src/Pure/PIDE/command_span.scala

       kind match { case k: Command_Span => k.pos case _ => Position.none }
 
     def keyword_pos(start: Token.Pos): Token.Pos =
       kind match {
         case _: Command_Span =>
-          (start /: content.iterator.takeWhile(tok => !tok.is_command))(_.advance(_))
+          content.iterator.takeWhile(tok => !tok.is_command).foldLeft(start)(_.advance(_))
         case _ => start
       }
 
     def is_kind(keywords: Keyword.Keywords, pred: String => Boolean, other: Boolean): Boolean =
       keywords.kinds.get(name) match {

     def is_begin: Boolean = content.exists(_.is_begin)
     def is_end: Boolean = content.exists(_.is_end)
 
     def content_reader: CharSequenceReader = Scan.char_reader(Token.implode(content))
 
-    def length: Int = (0 /: content)(_ + _.source.length)
+    def length: Int = content.foldLeft(0)(_ + _.source.length)
 
     def compact_source: (String, Span) =
     {
       val source = Token.implode(content)
       val content1 = new mutable.ListBuffer[Token]