On Sat, 2012-07-07 at 21:59 +0200, Gábor Lehel wrote:
An alternative solution is to encode all of the alignments in unary, which is more general; if they're all going to be a power of two you can "store" just the logarithm:
data One data Twice n -- not practical to call it Double :)
class AlignedToAtLeast n a instance AlignedToAtLeast One One instance AlignedToAtLeast One (Twice a) instance AlignedToAtLeast n a => AlignedToAtLeast (Twice n) (Twice a)
type A1 = One type A4 = Twice (Twice A1) type A8 = Twice A4 type A16 = Twice A8 type A32 = Twice A16
and you can apply the same private class thing from above if you want.
Very ingenious, thanks! I pushed this into [1], although export lists of all modules most likely will need some love once things get into shape. This also allows functions to become more general: unsafeXorSSE42 :: (Storable a, SV.AlignedToAtLeast SV.A16 o1, SV.Alignment o1, SV.AlignedToAtLeast SV.A16 o2, SV.Alignment o2, SV.AlignedToAtLeast SV.A16 o3, SV.Alignment o3) => SV.Vector o1 a -> SV.Vector o2 a -> SV.Vector o3 a I wonder whether GHC's upcoming type-level numerals could be useful in this situation as well. Nicolas [1] https://github.com/NicolasT/vector-simd/commit/a4f13745eb24d87a3628af13109f3...