[Zope] checking for elements in a list

[Christopher Rivard]

Hello,

I'm am trying to check for the membership of items in a list and think 
I'm missing something.
How is this done in dtml?

List allids: [15,16,17,18]

Check for multiple items in the list:

<dtml-in allids prefix="loop">
<dtml-if expr="loop_item == 17">
something
<dtml-elif expr="loop_item == 17 and loop_item != 18">
doesn't work
</dtml-if>
</dtml-in>

The goal is to check for combinations:
17 and not 18
18 only
17 only
17 and 15
18 and 16
...combinations.

I don't think that I really want to loop through the list, just want to 
check membership in the list.


Thanks in advance,
Chris