[Zope] <dtml-var expr="maand" missing=1>???

[Edwin Martin]

Hello,

How can I use an undefined variable in an expression?

I made a DTML document which gets parameters from the URL,
like "/nieuw?maand=1".

But I also want it to work when no parameters are given.

'Missing' should be the answer,  but the following doesn't work:
<dtml-var expr="_.int(maand)+1" missing=1>
<dtml-let defmaand=maand missing=1>...</dtml-let>
<dtml-in listbydate reverse size=20 start=maand missing=1>

I expected to find a solution in
http://www.zope.org/Members/michel/ZB/DTML.html
http://www.zope.org/Members/michel/ZB/AppendixA.html
but couldn't find it.

Edwin (who would be so happy with *good* documentation)

---
To be upset over what you don't have is to waste what you do have.
-- Unknown

Surf Edwin Martin's brainwaves: http://www.bitstorm.org/edwin/