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

--- returned arguments ---
PK_CURVE_t *const curve             --- its curve (possibly PK_ENTITY_null)
)


This function returns the nominal curve of the given edge, if it has one,
otherwise PK_ENTITY_null.


This function returns:
  - for an accurate edge: the same as PK_EDGE_ask_curve,
  - for a tolerant edge with a nominal curve: the nominal curve,
  - otherwise PK_ENTITY_null.

This behaviour is independent of whether nominal curves are currently enabled
for the edge's body (see PK_BODY_ask_curve_nmnl_state).