IO is a bit silly, so I suggest you
use the same buffer types in your Haskell code as you do in the OCaml code.
Otherwise the comparisons aren't very meaningful. The problem is not so much
laziness, as you suggest, but that you're using a completely unsuitable data
type: lists, instead of (packed) strings.
You can most likely just translate your other OCaml programs into Haskell as I
have done here, which would be a good basis for a reasonable comparison.
You may also find the Haskell performance resource useful,
http://www.haskell.org/haskellwiki/Performance
Cheers,
Don
{-# OPTIONS -O2 #-}
--
-- Translated from the OCaml version.
--
import Control.Monad
import Data.Char
import Data.Array.IO
import Data.Array.Base
import Data.Bits
import Data.Word
import System
import System.CPUTime
import System.IO
import Text.Printf
iter :: Int
iter = 10
main = do
f <- getArgs >>= return . head
(arr,l) <- slurp f
t0<- getCPUTime
(arr',l') <- replicateM iter (drop0xx arr (l*8)) >>= return . head
t1<- getCPUTime
printf "%.3f\n" $ (fromInteger (t1 - t0) :: Float) / (fromInteger 10 ^ 12
:: Float)
dump f arr' (1 + (snd . bounds) arr')
drop0xx = drop0xx' 0 0 0 []
drop0xx' :: Int -> Int -> Int -> [Int] -> Buffer -> Int -> IO (Buffer,Int)
drop0xx' inoff reg shifts acc str len
| inoff `seq` reg `seq` shifts `seq` acc `seq` str `seq` len `seq` False =
undefined
| inoff' > len = makeResult (reverse acc) reg shifts
| otherwise = do
triple <- getTriple str inoff
if triple >= 4
then let reg' = (reg `shiftL` 3) .|. triple
in if shifts == 7
then drop0xx' inoff' 00 (reg':acc) str len
else drop0xx' inoff' reg' (shifts+1) accstr len
else drop0xx' inoff' reg shifts acc str len
where inoff' = inoff + 3
getTriple :: Buffer -> Int -> IO Int
getTriple str inoff | str `seq` inoff `seq` False = undefined
getTriple str inoff = do
b0 <- str `unsafeRead` bitind >>= return . fromIntegral
b1 <- str `unsafeRead` (bitind+1) >>= return . fromIntegral
return $! (if bitoff < 6
then b0 `shiftR` (5-bitoff)
else (b0 `shiftL` (bitoff-5)) .|. (b1 `shiftR` (13-bitoff)))
.&. 7
where bitoff = inoff .&. 7
bitind = inoff `shiftR` 3
makeResult :: [Int] -> Int -> Int -> IO (Buffer,Int)
makeResult list0 endpiece shifts = do
arr <- newArray_ (0,triplebytesize + endpiecesize-1) :: IO Buffer
let packList (triple:rest) ind = do
unsafeWrite arr ind $ fromIntegral $ (triple `shiftR` 16) .&.
255
unsafeWrite arr (ind+1) $ fromIntegral $ (triple `shiftR` 8) .&.
255
unsafeWrite arr (ind+2) $ fromIntegral $ triple .&.
255
packList rest (ind+3)
packList [] ind =
let c1 = endpiece `shiftL` ((shifts*3 - 8) .&. 255)
s0 = shifts * 3 - 8
in case endpiecesize of
0 -> return ()
1 -> do unsafeWrite arr ind $ fromIntegral $
endpiece `shiftL` (s0 .&. 255)
2 -> do unsafeWrite arr ind $ fromIntegral $
endpiece `shiftL` (s0 .&. 255)
unsafeWrite arr (ind+1) $ fromIntegral $
endpiece `shiftL` ((s0-8) .&. 255)
packList list0 0
return (arr, triplebytesize * 8 + shifts * 3)
where endpiecesize = getNeededBytes shifts
triplebytesize = 3 * length list0
getNeededBytes shifts | shifts < 3 = 0
| shifts < 6 = 1
| otherwise = 2
type Buffer = IOUArray Int Word8
slurp :: FilePath -> IO (Buffer, Int)
slur
Re: [Haskell-cafe] Bit streams programs in Haskell
Per Gustafsson wrote:
>
> Haskell gurus,
>
I am not a guru, but I'll clean up some of this.
> Our experience in writing efficient (and beautiful) Haskell programs is
> close to (if not below) zero. Also, perhaps our mind might be suffering
> from severe case of strictness and might be completely unable to `think
> lazily'. So, we request your help in noticing obvious NO-NOs and stupid
> mistakes that we might have made. We even welcome completely different
> Haskell programs provided they adhere to the constraint mentioned
> above -- no mutation.
>
> Best regards,
>
> Kostis Sagonas and Per Gustafsson
>
I can't test this, but I have attached a new version of huffman.hs that may
perform a bit better. I don't know if all the changes I made helped instead of
hurt. I doubt it was sped up by much.
--
Chris Kuklewicz
--module Huffman where
import System.IO
import Data.Bits
import Data.Word
import Data.Array.IO
import Data.Array.Unboxed hiding ((!))
import Data.Array.Base(unsafeAt)
import System(getArgs)
import System.CPUTime(getCPUTime)
import Foreign.Marshal.Array (withArrayLen)
import Control.Exception(bracket)
data HuffTree = Leaf Word8 | Branch HuffTree HuffTree
type A = UArray Int Word8
(!) = unsafeAt
iter = 10
{-- the do_iter function repeats a function iter times
it is not pretty, but it is hard to convince haskell to
repeat a computation many times --}
do_iter 1 func input = let x = func input
in return x
do_iter k func input = let x = func input
in seq (last x) (do_iter (k-1) func input)
main =
do
[arg] <- getArgs
handle <- openFile arg ReadMode
let size = 200
arrM <- newArray (0,pred size) 0 :: IO (IOUArray Int Word8)
read_size <- hGetArray handle arrM size
-- convert to immutable array
arr <- unsafeFreeze arrM :: IO (UArray Int Word8)
t0 <- getCPUTime
res <- do_iter iter huff arr
t1 <- getCPUTime
putStr ((show ((fromInteger(t1-t0)::Float)/(1.0::Float
bracket (openBinaryFile (arg++".haskell") WriteMode)
hClose
(\file -> withArrayLen res (flip (hPutBuf file)))
huff:: A -> [Word8]
huff arr = let (hufftree, newindex) = build_tree 4 arr
limit = get_32bit_int newindex arr
in huffdecode ((newindex+4)*8) arr hufftree (limit+((newindex+4)*8))
huffdecode :: Int -> A -> HuffTree -> Int -> [Word8]
huffdecode index arr tree limit = helper index tree
where helper index (Leaf charval) | index == limit = []
| otherwise = charval : helper index
tree
helper index (Branch left right) | index `seq` True =
helper (index+1) (if get_bit arr index then right else left)
get_bit :: A -> Int -> Bool
{-# INLINE get_bit #-}
get_bit arr bitoffset =
let byte = arr ! (shiftR bitoffset 3)
in testBit (shiftL byte (bitoffset .&. 7)) 7
build_tree :: Int->A->(HuffTree,Int)
build_tree index arr =
let size = get_16_bitint index arr
build_tree_2 index limit
| (limit-index) == 1 = Leaf (arr ! index)
| otherwise = let left_size = get_16_bitint index arr
in Branch (build_tree_2 (index+2)
(index+2+left_size))
(build_tree_2 (index+4+left_size)
limit )
in (build_tree_2 (index+2) (index+2+size)
,(index+2+size))
get_16_bitint :: Int -> A -> Int
{-# INLINE get_16_bitint #-}
get_16_bitint index arr =
(shiftL (fromIntegral (arr ! index)) 8) .|.
(fromIntegral (arr ! (index+1)))
get_32bit_int :: Int -> A -> Int
{-# INLINE get_32bit_int #-}
get_32bit_int index arr =
(shiftL (fromIntegral (arr ! index)) 24) .|.
(shiftL (fromIntegral (arr ! (index+1))) 16) .|.
(shiftL (fromIntegral (arr ! (index+2))) 8) .|.
(fromIntegral (arr ! (index+3)))
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Re: [Haskell-cafe] Bit streams programs in Haskell
One thing I noticed, is that you are measuring IO in the Haskell version of drop3. hGetContents is lazy. On Mar 22, 2006, at 4:43 PM, Per Gustafsson wrote: Also, perhaps our mind might be suffering from severe case of strictness and might be completely unable to `think lazily'. So, we request your help in noticing obvious NO-NOs and stupid mistakes that we might have made. David F. Place mailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Code Review: Sudoku solver
Robert Dockins wrote: > > On Mar 22, 2006, at 2:16 PM, David F. Place wrote: > >> Hi All, >> >> I really appreciate all the help I received when I asked you to >> critique my PrefixMap module a few weeks ago. I think I am making >> good progress in correcting the "lisp" in my Haskell programming. The style of the code and choice of names is good. >> I'll be very grateful to anyone who can take a glance at the attached >> short program and say if any unidiomatic usages pop out. > > > That '(check s) . (take 1)' bit looks a little odd to me. I would > simply have written 'check' to match like: > > check puzzle [] = > check puzzle (solution : _ ) = > A simpler version of replace: replace :: Sudoku -> Int -> Int -> Int -> Sudoku replace s r c x = let (above,row:below) = splitAt r s (left,_:right) = splitAt c row in above++((left++(x:right)):below) And a simpler version of toList in keeping with your style: toList :: Set -> [Int] toList i = concatMap f [9,8..1] where f b = if testBit i b then [b] else [] (The above is also a little less prone to off-by-one errors since testBit is the opposite of setBit) > > Also, I like to put off doing IO as long as possible, so I'd probably > have 'sodoku' return a String or [String] and move the putStr into > main. Its an easy way to make your code more reusable. > > Also, your parser is pretty hackish (but I suspect you knew that already). > A minimal change to the parser that still does no sanity checking but may be a little more robust is import Data.Char readSudoku :: [String] -> String -> Sudoku readSudoku ["line"] input = takeBy 9 $ map digitToInt $ filter isDigit $ head $ lines input readSudoku _ input = map (map digitToInt . filter isDigit) $ lines input ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Bit streams programs in Haskell
Haskell gurus, We have made a proposal to extend the Erlang `binary' data type from being a sequence of bytes (a byte stream) to being a sequence of bits (a bitstream) with the ability to do pattern matching at the bit level. This proposal has now been fully implemented all these at the level of the BEAM virtual machine and in the HiPE compiler. Most probably, they will be part of the next major Erlang/OTP open source release. (We write "most probably" because we do not really control what Ericsson desides to release as part of its open source system.) We wanted to evaluate the performance of our implementation and the succintness of our syntax, particularly against other `similar' languages. For this reason, we wrote five reasonably representative benchmarks, showing the things that one could employ bit stream pattern matching and bit-level comprehensions for. The benchmarks (drop3, five11, huffman, uudecode, and uuendode) have all been written in Erlang, O'Caml and Haskell. For some of them, C and Java versions exist. They can be found in the following homepage: http://bitbenches.infogami.com/ As you will see there, the Haskell numbers are significantly slower than those of Erlang and O'Caml. We are wondering why this is so. For each language, we have spent a considerable effort in writing the benchmarks in -- at least what we feel -- is the most natural and efficient way one can write them. The only constraint we impose is that for functional languages, data structures without any explicit mutation have to be used in the part of the program for which measurements are taken. Our experience in writing efficient (and beautiful) Haskell programs is close to (if not below) zero. Also, perhaps our mind might be suffering from severe case of strictness and might be completely unable to `think lazily'. So, we request your help in noticing obvious NO-NOs and stupid mistakes that we might have made. We even welcome completely different Haskell programs provided they adhere to the constraint mentioned above -- no mutation. Best regards, Kostis Sagonas and Per Gustafsson ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Code Review: Sudoku solver
On Mar 22, 2006, at 2:16 PM, David F. Place wrote: Hi All, I really appreciate all the help I received when I asked you to critique my PrefixMap module a few weeks ago. I think I am making good progress in correcting the "lisp" in my Haskell programming. I'll be very grateful to anyone who can take a glance at the attached short program and say if any unidiomatic usages pop out. sudoku :: Sudoku -> IO () sudoku s = ((mapM_ putStrLn) . (check s) . (take 1) . solveSudoku) s check puzzle [] = [showSudoku puzzle,"No solutions."] check puzzle [solution] | solution `solves` puzzle = ["Puzzle:",showSudoku puzzle,"Solution:",showSudoku solution] | otherwise = ["Program Error. Incorrect Solution!"] That '(check s) . (take 1)' bit looks a little odd to me. I would simply have written 'check' to match like: check puzzle [] = check puzzle (solution : _ ) = Also, I like to put off doing IO as long as possible, so I'd probably have 'sodoku' return a String or [String] and move the putStr into main. Its an easy way to make your code more reusable. Also, your parser is pretty hackish (but I suspect you knew that already). FYI, solveSudoku has a bug; if you enter an invalid puzzle it will return non-solutions. It solves sudoku puzzles. (What pleasure do people get by doing these in their heads?!?) I have no idea. Rob Dockins Speak softly and drive a Sherman tank. Laugh hard; it's a long way to the bank. -- TMBG ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Code Review: Sudoku solver
On 3/22/06, David F. Place <[EMAIL PROTECTED]> wrote: > Hi All, > > I really appreciate all the help I received when I asked you to > critique my PrefixMap module a few weeks ago. I think I am making > good progress in correcting the "lisp" in my Haskell programming. > I'll be very grateful to anyone who can take a glance at the attached > short program and say if any unidiomatic usages pop out Try > cellIndex r c = 3*(r `div` 3) + c `div` 3 It's much much shorter and should produce the same results. > It solves > sudoku puzzles. (What pleasure do people get by doing these in their > heads?!?) > They are probably asking the same question: why take hours to write a program to do it when with my mad sudoku solving skills I can solve it in X seconds? My roommate is like this. Cheers, Jared. -- http://www.updike.org/~jared/ reverse ")-:" ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Code Review: Sudoku solver
Hi All, I really appreciate all the help I received when I asked you to critique my PrefixMap module a few weeks ago. I think I am making good progress in correcting the "lisp" in my Haskell programming. I'll be very grateful to anyone who can take a glance at the attached short program and say if any unidiomatic usages pop out. It solves sudoku puzzles. (What pleasure do people get by doing these in their heads?!?) Cheers, David sudoku.hs Description: Binary data David F. Place mailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Wheres this going wrong
Neil Rutland wrote:
> ttyyppee LLiinnee ==
> [[((((SSttrriinngg,,SSttrriinngg)),,((SSttrriinngg,,IInntt)),,((SSttrriinngg,,IInntt)),,((SSttrriinngg,,BBooooll)),,
> ((SSttrriinngg,,BBooooll)),,((SSttrriinngg,,BBooooll)),,((SSttrriinngg,,BBooooll)),,((SSttrriinngg,,BBooooll)),,((SSttrriinngg,,BBooooll)),,
> ((SSttrriinngg,,BBooooll)),,((SSttrriinngg,,BBooooll)),,((SSttrriinngg,,BBooooll))))]]
What's wrong with a record?
*> data Line = Line { a1 :: String, a2 :: Int, ... }
While you're at it, you might want to give the fields sensible names.
> Anyway when i enter something such as lookup "a1" i get back a load of stuff
> about Eq.
lookup expects a list of pairs, but you're passing it a tuple. A list
would have to be homogenous, your tuple isn't, therefore lookup cannot
do what you want. Just use a record.
Udo.
--
Languages shape the way we think, or don't. -- Erik Naggum
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Re: [Haskell-cafe] Wheres this going wrong
On 3/22/06, Neil Rutland <[EMAIL PROTECTED]> wrote:
>
>
>
> Hi there,
>
> Thanks to some advise by one of the other posters i have chosen to try and
> set up a list that uses lookup to find the values of the elements within it.
>
> However what i have attempted so far has resulted in odd answers or errors.
> Anyway here it is, i have given each element a string at the start to put
> the lookup domain in - anyway here it is
>
> type Line =
> [((String,String),(String,Int),(String,Int),(String,Bool),(String,Bool),(String,Bool),(String,Bool),(String,Bool),(String,Bool),(String,Bool),(String,Bool),(String,Bool))]
>
> vicsLine :: Line
> vicsLine = [(("a1","Walthamstow
> Central"),("a2",1),("a3",2),("a4", False), ("a5", True),
> ("a6", False), ("a7", False), ("a8", False), ("a9", False), ("a10", False),
> ("a11", False), ("a12", False))]
>
> Anyway when i enter something such as lookup "a1" i get back a load of stuff
> about Eq.
>
> So the question is - what am i doing wrong. I am hoping that when i enter a1
> it should return for me Walthamstow Central.
>
What shoul happen if you enter "a2"?
lookup takes a "key" and a list of key/value pairs, and maybe returns
the value.
For instance, one list may look like this:
db = [(1,"Hello"), (2,"world")]
If you then use 'lookup 1 db', you'd get 'Just "Hello"', if you type
'lookup 12 db' you'd get 'Nothing' since there is no pair where 12 is
the first value.
Now, it's important that the list you pass to lookup is of the form: [(a,b)]
In other words it MUST be a list of PAIRS. The second value of the
pair may be of any type (including a complex type with lists and
tuples and what-not) but it must be the SAME type for all the elements
in the list. This isn't just a restriction on lookup, btw, the
elements of a list must always be of the same type:
OK: [(1,"hello"),(2,"bye")]
Not OK: [(2,"hello"),(2,14)] -- 14 has a different type than "hello"!
So, what I think you want is something like this:
type Name = String
type Minutes = Int
type StationInfo = [Line] -- maybe something more here?
type Station = (Name,StationInfo)
type LineInfo = [(Minutes, Station)] -- maybe somthing more here?
type Line = (Name,LineInfo)
-- use lookups on these two
-- Its important that both Station, and Line are of the form (a,b)
(and not, say (a,b,c))
type StationDB = [Station]
type LineDB = [Line]
StationInfo would then be a large tuple, perhaps containing a list of
the names of the lines which pass through it (then you could have
another list containing these lines which would map the name of a line
to a LineInfo which would, I suppose, contain a list of station
names).
/S
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+46(0)736-818655
UIN: 44640862
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[Haskell-cafe] Wheres this going wrong
Hi there,
Thanks to some advise by one of the other posters i have chosen to try and set up a list that uses lookup to find the values of the elements within it.
However what i have attempted so far has resulted in odd answers or errors. Anyway here it is, i have given each element a string at the start to put the lookup domain in - anyway here it is
type Line = [((String,String),(String,Int),(String,Int),(String,Bool),(String,Bool),(String,Bool),(String,Bool),(String,Bool),(String,Bool),(String,Bool),(String,Bool),(String,Bool))]
vicsLine :: LinevicsLine = [(("a1","Walthamstow Central"),("a2",1),("a3",2),("a4", False), ("a5", True), ("a6", False), ("a7", False), ("a8", False), ("a9", False), ("a10", False), ("a11", False), ("a12", False))]
Anyway when i enter something such as lookup "a1" i get back a load of stuff about Eq.
So the question is - what am i doing wrong. I am hoping that when i enter a1 it should return for me Walthamstow Central.
Cheers everyone - i'm getting there slowly and all your help is much appreciated.
Neil
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[Haskell-cafe] planet.haskell.org? for Haskell blogs
I think someone should volunteer to set up "Planet Haskell" ala Planet Debian, Planet Gnome, Planet Perl, etc. These sites are "Blog aggregators". Basically they just collect the RSS feeds of the community and post their blogs to a web page in a cute format (the gnome one is especially cute, but you probably could have guessed that). There's already software out there for this, so nothing new needs to be written. I think we need a volunteer to set this up somewhere? Preferably someone with their own server, and we'll worry about setting up the DNS later :) peace, isaac See: http://planet.debian.org/ http://planet.gnome.org/ http://planet.perl.org/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Porting GHC to OSX86?
Hi, DP will support the i386 build as soon as Wolfgang makes his changes available. As I understand, from earlier messages on one of the ghc* lists, this is almost done for the pre-6.6 branch, but not yet backported to the 6.4.x branch. Also, DP uses a binary bootstrap compiler to build ghc, rather than starting from the .hc files. I've been meaning to try it, but I can't promise any schedule as work and life have distracted me from code recently. Best Wishes, Greg (darwinports ghc maintainer) On Mar 22, 2006, at 6:16 AM, Deling Ren wrote: It's not supported on i386 platform yet :( On Mar 22, 2006, at 12:34 AM, Thomas Davie wrote: On Mar 21, 2006, at 8:09 PM, Deling Ren wrote: Hi there, Has anyone made any attempt to port GHC to Mac OS X on x86? Wolfgang Thaller’s binary package runs over Rosetta but slow (not surprising). It can not be used to compile a native version either (I got some errors related to machine registers). I tried to do a bootstrap but can't find the ".HC" files mentioned in the manual. They don't seem to be on the download page of GHC. Any ideas? Why not use darwin ports to build it? Bob ___ 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] Re: Reading files efficiently
Donald Bruce Stewart wrote: Well, I know this works: $ cat A.lhs #!/usr/bin/env runhaskell > main = putStrLn "gotcha!" $ ./A.lhs gotcha! But for files with no .hs or .lhs extension? Anyone know of a trick? GHC 6.6 will allow this, because we added the -x flag (works just like gcc's -x flag). eg. "ghc -x hs foo.wibble" will interpret foo.wibble as a .hs file. I have an uncommitted patch for runghc that uses -x, I need to test & commit it. Cheers, Simon ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Porting GHC to OSX86?
It's not supported on i386 platform yet :( On Mar 22, 2006, at 12:34 AM, Thomas Davie wrote: On Mar 21, 2006, at 8:09 PM, Deling Ren wrote: Hi there, Has anyone made any attempt to port GHC to Mac OS X on x86? Wolfgang Thaller’s binary package runs over Rosetta but slow (not surprising). It can not be used to compile a native version either (I got some errors related to machine registers). I tried to do a bootstrap but can't find the ".HC" files mentioned in the manual. They don't seem to be on the download page of GHC. Any ideas? Why not use darwin ports to build it? Bob ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: strange ghc program behaviour
>From ghc-6.4, the runtime system no longer flushes open files; it >truncates them instead. You should close (or flush) the file explicitly >with 'hClose' or 'hFlush' before the program terminates. I added 'hClose' to processXmlWith in the Wrapper module. That solved the problem. Thank you! Malcolm, concerning HaXml choking on finding an ampersand (or %) in an attribute value (my earlier post): this occurred when the ampersand was part of an entity. I solved it by replacing the values for & and % in the Lex module (not very elegant, I admit). Cheers, K. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Porting GHC to OSX86?
On Mar 21, 2006, at 8:09 PM, Deling Ren wrote: Hi there, Has anyone made any attempt to port GHC to Mac OS X on x86? Wolfgang Thaller’s binary package runs over Rosetta but slow (not surprising). It can not be used to compile a native version either (I got some errors related to machine registers). I tried to do a bootstrap but can't find the ".HC" files mentioned in the manual. They don't seem to be on the download page of GHC. Any ideas? Why not use darwin ports to build it? Bob ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Returning a list element?
Donald Bruce Stewart cse.unsw.edu.au> writes: > > mainMenu = > >sequence_ $ map putStrLn ["line1", "line2", "line3"] > > I argue if you want to sequence_ a map you should write mapM_: > > mapM_ putStrLn ["line1", "line2", "line3"] Nice > > mapM is under-appreciated? More under-appreciated are line gaps: > > main = putStr "line1\n\ > \line2\n\ > \line3\n" > Or if you don't like hand writing in all the newlines you could use putStrLn . concat . intersperse "\n" ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
