aggstate_set_extra ensure_same_skiplist_subtype gsl_random48 MaxAllocSize pos_span_span pos_span_timestamptz random_level RelativeTimePos skiplist_alloc skiplist_delete skiplist_elempos skiplist_free SKIPLIST_GROW skiplist_headval SKIPLIST_INITIAL_CAPACITY SKIPLIST_INITIAL_FREELIST skiplist_make skiplist_splice skiplist_temporal_values skiplist_values

skiplist_headval() void * skiplist_headval ( SkipList *  list ) Return the value at the head of the skiplist.