[r2004-01-31 10:39:26 by beppe] Empty log message

Original author: beppe
Date: 2004-01-31 10:39:26+00:00

web/tutorial/errors.xml

@@ -25,13 +25,11 @@ test it on the <a href="cgi-bin/cduce">online interpreter</a>.
 <p>
 CDuce's type system can find very nasty errors. For instance look at this DTD declaration
 </p>
-<p>
-<tt>
-&lt;!ELEMENT person (name,children)><br/>
-&lt;!ELEMENT children (person+)><br/>
-&lt;!ELEMENT name (#PCDATA)><br/>
-</tt>
-</p>
+<xmlsample><![CDATA[
+<!ELEMENT person (name,children)>
+<!ELEMENT children (person+)>
+<!ELEMENT name (#PCDATA)>
+]]></xmlsample>
 <p>
 Apparently this declaration does not pose any problem. But if you consider it more carefully you will see that there exists no document that can be valid for such a DTD,
 as a person contains a sequence of children that contain a non empty
@@ -59,12 +57,11 @@ This definition yields an empty type for Person<br/>
 <p>
 The type checker correctly issues a "Warning" to signal that the first 
 two types  are empty. Note that instead the declarations</p>
-<p>
-<tt>
-type Person = &lt;person>[ Name Children ]<br/>
-type Children = &lt;children>[(<i  style="color:red">ref Person</i>)+]<br/>
-type Name = &lt;name>[PCDATA]<br/>
-</tt></p>
+<sample><![CDATA[
+type Person = <person>[ Name Children ]
+type Children = <children>[(<i  style="color:red">ref Person</i>)+]
+type Name = <name>[PCDATA]
+]]></sample>  
 <p>
 correctly do not yield any warning: in this case it is possible to build a value of type person (and thus of type children), for instance by using a recursive definition where a person is a child of itself.
 </p>