Here’s a very basic definition that demonstrates the power of data trees and [Pull Point] or [Closest Point].
From a basic 5 x 5 point grid it will determine which of those points are closest to any number of referenced points. Something like this could be the basis of an attraction/repulsion type definition.
DEFINITION
multiSource.ghx (Right-click on link and “Save link as…”)
thanks for such a simple + powerful def!