Georg Werner wrote:
hi,
Hi Georg,
can somebody explain why there is a "3rd rule of $-expansion: 'there is no $0 in message-boxes'".
The following is from an implementor's viewpoint, not a user's viewpoint, so be warned :)
I don't know why, but it makes parsing Pd patches 1000x less straightforward than required (you need a two-phase parser that has a special exception to detect message boxes and not expand dollars, allowing the message box objects to parse them itself later, while expanding dollars for everything else).
I ran into this problem implementing PotatoData (basically a proof of concept, it's a Pd patch interpreter written in Lua with minimal amounts of C for DSP, can run some trivial audio patches) a couple of months ago, and just ducked it completely - message boxes in my implementation don't support dollars at all (nor commas or semicolons for sequencing and redirection, but that's a separate issue).
I wish message boxes had used a different special character, it would have made life much much easier.
i stumble every now and then about it and it is IMHO not self-explanatory.
It's a mess. There are two similar concepts at work:
- replacing dollars with arguments at patch execution time
- replacing dollars with arguments at message passing time
But they both use the same $ symbol syntax in Pd, so you can't have both taking place (ie, use $ at patch execution to create a message box that has $ to replace at dataflow time). And $0 is in phase 1, so what should a message box do with $0 in phase 2?
The confusion arises partly because when Pd loads a patch, it's really internally passing messages around.
$ in message boxes is unfortunate. If there was a different symbol, perhaps #, you could combine both phases in one object box to avoid jumping through pointless hoops.
[$0-#1-$2-#3( would be nice, but as Pd is now, it's a nightmare.