1 (defun union-set-bintree (set1 set2)
2   (let* ((lset1 (tree->list-1 set1))
3 	 (lset2 (tree->list-1 set2))
4 	 (lunion (union-set lset1 lset2))
5 	 (union (list->tree lunion)))
6     union))
7 (defun intersection-set-bintree (set1 set2)
8   (let* ((lset1 (tree->list-1 set1))
9 	 (lset2 (tree->list-1 set2))
10 	 (lintersect (intersection-set lset1 lset2))
11 	 (intersect (list->tree lintersect)))
12     intersect))
13