+/*
+ Iterates over a tree.
+
+ CAUTION: while this construct supports deleting the current item,
+ it does *not* support deleting *other* nodes while iterating on the tree.
+ */
+#define splay_each(type, item, tree) (type *item = (type *)1; item; item = NULL) for(splay_node_t *node = (tree)->head, *next; item = node ? node->data : NULL, next = node ? node->next : NULL, node; node = next)
+