PK_ERROR_code_t   PK_FACE_find_edges_common
(
--- received arguments ---
PK_FACE_t         face_1,      --- first face
PK_FACE_t         face_2,      --- second face

--- returned arguments ---
int        *const n_edges,    --- number of common edges
PK_EDGE_t **const edges       --- common edges
)


This function finds edges which are common to two faces.


Specific Errors:
    PK_ERROR_not_in_same_body      faces don't belong to same body


The faces must belong to the same body.  All edges common to both faces
are returned.

If the same face is given as face_1 and face_2 then all edges of that
face are returned.  It is thus equivalent to PK_FACE_ask_edges but it is
not guaranteed that the edge order will be the same from the two functions.