Hi,
I am using ghc-5.04 and a code like:
with c ( \c' -> hPutBuf h c' (sizeOf c))
fails with "Fail: Prelude.undefined" when "c" is a user defined type,
such as a pair:
instance (Storable at,Storable bt) => Storable (at,bt) where
sizeOf (a,b) = sizeOf a + sizeOf b
alignment (a,b) = max (alignment a) (alignment b)
peek p = do a <- peek ((castPtr p):: Ptr at)
b <- peekByteOff ((castPtr p):: Ptr bt) (sizeOf a)
return (a,b)
poke p (a,b) = do poke ((castPtr p):: Ptr at) a
pokeByteOff ((castPtr p):: Ptr bt) (sizeOf a) b
On the other hand, if I replace 'with' with 'with1':
with1 :: (Storable a) => a -> ( Ptr a -> IO b ) -> IO b
with1 x f = do p <- mallocBytes (sizeOf x)
let p'=castPtr p :: Ptr a
poke p' x
y <- f p'
free p
return y
it seems to work. I could not even get to work 'malloc :: IO (Ptr
(Int,Int))', while 'malloc :: IO (Ptr Int)' works fine.
Am I doing something wrong, or is there a bug in
the library code?
Yours,
Jan
--
-------------------------------------------------------------------------
Jan Kybic <[EMAIL PROTECTED]> Odyssee, INRIA, Sophia-Antipolis, France
or <[EMAIL PROTECTED]>,tel. work +33 492 38 7589, fax 7845
http://www-sop.inria.fr/odyssee/team/Jan.Kybic/index.en.html
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