What are pointers and why should I learn about them? -- Part 2

OK, I was wrong about java -- probably because I'm rather a C/assembly dinosaur³ and I think in terms of nouns (e.g., pointers) rather than verbs (e.g., a method that sets the appropriate member of the structure).

So someone at work showed me the light -- you can do it with interfaces. Something like this:

public interface Selector {
    Node getFromSide(Node t);
    Node getToSide(Node t);
    void setFromSide(Node parent, Node newFromSide);
    void setToSide(Node parent, Node newToSide);
}

static class L2R implements Selector {
    public Node getFromSide(Node t) {
        return t.left;
    }
    public Node getToSide(Node t) {
        return t.right;
    }
    public void setFromSide(Node parent, Node newFromSide) {
        parent.left = newFromSide;
    }
    public void setToSide(Node parent, Node newToSide) {
        parent.right = newToSide;
    }
}
 
static class R2L implements Selector {
public Node getFromSide(Node t) {
        return t.right;
    }
    public Node getToSide(Node t) {
        return t.left;
    }
    public void setFromSide(Node parent, Node newFromSide) {
        parent.right = newFromSide;
    }
    public void setToSide(Node parent, Node newToSide) {
        parent.left = newToSide;
    }
}
  
private final static L2R Left2Right = new L2R();
private final static R2L Right2Left = new R2L();
  
Node move1(Selector dir) {
    Node newRoot;
    Node oldParent;
 
    oldParent = this;
    newRoot = dir.getFromSide(this);
    while(dir.getToSide(newRoot) != null) {
        oldParent = newRoot;
        newRoot = dir.getToSide(newRoot);
    }
   
    dir.setToSide(newRoot, this);
    if(oldParent != this) {
        dir.setToSide(oldParent, dir.getFromSide(newRoot));
        dir.setFromSide(newRoot, dir.getFromSide(this));  
    }
    dir.setFromSide(this, null);
    return newRoot;
} 

The key insight I was missing -- probably because of my programming-weltanshauung -- was that I was thinking too low-level. I can probably make the Python implementation more Pythonic, too, by using something like the above rather than a reference to an array written up at http://cpark.users.sonic.net/tree_stuff/