1 (defun square-tree-direct (tree)
2   (cond ((null tree) nil)
3 	((not (consp tree)) (square tree))
4 	(t (cons (square-tree-direct (car tree))
5 		 (square-tree-direct (cdr tree))))))
6 
7 (defun square-tree-map (tree)
8   (mapcar
9    (lambda (subtree)
10      (if (consp subtree)
11 	 (square-tre-map subtree)
12 	 (square subtree)))
13    tree))
14 
15 (defun tree-map (func tree)
16   (mapcar
17    (lambda (subtree)
18      (if (consp subtree)
19 	 (tree-map func subtree)
20 	 (funcall func subtree)))
21    tree))