/** @return the parent Node to this Node; that is, the action that
* occurred previously in the stack. */
Node * get_parent() const { return parent; }
bool add_future_value(uint64_t value, modelclock_t expiration);
/** @return the parent Node to this Node; that is, the action that
* occurred previously in the stack. */
Node * get_parent() const { return parent; }
bool add_future_value(uint64_t value, modelclock_t expiration);