+#ifdef TREE_WANT_BOUNDARY
+STATIC P(node) * P(boundary) (T *t, uns direction)
+{
+ P(bucket) *n = t->root, *ns;
+ if (!n)
+ return NULL;
+ else
+ {
+ uns son = !!direction;
+ while ((ns = P(tree_son) (n, son)))
+ n = ns;
+ return &n->n;
+ }
+}
+#endif
+