Re: [Haskell-cafe] GHC.Ptr, Foreign.Storable, Data.Storable.Endian, looking for good examples of usage

On 10 January 2011 16:36, Antoine Latter wrote:

On Mon, Jan 10, 2011 at 10:17 AM, Aaron Gray wrote:

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On 10 January 2011 16:13, Daniel Fischer < daniel.is.fischer@googlemail.com> wrote:

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On Monday 10 January 2011 16:45:36, Aaron Gray wrote:

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This is interesting, what does the following line do :-

data Int24 = I24# Int# deriving (Eq, Ord)

regarding the I24# and Int#, are these inbuilt ?

Int# is the raw machine int (4 or 8 bytes) and I24# is the constructor. GHC uses the magic hash '#' to denote raw unboxed types (and the

constructors

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making ordinary boxed Haskell types from these, e.g. there's

data Int = I# Int# data Word = W# Word# data Double = D# Double#

and more defined in base [GHC.Types, GHC.Word]).

So the 24 bit value is actually stored as a 32bit value. Meaning I will have to do my own IO reader and writer code to a ByteString. Thanks, Aaron

I don't think so - the Storable instance provided for the Int24 type peeks and pokes 24-bit values. At least, that what I understand John's earlier message to mean.

Yes looking at the code it does support 24bit peeks and pokes. Thanks, Aaron