(nam,t) <- return (span isIdChar s)
                return (c:nam, t)
           | isDigit c  = do
+{- Removed, 13/03/2000 by SDM.
+   Doesn't work, and not required by Haskell report.
                 let
                  (pred, s', isDec) =
                    case s of
                      ('x':rs) -> (isHexDigit, rs, False)
                      ('X':rs) -> (isHexDigit, rs, False)
                      _        -> (isDigit, s, True)
-
-                (ds,s)  <- return (span pred s')
-                (fe,t)  <- lexFracExp isDec s
+-}
+                (ds,s)  <- return (span isDigit s)
+                (fe,t)  <- lexFracExp s
                 return (c:ds++fe,t)
           | otherwise  = mzero    -- bad character
              where
               isSym c    =  c `elem` "!@#$%&*+./<=>?\\^|:-~"
               isIdChar c =  isAlphaNum c || c `elem` "_'"
 
-              lexFracExp True ('.':cs)   = do
+              lexFracExp ('.':c:cs) | isDigit c = do
                        (ds,t) <- lex0Digits cs
                        (e,u)  <- lexExp t
-                       return ('.':ds++e,u)
-              lexFracExp _ s        = return ("",s)
+                       return ('.':c:ds++e,u)
+              lexFracExp s        = return ("",s)
 
               lexExp (e:s) | e `elem` "eE" = 
                  (do