On Mon, 18 Jun 2012, Roman Leshchinskiy wrote:
There are type families, rank-n types, unboxed types and other goodies
deep in the guts of vector so the Storable part is very much
GHC-specific. To be honest, I don't think being portable is feasible for
high-performance code at the moment, the language standard simply
doesn't have enough tools for this. Which is a shame, really.
I am not mainly interested in the efficient implementation. I am
completely ok with having the definition of (Vector a) in a separate
package, such that it can be used by vector (GHC only) and storablevector
(portable).
However, I have just looked into Vector.Storable and it looks like
data Vector a = Vector Int (ForeignPtr a)
I thought it was
data Vector a = Vector {len :: Int, allocated :: ForeignPtr a, start :: Ptr a}
ByteString looks like:
data ByteString = PS {allocated :: ForeignPtr Word8, start, length :: Int}
Both forms allow efficient slicing.
How do you perform efficient 'take' and 'drop' ?
FWIW, Storable vectors are fundamentally broken, anyway, since a
Storable instance can perform arbitrary I/O in its methods but a pure
vector based on Storable will necessarily have to unsafePerformIO these
operations.
That's unfortunately true.
Storable should *really* live in ST but it's too late for that now.
How would this prevent from broken pointer arithmetic?
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