On Sun, 2012-07-08 at 01:40 +0200, Gábor Lehel wrote:
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 if you could get that a bit shorter... I suppose you could write:
instance (AlignedToAtLeast n a, AlignedToAtLeast n b) => AlignedToAtLeast n (a, b) instance (AlignedToAtLeast n a, AlignedToAtLeast n b, AlignedToAtLeast n c) => AlignedToAtLeast n (a, b, c) ...and so on...
Once again, nifty! And implemented in [1].
though it feels a little strange semantically (relating a tuple to a scalar), but I don't see what harm can come of it. And then you can just write SV.AlignedToAtLeast SV.A16 (o1, o2, o3) in signatures.
You can also make (Alignment n, Alignment a) a superclass constraint of AlignedToAtLeast, and write instances for Alignment inductively on One and Twice, and then you don't have to write Alignment o1 etc. separately either. So the signature would be just:
unsafeXorSSE42 :: (Storable a, SV.AlignedToAtLeast SV.A16 (o1, o2, o3)) => SV.Vector o1 a -> SV.Vector o2 a -> SV.Vector o3 a
which is friendlier.
I implemented the inductive alignment calculation over One and Twice (good idea, and easy to do), but I don't get the thing about superclasses. I've been trying several approaches (including definitions based on forall and other trickery I never used before), but didn't get things to work, at least: the compiler always said I'd need UndecidableInstances, and that sounds scary... Care to elaborate? Thanks! Nicolas [1] https://github.com/NicolasT/vector-simd/commit/aedf25460b410e04a3d103befea59...