a trigger used in combination with a zl.reg or alternatively inverting the operators within the vexpr should work in most cases if you post a specific case I can take a look...

thanks. I need both inlets to be hot so I can calulate the addition of list data elements that come in on either inlet. Specifically, I have streams of RGB values being sent as 3 part lists from two locations.

something of the like?

I don't think so. I have two separate RGB streams that are lists (f,f,f). I need to add the first R float to the second R float, first G float to second G float, and first B float to second B float. And I need it to add and output the resulting list whenever data is present from either stream.

[trigger b l]

thank you, doubleug. so simple.

my solution works just as well, I suggested the join object with triggers -1 so that in case you want more than two hot inlets you can do so easily. also join takes all kinds of variables i,f, s or l so it is more flexible

thanks, Michelez