On Thu, Mar 8, 2012 at 8:12 PM, Edward Kmett
I'm currently working with a lot of very short arrays of fixed length and as a thought experiment I thought I would try to play with fast numeric field accessors
...
This becomes more reasonable to consider when you are forced to make something like
data V4 a = V4 a a a a
using
unsafeIndex (V4 a _ _ _) 0 = a unsafeIndex (V4 _ b _ _) 1 = b unsafeIndex (V4 _ _ c _) 2 = c unsafeIndex (V4 _ _ _ d) 3 = d
rather than
unsafeIndex :: V4 a -> Int -> a unsafeIndex = unsafeField
I'm dealing with exactly this problem in unordered-containers. I'm dealing with small (16) element arrays that I need 1) index into and 2) update a single element off. I use Array# and MutableArray# for this, but they aren't optimal, mostly because they are optimized for the case of larger arrays (e.g. they use card tables and out-of-line allocation.) -- Johan