[Zope] How do I convert an id to a string?

[Farzad Farid]

 This may be a simple problem but I tried all I could yesterday, I browsed
the docs quickly and could not find the answer: I want to use the id of a
object as a string in an expression and I can't find how to
convert/extract the string representation of the id. I want to write some
code like this: 

<dtml-comment>Do not show backup files</dtml-comment>
<dtml-in "objectValues(['DTML Document'])">
  <dtml-if "_.string.rfind(id, '~') != -1">
            ^^^^^^^^^^^^^^^^^^^^^^^
    <LI><A HREF="<dtml-var "absolute_url()">"><dtml-var title_or_id></A>
  </dtml-if>
</dtml-in>

 What should I put in this expression in the place of 'id'?

   Thanks

-- 
Farzad FARID <farzy@via.ecp.fr>
Ingénieur Informatique Libre
Alcôve - http://www.alcove.fr/