On Sun, 2010-02-07 at 00:04 +0100, Marco De Oliveira wrote:
Hi Maciej,
Thanks to have take some time to read this code.
I rewrite using your comments:
import Foreign import Foreign.C
data CStruct = CStruct (CULong, CULong)
Hmm. You combined both newtype and data. While technically it is correct you have now one level more for program to consider.
instance Storable CStruct where sizeOf _ = 2*sizeOf (undefined::CULong) alignment _ = alignment (undefined::CULong)
test = with (CStruct (1,1)) (\ptr -> return ())
The class Storable does not need to make your own peek and poke method (the class provide a default implementation).
Not quite. It does in terms of peek/pokeElemOff. Which has in terms of peek/pokeByteOff which has implementation in terms of peek/poke itself. Therefore you have infinite recursion - poke calls pokeElemOff which calls pokeByteOff which calls poke etc. Even the documentation specifies this: "Minimal complete definition: sizeOf, alignment, one of peek, peekElemOff and peekByteOff, and one of poke, pokeElemOff and pokeByteOff."[1] Sorry - I forgot about this (I only noticed that something is missing).
But with, i have still the behavior when I try this code in ghci.
My other suggestions only caused to avoid extensions/have type safety and shorten the function respectively - they did not alter behaviour. Regards [1] http://www.haskell.org/ghc/docs/latest/html/libraries/base-4.2.0.0/Foreign-S...