# define USE_FAST_STRINGS 1
# define FAST_STRING FastString.FastString
# define SLIT(x) (FastString.mkFastCharString# (x#))
+# define FSLIT(x) (FastString.mkFastString# (x#))
# define _NULL_ FastString.nullFastString
# define _NIL_ (FastString.mkFastString "")
# define _CONS_ FastString.consFS