Ehm... I must be missing something very obvious:
How can I tell if the filter output thus far exists at all, i.e regardeless if it is a tiddler or a shadow?
For example
...is[tiddler+shadow] is an invalid oparand for the is operator
Maybe there is some way to tell if the filter output thus far is empty? I was thinking maybe is[blank] is intended for this but in that case {{{ "" +[is[blank]] }}} should return true or something similar (right?), but there is no output.
Ideas?
<:-)