public void insert (double item) {  



    first = insertH (first, item);

  }
  private static Node insertH (Node x, double item) { 
    if (x == null || x.item >= item) {
      return new Node (item, x);
    } else {
      x.next = insertH (x.next, item);
      return x;
    }
  }

Computes both forwards and backwards

Two separate function calls

• the sender makes the new node
• the receiver puts it in it's place

The receiver could be a call to the starter, or the helper

• Only check the termination condition once!

This pattern is really great with balanced trees (next quarter).