I am busy checking that I can exactprint all the RdrNames produced by the parser, and came across this isBuiltInOcc_maybe occ = case occNameString occ of "[]" -> choose_ns listTyCon nilDataCon ":" -> Just consDataConName "[::]" -> Just parrTyConName "(##)" -> choose_ns unboxedUnitTyCon unboxedUnitDataCon "()" -> choose_ns unitTyCon unitDataCon '(':'#':',':rest -> parse_tuple UnboxedTuple 2 rest '(':',':rest -> parse_tuple BoxedTuple 2 rest _other -> Nothing The above code does not allow any spaces between '[' and ']', or '[:' and ':]' (for example) However, the parse rules DO allow spaces | '[' ']' {% ams (sLL $1 $> $ listTyCon_RDR) [mos $1,mcs $2] } | '[:' ':]' {% ams (sLL $1 $> $ parrTyCon_RDR) [mo $1,mc $2] } Is this a problem? Alan