filter Lexicon.is_proper -- Lexicon.tokenize now includes improper tokens;

--- a/src/Pure/Syntax/simple_syntax.ML	Fri Aug 15 15:51:00 2008 +0200
+++ b/src/Pure/Syntax/simple_syntax.ML	Fri Aug 15 15:51:02 2008 +0200
@@ -24,6 +24,7 @@
   (case
       SymbolPos.explode (s, Position.none) |>
       Lexicon.tokenize lexicon false |>
+      filter Lexicon.is_proper |>
       Scan.read Lexicon.stopper scan of
     SOME x => x
   | NONE => error ("Malformed input: " ^ quote s));