IndexTest.hs

{-# LANGUAGE BangPatterns #-}
import qualified Data.Vector as V

{-# NOINLINE check #-}
check :: String -> Int -> IO ()
check testName _ = putStrLn $ testName ++ ": safe!" 

{-# NOINLINE test1 #-}
test1 :: V.Vector Int -> IO ()
test1 !v = check "test1" (V.unsafeIndex v 0)

{-# NOINLINE test2 #-}
test2 :: V.Vector Int -> IO ()
test2 !v = do
    a <- V.unsafeIndexM v 0
    check "test2" a

{-# NOINLINE test3 #-}
test3 :: V.Vector Int -> IO ()
test3 !v = check "test3" $! (V.unsafeIndex v 0)
    

main :: IO ()
main = do
    let v = V.replicate 1 undefined
    test1 v
    test2 v
    test3 v