+void ltt_event_field_element_select(LttEvent *e, LttField *f, unsigned i);
+
+
+/* A union is like a structure except that only a single member at a time
+ is present depending on the specific event instance. This function tells
+ the active member for a union field in an event. */
+
+unsigned ltt_event_field_union_member(LttEvent *e, LttField *f);