[ZPT] REQUEST argument

[Guido van Rossum]

> There are also the 'null' and 'missing' attributes of dtml-var:
> 
> <dtml-var spoon missing="">
> 
> This omits the tag (tal:replace="nothing") if there is no spoon.
> 
> <dtml-var spoon missing="there is no spoon">
> 
> This substitutes "there is no spoon" if there is no spoon.
> 
> <dtml-var spoon null="there is no spoon">
> 
> This substitutes "there is no spoon" if the spoon is empty, but
> raises an exception if there is actually no spoon.

Aha, this is much closer to the proposed a|b and a||b syntax than
dtml-if!

I'm much happier with this analogy.

--Guido van Rossum (home page: http://www.python.org/~guido/)