+extern GList *dive_trip_list;
+extern gboolean autogroup;
+/* random threashold: three days without diving -> new trip
+ * this works very well for people who usually dive as part of a trip and don't
+ * regularly dive at a local facility; this is why trips are an optional feature */
+#define TRIP_THRESHOLD 3600*24*3
+
+#define UNGROUPED_DIVE(_dive) ((_dive)->tripflag == NO_TRIP)
+#define DIVE_IN_TRIP(_dive) ((_dive)->tripflag == IN_TRIP)
+#define NEXT_TRIP(_entry, _list) ((_entry) ? g_list_next(_entry) : (_list))
+#define PREV_TRIP(_entry, _list) ((_entry) ? g_list_previous(_entry) : g_list_last(_list))
+#define DIVE_TRIP(_trip) ((struct dive *)(_trip)->data)
+#define DIVE_FITS_TRIP(_dive, _dive_trip) ((_dive_trip)->when - TRIP_THRESHOLD <= (_dive)->when)
+
+static inline int dive_date_cmp(gconstpointer _a, gconstpointer _b) {
+ return ((struct dive *)(_a))->when - ((struct dive *)(_b))->when;
+}
+
+#define INSERT_TRIP(_trip, _list) g_list_insert_sorted((_list), (_trip), dive_date_cmp)
+#define FIND_TRIP(_trip, _list) g_list_find_custom((_list), (_trip), dive_date_cmp)
+