[Haskell-cafe] C binding <-> safer haskell API

PICCA Frederic-Emmanuel frederic-emmanuel.picca at synchrotron-soleil.fr
Thu Feb 10 09:30:18 UTC 2022


 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

I a

> -- 
>     VIktor.
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