crazy ghc optimization

ghc-optimization.hs

module Test (test) where

test :: [Int] -> Bool
test l = all (==(-1)) $ zipWith (-) l (tail l)

{-

ghc -ddump-simpl -O ghc-optimization.hs
after clean up:

test1 :: Int -> Int -> Bool
test1 a b = (a-b) == (-1)

test :: [Int] -> Bool
test l = GHC.List.foldr2 test1 True l (case l of
                                          [] -> GHC.List.tail1
                                          (x:xs) -> xs
                                      )

-}