/* We can't allocate nodes ourselves, because only the caller knows how.
* Instead, insertion is split into two operations: `treap_probe' looks to
* see whether a matching node is already in the treap, and returns it if so;
/* We can't allocate nodes ourselves, because only the caller knows how.
* Instead, insertion is split into two operations: `treap_probe' looks to
* see whether a matching node is already in the treap, and returns it if so;