>>48
ん、ああそういう流れだっけ?
じゃこれで
module Main where
import Prelude hiding (length, head)
import Data.Vector.Unboxed

rev :: Vector Int -> Vector Int
rev v = generate (length v) $ \ i -> v ! (length v - 1 - i)

main :: IO ()
main = print $ head $ rev $ iterateN 1000000 (+1) (1 :: Int)

9 MB total memory in use (0 MB lost due to fragmentation)
Total time 0.06s ( 0.05s elapsed)

今度はgenerate自作しろって言い出すんでしょうかね(笑)