[pmwiki-users] Checking if a {$$var} is set

[DaveG]

Peter Bowers wrote:
> Is this a theoretical markup that you are using? I've never seen 
> anything like the val=myval or the VAL_IS_SET operator or the $$val 
> syntax...
> 
> If I'm confused maybe others are as well?  Or maybe I'm just being slow 
> today... :-)
Guess I was even more confused than you then. Even my subject header was 
wrong.

Here's what I meant to say.
Is there a way to determine whether a variable passed into an included 
page has a value, and whether the variable has actually been passed in? 
Doing something like:
   (:include mygroup.mypage var="myval" :)

and then inside mygroup.mypage:
   (:if !equal {$$var} "" :)

The above works, except when {$$var} is not actually passed into the 
included page, as:
   (:include mygroup.mypage var="myval" :)

in which case {$$var} evaluates to the string "{$$var}" (ie, no 
substitution, as there is nothing to substitute).

I can use a Markup Expression to do a test, but wondered if there was a 
'built-in' way.

  ~ ~ Dave
PS: Hopefully that makes a little more sense...