Let's say I have an abstraction that accepts a file path as a symbol argument.
[loadbang] | [symbol $1]
But maybe the user didn't provide a symbol. In that case, I'd like to stop the data flow: if the symbol is not empty, do
[open $1( and forward the message on; if the symbol is empty, don't trigger the "open" message at all.
[route] and [select] can match non-empty symbols but it isn't obvious how to match an empty symbol.
In any other programming environment, I could compare to an empty string... but I can't even find how to denote an empty string in Pd.
How to do this?