fixes #839 (#1028)

Author: martin-henz

xml/chapter3/section5/subsection1.xml

@@ -1057,7 +1057,7 @@ stream_ref(pair(10001, () => stream_enumerate_interval(10002, 1000000)), 100);
         <SNIPPET EVAL="no">
 	  <JAVASCRIPT>
 pair(head(stream), 
-     stream_filter(pred, stream_tail(stream)));
+     () => stream_filter(pred, stream_tail(stream)));
           </JAVASCRIPT>
 	</SNIPPET>
         which in this case is