Question

I have two trees (paths), defined by a node like

trait Node {
  def getParent : Node
  def op(n:Node)
}

and I want to travel two nodes up until the parent is null in parallel like:

Pseudo:

def simultanousUp(/*var*/ a:Node,/*var*/ b:Node) = 
     while(a != null) {
          a.op(b); 
          a = a.getParent;
          b = if(b!=null) b.getParent else null /*or throw somthing*/;
      }

Question: is there a more elegant and/or performant way in scala to do this?

To avoid misunderstandings: its not a question about concurrent execution!

Answer 1

@annotation.tailrec final def simultaneousUp(a: Node, b: Node) {
  if (a != null && b != null) {
    a op b
    simultaneousUp(a.getParent, b.getParent)
  }
  // Throw exception or whatever on mismatched lengths?
}