Sorry I sent the email before finishin it :))
----- PICCA Frederic-Emmanuel
Hello,
I am in this case, the Cube C struct contains at least two realy big arrays. I wan to modify them in place.
If however always copying the cube is too expensive, then you can take an approach similar to that used in Array or Vector, where Cubes are available in both immutable and mutable forms, with freeze, thaw, unsafeFreeze and unsafeThaw operations connecting the two.
data Cube = Cube ... data STCube s = STCube s ... data IOCube = IOCube ...
Mutable cubes can be modified in place in either the IO or ST Monads.
I like this idea, I looked a t the MVector implementation
data MVector s a = MVector {-# UNPACK #-} !Int -- ^ Offset in underlying array {-# UNPACK #-} !Int -- ^ Size of slice {-# UNPACK #-} !(MutableArray s a) -- ^ Underlying array deriving ( Typeable )
type IOVector = MVector RealWorld type STVector s = MVector s
I imagine that in my case I can can just define a.
data MCube s = MCube (ForeignPtr C'HklBinocularsCube)
and then
type IOCube = NCube RealWorld
Then it seems to me that I just need to define a merge function like this merge :: PrimMonad m => MCube (PrimState m) -> Frame -> m () and then an unsafeFreeze to avoid copy. It that correct ? Cheers Fred