On Tue, Dec 23, 2008 at 07:44:14PM -0500, wren ng thornton wrote:
AFAIK, Data.Word.Word is defined to be "the same size as Prelude.Int" (which it isn't on GHC 6.8.2 on Intel OS X: 32bits vs 31bits) and Int is defined to be at least 31bits but can be more. My interpretation of this is that Int and Word will generally be implemented by the architecture's natural word size in order to optimize performance, much like C's "int" and "unsigned int" but with better definition of allowed sizes. This seems to be supported by the existence of definite-sized variants Word8, Word16, Word32...
Of course, natural word size can mean 'natural pointer size' or 'natural int size'. Which are different on many architectures. So, you want to be careful about which you want.
So yeah, I'm meaning the machine word, but I think Word is intended to proxy for that. Maybe I'm wrong, but provided that Word contains (or can be persuaded to contain) a round number of Word8 and that operations on Word are cheaper than the analogous sequence of operations on the Word8 representation, that's good enough for my needs.
If you want to find out the 'natural' sizes, then look at the 'CInt', 'Ptr', and 'FunPtr' types, which follow the C 'int' 'void *' and 'void (*fn)()' types. So they will conform to the architecture ABI for the underlying spec/operating system. If you just want a type guarenteed to be able to hold a pointer or an integer, use 'IntPtr' or 'WordPtr' which are provided for just that case. John -- John Meacham - ⑆repetae.net⑆john⑈