Inorder Printing of Binary Tree
An ordered binary tree can be printed in sorted order by an inorder traversal. It is clear that inorder is the right algorithm since the parent is between the two children in the sort ordering.
(defun printbt (tree) (if (consp tree) (progn (printbt (lhs tree)) ; 1. L child (print (op tree)) ; 2. parent (printbt (rhs tree))) ; 3. R child (if tree (print tree)) ) )
>(printbt '(cat (bat ape bee) (elf dog fox))) APE BAT BEE CAT DOG ELF FOX