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
In particular, I'd like to use something like foreign prim to do something like > foreign import prim "cmm_getField" unsafeField# :: a -> Int# -> b > unsafeField :: a -> Int -> b > unsafeField a (I# i) = a' `pseq` unsafeField# a' i -- the pseq could be moved into the prim, I suppose. > where a' = unsafeCoerce a > fst :: (a,b) -> a > fst = unsafeField 0 > snd :: (a,b) -> b > snd = unsafeField 1 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 But I can only pass unboxed types to foreign prim. Is this an intrinsic limitation or just an artifact of the use cases that have presented themselves to date?
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