Re: H98 Text IO
Why not leave the defaults as they ARE OR USE utf-8 and give the programmer the capability to specify what encoding they want when they want to use a different one? John ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: Some problems writing a threaded program
Thankyou both Don Stewart and Simon Marlow for your responses. By adding yield and threadDelay in certain spots I have at least prevented some of the threads from being starved of CPU time. The only issue now is that terminateProcess doesn't always terminate netstat.exe in the cmd.exe so I don't get an exit condition. ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Some problems writing a threaded program
I am running my program in WinXP with ghc 2.6.8 If you install netstat and change the parameters it should still work in linux. Why does thread # 3 dominate over the over threads int the output? Why does thread # 4 never seem to run? I can't use the sleep function in System.Process.Win32 since it puts all the threads asleep at the same time. Is there a way to put only one thread asleep? That would allow more of a chance for thread #4 to run. The simplified program: --- module Main where import Data.IORef import Data.List import System.IO import System.Process import Control.Concurrent import Control.Concurrent.Chan data Connection = Null | Last | Active deriving (Eq) instance Show Connection where show Null = Null show Last = Last show Active = Active instance Read Connection where readsPrec _ s = case take 5 s of UDP - [(Active, )] TCP - [(Active, )] Last - [(Last,)] _ - [(Null,)] -- ptrints one 0 and 1 main = do stop - newIORef False cbuffer - newChan :: IO (Chan Connection) putStr 0 (_,output,_,ph) - runInteractiveCommand netstat -noa 5 sequence $ map forkIO $ [(processConnections ph output cbuffer), (stopNetstat ph stop False), (printChan cbuffer),(checkStop stop )] putStr 1 _ - waitForProcess ph --mapM killThread ts putStrLn \nDone -- thread # 2 processConnections :: ProcessHandle - Handle - (Chan Connection) - IO () processConnections ph hout chan = do h - hReady hout e - getProcessExitCode ph putStr 2 if (not h e /= Nothing) then do writeChan chan Last return () else do if h then do readConnection hout = writeChan chan else do processConnections ph hout chan readConnection :: Handle - IO Connection readConnection hout = do l - hGetLine hout let c = (read l :: Connection) if (c == Null) then do (readConnection hout) else do (return c) -- thread number 3 stopNetstat :: ProcessHandle - (IORef Bool) - Bool - IO () stopNetstat netstat _ True = terminateProcess netstat stopNetstat netstat gref False = putStr 3 yield readIORef gref = stopNetstat netstat gref --thread 4 printChan :: (Chan Connection) - IO () printChan chan = do putStr 4 c - readChan chan printConnection c printChan chan checkStop :: (IORef Bool) - String - IO () checkStop ref s = do if (take 4 s == stop) then do (writeIORef ref True) else do (getChar = (\x - checkStop ref ((tail s) ++ [x]))) printConnection :: Connection - IO () printConnection c = case c of Null - putStr N Last - putStr L _ - putStr A ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: [Haskell] Simulating client server communication with recursive monads
If you redefine as follows:
server :: [Integer] - Writer [String] [Integer]
server [] = return []
server (a:as) = do
tell [Server ++ show a]
rs - server as
return (a:rs)
You get this for the output:
[Server 0,Server 1,Server 2,Server 3,Server 4,Server 5,Server
6,Server 7,Server 8,Server 9,Server 1
0,Client 0,Client 1,Client 2,Client 3,Client 4,Client 5,Client
6,Client 7,Client 8,Client 9]
Then you just need to alternate the pattern. Though a real simulation
of sever traffic would account for the packets
not being recieved, rerequested, or recieved out of order. It also depends
whether you are simulating TCP or UDP.
On 1/14/08, Jan Stranik [EMAIL PROTECTED] wrote:
Hello,
I am trying to simulate a client server traffic using recursive lazy
evaluation. I am trying to do that in a recursive writer monad.
Following code is my attempt to simulate client server interaction and
collect its transcript:
{-# OPTIONS -fglasgow-exts #-}
module Main where
import Control.Monad.Writer.Lazy
simulation:: Writer [String] ()
simulation = mdo
a - server cr
cr - client $ take 10 a
return ()
server:: [Integer] - Writer [String] [Integer]
server (a:as) = do
tell [server ++ show a]
rs - server as
return ((a*2):rs)
server [] = return []
client:: [Integer] - Writer [String] [Integer]
client as = do
dc - doClient as
return (0:dc)
where
doClient (a:as) = do
tell [Client ++ show a]
as' - doClient as
return ((a+1):as')
doClient [] = return []
main = return $ snd $ runWriter simulation
The problem that I see is that the transcript collected contains first all
output from the server, and then output from the client.
Here is an example of output that I see:
:[server 0,server 1,server 3,server 7,server 15,server
31,server 63,server 127,server 255,server 511,server 1023,Client
0,Client 2,Client 6,Client 14,Client 30,Client 62,Client
126,Client 254,Client 510,Client 1022]
I would like to collect the output like:
:[client 0,server 0, client 1,…]
This would allow me to remove the ending condition in simulation (take
10), and instead rely fully on lazy evaluation to collect as many simulation
steps as needed by my computation.
I am still relatively new to the concepts of recursive monadic
computations, so I would appreciate any suggestions from experts on this
mailing list.
Thank you
Jan
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How do you get the process id out of the ProcessHandle in Win XP?
Here is what I have tried: module Main where import System.Process -- using runInteractiveProcess import System.Posix.Types import System.Process.Internals import Control.Concurrent.MVar main = do (input,output,err,ph) - runInteractiveProcess calc.exe ([]) Nothing Nothing p - Main.getPID ph putStrLn $ show p --- The output getPID :: ProcessHandle - IO CPid getPID (ProcessHandle p) = do (OpenHandle pp) - takeMVar p return (toPID pp) toPID :: PHANDLE - CPid toPID ph = toEnum $ fromEnum ph --- But the CPid always returns some const value (like 1904 in cygwin; 1916 in cmd.exe) I think, I saw that CPid was a newtype of Ptr () So, currently I need to get the process id from CPid or something else. All help is appreciated. John ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: Foreign C with pointers
You do realize that the example you gave is just as general as all the
tutorials.
Here is an example I was working, but it gives a *segmentation fault* for
some reason:
example.h
typedef struct
{
unsigned char a;
unsigned char b;
unsigned char c;
unsigned char d;
} IP;
IP* shiftIP(IP* addr);
example.c
#include example.h
IP* shiftIP(IP* addr){
unsigned char t;
t = addr-a;
addr-a = addr-b;
addr-b = addr-c;
addr-c = addr-d;
addr-d = t;
}
Example.hsc
{-# OPTIONS -ffi -fglasgow-exts #-}
module Example where
import Foreign
import Foreign.C.Types
import Control.Monad
#include buzz.h
data MyIP = MyIP
{ a :: CUChar
, b :: CUChar
, c :: CUChar
, d :: CUChar
} deriving (Show)
instance Storable MyIP where
sizeOf _ = #{size IP} -- 4
alignment _ = alignment (undefined :: CUChar) -- 1
peek p = return MyIP
`ap` (#{peek IP, a} p)
`ap` (#{peek IP, b} p)
`ap` (#{peek IP, c} p)
`ap` (#{peek IP, d} p)
poke p ip = do
#{poke IP, a} p $ a ip
#{poke IP, b} p $ b ip
#{poke IP, c} p $ c ip
#{poke IP, d} p $ d ip
foreign import ccall safe static buzzlib.h shiftIP
shiftIP :: Ptr MyIP - Ptr MyIP
shiftMyIP :: MyIP - MyIP
shiftMyIP ip = unsafePerformIO . alloca $ \ptr - poke ptr ip peek
(shiftIP ptr)
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Re: Can't seem to figure how to compile
Yup, that fixed the problem. Thanks for your help. :) On 10/22/07, Simon Marlow [EMAIL PROTECTED] wrote: John Vogel wrote: Running ghc 6.6.1 On Windows Vista I get this error when I run: ghc Main.hs gcc: installation problem, cannot exec `as': No such file or directory This is a known problem on Vista. The GHC 6.8.1 snapshot should work for you, e.g. http://www.haskell.org/ghc/dist/stable/dist/ghc-6.8.0.20071020-i386-unknown-mingw32.exe Please try it out and let us know if that helps. FYI, the bug we fixed is this: http://hackage.haskell.org/trac/ghc/ticket/1110 Cheers, Simon ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Can't seem to figure how to compile
Running ghc 6.6.1 On Windows Vista I get this error when I run: ghc Main.hs gcc: installation problem, cannot exec `as': No such file or directory On this code: module Main where main = do putStrLn Please enter your name: name - getLine putStrLn (Hello, ++ name ++ , how are you?) What is my problem? ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: Can't seem to figure how to compile
It is the default gcc with ghc. ghci works just fine which invokes ghc --interactive. But this command does work: ghc -e Main.main Main.hs But there is no executable. On 10/21/07, Matthew Danish [EMAIL PROTECTED] wrote: On Sun, Oct 21, 2007 at 01:46:16PM -0500, John Vogel wrote: gcc: installation problem, cannot exec `as': No such file or directory `as' is the assembler that gcc uses. Check your gcc. Can you even compile C programs successfully? -- -- Matthew Danish -- user: mrd domain: cmu.edu -- OpenPGP public key: C24B6010 on keyring.debian.org ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
