The tag <stack.empty> allows to know if the stack is empty. The stack can be indicated via the attribute name or passed as argument.

1 stack.empty

<stack.empty name='name'>
    <stack /> ?
</stack.empty>

See also

http://java.sun.com/j2se/1.4.2/docs/api/java/util/Stack.html

Example

Uses the function stack.empty to know if there is values in a stack.

Copy 
<xsql-script name='pop_test'>
    <body>
        <stack name='stack1'><number>10</number><string>hello</string></stack>        
        <if>
            <expr>
                <not><stack.empty><stack1/></stack.empty></not>
            </expr>
            <println>
                <stack.pop name='stack1' />
            </println>          
        </if>
    </body>
</xsql-script>
Example

Travel a stack and obtain its values while there is elements.

Copy 
<xsql-script name='pop_test'>
   <body>
       <stack name='stack1' />
       <stack.push name='stack1'>
           <number>10</number>
       </stack.push>
       <stack.push name='stack1'>
           <number>20</number>
       </stack.push>
       <stack.push name='stack1'>
           <number>30</number>
       </stack.push>
       <println>The stack is: <stack1 /></println>
       <while>
           <expr><not><stack.empty name='stack1'/></not></expr>
           <do>
               <println>Removed <stack.pop name='stack1' /> from stack</println>
           </do>
       </while>
   </body>

</xsql-script>