Hi, i'm writing a Scala library to add a functional layer to this library.
In my library i've defined a rule to edit the xml document.
This rule contains:

• a function NodeSeq => NodeSeq called Zoom
• an action to apply to the target(target = Zoom applied to the whole document)

With this rule instance i create a standard RewriteRule that will be applied to the whole document using a RuleTransformer.

The code is something like this:

val document : NodeSeq = ???
val rule : XmlRule = ???
val target : NodeSeq = rule.zoom(document)
val rwr = new RewriteRule {
 override def transform(ns: Seq[Node]): Seq[Node] = {
 if(ns == target)
 rule.action(target)
 else 
 ns 
 }
}

Problem
The problem is: when the document has nodes with the same values ns == target returns true multiple times, also if that node doesn't descends from the same parent.

Question
There is a way to obtain an unique id for each node ? If not, it should be a valid proposal generating an unique id during the node instantiation and keep it as node field ?

abstract class Node {
 private lazy val uuid : UUID = UUID.randomUUID() //or something else
 def sameInstance(that: Node) : Boolean = {
 this.equals(that) && this.uuid.equals(that.uuid)
 }
} 
val n1 : Node = <Node />
val n2 : Node = <Node />
n1.sameInstance(n2) //false