rev 537 - trunk/docs/tutorial

Author: mark
Date: 2004-05-23 15:45:09 -0400 (Sun, 23 May 2004)
New Revision: 537

Modified:
   trunk/docs/tutorial/tutorial9.htm
Log:
clarified upcasting and downcasting in tutorial

Modified: trunk/docs/tutorial/tutorial9.htm
===================================================================
--- trunk/docs/tutorial/tutorial9.htm	2004-05-23 05:46:26 UTC (rev 536)
+++ trunk/docs/tutorial/tutorial9.htm	2004-05-23 19:45:09 UTC (rev 537)
@@ -122,9 +122,12 @@
         <p><font face="Verdana, Arial, Helvetica, sans-serif" size="+2"><a name="oaok"></a></font>Now 
           I'd like to show you something useful that no object oriented language 
           can do. Most object-oriented languages will let you change an object 
-          instance's type from a sub-type to a parent type. In other words go 
-          from a narrower case to a broader case. Prothon will let you change 
-          types of an object in either direction. </p>
+          instance's type from a sub-type to a parent type, called &quot;upcasting&quot;. 
+          In other words go from a narrower case to a broader case. They will 
+          sometimes allow you to &quot;upcast&quot; and then &quot;downcast&quot; 
+          back to the original type. Prothon will let you create an original object 
+          and then change types in either direction, either &quot;upcast&quot; 
+          or &quot;downcast&quot;. </p>
         <p><font face="Verdana, Arial, Helvetica, sans-serif" size="+2"><a name="ctex"></a></font>In 
           this example we will modify the Rectangle prototype to intelligently 
           recognize squares and then change the Rectangle object type to the more