Fail: thread killed
I think I have raised the issue some time ago, but don't remember
why it hasn't been solved as I would like to.
Currently a thread which is killed displays Fail: thread killed,
e.g. in the following program:
import Concurrent
main:: IO ()
main = do
t <- forkIO (threadDelay 100)
threadDelay 50
killThread t
threadDelay 50
Since the very purpose of killThread is to kill the damn thread,
I find it inconvenient to have to wrap any thread which is supposed
to be killable with Exception.catch to avoid the message. Worse:
it should use block and unblock, otherwise there is a small window
where killing the thread will still display the message.
I can probably agree that other kinds of exceptions are displayed;
maybe the programmer didn't know that exceptions are being thrown and
wants the diagnostic. It implies that any well-written code should
catch exceptions in all threads it creates (unless he is sure that the
code will not throw exceptions), since there shouldn't be compiler's
error output from a correct program. Not nice but I can live with that.
Should asynchronous exceptions be really displayed in threads other
than the main thread? IMHO not.
--
__("< Marcin Kowalczyk * [EMAIL PROTECTED] http://qrczak.ids.net.pl/
\__/
^^ SYGNATURA ZASTÊPCZA
QRCZAK
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Re: Bagley shootout. Was: Lightningspeed haskell
I implemented the programs for hash1 and hash2, but I had to
make a lot of changes to FiniteMap to get them to work:
- I changed foldl to foldl' (as defined in Hugs).
- I made foldFM strict (like foldl').
- I made the datatype FiniteMap strict (put !'s everywhere).
I put the programs below, maybe there is a better way to do this.
Jan
-- Hash1
module Main(main) where
import FiniteMap
import System
writeHex' :: Int -> String
writeHex' 0 = ""
writeHex' n
= c:writeHex' y
where
x = n `mod` 16
y = n `div` 16
c | x <= 9= toEnum ((fromEnum '0') + x)
| otherwise = toEnum ((fromEnum 'A') + x - 10)
writeHex :: Int -> String
writeHex n
| n > 0 = reverse (writeHex' n)
| n == 0= "0"
| otherwise = '-':(reverse (writeHex' (-n)))
main :: IO()
main = do {
[arg] <- getArgs;
let
n = read arg
fm = listToFM [(writeHex i,i) | i <- [1..n]]
c = sum [if elemFM (show i) fm then 1 else 0 | i <- reverse [1..n]]
in
putStrLn (show c);
-- Hash2
module Main(main) where
import FiniteMap
import System
import Maybe
foldl' :: (a -> b -> a) -> a -> [b] -> a
foldl' _ a [] = a
foldl' f a (x:xs) = (foldl' f $! f a x) xs
f :: FiniteMap Int Int -> FiniteMap Int Int -> Int -> FiniteMap Int Int
f hash1 hash2 k
| isJust elt2 = addToFM hash2 k (fromJust elt1 + fromJust elt2)
| otherwise = addToFM hash2 k (fromJust elt1)
where
elt1 = lookupFM hash1 k
elt2 = lookupFM hash2 k
main :: IO()
main = do {
[arg] <- getArgs;
let
n = read arg
hash1 = listToFM [(i,i) | i <- [1..1]]
keys= concat (take n (repeat (keysFM hash1)))
hash2 = foldl' (f hash1) emptyFM keys;
h1_1= fromJust (lookupFM hash1 1)
h1_ = fromJust (lookupFM hash1 )
h2_1= fromJust (lookupFM hash2 1)
h2_ = fromJust (lookupFM hash2 )
in
putStrLn (show h1_1 ++ " " ++ show h1_ ++ " " ++
show h2_1 ++ " " ++ show h2_);
}
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