Hello, If I compile the attach code with GHC of the newest ghc-7.0 darcs branch, the compiled program is much slower than byte code. This phenomenon does not exist in GHC 6.12.3. 6.12.3 runghc -- 6.23s user 0.59s system 98% cpu 6.912 total ghc -- 5.72s user 0.70s system 99% cpu 6.422 total ghc -O -- 5.70s user 0.67s system 99% cpu 6.376 total ghc -O2 -- 5.69s user 0.67s system 99% cpu 6.373 total ghc-7.0 runghc -- 6.43s user 0.10s system 99% cpu 6.593 total ghc -- 9.20s user 0.09s system 99% cpu 9.302 total ghc -O -- 9.20s user 0.09s system 99% cpu 9.298 total ghc -O2 -- 9.38s user 0.09s system 99% cpu 9.478 total Is this a bug? My environment is Mac which runs Snow Leopard. --Kazu ---- import System.IO n :: Int n = 10000 main :: IO () main = withFile "/dev/null" WriteMode $ \h -> hPutStr h . foldr1 (++) . replicate n . replicate n $ 'a' ----