PK_EDGE_ask_first_fin

PK_ERROR_code_t PK_EDGE_ask_first_fin
(
--- received arguments ---
PK_EDGE_t       edge,              --- an edge

--- returned arguments ---
PK_FIN_t *const first_fin          --- the first fin (possibly PK_ENTITY_null)
)


This function returns the first fin belonging to the given edge.

If the edge is wireframe and so has no fins, then PK_ENTITY_null will be
returned.


This function should be used in conjuction with PK_FIN_ask_next_of_edge to
scan the fins of an edge.