Other Choices
	Ø Use an explicit List class as well as a Node class or structure Ø  pval() then is a List, rather than a pointer to Node Ø print_preorder() or other routines that traverse the tree would need some way to efficiently step through the nodes in the list. – I.e., don’t actually destroy the list using Pop() – You could let the List() give you it’s first node, or you could define a list iterator type as described in the textbook.