diff -r 095f90f8dca3 -r 1ed88ddf1268 src/Pure/Isar/token.scala
--- a/src/Pure/Isar/token.scala	Sat Jun 18 11:22:03 2011 +0200
+++ b/src/Pure/Isar/token.scala	Sat Jun 18 11:45:07 2011 +0200
@@ -64,7 +64,7 @@
 sealed case class Token(val kind: Token.Kind.Value, val source: String)
 {
   def is_command: Boolean = kind == Token.Kind.COMMAND
-  def is_keyword: Boolean = kind == Token.Kind.KEYWORD
+  def is_operator: Boolean = kind == Token.Kind.KEYWORD && !Symbol.is_ascii_identifier(source)
   def is_delimited: Boolean =
     kind == Token.Kind.STRING ||
     kind == Token.Kind.ALT_STRING ||