non-GHC compilers should also import Numeric.
import Data.Char ( isSpace, chr, ord )
import System.IO.Unsafe ( unsafePerformIO )
import Data.IORef
+import Numeric ( readDec )
#ifdef __GLASGOW_HASKELL__
import GHC.Show ( showSignedInt, showSpace )
-import Numeric ( readDec )
import GHC.IOBase ( unsafePerformIO, stToIO )
import System.Time ( getClockTime, ClockTime(..) )
#endif